get_page_by_title() lacks caching

[Viper007Bond]

get_page_by_title() always does a database query. It should use the object cache.

[solarissmoke]

Cache get_page_by_title queries

[SergeyBiryukov]

Related: #14983

[songsthatsaved]

Updated patch for 3.6

[songsthatsaved]

Updated the patch for 3.6, and find that it is working as expected. This is really just an update of solarissmoke's patch.

[SergeyBiryukov]

Note that 15805.diff​ performs an unnecessary database query before checking the cache.

15805.patch​ does not have this issue and still applies cleanly.

[tollmanz]

I think there are a few potential issues with the suggested patch.

1. $post_type should be considered in the cache key. If not, looking up the page with title "This is my title" will return the same result as a post with title "This is my title" if it is pulled from cache.
2. How is the cache invalidated? Theoretically, the value is being cached indefinitely (although different caching engine will likely naturally purge the cache over time), which can cause some bizarre behaviors. For instance, if a post with title "This is my title" is created, subsequently deleted, then a new post with title ""This is my title" is created, the cached value would be the ID of the original post. I think we would need something along the lines of the following code to run on post trash and delete:

$key = 'post_title_' . get_the_title( $post_id ) . get_post_type( $post_id );
wp_cache_delete( $key, 'posts' );

3. I think the patch needs further refreshing as get_page is used in the function, whereas current code uses get_post.

[tollmanz]

On further evaluation, I think that this ticket should be closed as wontfix. get_page_by_title is not used in core at all. To add a caching layer to the function and not address invalidation seems dangerous to me; however, to add invalidation into WordPress core for a function that is never used seems unnecessary. It seems that caching and cache invalidation of this function should be the responsibility of the plugin/theme author and not WordPress core.

[nacin]

I agree with tollmanz. Going further, I think the whole idea of fetching something by its title is wrong. It's not unique, or particularly identifying, and the field doesn't have an index. This is better left to WP_Query itself (i.e. a search), and I could even go for deprecating this in favor of a (new?) query variable in WP_Query.

[peterwilsoncc]

Replying to nacin:

This is better left to WP_Query itself (i.e. a search), and I could even go for deprecating this in favor of a (new?) query variable in WP_Query.

Now WP_Query has a title variable, is this worth reopening/a new ticket? My inclination is to set it up as a wrapper for get_pages.

[boonebgorges]

Now WP_Query has a title variable, is this worth reopening/a new ticket? My inclination is to set it up as a wrapper for get_pages.

Let's move discussion to #36905, which has a patch.