From 68d53c01b0b8e9a007a6a30158c19e34b2d2a34e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Wed, 18 May 2016 15:53:35 +0200 Subject: Update STDLIB documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Language cleaned up by the technical writers xsipewe and tmanevik from Combitech. Proofreading and corrections by Björn Gustavsson and Hans Bolinder. --- lib/stdlib/doc/src/ets.xml | 2279 ++++++++++++++++++++++++-------------------- 1 file changed, 1251 insertions(+), 1028 deletions(-) (limited to 'lib/stdlib/doc/src/ets.xml') diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml index 9fb7d227a3..b8e262208d 100644 --- a/lib/stdlib/doc/src/ets.xml +++ b/lib/stdlib/doc/src/ets.xml @@ -29,103 +29,131 @@ ets - Built-In Term Storage + Built-in term storage.

This module is an interface to the Erlang built-in term storage BIFs. These provide the ability to store very large quantities of data in an Erlang runtime system, and to have constant access time to the data. (In the case of ordered_set, see below, access time is proportional to the logarithm of the number of - objects stored).

+ stored objects.)

+

Data is organized as a set of dynamic tables, which can store tuples. Each table is created by a process. When the process terminates, the table is automatically destroyed. Every table has access rights set at creation.

+

Tables are divided into four different types, set, - ordered_set, bag and duplicate_bag. + ordered_set, bag, and duplicate_bag. A set or ordered_set table can only have one object - associated with each key. A bag or duplicate_bag can + associated with each key. A bag or duplicate_bag table can have many objects associated with each key.

+

The number of tables stored at one Erlang node is limited. - The current default limit is approximately 1400 tables. The upper - limit can be increased by setting the environment variable + The current default limit is about 1400 tables. The upper + limit can be increased by setting environment variable ERL_MAX_ETS_TABLES before starting the Erlang runtime - system (i.e. with the -env option to - erl/werl). The actual limit may be slightly higher + system (that is, with option -env to + erl/werl). The actual limit can be slightly higher than the one specified, but never lower.

-

Note that there is no automatic garbage collection for tables. + +

Notice that there is no automatic garbage collection for tables. Even if there are no references to a table from any process, it - will not automatically be destroyed unless the owner process - terminates. It can be destroyed explicitly by using - delete/1. The default owner is the process that created the - table. Table ownership can be transferred at process termination - by using the heir option or explicitly - by calling give_away/3.

+ is not automatically destroyed unless the owner process + terminates. To destroy a table explicitly, use function + delete/1. + The default owner is the process that created the + table. To transfer table ownership at process termination, use + option heir or call + give_away/3.

+

Some implementation details:

+ - In the current implementation, every object insert and - look-up operation results in a copy of the object. - '$end_of_table' should not be used as a key since - this atom is used to mark the end of the table when using - first/next. +

In the current implementation, every object insert and + look-up operation results in a copy of the object.

 +

'$end_of_table' is not to be used as a key, as + this atom is used to mark the end of the table when using functions + first/1 and + next/2.

 -

Also worth noting is the subtle difference between + +

Notice the subtle difference between matching and comparing equal, which is - demonstrated by the different table types set and - ordered_set. Two Erlang terms match if they are of - the same type and have the same value, so that 1 matches - 1, but not 1.0 (as 1.0 is a float() - and not an integer()). Two Erlang terms compare equal if they either are of the same type and value, or if - both are numeric types and extend to the same value, so that - 1 compares equal to both 1 and 1.0. The - ordered_set works on the Erlang term order and - there is no defined order between an integer() and a - float() that extends to the same value, hence the key - 1 and the key 1.0 are regarded as equal in an - ordered_set table.

+ demonstrated by table types set and ordered_set:

+ + + +

Two Erlang terms match if they are of + the same type and have the same value, so that 1 matches + 1, but not 1.0 (as 1.0 is a float() + and not an integer()).

+ + +

Two Erlang terms compare equal + if they either are of the same type and value, or if + both are numeric types and extend to the same value, so that + 1 compares equal to both 1 and 1.0.

+ + +

The ordered_set works on the Erlang term order and + no defined order exists between an integer() and a + float() that extends to the same value. Hence the key + 1 and the key 1.0 are regarded as equal in an + ordered_set table.

+ + +
Failure -

In general, the functions below will exit with reason - badarg if any argument is of the wrong format, if the - table identifier is invalid or if the operation is denied due to +

The functions in this module exits with reason + badarg if any argument has the wrong format, if the + table identifier is invalid, or if the operation is denied because of table access rights (protected or private).

+
Concurrency

This module provides some limited support for concurrent access. All updates to single objects are guaranteed to be both atomic - and isolated. This means that an updating operation towards - a single object will either succeed or fail completely without any - effect at all (atomicity). - Nor can any intermediate results of the update be seen by other - processes (isolation). Some functions that update several objects + and isolated. This means that an updating operation to + a single object either succeeds or fails completely without any + effect (atomicity) and that + no intermediate results of the update can be seen by other + processes (isolation). Some functions that update many objects state that they even guarantee atomicity and isolation for the entire operation. In database terms the isolation level can be seen as - "serializable", as if all isolated operations were carried out serially, + "serializable", as if all isolated operations are carried out serially, one after the other in a strict order.

-

No other support is available within ETS that would guarantee - consistency between objects. However, the safe_fixtable/2 - function can be used to guarantee that a sequence of - first/1 and next/2 calls will traverse the table - without errors and that each existing object in the table is visited - exactly once, even if another process (or the same process) + +

No other support is available within this module that would guarantee + consistency between objects. However, function + safe_fixtable/2 + can be used to guarantee that a sequence of + first/1 and + next/2 calls traverse the + table without errors and that each existing object in the table is + visited exactly once, even if another (or the same) process simultaneously deletes or inserts objects into the table. - Nothing more is guaranteed; in particular objects that are inserted - or deleted during such a traversal may be visited once or not at all. - Functions that internally traverse over a table, like select - and match, will give the same guarantee as safe_fixtable.

+ Nothing else is guaranteed; in particular objects that are inserted + or deleted during such a traversal can be visited once or not at all. + Functions that internally traverse over a table, like + select and + match, + give the same guarantee as + safe_fixtable.

+
Match Specifications -

Some of the functions uses a match specification, - match_spec. A brief explanation is given in - select/2. For a detailed - description, see chapter - Match Specifications in Erlang - in ERTS User's Guide.

+

Some of the functions use a match specification, + match_spec. For a brief explanation, see + select/2. For a detailed + description, see section + Match Specifications in Erlang in ERTS User's Guide.

@@ -137,8 +165,7 @@

Opaque continuation used by select/1,3, - select_reverse/1,3, + select_reverse/1,3, match/1,3, and match_object/1,3.

 @@ -159,26 +186,30 @@ -

A table identifier, as returned by new/2.

 +

A table identifier, as returned by + new/2.

 + Return a list of all ETS tables.

Returns a list of all tables at the node. Named tables are - given by their names, unnamed tables are given by their + specified by their names, unnamed tables are specified by their table identifiers.

-

There is no guarantee of consistency in the returned list. Tables created - or deleted by other processes "during" the ets:all() call may or may - not be included in the list. Only tables created/deleted before - ets:all() is called are guaranteed to be included/excluded.

+

There is no guarantee of consistency in the returned list. Tables + created or deleted by other processes "during" the ets:all() + call either are or are not included in the list. Only tables + created/deleted before ets:all() is called are + guaranteed to be included/excluded.

 + Delete an entire ETS table. @@ -186,175 +217,187 @@

Deletes the entire table Tab.

 + - Delete all objects with a given key from an ETS table. + Delete all objects with a specified key from an ETS + table. -

Deletes all objects with the key Key from the table +

Deletes all objects with key Key from table Tab.

 + Delete all objects in an ETS table.

Delete all objects in the ETS table Tab. - The operation is guaranteed to be - atomic and isolated.

+ The operation is guaranteed to be + atomic and isolated.

 + Deletes a specific from an ETS table. -

Delete the exact object Object from the ETS table, +

Delete the exact object Object from the + ETS table, leaving objects with the same key but other differences - (useful for type bag). In a duplicate_bag, all - instances of the object will be deleted.

+ (useful for type bag). In a duplicate_bag table, all + instances of the object are deleted.

 + Read an ETS table from a file. -

Reads a file produced by tab2file/2 or - tab2file/3 and creates the - corresponding table Tab.

-

Equivalent to file2tab(Filename, []).

+

Reads a file produced by + tab2file/2 or + tab2file/3 and + creates the corresponding table Tab.

+

Equivalent to file2tab(Filename, []).

 + Read an ETS table from a file. -

Reads a file produced by tab2file/2 or - tab2file/3 and creates the +

Reads a file produced by + tab2file/2 or + tab2file/3 and creates the corresponding table Tab.

-

The currently only supported option is {verify,boolean()}. If - verification is turned on (by means of specifying - {verify,true}), the function utilizes whatever - information is present in the file to assert that the - information is not damaged. How this is done depends on which - extended_info was written using - tab2file/3.

-

If no extended_info is present in the file and - {verify,true} is specified, the number of objects - written is compared to the size of the original table when the - dump was started. This might make verification fail if the - table was - public and objects were added or removed while the - table was dumped to file. To avoid this type of problems, - either do not verify files dumped while updated simultaneously - or use the {extended_info, [object_count]} option to - tab2file/3, which - extends the information in the file with the number of objects - actually written.

-

If verification is turned on and the file was written with - the option {extended_info, [md5sum]}, reading the file - is slower and consumes radically more CPU time than - otherwise.

+

The only supported option is {verify,boolean()}. + If verification is turned on (by specifying {verify,true}), + the function uses whatever information is present in the file to + assert that the information is not damaged. How this is done depends + on which extended_info was written using + tab2file/3.

+

If no extended_info is present in the file and + {verify,true} is specified, the number of objects + written is compared to the size of the original table when the + dump was started. This can make verification fail if the table was + public and objects were added or removed while the + table was dumped to file. To avoid this problem, + either do not verify files dumped while updated simultaneously + or use option {extended_info, [object_count]} to + tab2file/3, which + extends the information in the file with the number of objects + written.

+

If verification is turned on and the file was written with + option {extended_info, [md5sum]}, reading the file + is slower and consumes radically more CPU time than otherwise.

{verify,false} is the default.

 + Return the first key in an ETS table. -

Returns the first key Key in the table Tab. - If the table is of the ordered_set type, the first key - in Erlang term order will be returned. If the table is of any - other type, the first key according to the table's internal - order will be returned. If the table is empty, - '$end_of_table' will be returned.

-

Use next/2 to find subsequent keys in the table.

+

Returns the first key Key in table + Tab. For an ordered_set table, the first + key in Erlang term order is returned. For other + table types, the first key according to the internal + order of the table is returned. If the table is empty, + '$end_of_table' is returned.

+

To find subsequent keys in the table, use + next/2.

 + - Fold a function over an ETS table + Fold a function over an ETS table.

Acc0 is returned if the table is empty. - This function is similar to lists:foldl/3. The order in - which the elements of the table are traversed is unspecified, - except for tables of type ordered_set, for which they - are traversed first to last.

- -

If Function inserts objects into the table, or another - process inserts objects into the table, those objects may - (depending on key ordering) be included in the traversal.

+ This function is similar to + lists:foldl/3. + The table elements are traversed is unspecified order, except for + ordered_set tables, where they are traversed first to last.

+

If Function inserts objects into the table, + or another + process inserts objects into the table, those objects can + (depending on key ordering) be included in the traversal.

 + - Fold a function over an ETS table + Fold a function over an ETS table.

Acc0 is returned if the table is empty. - This function is similar to lists:foldr/3. The order in - which the elements of the table are traversed is unspecified, - except for tables of type ordered_set, for which they - are traversed last to first.

- -

If Function inserts objects into the table, or another - process inserts objects into the table, those objects may - (depending on key ordering) be included in the traversal.

+ This function is similar to + lists:foldr/3. + The table elements are traversed is unspecified order, except for + ordered_set tables, where they are traversed last to first.

+

If Function inserts objects into the table, + or another + process inserts objects into the table, those objects can + (depending on key ordering) be included in the traversal.

 + - Fill an ETS table with objects from a Dets table. + Fill an ETS table with objects from a Dets + table.

Fills an already created ETS table with the objects in the - already opened Dets table named DetsTab. The existing - objects of the ETS table are kept unless overwritten.

-

Throws a badarg error if any of the tables does not exist or the - dets table is not open.

+ already opened Dets table DetsTab. + Existing objects in the ETS table are kept unless + overwritten.

+

If any of the tables does not exist or the Dets table is + not open, a badarg exception is raised.

 + - Pseudo function that transforms fun syntax to a match_spec. + Pseudo function that transforms fun syntax to a match + specification. -

Pseudo function that by means of a parse_transform - translates LiteralFun typed as parameter in the - function call to a - match_spec. With - "literal" is meant that the fun needs to textually be written +

Pseudo function that by a parse_transform translates + LiteralFun typed as parameter in the function + call to a + match specification. + With "literal" is meant that the fun must textually be written as the parameter of the function, it cannot be held in a - variable which in turn is passed to the function).

-

The parse transform is implemented in the module - ms_transform and the source must include the - file ms_transform.hrl in STDLIB for this + variable that in turn is passed to the function.

+

The parse transform is provided in the ms_transform + module and the source must include + file ms_transform.hrl in STDLIB for this pseudo function to work. Failing to include the hrl file in - the source will result in a runtime error, not a compile - time ditto. The include file is easiest included by adding - the line + the source results in a runtime error, not a compile + time error. The include file is easiest included by adding line -include_lib("stdlib/include/ms_transform.hrl"). to the source file.

The fun is very restricted, it can take only a single parameter (the object to match): a sole variable or a - tuple. It needs to use the is_ guard tests. - Language constructs that have no representation - in a match_spec (like if, case, receive - etc) are not allowed.

-

The return value is the resulting match_spec.

-

Example:

+ tuple. It must use the is_ guard tests. + Language constructs that have no representation in a match + specification (if, case, receive, + and so on) are not allowed.

+

The return value is the resulting match specification.

+

Example:

 1> ets:fun2ms(fun({M,N}) when N > 3 -> M end).
 [{{'$1','$2'},[{'>','$2',3}],['$1']}]
-

Variables from the environment can be imported, so that this - works:

+

Variables from the environment can be imported, so that the + following works:

 2> X=3.
 3
 3> ets:fun2ms(fun({M,N}) when N > X -> M end).
 [{{'$1','$2'},[{'>','$2',{const,3}}],['$1']}]
-

The imported variables will be replaced by match_spec +

The imported variables are replaced by match specification const expressions, which is consistent with the - static scoping for Erlang funs. Local or global function - calls can not be in the guard or body of the fun however. - Calls to builtin match_spec functions of course is allowed:

+ static scoping for Erlang funs. However, local or global function + calls cannot be in the guard or body of the fun. Calls to built-in + match specification functions is of course allowed:

 4> ets:fun2ms(fun({M,N}) when N > X, is_atomm(M) -> M end).
 Error: fun containing local Erlang function calls
@@ -362,724 +405,832 @@ Error: fun containing local Erlang function calls
 {error,transform_error}
 5> ets:fun2ms(fun({M,N}) when N > X, is_atom(M) -> M end).
 [{{'$1','$2'},[{'>','$2',{const,3}},{is_atom,'$1'}],['$1']}]
-

As can be seen by the example, the function can be called - from the shell too. The fun needs to be literally in the call - when used from the shell as well. Other means than the - parse_transform are used in the shell case, but more or less - the same restrictions apply (the exception being records, - as they are not handled by the shell).

+

As shown by the example, the function can be called + from the shell also. The fun must be literally in the call + when used from the shell as well.

-

If the parse_transform is not applied to a module which - calls this pseudo function, the call will fail in runtime - (with a badarg). The module ets actually - exports a function with this name, but it should never - really be called except for when using the function in the +

If the parse_transform is not applied to a module that + calls this pseudo function, the call fails in runtime + (with a badarg). The ets module + exports a function with this name, but it is never to + be called except when using the function in the shell. If the parse_transform is properly applied by - including the ms_transform.hrl header file, compiled - code will never call the function, but the function call is - replaced by a literal match_spec.

+ including header file ms_transform.hrl, compiled + code never calls the function, but the function call is + replaced by a literal match specification.

 -

For more information, see - ms_transform(3).

+

For more information, see + ms_transform(3).

 + Change owner of a table. -

Make process Pid the new owner of table Tab. - If successful, the message - {'ETS-TRANSFER',Tab,FromPid,GiftData} will be sent - to the new owner.

-

The process Pid must be alive, local and not already the - owner of the table. The calling process must be the table owner.

-

Note that give_away does not at all affect the - heir option of the table. A table - owner can for example set the heir to itself, give the table - away and then get it back in case the receiver terminates.

+

Make process Pid the new owner of table + Tab. If successful, message + {'ETS-TRANSFER',Tab,FromPid,GiftData} + is sent to the new owner.

+

The process Pid must be alive, local, and not + already the owner of the table. + The calling process must be the table owner.

+

Notice that this function does not affect option + heir of the table. A table + owner can, for example, set heir to itself, give the table + away, and then get it back if the receiver terminates.

 + - Display information about all ETS tables on tty. + Display information about all ETS tables on a terminal. + -

Displays information about all ETS tables on tty.

+

Displays information about all ETS tables on a terminal.

 + - Browse an ETS table on tty. + Browse an ETS table on a terminal. -

Browses the table Tab on tty.

+

Browses table Tab on a terminal.

 + - Return information about an ETS table. + Return information about an table. -

Returns information about the table Tab as a list of +

Returns information about table Tab as a list of tuples. If Tab has the correct type - for a table identifier, but does not refer to an existing ETS - table, undefined is returned. If Tab is not of the - correct type, this function fails with reason badarg.

- - - {compressed, boolean()}

- - Indicates if the table is compressed or not. - {heir, pid() | none}

- - The pid of the heir of the table, or none if no heir is set. - {keypos, integer() >= 1}

- - The key position. - {memory, integer() >= 0

- - The number of words allocated to the table. - {name, atom()}

- - The name of the table. - {named_table, boolean()}

- - Indicates if the table is named or not. - {node, node()}

- - The node where the table is stored. This field is no longer - meaningful as tables cannot be accessed from other nodes. - {owner, pid()}

- - The pid of the owner of the table. - {protection, access()}

- - The table access rights. - {size, integer() >= 0

- - The number of objects inserted in the table. - {type, type()}

- - The table type. - {read_concurrency, boolean()}

- - Indicates whether the table uses read_concurrency or not. - {write_concurrency, boolean()}

- - Indicates whether the table uses write_concurrency or not. - + for a table identifier, but does not refer to an existing ETS + table, undefined is returned. If Tab is + not of the correct type, a badarg exception is raised.

+ + {compressed, boolean()} + +

Indicates if the table is compressed.

+ + {heir, pid() | none} + +

The pid of the heir of the table, or none if no heir + is set.

+ + {keypos, integer() >= 1} + +

The key position.

+ + {memory, integer() >= 0 + +

The number of words allocated to the table.

+ + {name, atom()} + +

The table name.

+ + {named_table, boolean()} + +

Indicates if the table is named.

+ + {node, node()} + +

The node where the table is stored. This field is no longer + meaningful, as tables cannot be accessed from other nodes.

+ + {owner, pid()} + +

The pid of the owner of the table.

+ + {protection, + access()} + +

The table access rights.

+ + {size, integer() >= 0 + +

The number of objects inserted in the table.

+ + {type, + type()} + +

The table type.

+ + {read_concurrency, boolean()} + +

Indicates whether the table uses read_concurrency or + not.

+ + {write_concurrency, boolean()} + +

Indicates whether the table uses write_concurrency.

+ + + - Return the information associated with given item for an ETS table. + Return the information associated with the specified item for + an ETS table. -

Returns the information associated with Item for - the table Tab, or returns undefined if Tab - does not refer an existing ETS table. - If Tab is not of the correct type, or if Item is not - one of the allowed values, this function fails with reason badarg.

- -

In R11B and earlier, this function would not fail but return - undefined for invalid values for Item.

- - -

In addition to the {Item,Value} - pairs defined for info/1, the following items are - allowed:

+

Returns the information associated with Item for table + Tab, or returns undefined if Tab + does not refer an existing ETS table. If + Tab is + not of the correct type, or if Item is not + one of the allowed values, a badarg exception is raised.

+ +

In Erlang/OTP R11B and earlier, this function would not fail but + return undefined for invalid values for Item.

+ +

In addition to the {Item,Value} + pairs defined for info/1, + the following items are allowed:

- Item=fixed, Value=boolean()

- - Indicates if the table is fixed by any process or not. - -

Item=safe_fixed|safe_fixed_monotonic_time, Value={FixationTime,Info}|false

-

+ +

Item=fixed, Value=boolean()

+

Indicates if the table is fixed by any process.

+ + +

+

Item=safe_fixed|safe_fixed_monotonic_time, + Value={FixationTime,Info}|false

If the table has been fixed using - safe_fixtable/2, + + safe_fixtable/2, the call returns a tuple where FixationTime is the - time when the table was first fixed by a process, which - may or may not be one of the processes it is fixed by - right now.

-

The format and value of FixationTime depends on - Item:

- - safe_fixed -

FixationTime will correspond to the result - returned by - erlang:timestamp/0 - at the time of fixation. Note that when the system is using - single or multi - time warp - modes this might produce strange results. This - since the usage of safe_fixed is not - time warp - safe. Time warp safe code need to use - safe_fixed_monotonic_time instead.

 - - safe_fixed_monotonic_time -

FixationTime will correspond to the result - returned by - erlang:monotonic_time/0 - at the time of fixation. The usage of safe_fixed_monotonic_time is - time warp - safe.

 - + time when the table was first fixed by a process, which either + is or is not one of the processes it is fixed by now.

+

The format and value of FixationTime depends on + Item:

+ + safe_fixed + +

FixationTime corresponds to the result returned by + + erlang:timestamp/0 at the time of fixation. + Notice that when the system uses single or multi + time + warp modes this can produce strange results, as + the use of safe_fixed is not + + time warp safe. Time warp safe code must use + safe_fixed_monotonic_time instead.

+ + safe_fixed_monotonic_time + +

FixationTime corresponds to the result returned by + + erlang:monotonic_time/0 at the time of + fixation. The use of safe_fixed_monotonic_time is + + time warp safe.

+ +

Info is a possibly empty lists of tuples {Pid,RefCount}, one tuple for every process the - table is fixed by right now. RefCount is the value - of the reference counter, keeping track of how many times + table is fixed by now. RefCount is the value + of the reference counter and it keeps track of how many times the table has been fixed by the process.

If the table never has been fixed, the call returns - false.

 -

Item=stats, Value=tuple()

- Returns internal statistics about set, bag and duplicate_bag tables on an internal format used by OTP test suites. - Not for production use.

 + false.

+ + +

Item=stats, Value=tuple()

+

Returns internal statistics about set, bag, and + duplicate_bag tables on an internal format used by OTP + test suites. Not for production use.

 + Replace all objects of an ETS table. -

Replaces the existing objects of the table Tab with - objects created by calling the input function InitFun, +

Replaces the existing objects of table Tab with + objects created by calling the input function + InitFun, see below. This function is provided for compatibility with the dets module, it is not more efficient than filling - a table by using ets:insert/2. -

-

When called with the argument read the function - InitFun is assumed to return end_of_input when + a table by using + insert/2.

+

When called with argument read, the function + InitFun is assumed to return + end_of_input when there is no more input, or {Objects, Fun}, where - Objects is a list of objects and Fun is a new - input function. Any other value Value is returned as an error - {error, {init_fun, Value}}. Each input function will be - called exactly once, and should an error occur, the last - function is called with the argument close, the reply + Objects is a list of objects and Fun is a + new input function. Any other value Value is returned as an + error {error, {init_fun, Value}}. Each input function is + called exactly once, and if an error occur, the last + function is called with argument close, the reply of which is ignored.

-

If the type of the table is set and there is more - than one object with a given key, one of the objects is +

If the table type is set and more than one object + exists with a given key, one of the objects is chosen. This is not necessarily the last object with the given key in the sequence of objects returned by the input functions. This holds also for duplicated objects stored in tables of type bag.

 + Insert an object into an ETS table. -

Inserts the object or all of the objects in the list - ObjectOrObjects into the table Tab. - If the table is a set and the key of the inserted - objects matches the key of any object in the table, - the old object will be replaced. If the table is an - ordered_set and the key of the inserted object - compares equal to the key of any object in the - table, the old object is also replaced. If the list contains - more than one object with matching keys and the table is a - set, one will be inserted, which one is - not defined. The same thing holds for ordered_set, but - will also happen if the keys compare equal.

+

Inserts the object or all of the objects in list + ObjectOrObjects into table + Tab.

+ + +

If the table type is set and the key of the inserted + objects matches the key of any object in the table, + the old object is replaced.

+ + +

If the table type is ordered_set and the key of the + inserted object compares equal to the key of any object + in the table, the old object is replaced.

+ + +

If the list contains more than one object with + matching keys and the table type is set, one is + inserted, which one is not defined. + The same holds for table type ordered_set + if the keys compare equal.

+ +

The entire operation is guaranteed to be atomic and isolated, even when a list of objects is inserted.

 + - Insert an object into an ETS table if the key is not already present. + Insert an object into an ETS table if the key is not + already present. -

This function works exactly like insert/2, with the - exception that instead of overwriting objects with the same - key (in the case of set or ordered_set) or - adding more objects with keys already existing in the table - (in the case of bag and duplicate_bag), it - simply returns false. If ObjectOrObjects is a - list, the function checks every key prior to - inserting anything. Nothing will be inserted if not +

Same as insert/2 + except that instead of overwriting objects with the same key + (for set or ordered_set) or adding more objects with + keys already existing in the table (for bag and + duplicate_bag), false is returned.

+

If ObjectOrObjects is a + list, the function checks every key before + inserting anything. Nothing is inserted unless all keys present in the list are absent from the table. Like insert/2, the entire operation is guaranteed to be atomic and isolated.

 + - Checks if an Erlang term is the result of ets:match_spec_compile + Check if an Erlang term is the result of + match_spec_compile. -

This function is used to check if a term is a valid - compiled match_spec. - The compiled match_spec is an opaque datatype which can - not be sent between Erlang nodes nor be stored on +

Checks if a term is a valid + compiled match specification. + The compiled match specification is an opaque datatype that + cannot be sent between Erlang nodes or be stored on disk. Any attempt to create an external representation of a - compiled match_spec will result in an empty binary - (>]]>). As an example, the following - expression:

+ compiled match specification results in an empty binary + (>]]>).

+

Examples:

+

The following expression yields true::

ets:is_compiled_ms(ets:match_spec_compile([{'_',[],[true]}])). -

will yield true, while the following expressions:

+

The following expressions yield false, as variable + Broken contains a compiled match specification that has + passed through external representation:

MS = ets:match_spec_compile([{'_',[],[true]}]), Broken = binary_to_term(term_to_binary(MS)), ets:is_compiled_ms(Broken). -

will yield false, as the variable Broken will contain - a compiled match_spec that has passed through external - representation.

-

The fact that compiled match_specs has no external - representation is for performance reasons. It may be subject - to change in future releases, while this interface will - still remain for backward compatibility reasons.

+

The reason for not having an external representation of + compiled match specifications is performance. It can be + subject to change in future releases, while this interface + remains for backward compatibility.

 + - Return the last key in an ETS table of typeordered_set. + Return the last key in an ETS table of type + ordered_set. -

Returns the last key Key according to Erlang term - order in the table Tab of the ordered_set type. - If the table is of any other type, the function is synonymous - to first/1. If the table is empty, - '$end_of_table' is returned.

-

Use prev/2 to find preceding keys in the table.

+

Returns the last key Key according to Erlang + term order in table Tab of type ordered_set. For + other table types, the function is synonymous to + first/1. + If the table is empty, '$end_of_table' is returned.

+

To find preceding keys in the table, use + prev/2.

 + - Return all objects with a given key in an ETS table. + Return all objects with a specified key in an ETS table. + -

Returns a list of all objects with the key Key in - the table Tab.

-

In the case of set, bag and duplicate_bag, an object - is returned only if the given key matches the key - of the object in the table. If the table is an - ordered_set however, an object is returned if the key - given compares equal to the key of an object in the - table. The difference being the same as between =:= - and ==. As an example, one might insert an object - with the +

Returns a list of all objects with key Key in + table Tab.

+ + +

For tables of type set, bag, or + duplicate_bag, an object is returned only if the specified + key matches the key of the object in the table.

+ + +

For tables of type ordered_set, an object is returned if + the specified key compares equal to the key of an object + in the table.

+ + +

The difference is the same as between =:= and ==.

+

As an example, one can insert an object with integer() 1 as a key in an ordered_set - and get the object returned as a result of doing a - lookup/2 with the float() 1.0 as the - key to search for.

-

If the table is of type set or ordered_set, + and get the object returned as a result of doing a lookup/2 + with float() 1.0 as the key to search for.

+

For tables of type set or ordered_set, the function returns either the empty list or a list with one element, as there cannot be more than one object with the same - key. If the table is of type bag or - duplicate_bag, the function returns a list of - arbitrary length.

-

Note that the time order of object insertions is preserved; - the first object inserted with the given key will be first + key. For tables of type bag or duplicate_bag, the + function returns a list of arbitrary length.

+

Notice that the time order of object insertions is preserved; + the first object inserted with the specified key is the first in the resulting list, and so on.

-

Insert and look-up times in tables of type set, - bag and duplicate_bag are constant, regardless - of the size of the table. For the ordered_set - data-type, time is proportional to the (binary) logarithm of +

Insert and lookup times in tables of type set, + bag, and duplicate_bag are constant, regardless + of the table size. For the ordered_set + datatype, time is proportional to the (binary) logarithm of the number of objects.

 + - Return the Pos:th element of all objects with a given key in an ETS table. + Return the Pos:th element of all objects with a + specified key in an ETS table. -

If the table Tab is of type set or - ordered_set, the function returns the Pos:th - element of the object with the key Key.

-

If the table is of type bag or duplicate_bag, - the functions returns a list with the Pos:th element of - every object with the key Key.

-

If no object with the key Key exists, the function - will exit with reason badarg.

-

The difference between set, bag and +

For a table Tab of type set or + ordered_set, the function returns the + Pos:th + element of the object with key Key.

+

For tables of type bag or duplicate_bag, + the functions returns a list with the Pos:th + element of every object with key Key.

+

If no object with key Key exists, the + function exits with reason badarg.

+

The difference between set, bag, and duplicate_bag on one hand, and ordered_set on - the other, regarding the fact that ordered_set's + the other, regarding the fact that ordered_set view keys as equal when they compare equal - whereas the other table types only regard them equal when - they match, naturally holds for - lookup_element as well as for lookup.

+ whereas the other table types regard them equal only when + they match, holds for lookup_element/3.

 + + + + Continues matching objects in an ETS table. + +

Continues a match started with + match/3. The next + chunk of the size specified in the initial match/3 + call is returned together with a new Continuation, + which can be used in subsequent calls to this function.

+

When there are no more objects in the table, '$end_of_table' + is returned.

+ + + - Match the objects in an ETS table against a pattern. + Match the objects in an ETS table against a pattern. + -

Matches the objects in the table Tab against the +

Matches the objects in table Tab against pattern Pattern.

-

A pattern is a term that may contain:

+

A pattern is a term that can contain:

- bound parts (Erlang terms), - '_' which matches any Erlang term, and - pattern variables: '$N' where - N=0,1,... + Bound parts (Erlang terms) + '_' that matches any Erlang term + Pattern variables '$N', where N=0,1,...

The function returns a list with one element for each matching object, where each element is an ordered list of - pattern variable bindings. An example:

+ pattern variable bindings, for example:

-6> ets:match(T, '$1'). % Matches every object in the table
+6> ets:match(T, '$1'). % Matches every object in table
 [[{rufsen,dog,7}],[{brunte,horse,5}],[{ludde,dog,5}]]
 7> ets:match(T, {'_',dog,'$1'}).
 [[7],[5]]
 8> ets:match(T, {'_',cow,'$1'}).
 []

If the key is specified in the pattern, the match is very - efficient. If the key is not specified, i.e. if it is a + efficient. If the key is not specified, that is, if it is a variable or an underscore, the entire table must be searched. The search time can be substantial if the table is very large.

-

On tables of the ordered_set type, the result is in - the same order as in a first/next traversal.

+

For tables of type ordered_set, the result is in + the same order as in a first/next traversal.

 + - Match the objects in an ETS table against a pattern and returns part of the answers. + Match the objects in an ETS table against a pattern + and return part of the answers. -

Works like ets:match/2 but only returns a limited - (Limit) number of matching objects. The - Continuation term can then be used in subsequent calls - to ets:match/1 to get the next chunk of matching - objects. This is a space efficient way to work on objects in a - table which is still faster than traversing the table object - by object using ets:first/1 and ets:next/1.

-

'$end_of_table' is returned if the table is empty.

+

Works like match/2, + but returns only a limited (Limit) number of + matching objects. Term Continuation can then + be used in subsequent calls to + match/1 to get the next chunk of matching + objects. This is a space-efficient way to work on objects in a + table, which is faster than traversing the table object + by object using + first/1 and + next/2.

+

If the table is empty, '$end_of_table' is returned.

 + - - Continues matching objects in an ETS table. + + Delete all objects that match a specified pattern from an + ETS table. -

Continues a match started with ets:match/3. The next - chunk of the size given in the initial ets:match/3 - call is returned together with a new Continuation - that can be used in subsequent calls to this function.

-

'$end_of_table' is returned when there are no more - objects in the table.

+

Deletes all objects that match pattern Pattern + from table Tab. For a description of patterns, + see match/2.

 + - - Delete all objects which match a given pattern from an ETS table. + + Continues matching objects in an ETS table. -

Deletes all objects which match the pattern Pattern - from the table Tab. See match/2 for a - description of patterns.

+

Continues a match started with + match_object/3. + The next chunk of the size specified in the initial + match_object/3 call is returned together with a new + Continuation, which can be used in subsequent + calls to this function.

+

When there are no more objects in the table, '$end_of_table' + is returned.

 + - Match the objects in an ETS table against a pattern. + Match the objects in an ETS table against a pattern. + -

Matches the objects in the table Tab against the - pattern Pattern. See match/2 for a description - of patterns. The function returns a list of all objects which +

Matches the objects in table Tab against + pattern Pattern. For a description of patterns, + see match/2. + The function returns a list of all objects that match the pattern.

If the key is specified in the pattern, the match is very - efficient. If the key is not specified, i.e. if it is a + efficient. If the key is not specified, that is, if it is a variable or an underscore, the entire table must be searched. The search time can be substantial if the table is very large.

-

On tables of the ordered_set type, the result is in - the same order as in a first/next traversal.

+

For tables of type ordered_set, the result is in + the same order as in a first/next traversal.

 + - Match the objects in an ETS table against a pattern and returns part of the answers. + Match the objects in an ETS table against a pattern and + return part of the answers. -

Works like ets:match_object/2 but only returns a - limited (Limit) number of matching objects. The - Continuation term can then be used in subsequent calls - to ets:match_object/1 to get the next chunk of matching - objects. This is a space efficient way to work on objects in a - table which is still faster than traversing the table object - by object using ets:first/1 and ets:next/1.

-

'$end_of_table' is returned if the table is empty.

- - - - - Continues matching objects in an ETS table. - -

Continues a match started with ets:match_object/3. - The next chunk of the size given in the initial - ets:match_object/3 call is returned together with a - new Continuation that can be used in subsequent calls - to this function.

-

'$end_of_table' is returned when there are no more - objects in the table.

+

Works like + match_object/2, but only returns a + limited (Limit) number of matching objects. Term + Continuation can then be used in subsequent + calls to + match_object/1 to get the next chunk of matching + objects. This is a space-efficient way to work on objects in a + table, which is faster than traversing the table object + by object using + first/1 and + next/2.

+

If the table is empty, '$end_of_table' is returned.

 + - Compiles a match specification into its internal representation + Compile a match specification into its internal representation. + -

This function transforms a - match_spec into an - internal representation that can be used in subsequent calls - to ets:match_spec_run/2. The internal representation is - opaque and can not be converted to external term format and - then back again without losing its properties (meaning it can - not be sent to a process on another node and still remain a - valid compiled match_spec, nor can it be stored on disk). - The validity of a compiled match_spec can be checked using - ets:is_compiled_ms/1.

-

If the term MatchSpec can not be compiled (does not - represent a valid match_spec), a badarg fault is - thrown.

+

Transforms a + match specification into an + internal representation that can be used in subsequent calls to + match_spec_run/2. + The internal representation is + opaque and cannot be converted to external term format and + then back again without losing its properties (that is, it cannot + be sent to a process on another node and still remain a + valid compiled match specification, nor can it be stored on disk). + To check the validity of a compiled match specification, use + is_compiled_ms/1. +

+

If term MatchSpec cannot be compiled (does not + represent a valid match specification), a badarg exception is + raised.

-

This function has limited use in normal code, it is used by - Dets to perform the dets:select operations.

+

This function has limited use in normal code. It is used by the + dets module + to perform the dets:select() operations.

 + - Performs matching, using a compiled match_spec, on a list of tuples + Perform matching, using a compiled match specification on a + list of tuples. -

This function executes the matching specified in a - compiled match_spec on - a list of tuples. The CompiledMatchSpec term should be - the result of a call to ets:match_spec_compile/1 and - is hence the internal representation of the match_spec one - wants to use.

-

The matching will be executed on each element in List - and the function returns a list containing all results. If an - element in List does not match, nothing is returned +

Executes the matching specified in a compiled + match specification on a list + of tuples. Term CompiledMatchSpec is to be + the result of a call to + match_spec_compile/1 and is hence the internal + representation of the match specification one wants to use.

+

The matching is executed on each element in List + and the function returns a list containing all results. If an element + in List does not match, nothing is returned for that element. The length of the result list is therefore - equal or less than the the length of the parameter - List. The two calls in the following example will give - the same result (but certainly not the same execution - time...):

+ equal or less than the length of parameter List. +

+

Example:

+

The following two calls give the same result (but certainly not the + same execution time):

Table = ets:new... -MatchSpec = .... +MatchSpec = ... % The following call... ets:match_spec_run(ets:tab2list(Table), ets:match_spec_compile(MatchSpec)), -% ...will give the same result as the more common (and more efficient) -ets:select(Table,MatchSpec), +% ...gives the same result as the more common (and more efficient) +ets:select(Table, MatchSpec), -

This function has limited use in normal code, it is used by - Dets to perform the dets:select operations and by +

This function has limited use in normal code. It is used by the + dets module + to perform the dets:select() operations and by Mnesia during transactions.

 + - Tests for occurrence of a key in an ETS table + Tests for occurrence of a key in an ETS table. -

Works like lookup/2, but does not return the objects. - The function returns true if one or more elements in - the table has the key Key, false otherwise.

+

Works like lookup/2, + but does not return the objects. Returns true if one or more + elements in the table has key Key, otherwise + false.

 + Create a new ETS table. -

Creates a new table and returns a table identifier which can +

Creates a new table and returns a table identifier that can be used in subsequent operations. The table identifier can be sent to other processes so that a table can be shared between different processes within a node.

-

The parameter Options is a list of atoms which - specifies table type, access rights, key position and if the - table is named or not. If one or more options are left out, - the default values are used. This means that not specifying - any options ([]) is the same as specifying - [set, protected, {keypos,1}, {heir,none}, {write_concurrency,false}, {read_concurrency,false}].

- +

Parameter Options is a list of atoms that + specifies table type, access rights, key position, and whether the + table is named. Default values are used for omitted options. + This means that not specifying any options ([]) is the same + as specifying [set, protected, {keypos,1}, {heir,none}, + {write_concurrency,false}, {read_concurrency,false}].

+ + set -

set - The table is a set table - one key, one object, +

The table is a set table: one key, one object, no order among objects. This is the default table type.

 + ordered_set -

ordered_set - The table is a ordered_set table - one key, one +

The table is a ordered_set table: one key, one object, ordered in Erlang term order, which is the order implied by the < and > operators. Tables of this type have a somewhat different behavior in some situations - than tables of the other types. Most notably the + than tables of other types. Most notably, the ordered_set tables regard keys as equal when they compare equal, not only when they match. This - means that to an ordered_set, the - integer() 1 and the float() 1.0 are regarded as equal. This also means that the + means that to an ordered_set table, integer() + 1 and float() 1.0 are regarded as equal. + This also means that the key used to lookup an element not necessarily - matches the key in the elements returned, if + matches the key in the returned elements, if float()'s and integer()'s are mixed in keys of a table.

 + bag -

bag - The table is a bag table which can have many +

The table is a bag table, which can have many objects, but only one instance of each object, per key.

 + duplicate_bag -

duplicate_bag - The table is a duplicate_bag table which can have +

The table is a duplicate_bag table, which can have many objects, including multiple copies of the same object, per key.

 + public -

public - Any process may read or write to the table.

+

Any process can read or write to the table.

+ + protected - -

protected - The owner process can read and write to the table. Other +

The owner process can read and write to the table. Other processes can only read the table. This is the default setting for the access rights.

+ + private - -

private - Only the owner process can read or write to the table.

+

Only the owner process can read or write to the table.

 + named_table -

named_table - If this option is present, the name Name is +

If this option is present, name Name is associated with the table identifier. The name can then be used instead of the table identifier in subsequent operations.

 + {keypos,Pos} -

{keypos,Pos} - Specifies which element in the stored tuples should be - used as key. By default, it is the first element, i.e. - Pos=1. However, this is not always appropriate. In +

Specifies which element in the stored tuples to use + as key. By default, it is the first element, that is, + Pos=1. However, this is not always + appropriate. In particular, we do not want the first element to be the key if we want to store Erlang records in a table.

-

Note that any tuple stored in the table must have at +

Notice that any tuple stored in the table must have at least Pos number of elements.

- - -

{heir,Pid,HeirData} | {heir,none}

- Set a process as heir. The heir will inherit the table if - the owner terminates. The message - {'ETS-TRANSFER',tid(),FromPid,HeirData} will be sent to - the heir when that happens. The heir must be a local process. - Default heir is none, which will destroy the table when - the owner terminates.

 + {heir,Pid,HeirData} | + {heir,none} +

Set a process as heir. The heir inherits the table if + the owner terminates. Message + {'ETS-TRANSFER',tid(),FromPid,HeirData} is + sent to the heir when that occurs. The heir must be a local + process. Default heir is none, which destroys the table + when the owner terminates.

-

{write_concurrency,boolean()} - Performance tuning. Default is false, in which case an operation that - mutates (writes to) the table will obtain exclusive access, - blocking any concurrent access of the same table until finished. - If set to true, the table is optimized towards concurrent - write access. Different objects of the same table can be mutated - (and read) by concurrent processes. This is achieved to some degree - at the expense of memory consumption and the performance of - sequential access and concurrent reading. - The write_concurrency option can be combined with the - read_concurrency - option. You typically want to combine these when large concurrent - read bursts and large concurrent write bursts are common (see the - documentation of the - read_concurrency - option for more information). - Note that this option does not change any guarantees about - atomicy and isolation. - Functions that makes such promises over several objects (like - insert/2) will gain less (or nothing) from this option.

-

In current implementation, table type ordered_set is not - affected by this option. Also, the memory consumption inflicted by - both write_concurrency and read_concurrency is a - constant overhead per table. This overhead can be especially large - when both options are combined.

 + {write_concurrency,boolean()} +

Performance tuning. Defaults to false, in which case an + operation that + mutates (writes to) the table obtains exclusive access, + blocking any concurrent access of the same table until finished. + If set to true, the table is optimized to concurrent + write access. Different objects of the same table can be mutated + (and read) by concurrent processes. This is achieved to some + degree at the expense of memory consumption and the performance + of sequential access and concurrent reading.

+

Option write_concurrency can be combined with option + + read_concurrency. You typically want to combine + these when large concurrent read bursts and large concurrent + write bursts are common; for more information, see option + + read_concurrency.

+

Notice that this option does not change any guarantees about + atomicity and isolation. + Functions that makes such promises over many objects (like + insert/2) + gain less (or nothing) from this option.

+

Table type ordered_set is not affected by this option. + Also, the memory consumption inflicted by + both write_concurrency and read_concurrency is a + constant overhead per table. This overhead can be especially + large when both options are combined.

-

{read_concurrency,boolean()} - Performance tuning. Default is false. When set to - true, the table is optimized for concurrent read - operations. When this option is enabled on a runtime system with - SMP support, read operations become much cheaper; especially on - systems with multiple physical processors. However, switching - between read and write operations becomes more expensive. You - typically want to enable this option when concurrent read - operations are much more frequent than write operations, or when - concurrent reads and writes comes in large read and write - bursts (i.e., lots of reads not interrupted by writes, and lots - of writes not interrupted by reads). You typically do - not want to enable this option when the common access - pattern is a few read operations interleaved with a few write - operations repeatedly. In this case you will get a performance - degradation by enabling this option. The read_concurrency - option can be combined with the - write_concurrency - option. You typically want to combine these when large concurrent - read bursts and large concurrent write bursts are common.

 + {read_concurrency,boolean()} +

Performance tuning. Defaults to false. When set to + true, the table is optimized for concurrent read + operations. When this option is enabled on a runtime system with + SMP support, read operations become much cheaper; especially on + systems with multiple physical processors. However, switching + between read and write operations becomes more expensive.

+

You typically want to enable this option when concurrent read + operations are much more frequent than write operations, or when + concurrent reads and writes comes in large read and write bursts + (that is, many reads not interrupted by writes, and many + writes not interrupted by reads).

+

You typically do + not want to enable this option when the common access + pattern is a few read operations interleaved with a few write + operations repeatedly. In this case, you would get a performance + degradation by enabling this option.

+

Option read_concurrency can be combined with option + + write_concurrency. + You typically want to combine these when large concurrent + read bursts and large concurrent write bursts are common.

-

compressed - If this option is present, the table data will be stored in a more compact format to - consume less memory. The downside is that it will make table operations slower. - Especially operations that need to inspect entire objects, - such as match and select, will get much slower. The key element - is not compressed in current implementation.

 - + compressed + +

If this option is present, the table data is stored in a more + compact format to consume less memory. However, it will make + table operations slower. Especially operations that need to + inspect entire objects, such as match and select, + get much slower. The key element is not compressed.

+ + + Return the next key in an ETS table. -

Returns the next key Key2, following the key - Key1 in the table Tab. If the table is of the - ordered_set type, the next key in Erlang term order is - returned. If the table is of any other type, the next key - according to the table's internal order is returned. If there - is no next key, '$end_of_table' is returned.

-

Use first/1 to find the first key in the table.

-

Unless a table of type set, bag or +

Returns the next key Key2, following key + Key1 in table Tab. For table + type ordered_set, the next key in Erlang term order is + returned. For other table types, the next key + according to the internal order of the table is returned. If no + next key exists, '$end_of_table' is returned.

+

To find the first key in the table, use + first/1.

+

Unless a table of type set, bag, or duplicate_bag is protected using - safe_fixtable/2, see below, a traversal may fail if - concurrent updates are made to the table. If the table is of + safe_fixtable/2, + a traversal can fail if + concurrent updates are made to the table. For table type ordered_set, the function returns the next key in order, even if the object does no longer exist.

 + - Return the previous key in an ETS table of typeordered_set. + Return the previous key in an ETS table of type + ordered_set. -

Returns the previous key Key2, preceding the key - Key1 according the Erlang term order in the table - Tab of the ordered_set type. If the table is of - any other type, the function is synonymous to next/2. - If there is no previous key, '$end_of_table' is - returned.

-

Use last/1 to find the last key in the table.

+

Returns the previous key Key2, preceding key + Key1 according to Erlang term order in table + Tab of type ordered_set. For other + table types, the function is synonymous to + next/2. + If no previous key exists, '$end_of_table' is returned.

+

To find the last key in the table, use + last/1.

 + Rename a named ETS table.

Renames the named table Tab to the new name - Name. Afterwards, the old name can not be used to + Name. Afterwards, the old name cannot be used to access the table. Renaming an unnamed table has no effect.

 + - Repair a continuation from ets:select/1 or ets:select/3 that has passed through external representation + Repair a continuation from ets:select/1 or ets:select/3 + that has passed through external representation. -

This function can be used to restore an opaque continuation - returned by ets:select/3 or ets:select/1 if the +

Restores an opaque continuation returned by + select/3 or + select/1 if the continuation has passed through external term format (been sent between nodes or stored on disk).

The reason for this function is that continuation terms - contain compiled match_specs and therefore will be - invalidated if converted to external term format. Given that - the original match_spec is kept intact, the continuation can + contain compiled match specifications and therefore are + invalidated if converted to external term format. Given that the + original match specification is kept intact, the continuation can be restored, meaning it can once again be used in subsequent - ets:select/1 calls even though it has been stored on + select/1 calls even though it has been stored on disk or on another node.

-

As an example, the following sequence of calls will fail:

+

Examples:

+

The following sequence of calls fails:

T=ets:new(x,[]), ... @@ -1089,7 +1240,9 @@ A end),10), Broken = binary_to_term(term_to_binary(C)), ets:select(Broken). -

...while the following sequence will work:

+

The following sequence works, as the call to + repair_continuation/2 reestablishes the (deliberately) + invalidated continuation Broken.

T=ets:new(x,[]), ... @@ -1100,45 +1253,44 @@ end), {_,C} = ets:select(T,MS,10), Broken = binary_to_term(term_to_binary(C)), ets:select(ets:repair_continuation(Broken,MS)). -

...as the call to ets:repair_continuation/2 will - reestablish the (deliberately) invalidated continuation - Broken.

-

This function is very rarely needed in application code. It - is used by Mnesia to implement distributed select/3 +

This function is rarely needed in application code. It is used + by Mnesia to provide distributed select/3 and select/1 sequences. A normal application would either use Mnesia or keep the continuation from being converted to external format.

The reason for not having an external representation of a - compiled match_spec is performance. It may be subject to - change in future releases, while this interface will remain + compiled match specification is performance. It can be subject to + change in future releases, while this interface remains for backward compatibility.

 + Fix an ETS table for safe traversal. -

Fixes a table of the set, bag or - duplicate_bag table type for safe traversal.

+

Fixes a table of type set, bag, or + duplicate_bag for safe traversal.

A process fixes a table by calling - safe_fixtable(Tab, true). The table remains fixed until - the process releases it by calling + safe_fixtable(Tab, true). The table remains + fixed until the process releases it by calling safe_fixtable(Tab, false), or until the process terminates.

-

If several processes fix a table, the table will remain fixed +

If many processes fix a table, the table remains fixed until all processes have released it (or terminated). A reference counter is kept on a per process basis, and N - consecutive fixes requires N releases to actually release - the table.

-

When a table is fixed, a sequence of first/1 and - next/2 calls are guaranteed to succeed and each object in - the table will only be returned once, even if objects - are removed or inserted during the traversal. - The keys for new objects inserted during the traversal may - be returned by next/2 - (it depends on the internal ordering of the keys). An example:

+ consecutive fixes requires N releases to release the table.

+

When a table is fixed, a sequence of + first/1 and + next/2 calls are + guaranteed to succeed, and each object in + the table is returned only once, even if objects + are removed or inserted during the traversal. The keys for new + objects inserted during the traversal can be returned by + next/2 (it depends on the internal ordering of the keys).

+

Example:

clean_all_with_value(Tab,X) -> safe_fixtable(Tab,true), @@ -1155,218 +1307,205 @@ clean_all_with_value(Tab,X,Key) -> true end, clean_all_with_value(Tab,X,ets:next(Tab,Key)). -

Note that no deleted objects are actually removed from a +

Notice that no deleted objects are removed from a fixed table until it has been released. If a process fixes a table but never releases it, the memory used by the deleted - objects will never be freed. The performance of operations on - the table will also degrade significantly.

-

Use - info(Tab, - safe_fixed_monotonic_time) to retrieve information - about which processes have fixed which tables. A system with a lot - of processes fixing tables may need a monitor which sends alarms + objects is never freed. The performance of operations on + the table also degrades significantly.

+

To retrieve information about which processes have fixed which + tables, use + info(Tab, safe_fixed_monotonic_time). A system with + many processes fixing tables can need a monitor that sends alarms when tables have been fixed for too long.

-

Note that for tables of the ordered_set type, - safe_fixtable/2 is not necessary as calls to - first/1 and next/2 will always succeed.

+

Notice that for table type ordered_set, + safe_fixtable/2 is not necessary, as calls to + first/1 and next/2 always succeed.

 + + + + Continue matching objects in an ETS table. + +

Continues a match started with + select/3. The next + chunk of the size specified in the initial select/3 + call is returned together with a new Continuation, + which can be used in subsequent calls to this function.

+

When there are no more objects in the table, '$end_of_table' + is returned.

+ + + - Match the objects in an ETS table against a match_spec. + Match the objects in an ETS table against a + match specification. -

Matches the objects in the table Tab using a - match_spec. This is a - more general call than the ets:match/2 and - ets:match_object/2 calls. In its simplest forms the - match_specs look like this:

- - MatchSpec = [MatchFunction] - MatchFunction = {MatchHead, [Guard], [Result]} - MatchHead = "Pattern as in ets:match" - Guard = {"Guardtest name", ...} - Result = "Term construct" - -

This means that the match_spec is always a list of one or - more tuples (of arity 3). The tuples first element should be - a pattern as described in the documentation of - ets:match/2. The second element of the tuple should +

Matches the objects in table Tab using a + match specification. + This is a more general call than + match/2 and + match_object/2 + calls. In its simplest form, the match specification is as + follows:

+ +MatchSpec = [MatchFunction] +MatchFunction = {MatchHead, [Guard], [Result]} +MatchHead = "Pattern as in ets:match" +Guard = {"Guardtest name", ...} +Result = "Term construct" +

This means that the match specification is always a list of one or + more tuples (of arity 3). The first element of the tuple is to be + a pattern as described in + match/2. + The second element of the tuple is to be a list of 0 or more guard tests (described below). The - third element of the tuple should be a list containing a - description of the value to actually return. In almost all - normal cases the list contains exactly one term which fully + third element of the tuple is to be a list containing a + description of the value to return. In almost all + normal cases, the list contains exactly one term that fully describes the value to return for each object.

The return value is constructed using the "match variables" - bound in the MatchHead or using the special match variables + bound in MatchHead or using the special match variables '$_' (the whole matching object) and '$$' (all match variables in a list), so that the following - ets:match/2 expression:

+ match/2 expression:

ets:match(Tab,{'$1','$2','$3'})

is exactly equivalent to:

ets:select(Tab,[{{'$1','$2','$3'},[],['$$']}]) -

- and the following ets:match_object/2 call:

+

And that the following match_object/2 call:

ets:match_object(Tab,{'$1','$2','$1'})

is exactly equivalent to

ets:select(Tab,[{{'$1','$2','$1'},[],['$_']}])

Composite terms can be constructed in the Result part - either by simply writing a list, so that this code:

+ either by simply writing a list, so that the following code:

ets:select(Tab,[{{'$1','$2','$3'},[],['$$']}])

gives the same output as:

ets:select(Tab,[{{'$1','$2','$3'},[],[['$1','$2','$3']]}]) -

i.e. all the bound variables in the match head as a list. If +

That is, all the bound variables in the match head as a list. If tuples are to be constructed, one has to write a tuple of - arity 1 with the single element in the tuple being the tuple - one wants to construct (as an ordinary tuple could be mistaken - for a Guard). Therefore the following call:

+ arity 1 where the single element in the tuple is the tuple + one wants to construct (as an ordinary tuple can be mistaken + for a Guard).

+

Therefore the following call:

ets:select(Tab,[{{'$1','$2','$1'},[],['$_']}])

gives the same output as:

ets:select(Tab,[{{'$1','$2','$1'},[],[{{'$1','$2','$3'}}]}]) -

- this syntax is equivalent to the syntax used in the trace - patterns (see - dbg(3)).

-

The Guards are constructed as tuples where the first - element is the name of the test and the rest of the elements - are the parameters of the test. To check for a specific type +

This syntax is equivalent to the syntax used in the trace + patterns (see the + + dbg(3)) module in Runtime_Tools.

+

The Guards are constructed as tuples, where the first + element is the test name and the remaining elements + are the test parameters. To check for a specific type (say a list) of the element bound to the match variable '$1', one would write the test as {is_list, '$1'}. If the test fails, the object in the - table will not match and the next MatchFunction (if - any) will be tried. Most guard tests present in Erlang can be + table does not match and the next MatchFunction (if + any) is tried. Most guard tests present in Erlang can be used, but only the new versions prefixed is_ are - allowed (like is_float, is_atom etc).

+ allowed (is_float, is_atom, and so on).

The Guard section can also contain logic and arithmetic operations, which are written with the same syntax - as the guard tests (prefix notation), so that a guard test - written in Erlang looking like this:

+ as the guard tests (prefix notation), so that the following + guard test written in Erlang:

-

is expressed like this (X replaced with '$1' and Y with - '$2'):

+

is expressed as follows (X replaced with '$1' and + Y with '$2'):

-

On tables of the ordered_set type, objects are visited - in the same order as in a first/next - traversal. This means that the match specification will be - executed against objects with keys in the first/next - order and the corresponding result list will be in the order of that +

For tables of type ordered_set, objects are visited + in the same order as in a first/next + traversal. This means that the match specification is + executed against objects with keys in the first/next + order and the corresponding result list is in the order of that execution.

- + - Match the objects in an ETS table against a match_spec and returns part of the answers. + Match the objects in an ETS table against a match + specification and return part of the answers. -

Works like ets:select/2 but only returns a limited - (Limit) number of matching objects. The - Continuation term can then be used in subsequent calls - to ets:select/1 to get the next chunk of matching - objects. This is a space efficient way to work on objects in a - table which is still faster than traversing the table object - by object using ets:first/1 and ets:next/1.

-

'$end_of_table' is returned if the table is empty.

- - - - - Continue matching objects in an ETS table. - -

Continues a match started with - ets:select/3. The next - chunk of the size given in the initial ets:select/3 - call is returned together with a new Continuation - that can be used in subsequent calls to this function.

-

'$end_of_table' is returned when there are no more - objects in the table.

+

Works like select/2, + but only returns a limited + (Limit) number of matching objects. Term + Continuation can then be used in subsequent + calls to select/1 + to get the next chunk of matching + objects. This is a space-efficient way to work on objects in a + table, which is still faster than traversing the table object by + object using first/1 + and next/2.

+

If the table is empty, '$end_of_table' is returned.

 + - Match the objects in an ETS table against a match_spec and returns the number of objects for which the match_spec returned 'true' + Match the objects in an ETS table against a match + specification and return the number of objects for which the match + specification returned true. -

Matches the objects in the table Tab using a - match_spec. If the - match_spec returns true for an object, that object +

Matches the objects in table Tab using a + match specificationc. If the + match specification returns true for an object, that object considered a match and is counted. For any other result from - the match_spec the object is not considered a match and is + the match specification the object is not considered a match and is therefore not counted.

-

The function could be described as a match_delete/2 - that does not actually delete any elements, but only counts - them.

+

This function can be described as a + match_delete/2 + function that does not delete any elements, but only counts them.

The function returns the number of objects matched.

 + - Match the objects in an ETS table against a match_spec and deletes objects where the match_spec returns 'true' + Match the objects in an ETS table against a match + specification and delete objects where the match specification + returns true. -

Matches the objects in the table Tab using a - match_spec. If the - match_spec returns true for an object, that object is - removed from the table. For any other result from the - match_spec the object is retained. This is a more general - call than the ets:match_delete/2 call.

-

The function returns the number of objects actually +

Matches the objects in table Tab using a + match specification. If the + match specification returns true for an object, that object is + removed from the table. For any other result from the match + specification the object is retained. This is a more general + call than the + match_delete/2 call.

+

The function returns the number of objects deleted from the table.

-

The match_spec has to return the atom true if - the object is to be deleted. No other return value will get the - object deleted, why one can not use the same match specification for +

The match specification has to return the atom true if + the object is to be deleted. No other return value gets the + object deleted. So one cannot use the same match specification for looking up elements as for deleting them.

 - - - Match the objects in an ETS table against a match_spec. - - -

Works like select/2, but returns the list in reverse - order for the ordered_set table type. For all other table - types, the return value is identical to that of select/2.

- - - - - - Match the objects in an ETS table against a match_spec and returns part of the answers. - - -

Works like select/3, but for the ordered_set - table type, traversing is done starting at the last object in - Erlang term order and moves towards the first. For all other - table types, the return value is identical to that of - select/3.

-

Note that this is not equivalent to - reversing the result list of a select/3 call, as the result list - is not only reversed, but also contains the last Limit - matching objects in the table, not the first.

- - - Continue matching objects in an ETS table. - -

Continues a match started with - ets:select_reverse/3. If the table is an - ordered_set, the traversal of the table will continue - towards objects with keys earlier in the Erlang term order. The - returned list will also contain objects with keys in reverse - order.

- -

For all other table types, the behaviour is exactly that of select/1.

-

Example:

+

Continues a match started with + select_reverse/3. For tables of type + ordered_set, the traversal of the table continues + to objects with keys earlier in the Erlang term order. The + returned list also contains objects with keys in reverse order. + For all other table types, the behavior is exactly that of + select/1.

+

Example:

1> T = ets:new(x,[ordered_set]). 2> [ ets:insert(T,{N}) || N <- lists:seq(1,10) ]. @@ -1384,217 +1523,288 @@ is_integer(X), is_integer(Y), X + Y < 4711]]> 8> R2. [{2},{1}] 9> '$end_of_table' = ets:select_reverse(C2). -... - +... + + + + Match the objects in an ETS table against a + match specification. + +

Works like select/2, + but returns the list in reverse order for table type ordered_set. + For all other table types, the return value is identical to that of + select/2.

+ + + + + + Match the objects in an ETS table against a + match specification and return part of the answers. + +

Works like select/3, + but for table type ordered_set + traversing is done starting at the last object in + Erlang term order and moves to the first. For all other table + types, the return value is identical to that of select/3.

+

Notice that this is not equivalent to + reversing the result list of a select/3 call, as the result list + is not only reversed, but also contains the last + Limit + matching objects in the table, not the first.

+ + + Set table options. -

Set table options. The only option that currently is allowed to be - set after the table has been created is - heir. The calling process must be - the table owner.

+

Sets table options. The only allowed option to be set after the + table has been created is + heir. + The calling process must be the table owner.

 + - Return all objects in a given slot of an ETS table. + Return all objects in a specified slot of an ETS table. +

This function is mostly for debugging purposes, Normally - one should use first/next or last/prev instead.

-

Returns all objects in the I:th slot of the table - Tab. A table can be traversed by repeatedly calling - the function, starting with the first slot I=0 and + first/next or last/prev are to be used + instead.

+

Returns all objects in slot I of table + Tab. A table can be traversed by repeatedly + calling the function, + starting with the first slot I=0 and ending when '$end_of_table' is returned. - The function will fail with reason badarg if the - I argument is out of range.

-

Unless a table of type set, bag or + If argument I is out of range, + the function fails with reason badarg.

+

Unless a table of type set, bag, or duplicate_bag is protected using - safe_fixtable/2, see above, a traversal may fail if - concurrent updates are made to the table. If the table is of - type ordered_set, the function returns a list - containing the I:th object in Erlang term order.

+ safe_fixtable/2, + a traversal can fail if + concurrent updates are made to the table. For table type + ordered_set, the function returns a list containing + object I in Erlang term order.

 + Dump an ETS table to a file. -

Dumps the table Tab to the file Filename.

-

Equivalent to tab2file(Tab, Filename,[])

- +

Dumps table Tab to file + Filename.

+

Equivalent to + tab2file(Tab, Filename,[])

 + Dump an ETS table to a file. -

Dumps the table Tab to the file Filename.

-

When dumping the table, certain information about the table - is dumped to a header at the beginning of the dump. This - information contains data about the table type, - name, protection, size, version and if it's a named table. It - also contains notes about what extended information is added - to the file, which can be a count of the objects in the file - or a MD5 sum of the header and records in the file.

-

The size field in the header might not correspond to the - actual number of records in the file if the table is public - and records are added or removed from the table during - dumping. Public tables updated during dump, and that one wants - to verify when reading, needs at least one field of extended - information for the read verification process to be reliable - later.

-

The extended_info option specifies what extra - information is written to the table dump:

- - object_count -

The number of objects actually written to the file is - noted in the file footer, why verification of file truncation - is possible even if the file was updated during - dump.

 - md5sum -

The header and objects in the file are checksummed using - the built in MD5 functions. The MD5 sum of all objects is - written in the file footer, so that verification while reading - will detect the slightest bitflip in the file data. Using this - costs a fair amount of CPU time.

 - -

Whenever the extended_info option is used, it - results in a file not readable by versions of ets prior to - that in stdlib-1.15.1

-

The sync option, if set to true, ensures that - the content of the file is actually written to the disk before - tab2file returns. Default is {sync, false}.

+

Dumps table Tab to file + Filename.

+

When dumping the table, some information about the table + is dumped to a header at the beginning of the dump. This + information contains data about the table type, + name, protection, size, version, and if it is a named table. It + also contains notes about what extended information is added + to the file, which can be a count of the objects in the file + or a MD5 sum of the header and records in the file.

+

The size field in the header might not correspond to the + number of records in the file if the table is public + and records are added or removed from the table during + dumping. Public tables updated during dump, and that one wants + to verify when reading, needs at least one field of extended + information for the read verification process to be reliable + later.

+

Option extended_info specifies what extra + information is written to the table dump:

+ + object_count + +

The number of objects written to the file is + noted in the file footer, so file truncation can be + verified even if the file was updated during dump.

+ + md5sum + +

The header and objects in the file are checksummed using + the built-in MD5 functions. The MD5 sum of all objects is + written in the file footer, so that verification while reading + detects the slightest bitflip in the file data. Using this + costs a fair amount of CPU time.

+ + +

Whenever option extended_info is used, it + results in a file not readable by versions of ETS before + that in STDLIB 1.15.1

+

If option sync is set to true, it ensures that + the content of the file is written to the disk before + tab2file returns. Defaults to {sync, false}.

 + Return a list of all objects in an ETS table. -

Returns a list of all objects in the table Tab.

+

Returns a list of all objects in table Tab.

 + Return a list of all objects in an ETS table. -

Returns information about the table dumped to file by - tab2file/2 or - tab2file/3

-

The following items are returned:

- - name -

The name of the dumped table. If the table was a - named table, a table with the same name cannot exist when the - table is loaded from file with - file2tab/2. If the table is - not saved as a named table, this field has no significance - at all when loading the table from file.

 - type - The ets type of the dumped table (i.e. set, bag, - duplicate_bag or ordered_set). This type will be used - when loading the table again. - protection - The protection of the dumped table (i.e. private, - protected or public). A table loaded from the file - will get the same protection. - named_table - true if the table was a named table when dumped - to file, otherwise false. Note that when a named table - is loaded from a file, there cannot exist a table in the - system with the same name. - keypos - The keypos of the table dumped to file, which - will be used when loading the table again. - size - The number of objects in the table when the table dump - to file started, which in case of a public table need - not correspond to the number of objects actually saved to the - file, as objects might have been added or deleted by another - process during table dump. - extended_info - The extended information written in the file footer to - allow stronger verification during table loading from file, as - specified to tab2file/3. Note that this - function only tells which information is present, not - the values in the file footer. The value is a list containing - one or more of the atoms object_count and - md5sum. - version - A tuple {Major,Minor} containing the major and - minor version of the file format for ets table dumps. This - version field was added beginning with stdlib-1.5.1, files - dumped with older versions will return {0,0} in this - field. - -

An error is returned if the file is inaccessible, - badly damaged or not an file produced with tab2file/2 or tab2file/3.

+

Returns information about the table dumped to file by + tab2file/2 or + tab2file/3.

+

The following items are returned:

+ + name + +

The name of the dumped table. If the table was a + named table, a table with the same name cannot exist when the + table is loaded from file with + file2tab/2. + If the table is + not saved as a named table, this field has no significance + when loading the table from file.

+ + type + +

The ETS type of the dumped table (that is, set, + bag, duplicate_bag, or ordered_set). This + type is used when loading the table again.

+ + protection + +

The protection of the dumped table (that is, private, + protected, or public). A table loaded from the + file gets the same protection.

+ + named_table + +

true if the table was a named table when dumped + to file, otherwise false. Notice that when a named table + is loaded from a file, there cannot exist a table in the + system with the same name.

+ + keypos + +

The keypos of the table dumped to file, which + is used when loading the table again.

+ + size + +

The number of objects in the table when the table dump + to file started. For a public table, this number + does not need to correspond to the number of objects saved to + the file, as objects can have been added or deleted by another + process during table dump.

+ + extended_info + +

The extended information written in the file footer to + allow stronger verification during table loading from file, as + specified to + tab2file/3. Notice that this + function only tells which information is present, not + the values in the file footer. The value is a list containing one + or more of the atoms object_count and md5sum.

+ + version + +

A tuple {Major,Minor} + containing the major and + minor version of the file format for ETS table dumps. This + version field was added beginning with STDLIB 1.5.1. + Files dumped with older versions return {0,0} in this + field.

+ + +

An error is returned if the file is inaccessible, + badly damaged, or not produced with + tab2file/2 or + tab2file/3.

 + Return a QLC query handle. -

Returns a QLC (Query List - Comprehension) query handle. The module qlc implements - a query language aimed mainly at Mnesia but ETS tables, Dets - tables, and lists are also recognized by QLC as sources of - data. Calling ets:table/1,2 is the means to make the +

Returns a Query List + Comprehension (QLC) query handle. The + qlc module provides + a query language aimed mainly at Mnesia, but ETS + tables, Dets tables, + and lists are also recognized by QLC as sources of + data. Calling table/1,2 is the means to make the ETS table Tab usable to QLC.

-

When there are only simple restrictions on the key position - QLC uses ets:lookup/2 to look up the keys, but when - that is not possible the whole table is traversed. The - option traverse determines how this is done:

- +

When there are only simple restrictions on the key position, + QLC uses lookup/2 + to look up the keys. When + that is not possible, the whole table is traversed. + Option traverse determines how this is done:

+ + first_next -

first_next. The table is traversed one key at - a time by calling ets:first/1 and - ets:next/2.

+

The table is traversed one key at a time by calling + first/1 and + next/2.

 + last_prev -

last_prev. The table is traversed one key at - a time by calling ets:last/1 and - ets:prev/2.

+

The table is traversed one key at a time by calling + last/1 and + prev/2.

 + select -

select. The table is traversed by calling - ets:select/3 and ets:select/1. The option - n_objects determines the number of objects +

The table is traversed by calling + select/3 and + select/1. + Option n_objects determines the number of objects returned (the third argument of select/3); the default is to return 100 objects at a time. The - match_spec (the - second argument of select/3) is assembled by QLC: - simple filters are translated into equivalent match_specs - while more complicated filters have to be applied to all - objects returned by select/3 given a match_spec + match specification (the + second argument of select/3) is assembled by QLC: simple + filters are translated into equivalent match specifications + while more complicated filters must be applied to all + objects returned by select/3 given a match specification that matches all objects.

 + {select, MatchSpec} -

{select, MatchSpec}. As for select - the table is traversed by calling ets:select/3 and - ets:select/1. The difference is that the - match_spec is explicitly given. This is how to state - match_specs that cannot easily be expressed within the - syntax provided by QLC.

+

As for select, the table is traversed by calling + select/3 and + select/1. + The difference is that the match specification is explicitly + specified. This is how to state match specifications that cannot + easily be expressed within the syntax provided by QLC.

 - -

The following example uses an explicit match_spec to - traverse the table:

+ +

Examples:

+

An explicit match specification is here used to traverse the + table:

 9> true = ets:insert(Tab = ets:new(t, []), [{1,a},{2,b},{3,c},{4,d}]),
 MS = ets:fun2ms(fun({X,Y}) when (X > 1) or (X < 5) -> {Y} end),
 QH1 = ets:table(Tab, [{traverse, {select, MS}}]).
-

An example with implicit match_spec:

+

An example with an implicit match specification:

 10> QH2 = qlc:q([{Y} || {X,Y} <- ets:table(Tab), (X > 1) or (X < 5)]).
-

The latter example is in fact equivalent to the former which - can be verified using the function qlc:info/1:

+

The latter example is equivalent to the former, which + can be verified using function qlc:info/1:

 11> qlc:info(QH1) =:= qlc:info(QH2).
 true
@@ -1603,52 +1813,60 @@ true two query handles.

 + + + + Return and remove all objects with a specified key from an + ETS table. + +

Returns and removes a list of all objects with key + Key in table Tab.

+

The specified Key is used to identify the object + by either comparing equal the key of an object in an + ordered_set table, or matching in other types of + tables (for details on the difference, see + lookup/2 and + new/2).

+ + - Test a match_spec for use in ets:select/2. + Test a match specification for use in select/2. +

This function is a utility to test a - match_spec used in - calls to ets:select/2. The function both tests - MatchSpec for "syntactic" correctness and runs the - match_spec against the object Tuple. If the match_spec - contains errors, the tuple {error, Errors} is returned + match specification used in + calls to select/2. + The function both tests MatchSpec for "syntactic" + correctness and runs the match specification against object + Tuple.

+

If the match specification is syntactically correct, the function + either returns {ok,Result}, where + Result is what would have been the result in a + real select/2 call, or false if the match specification + does not match object Tuple.

+

If the match specification contains errors, tuple + {error, Errors} is returned, where Errors is a list of natural language - descriptions of what was wrong with the match_spec. If the - match_spec is syntactically OK, the function returns - {ok,Result} where Result is what would have been - the result in a real ets:select/2 call or false - if the match_spec does not match the object Tuple.

+ descriptions of what was wrong with the match specification.

This is a useful debugging and test tool, especially when - writing complicated ets:select/2 calls.

+ writing complicated select/2 calls.

See also: erlang:match_spec_test/3.

 - - - Return and remove all objects with a given key from an ETS - table. - -

Returns a list of all objects with the key Key in - the table Tab and removes.

-

The given Key is used to identify the object by - either comparing equal the key of an object in an - ordered_set table, or matching in other types of - tables (see lookup/2 and - new/2 for details on the - difference).

- - + - Fill a Dets table with objects from an ETS table. + Fill a Dets table with objects from an ETS table. +

Fills an already created/opened Dets table with the objects - in the already opened ETS table named Tab. The Dets - table is emptied before the objects are inserted.

+ in the already opened ETS table named Tab. + The Dets table is emptied before the objects are inserted.

 + @@ -1666,107 +1884,112 @@ true

This function provides an efficient way to update one or more - counters, without the hassle of having to look up an object, update - the object by incrementing an element and insert the resulting object - into the table again. (The update is done atomically; i.e. no process - can access the ets table in the middle of the operation.) -

-

It will destructively update the object with key Key - in the table Tab by adding Incr to the element - at the Pos:th position. The new counter value is + counters, without the trouble of having to look up an object, update + the object by incrementing an element, and insert the resulting + object into the table again. (The update is done atomically, + that is, no process + can access the ETS table in the middle of the operation.)

+

This function destructively update the object with key + Key in table Tab by adding + Incr to the element at position + Pos. The new counter value is returned. If no position is specified, the element directly - following the key (+1]]>) is updated.

-

If a Threshold is specified, the counter will be - reset to the value SetValue if the following + following key (+1]]>) is updated.

+

If a Threshold is specified, the counter is + reset to value SetValue if the following conditions occur:

- The Incr is not negative (>= 0) and the - result would be greater than (>) Threshold - The Incr is negative () and the - result would be less than () - Threshold +

Incr is not negative (>= 0) and + the result would be greater than (>) + Threshold.

+ +

Incr is negative + () and the result would be less than + () Threshold.

+ -

A list of UpdateOp can be supplied to do several update - operations within the object. The operations are carried out in the - order specified in the list. If the same counter position occurs - more than one time in the list, the corresponding counter will thus - be updated several times, each time based on the previous result. - The return value is a list of the new counter values from each - update operation in the same order as in the operation list. If an - empty list is specified, nothing is updated and an empty list is - returned. If the function should fail, no updates will be done at - all. -

-

The given Key is used to identify the object by either - matching the key of an object in a set table, - or compare equal to the key of an object in an - ordered_set table (see - lookup/2 and - new/2 - for details on the difference).

-

If a default object Default is given, it is used +

A list of UpdateOp can be supplied to do many + update operations within the object. + The operations are carried out in the + order specified in the list. If the same counter position occurs + more than once in the list, the corresponding counter is thus + updated many times, each time based on the previous result. + The return value is a list of the new counter values from each + update operation in the same order as in the operation list. If an + empty list is specified, nothing is updated and an empty list is + returned. If the function fails, no updates is done.

+

The specified Key is used to identify the object + by either matching the key of an object in a set + table, or compare equal to the key of an object in an + ordered_set table (for details on the difference, see + lookup/2 and + new/2).

+

If a default object Default is specified, + it is used as the object to be updated if the key is missing from the table. The value in place of the key is ignored and replaced by the proper key value. The return value is as if the default object had not been used, - that is a single updated element or a list of them.

-

The function will fail with reason badarg if:

+ that is, a single updated element or a list of them.

+

The function fails with reason badarg in the following + situations:

- the table is not of type set or - ordered_set, - no object with the right key exists and no default object were - supplied, - the object has the wrong arity, - the default object arity is smaller than - ]]> - any field from the default object being updated is not an - integer - the element to update is not an integer, - the element to update is also the key, or, - any of Pos, Incr, Threshold or - SetValue is not an integer + The table type is not set or + ordered_set. + No object with the correct key exists and no default object was + supplied. + The object has the wrong arity. + The default object arity is smaller than + ]]>. + Any field from the default object that is updated is not an + integer. + The element to update is not an integer. + The element to update is also the key. + Any of Pos, Incr, + Threshold, or SetValue + is not an integer. + - Updates the Pos:th element of the object with a given key in an ETS table. + Update the Pos:th element of the object with a + specified key in an ETS table.

This function provides an efficient way to update one or more - elements within an object, without the hassle of having to look up, - update and write back the entire object. -

-

It will destructively update the object with key Key - in the table Tab. The element at the Pos:th position - will be given the value Value.

-

A list of {Pos,Value} can be supplied to update several - elements within the same object. If the same position occurs more - than one in the list, the last value in the list will be written. If - the list is empty or the function fails, no updates will be done at - all. The function is also atomic in the sense that other processes - can never see any intermediate results. -

-

The function returns true if an object with the key - Key was found, false otherwise. -

-

The given Key is used to identify the object by either - matching the key of an object in a set table, - or compare equal to the key of an object in an - ordered_set table (see - lookup/2 and - new/2 - for details on the difference).

-

The function will fail with reason badarg if:

+ elements within an object, without the trouble of having to look up, + update, and write back the entire object.

+

This function destructively updates the object with key + Key in table Tab. + The element at position Pos is given + the value Value.

+

A list of {Pos,Value} can be + supplied to update many + elements within the same object. If the same position occurs more + than once in the list, the last value in the list is written. If + the list is empty or the function fails, no updates are done. + The function is also atomic in the sense that other processes + can never see any intermediate results.

+

Returns true if an object with key Key + is found, otherwise false.

+

The specified Key is used to identify the object + by either matching the key of an object in a set + table, or compare equal to the key of an object in an + ordered_set table (for details on the difference, see + lookup/2 and + new/2).

+

The function fails with reason badarg in the following + situations:

- the table is not of type set or - ordered_set, - Pos is less than 1 or greater than the object - arity, or, - the element to update is also the key + The table type is not set or ordered_set. + Pos < 1. + Pos > object arity. + The element to update is also the key. -- cgit v1.2.3