[MDEV-31589] Secondary index MVCC access is unnecessarily inefficient - Jira

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Details

Type: Bug
Status: Stalled (View Workflow)
Priority: Critical
Resolution: Unresolved
Affects Version/s: 10.4(EOL), 10.5, 10.6, 10.7(EOL), 10.8(EOL), 10.9(EOL), 10.10(EOL), 10.11, 11.0(EOL), 11.1(EOL), 11.2
Fix Version/s: 10.6, 10.11, 11.2
Component/s: Storage Engine - InnoDB
Labels:
- performance

Description

As noted in ~~MDEV-31558~~, a covering secondary index read in InnoDB would look up the clustered index record twice and retrieve the matching version. In the test innodb.mvcc_secondary we have a table with 2 versions of 1 row, and the first SELECT statement would construct the old version of the clustered index not once, but twice.

~~MDEV-20301~~ replaced row_sel_get_clust_rec_for_mysql() with Row_sel_get_clust_rec_for_mysql::operator(), which adds some caching. It missed an opportunity to remove the call row_sel_sec_rec_is_for_clust_rec() and to perform those checks as part of the loop that invokes row_sel_build_prev_vers_for_mysql().

Attachments

Issue Links

relates to

MDEV-32286 ANALYZE displays a huge number of InnoDB secondary index pages_accessed

Confirmed

MDEV-17598 InnoDB index option for per-record transaction ID

Open

MDEV-20301 InnoDB's MVCC has O(N^2) behaviors

Closed

MDEV-31558 Add InnoDB engine information to the slow query log

Closed

Activity

People

Assignee:: Vladislav Lesin

Reporter:: Marko Mäkelä

Votes:: 1 Vote for this issue

Watchers:: 4 Start watching this issue

Dates

Created:: 2023-06-30 10:10

Updated:: 2024-09-27 09:02

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