Monty a9d443c59d MDEV-39949 Add per-table "SQL_CACHE" option ...

Add SQL_CACHE=0|1 option for tables to disable/enable query caches if
table is part of the query.
SQL_CACHE option can be disable for a table by using SQL_CACHE=DEFAULT

Also provide a workaround for the problem described at:
MDEV-6631 "No cache directive(SQL_CACHE) query still wait for
query cache lock" on query_cache_type=DEMAND mode"
by adding DEMAND_STRICT mode.
The new mode is needed as modifying how DEMAND works would made the
change backward incompatible.

query_cache_type has now following options (0-2 are same as before)
OFF    (0) = Query cache off
ON     (1) = Query cache on, all queries are cached except queries marked
             with SQL_NO_CACHE
DEMAND (2) = Query cache on, only queries marked with SQL_CACHE are cached
DEMAND_STRICT
       (3) = Query cache on, only queries starting with SELECT SQL_CACHE
             are cached. This avoids a query cache lock+lookup for every
             query.
TABLES (4) = Query cache on, only cache queries marked with SQL_CACHE or
             where all used tables are using the create option SQL_CACHE=1

Note that if any of the tables used in the query has the create option
SQL_CACHE=0 or is a system table, temporary table or other non
cacheable table, then the query will not be cached.

SHOW CREATE TABLE prints SQL_CACHE=0|1 when the option is set. For tables
where the option can never apply (temporary tables, tables in the mysql
database, and engines that do not support the query cache) it is printed
as /* SQL_CACHE=1 */.

co-author: Seunguck Lee
- Took some changes related to MDEV-6631 from his patch.

2026-10-09 16:48:02 +03:00

642 KiB

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