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MDEV-32148 Inefficient WHERE timestamp_column=datetime_const_expr

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Changing the way how a the following conditions are evaluated:

    WHERE timestamp_column=datetime_const_expr

(for all comparison operators: =, <=>, <, >, <=, >=, <> and for NULLIF)

Before the change it was always performed as DATETIME.
That was not efficient, as involved per-row TIMESTAMP->DATETIME conversion
for timestamp_column. For example, in case of the SYSTEM time zone
it involved a localtime_r() call, which is known to be slow.

After the change it's performed as TIMESTAMP in many cases.
This allows to avoid per-row conversion, as it works the other way around:
datetime_const_expr is converted to TIMESTAMP once before the execution stage.

Note, datetime_const_expr must be inside monotone continuous periods of
the current time zone, i.e. not near these anomalies:
- DST changes (spring forward, fall back)
- leap seconds
This commit is contained in:
Alexander Barkov
2023-09-12 11:27:54 +04:00
parent af4f9daeb8
commit 351a8eecf0
23 changed files with 1543 additions and 24 deletions
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6
mysql-test/suite/versioning/r/select.result
View File

@@ -155,21 +155,21 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3 100.00 Using where
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`t1`.`x` AS `IJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` where `test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t2`.`row_end` > @`t0` and `test`.`t2`.`row_start` <= @`t0` and `test`.`t1`.`row_end` > @`t0` and `test`.`t1`.`row_start` <= @`t0`
Note 1003 select `test`.`t1`.`x` AS `IJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` where `test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t2`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t2`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu'
explain extended select * from (select t1.x as LJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2 from t1 left join t2 on t1.x = t2.x)
for system_time as of timestamp @t0 as t;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 100.00 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 3 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`t1`.`x` AS `LJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` left join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` on(`test`.`t2`.`x` = `test`.`t1`.`x` and `test`.`t2`.`row_end` > @`t0` and `test`.`t2`.`row_start` <= @`t0`) where `test`.`t1`.`row_end` > @`t0` and `test`.`t1`.`row_start` <= @`t0`
Note 1003 select `test`.`t1`.`x` AS `LJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` left join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` on(`test`.`t2`.`x` = `test`.`t1`.`x` and `test`.`t2`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t2`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu') where `test`.`t1`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu'
explain extended select * from (select t1.x as RJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2 from t1 right join t2 on t1.x = t2.x)
for system_time as of timestamp @t0 as t;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3 100.00 Using where
1 SIMPLE t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`t1`.`x` AS `RJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` left join `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` on(`test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t1`.`row_end` > @`t0` and `test`.`t1`.`row_start` <= @`t0`) where `test`.`t2`.`row_end` > @`t0` and `test`.`t2`.`row_start` <= @`t0`
Note 1003 select `test`.`t1`.`x` AS `RJ2_x1`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` left join `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP @`t0` on(`test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t1`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu') where `test`.`t2`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t2`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu'
select * from (select t1.x as IJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2 from t1 inner join t2 on t1.x = t2.x)
for system_time as of timestamp @t0 as t;
IJ2_x1 y1 x2 y2