WP_Query: force deterministic ordering #10262

ramonjd · 2025-10-15T02:25:19Z

I'm testing out an approach to fix a long-standing issue:

https://core.trac.wordpress.org/ticket/47642
https://core.trac.wordpress.org/ticket/52907
https://core.trac.wordpress.org/ticket/64042
https://core.trac.wordpress.org/ticket/44349
https://core.trac.wordpress.org/ticket/8107 (17 years! 🏅 )

Unit tests to come once I've validated the approach.

This change addresses potential duplicate records across pages when multiple posts share the same value for a field.

It updates WP_Query ordering to ensure deterministic results by adding ID as a secondary sort field.

ramonjd · 2025-10-15T02:30:55Z

src/wp-includes/class-wp-query.php

+				'post_date', 
+				'post_title',
+				'post_modified',
+				'post_mime_type',


Added to test #10135

ramonjd · 2025-10-15T02:38:20Z

src/wp-includes/class-wp-query.php

 			$orderby = '';
 		} else {
-			$orderby_array = array();
+			/*


@peterwilsoncc When you get a spare moment (can be after 6.9 or whenever you have head space) could you sanity check this approach for me?

The TL;DR is:

When multiple posts have identical values for the primary sort field (like post_date, post_title, menu_order), the database doesn't guarantee consistent ordering across pagination.

This causes inconsistent pagination results, mainly in the form of dupes.

The solution here (and in all the other attempts from 6 years ago) has been to automatically add ID as a secondary sort field when ordering by fields that can have duplicate values. This ensures records with identical primary sort values always appear in the same order.

github-actions · 2025-10-15T02:59:39Z

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ramonjd · 2025-10-17T06:48:31Z

src/wp-includes/class-wp-query.php

+					$orderby = "{$wpdb->posts}.post_date " . $query_vars['order'] . ', ' . "{$wpdb->posts}.ID " . $query_vars['order'];
+				} elseif ( $needs_deterministic_orderby && ! $has_id_orderby ) {
+					// Add ID as tie-breaker for deterministic ordering
+					$orderby .= ", {$wpdb->posts}.ID " . $query_vars['order'];


TODO - don't forget search below. Might need it as well.

See https://github.com/WordPress/wordpress-develop/pull/1762/files#diff-1d050668621cbc3028e027d15e68438f4d879dd6e80ba98f9c9f69b9fb5469d0R2425

github-actions · 2025-10-21T22:33:44Z

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ramonjd · 2025-10-22T05:50:29Z

src/wp-includes/class-wp-query.php

+			$new_request = $this->request;
+			// Split SQL into parts.
+			$parts = explode( 'ORDER BY', $new_request );
+			if ( count( $parts ) === 2 ) {
+				// Replace only in the SELECT part, preserve ORDER BY.
+				$select_part = str_replace( $fields, "{$wpdb->posts}.*", $parts[0] );
+				$new_request = $select_part . 'ORDER BY' . $parts[1];
+			} else {
+				// No ORDER BY clause, safe to replace.
+				$new_request = str_replace( $fields, "{$wpdb->posts}.*", $new_request );
+			}


The current str_replace is too greedy in that it will replace strings in the ORDER BY clause as well.

…D as a secondary sort field. This change addresses potential duplicate records across pages when multiple posts share the same value for a field. A list of fields requiring deterministic ordering has been introduced to improve query consistency

…nding ID as a secondary sort field. Update related unit tests to reflect changes in expected SQL output for various orderby scenarios

…unit tests for orderby scenarios.

…and ensure ID is consistently used as a tie-breaker. Update unit tests to reflect changes in expected SQL output for various orderby cases.

…secondary sort field in various scenarios. Update unit tests to reflect changes in expected SQL output for orderby cases, enhancing determinism in query results.

…or consistent cache key generation. This change ensures deterministic results when 'date' is specified as the orderby value, improving query consistency.

…osts with identical dates, ensuring deterministic ordering in adjacent post queries.

ramonjd · 2025-10-22T07:05:15Z

src/wp-includes/link-template.php

 	 * @param WP_Post      $post           WP_Post object.
 	 */
-	$where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare( "WHERE p.post_date $op %s AND p.post_type = %s $where", $current_post_date, $post->post_type ), $in_same_term, $excluded_terms, $taxonomy, $post );
+	$where = apply_filters( "get_{$adjacent}_post_where", $wpdb->prepare( "WHERE (p.post_date $op %s OR (p.post_date = %s AND p.ID $op %d)) AND p.post_type = %s $where", $current_post_date, $current_post_date, $post->ID, $post->post_type ), $in_same_term, $excluded_terms, $taxonomy, $post );


This should be a separate patch.

I'm just testing things out for https://core.trac.wordpress.org/ticket/8107

peterwilsoncc · 2025-10-27T01:04:10Z

tests/phpunit/tests/query/deterministicOrdering.php

+			$post_ids[] = self::factory()->post->create(
+				array(
+					'post_title' => $identical_title,
+					'post_date'  => "2023-01-0$i 10:00:00",


This will end up with the dates 2023-01-010 through 2023-01-015 -- you could use str_pad( (string) $i, 2, '0', STR_PAD_LEFT ) instead

peterwilsoncc · 2025-10-27T01:08:39Z

src/wp-includes/class-wp-query.php

+			 * When multiple posts have the same value for a field, add ID as secondary sort to guarantee consistent ordering.
+			 * Note: this is to circumvent a bug that is currently being tracked in https://core.trac.wordpress.org/ticket/44349.
+			 */
+			$fields_requiring_deterministic_orderby = array(


Meta data (both values and keys) can be identical too. That will be a little messy because orderby also accepts the array keys in $meta_query.

The tickets are very long, so I'm wondering if it was considered to add the ID to the ordering if it wasn't included in the parameter already.

so I'm wondering if it was considered to add the ID to the ordering if it wasn't included in the parameter already.

Thanks, do you mean just include ID by default?

The whitelist is a bit janky and will add maintenance burden. I just did it as a very naive, first version to get a discussion going.

A previous, much older patch used a black list 'ID', 'rand', 'relevance'.

Not sure it would address the maintenance burden side of things, but it'd be more permissive.

peterwilsoncc · 2025-10-27T01:13:11Z

tests/phpunit/tests/query/deterministicOrdering.php

You could use some shared fixtures in this class to avoid creating the posts in each test for the ascending and descending equivalents.

For ease, you might want to register some post types wptests_time_ident, wptests_title_ident

Ooh! I'll look into it, cheers.

ramonjd force-pushed the try/add-id-for-deterministic-ordering-to-prevent-duplicate-records branch from 8f83b7e to 85339ff Compare October 15, 2025 02:30

ramonjd commented Oct 15, 2025

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ramonjd self-assigned this Oct 15, 2025

ramonjd changed the title ~~Modifies the resolve_pattern_blocks function to include metadata fo…~~ WP_Query: force deterministic ordering Oct 15, 2025

ramonjd commented Oct 15, 2025

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ramonjd added bug help wanted labels Oct 15, 2025

ramonjd commented Oct 17, 2025

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ramonjd commented Oct 22, 2025

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ramonjd added 12 commits October 22, 2025 17:28

WHITESPACE! Oh no!

75d6301

Refactor WP_Query ordering logic to ensure consistent results by appe…

3bddb55

…nding ID as a secondary sort field. Update related unit tests to reflect changes in expected SQL output for various orderby scenarios

Consolidate ID tie-breaker logic and ensure consistent SQL output in …

602c600

…unit tests for orderby scenarios.

whitespace in unit test

c2524e4

Refine WP_Query ordering logic to handle 'none' in orderby scenarios …

b7e002d

…and ensure ID is consistently used as a tie-breaker. Update unit tests to reflect changes in expected SQL output for various orderby cases.

lint

1552461

Remove ticket number in tests for now

81425bc

Refactor WP_Query to ensure consistent ordering by appending ID as a …

eac001e

…secondary sort field in various scenarios. Update unit tests to reflect changes in expected SQL output for orderby cases, enhancing determinism in query results.

Enhance WP_Query ordering logic by normalizing 'date' to 'date, ID' f…

4e17686

…or consistent cache key generation. This change ensures deterministic results when 'date' is specified as the orderby value, improving query consistency.

lint

377d50d

linto

03ff908

ramonjd force-pushed the try/add-id-for-deterministic-ordering-to-prevent-duplicate-records branch from 9c77315 to 03ff908 Compare October 22, 2025 06:30

Enhance get_adjacent_post function to include ID-based fallback for p…

a204b0d

…osts with identical dates, ensuring deterministic ordering in adjacent post queries.

ramonjd commented Oct 22, 2025

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ramonjd mentioned this pull request Oct 22, 2025

get_adjacent_post: Fix adjacent post navigation for posts with identical dates #10394

Closed

peterwilsoncc reviewed Oct 27, 2025

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ramonjd commented Oct 15, 2025 •

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