Get archives: add filter to customize query LIMIT clause

[jeherve]

wp_get_archives already comes with 2 filters allowing one to customize some of the aspects of the queries to fetch archives on a site:

• getarchives_where allows you to customize the WHERE clause
• getarchives_join allows you to customize the JOIN clause

I think it would be useful to add a new filter, to allow customizing the LIMIT clause as well. In some environments, with sites with lots of posts with longform content, some of those queries can be really resource-intensive.

Note

I have 2 notes about my PR:

1. I used 7.0.0 as the since value. I'm not sure if I'm supposed to use a placeholder until this is ready for commit.
2. I used the same filter prefix as the other filters in the function, even though they do not follow the typical wp_ prefix of other, newer filters. Let me know if I should change that.

---

Trac ticket: https://core.trac.wordpress.org/ticket/64304

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[westonruter]

Is there a need to filter the actual LIMIT clause? Instead of filtering the clause, what about filtering the number for the limit? So up above instead of:

wordpress-develop/src/wp-includes/general-template.php

Lines 2034 to 2037 in 4cac4dc

	if ( ! empty( $parsed_args['limit'] ) ) {
	$parsed_args['limit'] = absint( $parsed_args['limit'] );
	$parsed_args['limit'] = ' LIMIT ' . $parsed_args['limit'];
	}

It could be:

	/**
	 * Filters the limit for the number of posts to include in the archive.
	 *
	 * @since 7.0.0
	 *
	 * @param int   $limit       The limit for the number of posts to include in the archive. Default 0.
	 * @param array $parsed_args An array of default arguments.
	 */
	$limit_number = (int) apply_filters( 'getarchives_limit', absint( $parsed_args['limit'] ), $parsed_args );
	if ( $limit_number > 0 ) {
		$limit = " LIMIT $limit_number";
	} else {
		$limit = '';
	}

[westonruter]

(I updated the code sample to set the $limit variable.)

[jeherve]

We can certainly do that. I pushed b4c617d with your exact suggestion.

I wondered if we needed to both cast as an integer and use absint.

[westonruter]

Yeah, I personally wouldn't have used absint() to begin with.

[westonruter]

Something that just came to mind: instead of introducing a filer specifically for the limit arg, what if there was a getarchives_args filter instead which filters the $parsed_args? This would be similar to other such filters like:

• wp_nav_menu_args
• wp_terms_checklist_args
• widget_archives_dropdown_args (and other widget filters)

[jeherve]

instead of introducing a filer specifically for the limit arg, what if there was a getarchives_args filter instead which filters the $parsed_args?

This would work ; I suppose it would then not be consistent with the existing filters for the archives though.

[westonruter]

I think that's OK. The other filters are explicitly lower-level for manipulating the SQL, whereas this limit filter is really just a subset of filtering all of the parsed args.

[jeherve]

I just pushed a new commit to try that.

[westonruter]

Any thoughts about placement of the filter before or after the $parsed_args are collected? Core is inconsistent on this, it seems. The wp_nav_menu_args filter applies after merging the passed $args with the $defaults (and some validation), whereas the wp_terms_checklist_args filter applies before merging the args with the defaults.

[westonruter]

This is a curious bit of code, isn't it. Wouldn't this already be the same as $parsed_args['post_type']?

[jeherve]

I suppose that may be a way to get capitalization right? It looks like it was added in https://core.trac.wordpress.org/ticket/21596

[jeherve]

Any thoughts about placement of the filter before or after the $parsed_args are collected?

I thought about it too, and figured it may be nice to have the filtering happen before, so we still come out with a consistently formatted $parsed_args.