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-rw-r--r--lib/stdlib/doc/src/ets.xml107
-rw-r--r--lib/stdlib/test/ets_SUITE.erl69
2 files changed, 159 insertions, 17 deletions
diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml
index 5df60a92e5..dd4a289c61 100644
--- a/lib/stdlib/doc/src/ets.xml
+++ b/lib/stdlib/doc/src/ets.xml
@@ -1385,6 +1385,28 @@ 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 +1433,82 @@ 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 &lt;- 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>
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 5d7e558601..6a123da792 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -94,6 +94,8 @@
do_heavy_concurrent/1
]).
+-export([t_select_reverse/1]).
+
-include("test_server.hrl").
init_per_testcase(Case, Config) ->
@@ -128,7 +130,7 @@ all(suite) ->
match_heavy, fold, member,
t_delete_object, t_init_table, t_whitebox,
t_delete_all_objects, t_insert_list, t_test_ms,
- t_select_delete, t_ets_dets, memory,
+ t_select_delete, t_ets_dets, memory, t_select_reverse,
t_bucket_disappears,
select_fail,t_insert_new, t_repair_continuation, otp_5340, otp_6338,
otp_6842_select_1000, otp_7665, otp_8732,
@@ -788,6 +790,67 @@ t_test_ms(Config) when is_list(Config) ->
?line true = (if is_list(String) -> true; true -> false end),
?line verify_etsmem(EtsMem).
+t_select_reverse(doc) ->
+ ["Test the select reverse BIF's"];
+t_select_reverse(suite) ->
+ [];
+t_select_reverse(Config) when is_list(Config) ->
+ ?line Table = ets:new(xxx, [ordered_set]),
+ ?line filltabint(Table,1000),
+ ?line A = lists:reverse(ets:select(Table,[{{'$1', '_'},
+ [{'>',
+ {'rem',
+ '$1', 5},
+ 2}],
+ ['$_']}])),
+ ?line A = ets:select_reverse(Table,[{{'$1', '_'},
+ [{'>',
+ {'rem',
+ '$1', 5},
+ 2}],
+ ['$_']}]),
+ ?line A = reverse_chunked(Table,[{{'$1', '_'},
+ [{'>',
+ {'rem',
+ '$1', 5},
+ 2}],
+ ['$_']}],3),
+ % A set/bag/duplicate_bag should get the same result regardless
+ % of select or select_reverse
+ ?line Table2 = ets:new(xxx, [set]),
+ ?line filltabint(Table2,1000),
+ ?line Table3 = ets:new(xxx, [bag]),
+ ?line filltabint(Table3,1000),
+ ?line Table4 = ets:new(xxx, [duplicate_bag]),
+ ?line filltabint(Table4,1000),
+ ?line lists:map(fun(Tab) ->
+ B = ets:select(Tab,[{{'$1', '_'},
+ [{'>',
+ {'rem',
+ '$1', 5},
+ 2}],
+ ['$_']}]),
+ B = ets:select_reverse(Tab,[{{'$1', '_'},
+ [{'>',
+ {'rem',
+ '$1', 5},
+ 2}],
+ ['$_']}])
+ end,[Table2, Table3, Table4]),
+ ok.
+
+
+
+reverse_chunked(T,MS,N) ->
+ do_reverse_chunked(ets:select_reverse(T,MS,N),[]).
+
+do_reverse_chunked('$end_of_table',Acc) ->
+ lists:reverse(Acc);
+do_reverse_chunked({L,C},Acc) ->
+ NewAcc = lists:reverse(L)++Acc,
+ do_reverse_chunked(ets:select_reverse(C), NewAcc).
+
+
t_select_delete(doc) ->
["Test the ets:select_delete/2 and ets:select_count/2 BIF's"];
t_select_delete(suite) ->
@@ -3942,7 +4005,7 @@ do_lookup_element(Tab, N, M) ->
end.
-heavy_concurrent(Config) ->
+heavy_concurrent(_Config) ->
repeat_for_opts(do_heavy_concurrent).
do_heavy_concurrent(Opts) ->
@@ -3961,7 +4024,7 @@ do_heavy_concurrent(Opts) ->
?line lists:foreach(fun (P) ->
M = erlang:monitor(process, P),
receive
- {'DOWN', Mon, process, P, _} ->
+ {'DOWN', M, process, P, _} ->
ok
end
end,