Details
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Type:
Task
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Status: Closed
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Priority:
Major
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Resolution: Fixed
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Fix Version/s: None
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Component/s: None
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Labels:None
Description
I am looking at Q4.
ts ( select * from lineitem where l_orderkey = o_orderkey and l_commitdate < l_receiptdate ) group by o_orderpriority order by o_orderpriority;
+------+--------------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+---------------------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+------+--------------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+---------------------------------------------------------------------+
| 1 | PRIMARY | orders | range | i_o_orderdate | i_o_orderdate | 4 | NULL | 137994 | 100.00 | Using index condition; Using where; Using temporary; Using filesort |
| 2 | DEPENDENT SUBQUERY | lineitem | ref | PRIMARY,i_l_orderkey,i_l_orderkey_quantity | PRIMARY | 4 | dbt3sf1.orders.o_orderkey | 2 | 100.00 | Using where |
+------+--------------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+---------------------------------------------------------------------+
2 rows in set, 2 warnings (0.00 sec)
MariaDB [dbt3sf1]> set optimizer_switch='exists_to_in=on';
Query OK, 0 rows affected (0.00 sec)
MariaDB [dbt3sf1]> explain extended select o_orderpriority, count(*) as order_count from orders where o_orderdate >= '1995-06-06' and o_orderdate < date_add('1995-06-06', interval 3 month) and exists ( select * from lineitem where l_orderkey = o_orderkey and l_commitdate < l_receiptdate ) group by o_orderpriority order by o_orderpriority;
+------+-------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+--------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+------+-------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+--------------------------------------------------------+
| 1 | PRIMARY | orders | range | PRIMARY,i_o_orderdate | i_o_orderdate | 4 | NULL | 137994 | 100.00 | Using index condition; Using temporary; Using filesort |
| 1 | PRIMARY | lineitem | ref | PRIMARY,i_l_orderkey,i_l_orderkey_quantity | PRIMARY | 4 | dbt3sf1.orders.o_orderkey | 2 | 100.00 | Using where; FirstMatch(orders) |
+------+-------------+----------+-------+--------------------------------------------+---------------+---------+---------------------------+--------+----------+--------------------------------------------------------+
2 rows in set, 2 warnings (0.00 sec)
The query plan is similar. However, the second query should be able to use BKA. Run the query with and without BKA and measure the impact.
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Query Q22, EXPLAINs with exists_to_in=on|off.
The query uses WHERE .... AND NOT EXISTS(SELECT * FROM orders WHERE o_custkey = c_custkey).
It seems, that the best way run the subquery is to use index lookup on "o_custkey = c_custkey". This is used for both exists_to_in=ON and exists_to_in=OFF.
BKA is not possible in either case, because the subquery uses NOT EXISTS. It is not a semi-join.
Results from running DBT3/Q4/SF30 on MariaDB-10.0.10 with exits-to-in either on or off. Execution times:
exists_to_in=off -> 284, 276, 280 (sec)
exists_to_in=on -> 261, 255, 257 (sec)
EXPLAIN plans attached.
Thanks.
Looking at the EXPLAINs. The query plans have the same structure. Exists-to-in conversion has enabled BKA for table lineitem. However, it didn't bring a lot of speedup.
Graphic trace of query's io when running with scale=1, cold buffer cache.
IO trace for exists_to_in=off. Things to note
1. there is no BKA (reads go back and forth)
2 the data seems to be highly correlated - lookups in lineitem are linear.
The Q4 variant I am using:
select o_orderpriority, count(*) as order_count from orders where o_orderdate >= '1995-06-06' and o_orderdate < date_add('1995-06-06', interval 3 month) and exists ( select * from lineitem where l_orderkey = o_orderkey and l_commitdate < l_receiptdate ) group by o_orderpriority order by o_orderpriority;