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Fixed bug #52636.

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Applied the fix for bug #47217 from the mysql-6.0 codebase.
The patch adds not null predicates generated for the left parts
of the equality predicates used for ref accesses. This is done
for such predicates both in where conditions and on conditions.
For the where conditions the not null predicates were generated
but in 5.0/5.1 they actually never were used due to some lame
merge from 4.1 to 5.0. The fix for bug #47217 made these 
predicates to be used in the condition pushed to the tables.
Yet only this patch generates not null predicates for equality
predicated from on conditions of outer joins.
This patch introduces a performance regression that can be
observed on a test case from null_key.test. The regression
will disappear after the fix for bug #57024 from mariadb-5.1
is pulled into mariadb-5.3.
The patch contains many changes in the outputs of the EXPLAIN 
commands since generated not null predicates are considered as
parts of the conditions pushed to join tables and may add
'Usingwhere' in some rows of EXPLAINs where there used
to be no such comments.
This commit is contained in:
Igor Babaev
2010-09-28 12:39:33 -07:00
parent db37f2db82
commit 21b1b5f040
40 changed files with 404 additions and 238 deletions
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2
mysql-test/r/key_cache.result
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@ -642,7 +642,7 @@ i
3
explain select count(*) from t1, t2 where t1.p = t2.i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index k1 k1 5 NULL 1024 Using index
1 SIMPLE t2 index k1 k1 5 NULL 1024 Using where; Using index
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.i 1 Using index
select count(*) from t1, t2 where t1.p = t2.i;
count(*)