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Fixed LP bug #939009.

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The result of materialization of the right part of an IN subquery predicate
is placed into a temporary table. Each row of the materialized table is
distinct. A unique key over all fields of the temporary table is defined and
created. It allows to perform key look-ups into the table.
The table created for a materialized subquery can be accessed by key as
any other table. The function best_access-path search for the best access
to join a table to a given partial join. With some where conditions this
function considers a possibility of a ref_or_null access. If such access
employs the unique key on the temporary table then when estimating
the cost this access the function tries to use the array rec_per_key. Yet,
such array is not built for this unique key. This causes a crash of the server.

Rows returned by the subquery that contain nulls don't have to be placed
into temporary table, as they cannot be match any row produced by the
left part of the subquery predicate. So all fields of the temporary table
can be defined as non-nullable. In this case any ref_or_null access
to the temporary table does not make any sense and it does not make sense
to estimate such an access.

The fix makes sure that the temporary table for a materialized IN subquery
is defined with columns that are all non-nullable. The also ensures that 
any row with nulls returned by the subquery is not placed into the
temporary table.
This commit is contained in:
Igor Babaev
2012-02-24 16:50:22 -08:00
parent 567d871ff0
commit 841a74a4d6
26 changed files with 279 additions and 114 deletions
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14
mysql-test/r/subselect_sj.result
View File

@ -802,7 +802,7 @@ INSERT INTO t2 VALUES (1,'i','iiii','iiii','iiii','iiii','ffff','ffff','ffff','f
EXPLAIN EXTENDED SELECT pk FROM t1 WHERE (a, b) IN (SELECT a, b FROM t2 WHERE pk > 0);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 100.00
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 13 func,func 1 100.00
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 11 func,func 1 100.00
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 100.00 Using index condition; Rowid-ordered scan
Warnings:
Note 1003 select `test`.`t1`.`pk` AS `pk` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t2`.`pk` > 0))
@ -1053,8 +1053,8 @@ AND t1.val IN (SELECT t3.val FROM t3
WHERE t3.val LIKE 'a%' OR t3.val LIKE 'e%');
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 5
1 PRIMARY <subquery3> eq_ref distinct_key distinct_key 14 func 1
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 14 func 1
1 PRIMARY <subquery3> eq_ref distinct_key distinct_key 13 func 1
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 13 func 1
3 MATERIALIZED t3 ALL NULL NULL NULL NULL 5 Using where
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 6 Using where
SELECT *
@ -1633,9 +1633,9 @@ select * from t1 A, t1 B
where A.a = B.a and A.a in (select a from t2 C) and B.a in (select a from t2 D);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY A ALL NULL NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 5 func 1
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
1 PRIMARY B ALL NULL NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 PRIMARY <subquery3> eq_ref distinct_key distinct_key 5 func 1
1 PRIMARY <subquery3> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED C ALL NULL NULL NULL NULL 3
3 MATERIALIZED D ALL NULL NULL NULL NULL 3
drop table t1, t2;
@ -2323,7 +2323,7 @@ explain
SELECT * FROM t1 WHERE (a) IN (SELECT a FROM t2 JOIN t3 ON b = a);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 9
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 5 func 1
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t3 ALL NULL NULL NULL NULL 13 Using where
2 MATERIALIZED t2 ref b b 4 test.t3.a 1 Using index
SELECT * FROM t1 WHERE (a) IN (SELECT a FROM t2 JOIN t3 ON b = a);
@ -2443,7 +2443,7 @@ EXPLAIN
SELECT * FROM t1 RIGHT JOIN t2 ON b = a WHERE t2.b IN (SELECT c FROM t3);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 2
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 5 func 1
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 MATERIALIZED t3 ALL NULL NULL NULL NULL 2
SELECT * FROM t1 RIGHT JOIN t2 ON b = a WHERE t2.b IN (SELECT c FROM t3);