MDEV-38295, MDEV-38272 Sig11 in LEX::resolve_references_to_cte at sql/sql_cte.cc, mem leak #4486
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…ause CTE's are read only i.e It cannot have their columns updated in updates set clause. Attempting to do so , should throw error ERROR 1288 (HY000): The target table cte of the UPDATE is not updatable with cte as (select * from t1 where c < 5) update cte set cte.a =(select a from cte); Here, conversion from a single table to a multi table update bypasses the normal check by setting the TABLE_LIST object representing cte to be merge derived. This is incorrect, so we prohibit this conversion in TABLE_LIST::init_derived.
Lex::save_list contents remain from a previous query that has invalid syntax and isn't reset when processing a new query. We initialize this structure along with it's peer in LEX::start. MDEV-38295 Recursive CTE usage leaks memory when not used in a top level select During st_select_lex::cleanup() we assume that leaf tables and any associated recursive table references can only be present when a join structure is present. After MDEV-37220 this is no longer true. We shift our cleanup routine out of the test for a join. We add Multidelete_prelocking_strategy::handle_end() in the same manner as Multiupdate_prelocking_strategy::handle_end() (but with minimal processing as yet) to populate these leaf_tables in the outermost select when it is a delete statement. We add in a call to free_underlaid_joins() to the error processing section of Sql_cmd_dml::execute to free up temporary tables that were allocated in prepare, but not freed up when execute is bypassed because an error occured during prepare.
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Hi @sanja-byelkin you've already reviewed the previous commit in this tree. I've squashed the 2 bugfixes together, maybe i should squash the already reviewed fix too? |
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Description
Bugs fixes related to testing MDEV-37220 Allow UPDATE/DELETE to read from a CTE
Release Notes
N/A
How can this PR be tested?
mtr main.cte_update_delete
If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.
Basing the PR against the correct MariaDB version
mainbranch.PR quality check