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Small semi-join optimization improvement:

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- if we're considering FirstMatch access with one inner table, and 
  @@optimizer_switch has semijoin_with_cache flag, calculate costs
  as if we used join cache (because we will be able to do so)
This commit is contained in:
Sergey Petrunya
2011-12-08 04:22:38 +04:00
parent 8e96081764
commit ae480437ce
10 changed files with 56 additions and 49 deletions
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6
mysql-test/r/subselect3.result
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@ -105,7 +105,7 @@ oref a
1 1
show status like '%Handler_read_rnd_next';
Variable_name Value
Handler_read_rnd_next 14
Handler_read_rnd_next 5
delete from t2;
insert into t2 values (NULL, 0),(NULL, 0), (NULL, 0), (NULL, 0);
set optimizer_switch='subquery_cache=off';
@ -1308,7 +1308,7 @@ insert into t1 select * from t0;
explain select * from t0 where a in (select a from t1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t0 ALL NULL NULL NULL NULL 2
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where; Start temporary; End temporary; Using join buffer (flat, BNL join)
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where; FirstMatch(t0); Using join buffer (flat, BNL join)
select * from t0 where a in (select a from t1);
a
10.24
@ -1321,7 +1321,7 @@ insert into t1 select * from t0;
explain select * from t0 where a in (select a from t1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t0 ALL NULL NULL NULL NULL 2
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where; Start temporary; End temporary; Using join buffer (flat, BNL join)
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where; FirstMatch(t0); Using join buffer (flat, BNL join)
select * from t0 where a in (select a from t1);
a
2008-01-01