[sawfly]

Allows meta queries to keep objects that have no value for a given meta key, e.g. when ordering by a meta field.

Trac ticket: https://core.trac.wordpress.org/ticket/19653

What

• New exclude_empty meta query clause argument and meta_exclude_empty query var. Both default to true, so current behavior is unchanged.
• When false, the meta table is LEFT JOINed with the key condition in the ON clause. With a value, the WHERE becomes ( id IS NULL OR <value condition> ).
• Key-restricted joins are never shared with sibling clauses, so OR relations stay correct.
• Only honored for compare_key = / EXISTS / IN. Ignored for compare => 'NOT EXISTS'.
• Documented in WP_Meta_Query and in the WP_Query, WP_User_Query, WP_Comment_Query, WP_Term_Query and WP_Site_Query docblocks.

Why the old patch was replaced

The 2013 patch only swapped INNER for LEFT JOIN. It kept meta_key = 'foo' in WHERE, which still filtered out the rows with no meta.

Testing

21 new tests in tests/query/metaQuery.php and tests/meta/query.php (--group 19653). They cover:

• default behavior and ordering by meta_value / meta_value_num
• combining with meta_query, multiple LEFT-joined clauses with named orderby, and OR / nested relations
• IN keys and the cases where the flag is ignored
• WP_User_Query
• the generated SQL

Notes

• With ASC, objects without the meta sort first because MySQL orders NULLs first (see comment Patch for track ticket 42724 #10). Sorting them last could be a follow-up.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude (Antropic)
Model(s): Opus 5.5
Used for: Refreshing patch, writing code, generating PR description. Code was reviewed and tested by me.

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