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Bug#30302: Tables that were optimized away are printed in the

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EXPLAIN EXTENDED warning.

Query optimizer searches for the constant tables and optimizes them away. This
means that fields of such tables are substituted for their values and on later
phases they are treated as constants. After this constant tables are removed
from the query execution plan. Nevertheless constant tables were shown in 
the EXPLAIN EXTENDED warning thus producing query that might be not an
equivalent of the original query.
        
Now the print_join function skips all tables that were optimized away from
printing to the EXPLAIN EXTENDED warning. If all tables were optimized away it
produces the 'FROM dual' clause.
This commit is contained in:
Evgeny Potemkin
2009-10-19 15:13:26 +04:00
parent 68c55462ef
commit 14994d2148
12 changed files with 76 additions and 22 deletions
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2
mysql-test/r/func_test.result
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@ -87,7 +87,7 @@ explain extended select - a from t1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select -('1') AS `- a` from `test`.`t1`
Note 1003 select -('1') AS `- a` from dual
drop table t1;
select 5 between 0 and 10 between 0 and 1,(5 between 0 and 10) between 0 and 1;
5 between 0 and 10 between 0 and 1 (5 between 0 and 10) between 0 and 1