diff options
Diffstat (limited to 'lib/stdlib/doc/src/ets.xml')
| -rw-r--r-- | lib/stdlib/doc/src/ets.xml | 129 |
1 files changed, 107 insertions, 22 deletions
diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml index 5df60a92e5..702e1b928e 100644 --- a/lib/stdlib/doc/src/ets.xml +++ b/lib/stdlib/doc/src/ets.xml @@ -56,8 +56,8 @@ 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 - <c>delete/1</c>.</p> - <p>Since R13B01, table ownership can be transferred at process termination + <c>delete/1</c>. The default owner is the process that created the + table. Table ownership can be transferred at process termination by using the <seealso marker="#heir">heir</seealso> option or explicitly by calling <seealso marker="#give_away/3">give_away/3</seealso>.</p> <p>Some implementation details:</p> @@ -82,11 +82,15 @@ <c>float()</c> that extends to the same value, hence the key <c>1</c> and the key <c>1.0</c> are regarded as equal in an <c>ordered_set</c> table.</p> - <p>In general, the functions below will exit with reason - <c>badarg</c> if any argument is of the wrong format, or if the - table identifier is invalid.</p> </description> - + <section> + <title>Failure</title> + <p>In general, the functions below will exit with reason + <c>badarg</c> if any argument is of the wrong format, if the + table identifier is invalid or if the operation is denied due to + table access rights (<seealso marker="#protected">protected</seealso> + or <seealso marker="#private">private</seealso>).</p> + </section> <section><marker id="concurrency"></marker> <title>Concurrency</title> <p>This module provides some limited support for concurrent access. @@ -947,7 +951,7 @@ ets:select(Table,MatchSpec),</code> <type> <v>Name = atom()</v> <v>Options = [Option]</v> - <v> Option = Type | Access | named_table | {keypos,Pos} | {heir,pid(),HeirData} | {heir,none} | {write_concurrency,bool()}</v> + <v> Option = Type | Access | named_table | {keypos,Pos} | {heir,pid(),HeirData} | {heir,none} | {write_concurrency,bool()} | {read_concurrency,bool()}</v> <v> Type = set | ordered_set | bag | duplicate_bag</v> <v> Access = public | protected | private</v> <v> Pos = int()</v> @@ -963,7 +967,7 @@ ets:select(Table,MatchSpec),</code> 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 (<c>[]</c>) is the same as specifying - <c>[set,protected,{keypos,1},{heir,none},{write_concurrency,false}]</c>.</p> + <c>[set,protected,{keypos,1},{heir,none},{write_concurrency,false},{read_concurrency,false}]</c>.</p> <list type="bulleted"> <item> <p><c>set</c> @@ -1002,12 +1006,14 @@ ets:select(Table,MatchSpec),</code> Any process may read or write to the table.</p> </item> <item> + <marker id="protected"></marker> <p><c>protected</c> 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.</p> </item> <item> + <marker id="private"></marker> <p><c>private</c> Only the owner process can read or write to the table.</p> </item> @@ -1385,6 +1391,28 @@ is_integer(X), is_integer(Y), X + Y < 4711]]></code> </desc> </func> <func> + <name>select_count(Tab, MatchSpec) -> NumMatched</name> + <fsummary>Match the objects in an ETS table against a match_spec and returns the number of objects for which the match_spec returned 'true'</fsummary> + <type> + <v>Tab = tid() | atom()</v> + <v>Object = tuple()</v> + <v>MatchSpec = match_spec()</v> + <v>NumMatched = integer()</v> + </type> + <desc> + <p>Matches the objects in the table <c>Tab</c> using a + <seealso marker="#match_spec">match_spec</seealso>. If the + match_spec returns <c>true</c> 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 + therefore not counted.</p> + <p>The function could be described as a <c>match_delete/2</c> + that does not actually delete any elements, but only counts + them.</p> + <p>The function returns the number of objects matched.</p> + </desc> + </func> + <func> <name>select_delete(Tab, MatchSpec) -> NumDeleted</name> <fsummary>Match the objects in an ETS table against a match_spec and deletes objects where the match_spec returns 'true'</fsummary> <type> @@ -1411,25 +1439,82 @@ is_integer(X), is_integer(Y), X + Y < 4711]]></code> </desc> </func> <func> - <name>select_count(Tab, MatchSpec) -> NumMatched</name> - <fsummary>Match the objects in an ETS table against a match_spec and returns the number of objects for which the match_spec returned 'true'</fsummary> + <name>select_reverse(Tab, MatchSpec) -> [Match]</name> + <fsummary>Match the objects in an ETS table against a match_spec.</fsummary> <type> <v>Tab = tid() | atom()</v> - <v>Object = tuple()</v> + <v>Match = term()</v> <v>MatchSpec = match_spec()</v> - <v>NumMatched = integer()</v> </type> <desc> - <p>Matches the objects in the table <c>Tab</c> using a - <seealso marker="#match_spec">match_spec</seealso>. If the - match_spec returns <c>true</c> 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 - therefore not counted.</p> - <p>The function could be described as a <c>match_delete/2</c> - that does not actually delete any elements, but only counts - them.</p> - <p>The function returns the number of objects matched.</p> + + <p>Works like <c>select/2</c>, but returns the list in reverse + order for the <c>ordered_set</c> table type. For all other table + types, the return value is identical to that of <c>select/2</c>.</p> + + </desc> + </func> + <func> + <name>select_reverse(Tab, MatchSpec, Limit) -> {[Match],Continuation} | '$end_of_table'</name> + <fsummary>Match the objects in an ETS table against a match_spec and returns part of the answers.</fsummary> + <type> + <v>Tab = tid() | atom()</v> + <v>Match = term()</v> + <v>MatchSpec = match_spec()</v> + <v>Continuation = term()</v> + </type> + <desc> + + <p>Works like <c>select/3</c>, but for the <c>ordered_set</c> + table type, traversing is done starting at the last object in + Erlang term order and moves towards the first. For all other + table types, the return value is identical to that of + <c>select/3</c>.</p> + + <p>Note that this is <em>not</em> equivalent to + reversing the result list of a <c>select/3</c> call, as the result list + is not only reversed, but also contains the last <c>Limit</c> + matching objects in the table, not the first.</p> + + </desc> + </func> + <func> + <name>select_reverse(Continuation) -> {[Match],Continuation} | '$end_of_table'</name> + <fsummary>Continue matching objects in an ETS table.</fsummary> + <type> + <v>Match = term()</v> + <v>Continuation = term()</v> + </type> + <desc> + + <p>Continues a match started with + <c>ets:select_reverse/3</c>. If the table is an + <c>ordered_set</c>, 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.</p> + + <p>For all other table types, the behaviour is exatly that of <c>select/1</c>.</p> + <p>Example:</p> + <code> +1> T = ets:new(x,[ordered_set]). +2> [ ets:insert(T,{N}) || N <- lists:seq(1,10) ]. +... +3> {R0,C0} = ets:select_reverse(T,[{'_',[],['$_']}],4). +... +4> R0. +[{10},{9},{8},{7}] +5> {R1,C1} = ets:select_reverse(C0). +... +6> R1. +[{6},{5},{4},{3}] +7> {R2,C2} = ets:select_reverse(C1). +... +8> R2. +[{2},{1}] +9> '$end_of_table' = ets:select_reverse(C2). +... + </code> </desc> </func> <func> |