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authorSverker Eriksson <[email protected]>2017-05-10 11:47:25 +0200
committerSverker Eriksson <[email protected]>2017-05-10 11:47:25 +0200
commit42d240e9144bd6219c9fd3b59ef9bc4f29bcf5f5 (patch)
tree4229ac7f656110a30c45d492b86a67991359488d
parent381a47d5219407f9c734cf0b081776129e7c180f (diff)
parent6c3265b86582d4848e1c77efee3a649a137694d6 (diff)
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Merge branch 'sverker/ets-select-replace-const'
* sverker/ets-select-replace-const: stdlib: Add examples for ets:select_replace docs erts: Fix ets:select_replace with {const, NewTuple}
-rw-r--r--erts/emulator/beam/erl_db_util.c41
-rw-r--r--lib/stdlib/doc/src/ets.xml36
-rw-r--r--lib/stdlib/test/ets_SUITE.erl20
3 files changed, 74 insertions, 23 deletions
diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c
index 91ac53ad0b..eaed15b14b 100644
--- a/erts/emulator/beam/erl_db_util.c
+++ b/erts/emulator/beam/erl_db_util.c
@@ -1125,12 +1125,11 @@ error:
* Returns true if 'b' is guaranteed to always construct
* the same term as 'a' has matched.
*/
-static int db_match_eq_body(Eterm a, Eterm b)
+static int db_match_eq_body(Eterm a, Eterm b, int const_mode)
{
DECLARE_ESTACK(s);
Uint arity;
Eterm *ap, *bp;
- int const_mode = 0;
const Eterm CONST_MODE_OFF = THE_NON_VALUE;
while (1) {
@@ -1224,6 +1223,7 @@ int db_match_keeps_key(int keypos, Eterm match, Eterm guard, Eterm body)
Eterm single_body_subterm;
Eterm single_body_subterm_key;
Eterm* single_body_subterm_key_tpl;
+ int const_mode;
if (!is_list(body)) {
return 0;
@@ -1244,42 +1244,53 @@ int db_match_keeps_key(int keypos, Eterm match, Eterm guard, Eterm body)
return 0;
}
- single_body_term_tpl = tuple_val(single_body_term);
- if (arityval(*single_body_term_tpl) != 1) {
- // not the 1-element tuple we're expecting
- return 0;
- }
-
match_key = db_getkey(keypos, match);
if (!is_value(match_key)) {
// can't get key out of match
return 0;
}
- single_body_subterm = single_body_term_tpl[1];
+ single_body_term_tpl = tuple_val(single_body_term);
+ if (single_body_term_tpl[0] == make_arityval(2) &&
+ single_body_term_tpl[1] == am_const) {
+ /* {const, {"ets-tuple constant"}} */
+ single_body_subterm = single_body_term_tpl[2];
+ const_mode = 1;
+ }
+ else if (*single_body_term_tpl == make_arityval(1)) {
+ /* {{"ets-tuple construction"}} */
+ single_body_subterm = single_body_term_tpl[1];
+ const_mode = 0;
+ }
+ else {
+ /* not a tuple construction */
+ return 0;
+ }
+
single_body_subterm_key = db_getkey(keypos, single_body_subterm);
if (!is_value(single_body_subterm_key)) {
// can't get key out of single body subterm
return 0;
}
- if (db_match_eq_body(match_key, single_body_subterm_key)) {
+ if (db_match_eq_body(match_key, single_body_subterm_key, const_mode)) {
/* tuple with same key is returned */
return 1;
}
- if (!is_tuple(single_body_subterm_key)) {
- /* can't possibly be an element instruction */
+ if (const_mode) {
+ /* constant key did not match */
return 0;
}
- single_body_subterm_key_tpl = tuple_val(single_body_subterm_key);
- if (arityval(*single_body_subterm_key_tpl) != 3) {
+ if (!is_tuple(single_body_subterm_key)) {
/* can't possibly be an element instruction */
return 0;
}
- if (single_body_subterm_key_tpl[1] == am_element &&
+ single_body_subterm_key_tpl = tuple_val(single_body_subterm_key);
+ if (single_body_subterm_key_tpl[0] == make_arityval(3) &&
+ single_body_subterm_key_tpl[1] == am_element &&
single_body_subterm_key_tpl[3] == am_DollarUnderscore &&
single_body_subterm_key_tpl[2] == make_small(keypos))
{
diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml
index 0d1e5c6e3a..342be80f98 100644
--- a/lib/stdlib/doc/src/ets.xml
+++ b/lib/stdlib/doc/src/ets.xml
@@ -1495,17 +1495,37 @@ is_integer(X), is_integer(Y), X + Y < 4711]]></code>
<fsummary>Match and replace objects atomically in an ETS table</fsummary>
<desc>
<p>Matches the objects in the table <c><anno>Tab</anno></c> using a
- <seealso marker="#match_spec">match specification</seealso>. If
- an object is matched, the existing object is replaced with
- the match specification result, which <em>must</em> retain
- the original key or the operation will fail with <c>badarg</c>.</p>
+ <seealso marker="#match_spec">match specification</seealso>. For each
+ matched object, the existing object is replaced with
+ the match specification result.</p>
+ <p>The match-and-replace operation for each individual object is guaranteed to be
+ <seealso marker="#concurrency">atomic and isolated</seealso>. The
+ <c>select_replace</c> table iteration as a whole, like all other select functions,
+ does not give such guarantees.</p>
+ <p>The match specifiction must be guaranteed to <em>retain the key</em>
+ of any matched object. If not, <c>select_replace</c> will fail with <c>badarg</c>
+ without updating any objects.</p>
<p>For the moment, due to performance and semantic constraints,
tables of type <c>bag</c> are not yet supported.</p>
<p>The function returns the total number of replaced objects.</p>
- <note>
- <p>The match/replacement operation atomicity scope is limited
- to each individual object.</p>
- </note>
+ <p><em>Example</em></p>
+ <p>For all 2-tuples with a list in second position, add atom <c>'marker'</c> first in the list:</p>
+ <pre>
+1> <input>T = ets:new(x,[]), ets:insert(T, {key, [1, 2, 3]}).</input>
+true
+2> <input>MS = ets:fun2ms(fun({K, L}) when is_list(L) -> {K, [marker | L]} end).</input>
+[{{'$1','$2'},[{is_list,'$2'}],[{{'$1',[marker|'$2']}}]}]
+3> <input>ets:select_replace(T, MS).</input>
+1
+4> <input>ets:tab2list(T).</input>
+[{key,[marker,1,2,3]}]
+ </pre>
+ <p>A generic single object compare-and-swap operation:</p>
+ <pre>
+[Old] = ets:lookup(T, Key),
+New = update_object(Old),
+Success = (1 =:= ets:select_replace(T, [{Old, [], [{const, New}]}])),
+ </pre>
</desc>
</func>
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 4c2f6cfe9e..05451a83fb 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -1349,6 +1349,26 @@ t_select_replace(Config) when is_list(Config) ->
NeqPairs(X,Y)) || X <- Terms, Y <- Terms],
+ %% Wrap entire tuple with 'const'
+ [[begin
+ Old = {Key, 1, 2},
+ ets:insert(T2, Old),
+ 1 = ets:select_replace(T2, [{Old, [], [{const, New}]}]),
+ [New] = ets:lookup(T2, Key),
+ ets:delete(T2, Key)
+ end || New <- [{Key, 1, 2}, {Key, 3, 4}, {Key, 1}, {Key, 1, 2, 3}, {Key}]
+ ]
+ || Key <- [{1, tuple}, {nested, {tuple, {a,b}}} | Terms]],
+
+ %% 'const' wrap does not work with maps or variables in keys
+ [[begin
+ Old = {Key, 1, 2},
+ {'EXIT',{badarg,_}} = (catch ets:select_replace(T2, [{Old, [], [{const, New}]}]))
+ end || New <- [{Key, 1, 2}, {Key, 3, 4}, {Key, 1}, {Key, 1, 2, 3}, {Key}]
+ ]
+ || Key <- [#{a => 1}, {nested, #{a => 1}}, '$1']],
+
+
ets:delete(T2),
verify_etsmem(EtsMem).