Comment and term meta lazyloading for `WP_Query` loops, introduced in 4.4,
depended on filter callback methods belonging to `WP_Query` objects. This meant
storing `WP_Query` objects in the `$wp_filter` global (via `add_filter()`),
requiring that PHP retain the objects in memory, even when the local variables
would typically be expunged during normal garbage collection. In cases where a
large number of `WP_Query` objects were instantiated on a single pageload,
and/or where the contents of the `WP_Query` objects were quite large, serious
performance issues could result.
We skirt this problem by moving metadata lazyloading out of `WP_Query`. The
new `WP_Metadata_Lazyloader` class acts as a lazyload queue. Query instances
register items whose metadata should be lazyloaded - such as post terms, or
comments - and a `WP_Metadata_Lazyloader` method will intercept comment and
term meta requests to perform the cache priming. Since `WP_Metadata_Lazyloader`
instances are far smaller than `WP_Query` (containing only object IDs), and
clean up after themselves far better than the previous `WP_Query` methods (bp
only running their callbacks a single time for a given set of queued objects),
the resource use is decreased dramatically.
See [36525] for an earlier step in this direction.
Props lpawlik, stevegrunwell, boonebgorges.
Fixes#35816.
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The `$delete_all` flag in `delete_metadata()` triggers cache invalidation for
multiple objects. Previously, invalidation took place for all objects matching
the `$meta_key` parameter, regardless of whether `$meta_value` was also set.
This resulted in overly aggressive invalidation.
Props rahal.aboulfeth.
Fixes#35797.
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A meta_query containing an `OR` relation can result in the same record matching
multiple clauses, leading to duplicate results. The previous prevention against
duplicates [18178] #17582 became unreliable in 4.1 when `WP_Meta_Query`
introduced support for nested clauses. The current changeset adds a new method
`WP_Meta_Query::has_or_relation()` for checking whether an `OR` relation
appears anywhere in the query, and uses the new method in `WP_User_Query` to
enforce distinct results as necessary.
Props maxxsnake.
Fixes#32592.
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The implementation of `meta_query` orderby introduced in [31312] put clause
identifiers into a 'name' parameter of the clause. For greater clarity, this
changeset updates the syntax to use the associative array key used when
defining `meta_query` parameters, instead of the 'name' parameter.
Props Funkatronic, DrewAPicture.
Fixes#31045.
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`WP_Meta_Query` clauses now support a 'name' parameter. When building a
`WP_Query` object, the value of 'orderby' can reference this 'name', so that
it's possible to order by any clause in a meta_query, not just the first one
(as when using 'orderby=meta_value'). This improvement also makes it possible
to order by multiple meta query clauses (or by any other eligible field plus
a meta query clause), using the array syntax for 'orderby' introduced in [29027].
Props Funkatronic, boonebgorges.
Fixes#31045.
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It's necessary for hook docs to directly precede hook lines so the parser can correctly match them up. This change relocates hook docs for `update_{$meta_type}_meta`, `update_postmeta`, `updated_{$meta_type}_meta`, and `updated_postmeta`.
Fixes#11683.
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Per our inline documentation standards, no further use of the `@uses` tag is recommended as used and used-by relationships can be derived through other means. This removes most uses of the tag in core documentation, with remaining tags to be converted to `@global` or `@see` as they apply.
Fixes#30191.
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Passing orderby=meta_value and meta_key=foo to WP_Query should require that
each matched post have a meta value with the key 'foo'. To make this
requirement compatible with meta_query params that have the relation OR, we
nest the meta_query param, and join it using AND to a meta_query clause
generated from the meta_key/meta_compare/meta_type query vars.
Fixes#25538.
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The logic used to generate clause SQL in `WP_Meta_Query` is somewhat arcane,
stemming mostly from an ongoing effort to eliminate costly table joins when
they are not necessary. By systematizing the process of looking for shareable
joins - as was done in `WP_Tax_Query` [29902] - it becomes possible to simplify
the construction of SQL queries in `get_sql_for_clause()`. Moreover, the
simplified logic is actually considerably better at identifying shareable
joins, such that certain uses of `WP_Meta_Query` will see joins reduced by 50%
or more.
Includes integration tests for a representative cross-section of the query
clause combinations that result in shared table aliases.
Props boonebgorges, sc0ttkclark.
See #24093.
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Previously, meta query arguments could be joined by a single AND or OR relation.
Now, these queries can be arbitrarily nested, allowing clauses to be linked
together with multiple relations.
Adds unit tests for the new nesting syntax. Modifies a few existing unit tests
that were overly specific for the old SQL syntax. Backward compatibility with
existing syntax is fully maintained.
Props boonebgorges, DrewAPicture.
See #29642.
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