Fixed bug lp:1000649

Analysis:

When the method JOIN::choose_subquery_plan() decided to apply
the IN-TO-EXISTS strategy, it set the unit and select_lex
uncacheable flag to UNCACHEABLE_DEPENDENT_INJECTED unconditionally.
As result, even if IN-TO-EXISTS injected non-correlated predicates,
the subquery was still treated as correlated.

Solution:
Set the subquery as correlated only if the injected predicate(s) depend
on the outer query.

1 files changed, 10 insertions, 4 deletions

diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc
index 967981bcc9d..0273c947ef6 100644
--- a/sql/opt_subselect.cc
+++ b/sql/opt_subselect.cc
@@ -5438,11 +5438,17 @@ bool JOIN::choose_subquery_plan(table_map join_tables)
     if (in_subs->inject_in_to_exists_cond(this))
       return TRUE;
     /*
-      It is IN->EXISTS transformation so we should mark subquery as
-      dependent
+      If the injected predicate is correlated the IN->EXISTS transformation
+      make the subquery dependent.
     */
-    in_subs->unit->uncacheable|= UNCACHEABLE_DEPENDENT_INJECTED;
-    select_lex->uncacheable|= UNCACHEABLE_DEPENDENT_INJECTED;
+    if ((in_to_exists_where &&
+         in_to_exists_where->used_tables() & OUTER_REF_TABLE_BIT) ||
+        (in_to_exists_having &&
+         in_to_exists_having->used_tables() & OUTER_REF_TABLE_BIT))
+    {
+      in_subs->unit->uncacheable|= UNCACHEABLE_DEPENDENT_INJECTED;
+      select_lex->uncacheable|= UNCACHEABLE_DEPENDENT_INJECTED;
+    }
     select_limit= 1;
   }
   else