commit c36720388d5

Author: Sergei Petrunia <psergey@askmonty.org>

Date:   Thu Jan 28 21:43:55 2021 +0300

    MDEV-9750: Quick memory exhaustion with 'extended_keys=on' ...

    (Variant #5, full patch, for 10.5)

    Do not produce SEL_ARG graphs that would yield huge numbers of ranges.

    Introduce a concept of SEL_ARG graph's "weight". If we are about to

    produce a graph whose "weight" exceeds the limit, remove the parts

    of SEL_ARG graph that represent the biggest key parts. Do so until

    the graph's is within the limit.

    Includes

    - debug code to verify SEL_ARG graph weight

    - A user-visible @@optimizer_max_sel_arg_weight to control the optimization

    - Logging the optimization into the optimizer trace.

CREATE TABLE IF NOT EXISTS `mariadb_bug` (

  `SubID` int(7) NOT NULL,

  `Token` bigint(20) unsigned NOT NULL,

  `Date` datetime NOT NULL DEFAULT current_timestamp(),

  `SteamID` varchar(20) CHARACTER SET ascii COLLATE ascii_bin NOT NULL DEFAULT '',

  `IpAddress` varchar(40) CHARACTER SET ascii COLLATE ascii_bin DEFAULT NULL,

  UNIQUE KEY `SubID` (`SubID`,`Token`,`SteamID`) USING BTREE

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

SELECT `SubID`, `Token` 

FROM `mariadb_bug` 

WHERE `SubID` IN (<13800 constants in quotes>);