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Overhaul SQL generating logic in WP_Meta_Query to avoid unnecessary table joins.
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. Built from https://develop.svn.wordpress.org/trunk@29940 git-svn-id: http://core.svn.wordpress.org/trunk@29691 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This commit is contained in:
Boone Gorges
parent
ea679e358e
commit
9345e9ffa5
@ -987,6 +987,10 @@ class WP_Meta_Query {
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// First-order clause.
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} else if ( $this->is_first_order_clause( $query ) ) {
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if ( isset( $query['value'] ) && array() === $query['value'] ) {
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unset( $query['value'] );
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}
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$clean_queries[] = $query;
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// Otherwise, it's a nested query, so we recurse.
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@ -1167,7 +1171,12 @@ class WP_Meta_Query {
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* }
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*/
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protected function get_sql_clauses() {
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$sql = $this->get_sql_for_query( $this->queries );
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/*
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* $queries are passed by reference to get_sql_for_query() for recursion.
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* To keep $this->queries unaltered, pass a copy.
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*/
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$queries = $this->queries;
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$sql = $this->get_sql_for_query( $queries );
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if ( ! empty( $sql['where'] ) ) {
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$sql['where'] = ' AND ' . $sql['where'];
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@ -1195,7 +1204,7 @@ class WP_Meta_Query {
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* @type string $where SQL fragment to append to the main WHERE clause.
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* }
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*/
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protected function get_sql_for_query( $query, $depth = 0 ) {
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protected function get_sql_for_query( &$query, $depth = 0 ) {
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$sql_chunks = array(
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'join' => array(),
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'where' => array(),
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@ -1211,7 +1220,7 @@ class WP_Meta_Query {
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$indent .= " ";
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}
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foreach ( $query as $key => $clause ) {
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foreach ( $query as $key => &$clause ) {
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if ( 'relation' === $key ) {
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$relation = $query['relation'];
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} else if ( is_array( $clause ) ) {
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@ -1278,7 +1287,7 @@ class WP_Meta_Query {
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* @type string $where SQL fragment to append to the main WHERE clause.
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* }
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*/
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public function get_sql_for_clause( $clause, $parent_query ) {
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public function get_sql_for_clause( &$clause, $parent_query ) {
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global $wpdb;
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$sql_chunks = array(
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@ -1286,16 +1295,13 @@ class WP_Meta_Query {
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'join' => array(),
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);
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$i = count( $this->table_aliases );
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$alias = $i ? 'mt' . $i : $this->meta_table;
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if ( isset( $clause['compare'] ) ) {
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$meta_compare = strtoupper( $clause['compare'] );
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$clause['compare'] = strtoupper( $clause['compare'] );
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} else {
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$meta_compare = isset( $clause['value'] ) && is_array( $clause['value'] ) ? 'IN' : '=';
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$clause['compare'] = isset( $clause['value'] ) && is_array( $clause['value'] ) ? 'IN' : '=';
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}
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if ( ! in_array( $meta_compare, array(
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if ( ! in_array( $clause['compare'], array(
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'=', '!=', '>', '>=', '<', '<=',
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'LIKE', 'NOT LIKE',
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'IN', 'NOT IN',
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@ -1303,58 +1309,62 @@ class WP_Meta_Query {
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'EXISTS', 'NOT EXISTS',
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'REGEXP', 'NOT REGEXP', 'RLIKE'
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) ) ) {
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$meta_compare = '=';
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$clause['compare'] = '=';
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}
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/*
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* There are a number of different query structures that get
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* built in different ways.
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* 1. Key-only clauses - (a) clauses without a 'value' key that
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* appear in the context of an OR relation and do not use
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* 'NOT EXISTS' as the 'compare', or (b) clauses with an
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* empty array for 'value'.
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*/
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if ( ! empty( $clause['key'] ) && (
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( ! array_key_exists( 'value', $clause ) && 'NOT EXISTS' !== $meta_compare && 'OR' === $parent_query['relation'] ) ||
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( isset( $clause['value'] ) && is_array( $clause['value'] ) && empty( $clause['value'] ) )
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) ) {
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$meta_compare = $clause['compare'];
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$alias = $this->meta_table;
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$sql_chunks['join'][] = " INNER JOIN $this->meta_table ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column)";
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$sql_chunks['where'][] = $wpdb->prepare( "$this->meta_table.meta_key = %s", trim( $clause['key'] ) );
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// First build the JOIN clause, if one is required.
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$join = '';
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// 2. NOT EXISTS.
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} else if ( 'NOT EXISTS' === $meta_compare ) {
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$join = " LEFT JOIN $this->meta_table";
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// We prefer to avoid joins if possible. Look for an existing join compatible with this clause.
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$alias = $this->find_compatible_table_alias( $clause, $parent_query );
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if ( false === $alias ) {
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$i = count( $this->table_aliases );
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$alias = $i ? 'mt' . $i : $this->meta_table;
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// JOIN clauses for NOT EXISTS have their own syntax.
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if ( 'NOT EXISTS' === $meta_compare ) {
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$join .= " LEFT JOIN $this->meta_table";
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$join .= $i ? " AS $alias" : '';
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$join .= $wpdb->prepare( " ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key = %s )", $clause['key'] );
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$sql_chunks['join'][] = $join;
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$sql_chunks['where'][] = $alias . '.' . $this->meta_id_column . ' IS NULL';
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// All other JOIN clauses.
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} else {
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$alias = $this->find_compatible_table_alias( $clause, $parent_query );
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if ( false === $alias ) {
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$alias = $i ? 'mt' . $i : $this->meta_table;
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// 3. EXISTS and other key-only queries.
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} else if ( 'EXISTS' === $meta_compare || ( ! empty( $clause['key'] ) && ! array_key_exists( 'value', $clause ) ) ) {
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$join = " INNER JOIN $this->meta_table";
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$join .= " INNER JOIN $this->meta_table";
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$join .= $i ? " AS $alias" : '';
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$join .= " ON ( $this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column )";
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$sql_chunks['join'][] = $join;
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$sql_chunks['where'][] = $wpdb->prepare( $alias . '.meta_key = %s', trim( $clause['key'] ) );
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// 4. Clauses that have a value.
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} else if ( array_key_exists( 'value', $clause ) ) {
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$join = " INNER JOIN $this->meta_table";
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$join .= $i ? " AS $alias" : '';
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$join .= " ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column)";
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$sql_chunks['join'][] = $join;
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if ( ! empty( $clause['key'] ) ) {
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$sql_chunks['where'][] = $wpdb->prepare( "$alias.meta_key = %s", trim( $clause['key'] ) );
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}
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}
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$meta_type = $this->get_cast_for_type( isset( $clause['type'] ) ? $clause['type'] : '' );
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$this->table_aliases[] = $alias;
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$sql_chunks['join'][] = $join;
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}
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$meta_value = isset( $clause['value'] ) ? $clause['value'] : '';
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// Save the alias to this clause, for future siblings to find.
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$clause['alias'] = $alias;
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// Next, build the WHERE clause.
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$where = '';
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// meta_key.
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if ( array_key_exists( 'key', $clause ) ) {
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if ( 'NOT EXISTS' === $meta_compare ) {
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$sql_chunks['where'][] = $alias . '.' . $this->meta_id_column . ' IS NULL';
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} else {
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$sql_chunks['where'][] = $wpdb->prepare( "$alias.meta_key = %s", trim( $clause['key'] ) );
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}
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}
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// meta_value.
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if ( array_key_exists( 'value', $clause ) ) {
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$meta_value = $clause['value'];
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$meta_type = $this->get_cast_for_type( isset( $clause['type'] ) ? $clause['type'] : '' );
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if ( in_array( $meta_compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ) ) ) {
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if ( ! is_array( $meta_value ) ) {
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@ -1364,19 +1374,34 @@ class WP_Meta_Query {
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$meta_value = trim( $meta_value );
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}
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if ( 'IN' == substr( $meta_compare, -2 ) ) {
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switch ( $meta_compare ) {
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case 'IN' :
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case 'NOT IN' :
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$meta_compare_string = '(' . substr( str_repeat( ',%s', count( $meta_value ) ), 1 ) . ')';
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} elseif ( 'BETWEEN' == substr( $meta_compare, -7 ) ) {
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$where = $wpdb->prepare( $meta_compare_string, $meta_value );
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break;
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case 'BETWEEN' :
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case 'NOT BETWEEN' :
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$meta_value = array_slice( $meta_value, 0, 2 );
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$meta_compare_string = '%s AND %s';
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} elseif ( 'LIKE' == $meta_compare || 'NOT LIKE' == $meta_compare ) {
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$where = $wpdb->prepare( '%s AND %s', $meta_value );
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break;
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case 'LIKE' :
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case 'NOT LIKE' :
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$meta_value = '%' . $wpdb->esc_like( $meta_value ) . '%';
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$meta_compare_string = '%s';
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} else {
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$meta_compare_string = '%s';
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$where = $wpdb->prepare( '%s', $meta_value );
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break;
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default :
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$where = $wpdb->prepare( '%s', $meta_value );
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break;
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}
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$sql_chunks['where'][] = $wpdb->prepare( "CAST($alias.meta_value AS {$meta_type}) {$meta_compare} {$meta_compare_string}", $meta_value );
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if ( $where ) {
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$sql_chunks['where'][] = "CAST($alias.meta_value AS {$meta_type}) {$meta_compare} {$where}";
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}
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}
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/*
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@ -1387,10 +1412,62 @@ class WP_Meta_Query {
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$sql_chunks['where'] = array( '( ' . implode( ' AND ', $sql_chunks['where'] ) . ' )' );
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}
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$this->table_aliases[] = $alias;
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return $sql_chunks;
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}
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/**
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* Identify an existing table alias that is compatible with the current query clause.
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*
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* We avoid unnecessary table joins by allowing each clause to look for
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* an existing table alias that is compatible with the query that it
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* needs to perform. An existing alias is compatible if (a) it is a
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* sibling of $clause (ie, it's under the scope of the same relation),
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* and (b) the combination of operator and relation between the clauses
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* allows for a shared table join. In the case of WP_Meta_Query, this
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* only applies to IN clauses that are connected by the relation OR.
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*
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* @since 4.1.0
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* @access protected
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*
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* @param array $clause Query clause.
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* @param array $parent_query Parent query of $clause.
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* @return string|bool Table alias if found, otherwise false.
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*/
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protected function find_compatible_table_alias( $clause, $parent_query ) {
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$alias = false;
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foreach ( $parent_query as $sibling ) {
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// If the sibling has no alias yet, there's nothing to check.
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if ( empty( $sibling['alias'] ) ) {
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continue;
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}
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// We're only interested in siblings that are first-order clauses.
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if ( ! is_array( $sibling ) || ! $this->is_first_order_clause( $sibling ) ) {
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continue;
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}
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$compatible_compares = array();
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// Clauses connected by OR can share joins as long as they have "positive" operators.
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if ( 'OR' === $parent_query['relation'] ) {
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$compatible_compares = array( '=', 'IN', 'BETWEEN', 'LIKE', 'REGEXP', 'RLIKE', '>', '>=', '<', '<=' );
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// Clauses joined by AND with "negative" operators share a join only if they also share a key.
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} else if ( isset( $sibling['key'] ) && isset( $clause['key'] ) && $sibling['key'] === $clause['key'] ) {
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$compatible_compares = array( '!=', 'NOT IN', 'NOT LIKE' );
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}
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$clause_compare = strtoupper( $clause['compare'] );
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$sibling_compare = strtoupper( $sibling['compare'] );
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if ( in_array( $clause_compare, $compatible_compares ) && in_array( $sibling_compare, $compatible_compares ) ) {
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$alias = $sibling['alias'];
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break;
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}
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}
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return apply_filters( 'meta_query_find_compatible_table_alias', $alias, $clause, $parent_query, $this ) ;
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}
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}
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/**
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