database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

Small semi-join optimization improvement:

Browse Source 
- 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
Download Patch File Download Diff File Expand all files Collapse all files

8
mysql-test/r/subselect4.result
View File

@ -1230,16 +1230,16 @@ EXPLAIN
SELECT * FROM t1 RIGHT JOIN t2 ON t1.c1 WHERE 's' IN (SELECT c1 FROM t2);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 0 const row not found
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; FirstMatch(t1)
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using join buffer (flat, BNL join)
1 PRIMARY t2 ALL NULL NULL NULL NULL 2
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; FirstMatch(t2); Using join buffer (flat, BNL join)
SELECT * FROM t1 RIGHT JOIN t2 ON t1.c1 WHERE 's' IN (SELECT c1 FROM t2);
c1 c1
EXPLAIN
SELECT * FROM t2 LEFT JOIN t1 ON t1.c1 WHERE 's' IN (SELECT c1 FROM t2);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 0 const row not found
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; FirstMatch(t1)
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using join buffer (flat, BNL join)
1 PRIMARY t2 ALL NULL NULL NULL NULL 2
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; FirstMatch(t2); Using join buffer (flat, BNL join)
SELECT * FROM t2 LEFT JOIN t1 ON t1.c1 WHERE 's' IN (SELECT c1 FROM t2);
c1 c1
EXPLAIN