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authorunknown <timour@askmonty.org>2012-06-06 22:26:40 +0300
committerunknown <timour@askmonty.org>2012-06-06 22:26:40 +0300
commitc2677de7aca09a0ba4b680b5227bda3865ab9290 (patch)
tree980157e9eaf1062641572da371d1ae7fcc371625 /sql/item.h
parent8efc63ba5d32b77501226921ee503b9ae513a365 (diff)
parent7ddd5418d01e60dba2ae69a668e7c9f811613451 (diff)
downloadmariadb-git-c2677de7aca09a0ba4b680b5227bda3865ab9290.tar.gz
Merge the fix for lp:944706, mdev-193
Diffstat (limited to 'sql/item.h')
-rw-r--r--sql/item.h12
1 files changed, 6 insertions, 6 deletions
diff --git a/sql/item.h b/sql/item.h
index a9c1153d236..f7f3edda384 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1395,21 +1395,21 @@ public:
{
return cmp_context == IMPOSSIBLE_RESULT || item->cmp_context == cmp_context;
}
- /*
+ /**
Test whether an expression is expensive to compute. Used during
optimization to avoid computing expensive expressions during this
phase. Also used to force temp tables when sorting on expensive
functions.
- TODO:
+ @todo
Normally we should have a method:
cost Item::execution_cost(),
where 'cost' is either 'double' or some structure of various cost
parameters.
- NOTE
- This function is now used to prevent evaluation of materialized IN
- subquery predicates before it is allowed. grep for
- DontEvaluateMaterializedSubqueryTooEarly to see the uses.
+ @note
+ This function is now used to prevent evaluation of expensive subquery
+ predicates during the optimization phase. It also prevents evaluation
+ of predicates that are not computable at this moment.
*/
virtual bool is_expensive()
{