database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00
Code Activity

BNLH algorithm always used a full table scan over the joined table

Browse Source 
even in the cases when there existed range/index-merge scans that
were cheaper than the full table scan.
This was a defect/bug of the implementation of mwl #128. 
Now hash join can work not only with full table scan of the joined
table, but also with full index scan, range and index-merge scans.
Accordingly, in the cases when hash join is used the column 'type'
in the EXPLAINs can contain now 'hash_ALL', 'hash_index', 'hash_range'
and 'hash_index_merge'. If hash join is coupled with a range/index_merge
scan then the columns 'key' and 'key_len' contain info not only on
the used hash index, but also on the indexes used for the scan.
This commit is contained in:
Igor Babaev
2011-02-23 22:23:12 -08:00
parent 6c7360b540
commit 272e5e6212
10 changed files with 441 additions and 157 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
mysql-test/suite/innodb/r/innodb_mysql.result
View File

@ -2656,7 +2656,7 @@ SELECT t1.pk FROM t1,t2
WHERE t1.pk = t2.pk AND t2.pk <> 8;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index PRIMARY PRIMARY 4 NULL 11 Using where; Using index
1 SIMPLE t2 hash PRIMARY PRIMARY 4 test.t1.pk 13 Using index; Using join buffer (flat, BNLH join)
1 SIMPLE t2 hash_range PRIMARY #hash#PRIMARY:PRIMARY 4:4 test.t1.pk 7 Using where; Using index; Using join buffer (flat, BNLH join)
SELECT t1.pk FROM t1,t2
WHERE t1.pk = t2.pk AND t2.pk <> 8;
pk