rdbms: Add way to issue UNION queries without raw SQL
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	Lucas_Werkmeister_WMDE
	Mar 31 2023, 2:15 PM

Description

Currently, the only way to issue a UNION query is to call $dbr->unionQueries(), which takes an array of SQL strings (that you hopefully got from $dbr->selectSQLText() or $selectQueryBuilder->getSQL(), rather than writing them by hand), and passing the resulting SQL string into $dbr->query(). If we want to phase out SQL strings in favor of Query objects (compare the end of the T326181 task description), we need some better way to make these queries.

Details

	Subject	Repo	Branch	Lines +/-
	EntityUsageTable: Use UnionQueryBuilder	mediawiki/extensions/Wikibase	master	+15 -13
	rdbms: Introduce UnionQueryBuilder	mediawiki/core	master	+148 -41

Customize query in gerrit

Related Objects
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Status	Assigned	Task
Open	Ladsgroup	T343098 [epic] Data Persistence Hypothesis WE 3.2.1
Open	Ladsgroup	T210206 Deprecate raw SQL conditions for IDatabase methods (select, insert, etc.)
Resolved	Ladsgroup	T326181 Stop doing regex on SQL in Database
Resolved	Lucas_Werkmeister_WMDE	T333690 rdbms: Add way to issue UNION queries without raw SQL

Event Timeline

Lucas_Werkmeister_WMDE created this task.Mar 31 2023, 2:15 PM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptMar 31 2023, 2:15 PM

One option might be a new UnionQueryBuilder class, with very few methods.

$uqb = $dbr->newUnionQueryBuilder();
$uqb->add( $dbr->newSelectQueryBuilder()
	->select( 'field1' )
	->from( 'table1' )
	->where( [ 'field2' => 'value' ] ) );
$res = $uqb->fetchResultSet();

It would probably just start out with a method to add a SelectQueryBuilder (maybe it could also accept strings for backwards compatibility?), and fetchResultSet(). Additional fetch*() methods could maybe be added later if needed, but I wouldn’t include them to begin with.

Lucas_Werkmeister_WMDE mentioned this in T333686: Warning: SQLPlatform::isWriteQuery fallback to regex (GoogleNewsSitemap).Mar 31 2023, 2:21 PM