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.

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Related Changes in Gerrit:

	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
Resolved	Ladsgroup	T343098 [epic] Data Persistence Hypothesis WE 3.2.1
Resolved	Ladsgroup	T326181 Stop doing regex on SQL in Database
Open	None	T210206 Deprecate raw SQL conditions for IDatabase methods (select, insert, etc.)
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