This bug is the result of an incomplete/inconsistent change introduced into
5.3 code when the cond_equal parameter were added to the function optimize_cond.
The change was made during a merge from 5.2 in October 2010.
The bug could affect only queries with HAVING.
An outer join query with a semi-join subquery could return a wrong result
if the optimizer chose to materialize the subquery.
It happened because when substituting for the best field into a ref item
used to build access keys not all COND_EQUAL objects that could be employed
at substitution were checked.
Also refined some code in the function check_join_cache_usage to make it
safer.
- equality substitution code was geared towards processing WHERE/ON clauses.
that is, it assumed that it was doing substitions on the code that
= wasn't attached to any particular join_tab yet
= was going to be fed to make_join_select() which would take the condition
apart and attach various parts of it to tables inside/outside semi-joins.
- However, somebody added equality substition for ref access. That is, if
we have a ref access on TBL.key=expr, they would do equality substition in
'expr'. This possibility wasn't accounted for.
- Fixed equality substition code by adding a mode that does equality
substition under assumption that the processed expression will be
attached to a certain particular table TBL.
This bug in the function setup_semijoin_dups_elimination() could
lead to invalid choice of the sequence of tables for which semi-join
duplicate elimination was applied.
of the 5.3 code line after a merge with 5.2 on 2010-10-28
in order not to allow the cost to access a joined table to be equal
to 0 ever.
Expanded data sets for many test cases to get the same execution plans
as before.
- Set the default
- Adjust the testcases so that 'new' tests are run with optimizations turned on.
- Pull out relevant tests from "irrelevant" tests and run them with optimizations on.
- Run range.test and innodb.test with both mrr=on and mrr=off
semijoin=on,firstmatch=on,loosescan=on
to
semijoin=off,firstmatch=off,loosescan=off
Adjust the testcases:
- Modify subselect*.test and join_cache.test so that all tests
use the same execution paths as before (i.e. optimizations that
are being tested are enabled)
- Let all other test files run with the new default settings (i.e.
with new optimizations disabled)
- Copy subquery testcases from these files into t/subselect_extra.test
which will run them with new optimizations enabled.
- 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:
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