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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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2
sql/sql_base.cc
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@@ -1214,7 +1214,7 @@ retry:
}
}
else if (thd->lex->sql_command == SQLCOM_DELETE)
{
{
Sql_cmd_delete *cmd= (Sql_cmd_delete *) (thd->lex->m_sql_cmd);
if (cmd->is_multitable() || derived->derived->outer_select())
materialize= false;