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MDEV-7487 Semi-join optimization for single-table update/delete statements

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This patch allows to use semi-join optimization at the top level of
single-table update and delete statements.
The problem of supporting such optimization became easy to resolve after
processing a single-table update/delete statement started using JOIN
structure. This allowed to use JOIN::prepare() not only for multi-table
updates/deletes but for single-table ones as well. This was done in the
patch for mdev-28883:
Re-design the upper level of handling UPDATE and DELETE statements.

Note that JOIN::prepare() detects all subqueries that can be considered
as candidates for semi-join optimization. The code added by this patch
looks for such candidates at the top level and if such candidates are found
in the processed single-table update/delete the statement is handled in
the same way as a multi-table update/delete.

    Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2023-01-09 22:39:39 -08:00
parent e2e3524d72
commit 554278e24d
14 changed files with 6198 additions and 35 deletions
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4
sql/opt_subselect.cc
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@@ -567,11 +567,11 @@ bool SELECT_LEX::is_sj_conversion_prohibited(THD *thd)
switch (thd->lex->sql_command) {
case SQLCOM_UPDATE:
return
!((Sql_cmd_update *) cmd)->is_multitable() ||
!((Sql_cmd_update *) cmd)->is_multitable() &&
((Sql_cmd_update *) cmd)->processing_as_multitable_update_prohibited(thd);
case SQLCOM_DELETE:
return
!((Sql_cmd_delete *) cmd)->is_multitable() ||
!((Sql_cmd_delete *) cmd)->is_multitable() &&
((Sql_cmd_delete *) cmd)->processing_as_multitable_delete_prohibited(thd);
default:
return false;