BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off

- The problem was that DuplicateWeedout strategy setup code wasn't aware of the 
  fact that join buffering will be used and applied optimization that doesn't work
  together with join buffering. Fixed by making DuplicateWeedout setup code to have 
  a pessimistic check about whether there is a chance that join buffering will be 
  used.
- Make JOIN_CACHE_BKA::init() correctly process Copy_field elements that denote saving
  current rowids in the join buffer.

mysql-test/r/subselect_sj2.result:
  Update test results
mysql-test/r/subselect_sj2_jcl6.result:
  Update test results
mysql-test/r/subselect_sj_jcl6.result:
  Testcase
mysql-test/t/subselect_sj2.test:
  Update test results
mysql-test/t/subselect_sj_jcl6.test:
  Testcase
sql/opt_subselect.cc:
  - The problem was that DuplicateWeedout strategy setup code wasn't aware of the 
    fact that join buffering will be used and applied optimization that doesn't work
    together with join buffering. Fixed by making DuplicateWeedout setup code to have 
    a pessimistic check about whether there is a chance that join buffering will be 
    used.
sql/sql_join_cache.cc:
  Make JOIN_CACHE_BKA::init() correctly process Copy_field elements that denote saving current rowids in the join buffer.
sql/sql_select.cc:
  Added a question note

1 files changed, 1 insertions, 1 deletions

diff --git a/mysql-test/t/subselect_sj2.test b/mysql-test/t/subselect_sj2.test
index 5578015ec29..e73e7cfade2 100644
--- a/mysql-test/t/subselect_sj2.test
+++ b/mysql-test/t/subselect_sj2.test
@@ -583,7 +583,7 @@ update t2 set b=11 where a=3;
 
 if (`select @@join_cache_level=6`)
 {
-  --echo 
+  --echo # Not anymore:
   --echo # The following query gives wrong result due to Bug#49129
 }
 select * from t0 where t0.a in