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BUG#823930: Wrong result with semijoin materialization and blob fields

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- Make subquery_types_allow_materialization() detect a case where 
  create_tmp_table() would create a blob column which would make it 
  impossible to use materialization
  Non-semi-join materialization worked because it detected that this case
  and felt back to use IN->EXISTS. Semi-join Materialization cannot easily
  fallback, so we have to detect this case early.
This commit is contained in:
Sergey Petrunya 2011-09-06 17:06:04 +04:00
parent e1435a5178
commit fc6b6435b4
3 changed files with 22 additions and 6 deletions
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14
mysql-test/r/subselect_sj_mat.result
View File

@ -856,15 +856,16 @@ explain extended select left(a1,7), left(a2,7)
from t1_1024
where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1_1024 ALL NULL NULL NULL NULL 3 100.00
1 PRIMARY <subquery2> eq_ref NULL distinct_key 15 func,func 1 100.00
2 SUBQUERY t2_1024 ALL NULL NULL NULL NULL 3 100.00 Using where
1 PRIMARY t1_1024 ALL NULL NULL NULL NULL 3 100.00 Start temporary
1 PRIMARY t2_1024 ALL NULL NULL NULL NULL 3 100.00 Using where; End temporary; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select left(`test`.`t1_1024`.`a1`,7) AS `left(a1,7)`,left(`test`.`t1_1024`.`a2`,7) AS `left(a2,7)` from `test`.`t1_1024` semi join (`test`.`t2_1024`) where ((`test`.`t2_1024`.`b1` > '0') and (`test`.`t1_1024`.`a1` = substr(`test`.`t2_1024`.`b1`,1,1024)))
select left(a1,7), left(a2,7)
from t1_1024
where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0');
left(a1,7) left(a2,7)
1 - 01x 2 - 01x
1 - 02x 2 - 02x
explain extended select left(a1,7), left(a2,7)
from t1_1024
where a1 in (select group_concat(b1) from t2_1024 group by b2);
@ -950,15 +951,16 @@ explain extended select left(a1,7), left(a2,7)
from t1_1025
where a1 in (select substring(b1,1,1025) from t2_1025 where b1 > '0');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1_1025 ALL NULL NULL NULL NULL 3 100.00
1 PRIMARY <subquery2> eq_ref NULL distinct_key 15 func,func 1 100.00
2 SUBQUERY t2_1025 ALL NULL NULL NULL NULL 3 100.00 Using where
1 PRIMARY t1_1025 ALL NULL NULL NULL NULL 3 100.00 Start temporary
1 PRIMARY t2_1025 ALL NULL NULL NULL NULL 3 100.00 Using where; End temporary; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select left(`test`.`t1_1025`.`a1`,7) AS `left(a1,7)`,left(`test`.`t1_1025`.`a2`,7) AS `left(a2,7)` from `test`.`t1_1025` semi join (`test`.`t2_1025`) where ((`test`.`t2_1025`.`b1` > '0') and (`test`.`t1_1025`.`a1` = substr(`test`.`t2_1025`.`b1`,1,1025)))
select left(a1,7), left(a2,7)
from t1_1025
where a1 in (select substring(b1,1,1025) from t2_1025 where b1 > '0');
left(a1,7) left(a2,7)
1 - 01x 2 - 01x
1 - 02x 2 - 02x
explain extended select left(a1,7), left(a2,7)
from t1_1025
where a1 in (select group_concat(b1) from t2_1025 group by b2);

4
sql/item.cc
View File

@ -5191,6 +5191,10 @@ Field *Item::make_string_field(TABLE *table)
{
Field *field;
DBUG_ASSERT(collation.collation);
/*
Note: the following check is repeated in
subquery_types_allow_materialization():
*/
if (max_length/collation.collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB)
field= new Field_blob(max_length, maybe_null, name,
collation.collation);

10
sql/opt_subselect.cc
View File

@ -559,6 +559,16 @@ bool subquery_types_allow_materialization(Item_in_subselect *in_subs)
if (inner->field_type() == MYSQL_TYPE_BLOB ||
inner->field_type() == MYSQL_TYPE_GEOMETRY)
DBUG_RETURN(FALSE);
/*
Materialization also is unable to work when create_tmp_table() will
create a blob column because item->max_length is too big.
The following check is copied from Item::make_string_field():
*/
if (inner->max_length / inner->collation.collation->mbmaxlen >
CONVERT_IF_BIGGER_TO_BLOB)
{
DBUG_RETURN(FALSE);
}
break;
case TIME_RESULT:
if (mysql_type_to_time_type(outer->field_type()) !=