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WL#3527: Extend IGNORE INDEX so places where index is ignored

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Currently MySQL allows one to specify what indexes to ignore during
join optimization. The scope of the current USE/FORCE/IGNORE INDEX 
statement is only the FROM clause, while all other clauses are not 
affected.

However, in certain cases, the optimizer
may incorrectly choose an index for sorting and/or grouping, and
produce an inefficient query plan.

This task provides the means to specify what indexes are
ignored/used for what operation in a more fine-grained manner, thus
making it possible to manually force a better plan. We do this
by extending the current IGNORE/USE/FORCE INDEX syntax to:

IGNORE/USE/FORCE INDEX [FOR {JOIN | ORDER | GROUP BY}]

so that:
- if no FOR is specified, the index hint will apply everywhere.
- if MySQL is started with the compatibility option --old_mode then
  an index hint without a FOR clause works as in 5.0 (i.e, the 
  index will only be ignored for JOINs, but can still be used to
  compute ORDER BY).

See the WL#3527 for further details.
This commit is contained in:
gkodinov/kgeorge@macbook.gmz
2007-03-05 19:08:41 +02:00
parent 6a49f0cd93
commit b9c82eaa89
25 changed files with 727 additions and 458 deletions
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15
mysql-test/r/endspace.result
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@@ -25,10 +25,11 @@ insert into t1 values ('teststring'), ('nothing'), ('teststring\t');
check table t1;
Table Op Msg_type Msg_text
test.t1 check status OK
select * from t1 ignore key (key1) where text1='teststring' or text1 like 'teststring_%';
select * from t1 ignore key (key1) where text1='teststring' or
text1 like 'teststring_%' ORDER BY text1;
text1
teststring
teststring
teststring
select * from t1 where text1='teststring' or text1 like 'teststring_%';
text1
teststring
@@ -48,10 +49,11 @@ alter table t1 modify text1 char(32) binary not null;
check table t1;
Table Op Msg_type Msg_text
test.t1 check status OK
select * from t1 ignore key (key1) where text1='teststring' or text1 like 'teststring_%';
select * from t1 ignore key (key1) where text1='teststring' or
text1 like 'teststring_%' ORDER BY text1;
text1
teststring
teststring
teststring
select concat('|', text1, '|') from t1 where text1='teststring' or text1 like 'teststring_%';
concat('|', text1, '|')
|teststring |
@@ -132,10 +134,11 @@ concat('|', text1, '|')
drop table t1;
create table t1 (text1 varchar(32) not NULL, KEY key1 using BTREE (text1)) engine=heap;
insert into t1 values ('teststring'), ('nothing'), ('teststring\t');
select * from t1 ignore key (key1) where text1='teststring' or text1 like 'teststring_%';
select * from t1 ignore key (key1) where text1='teststring' or
text1 like 'teststring_%' ORDER BY text1;
text1
teststring
teststring
teststring
select * from t1 where text1='teststring' or text1 like 'teststring_%';
text1
teststring