+ /**
+ * Generate SQL clauses for a single query array.
+ *
+ * If nested subqueries are found, this method recurses the tree to
+ * produce the properly nested SQL.
+ *
+ * @since 4.1.0
+ * @access protected
+ *
+ * @param array $query Query to parse, passed by reference.
+ * @param int $depth Optional. Number of tree levels deep we currently are.
+ * Used to calculate indentation. Default 0.
+ * @return array {
+ * Array containing JOIN and WHERE SQL clauses to append to a single query array.
+ *
+ * @type string $join SQL fragment to append to the main JOIN clause.
+ * @type string $where SQL fragment to append to the main WHERE clause.
+ * }
+ */
+ protected function get_sql_for_query( &$query, $depth = 0 ) {
+ $sql_chunks = array(
+ 'join' => array(),
+ 'where' => array(),
+ );
+
+ $sql = array(
+ 'join' => '',
+ 'where' => '',
+ );
+
+ $indent = '';
+ for ( $i = 0; $i < $depth; $i++ ) {
+ $indent .= " ";
+ }
+
+ foreach ( $query as $key => &$clause ) {
+ if ( 'relation' === $key ) {
+ $relation = $query['relation'];
+ } else if ( is_array( $clause ) ) {
+
+ // This is a first-order clause.
+ if ( $this->is_first_order_clause( $clause ) ) {
+ $clause_sql = $this->get_sql_for_clause( $clause, $query );
+
+ $where_count = count( $clause_sql['where'] );
+ if ( ! $where_count ) {
+ $sql_chunks['where'][] = '';
+ } else if ( 1 === $where_count ) {
+ $sql_chunks['where'][] = $clause_sql['where'][0];
+ } else {
+ $sql_chunks['where'][] = '( ' . implode( ' AND ', $clause_sql['where'] ) . ' )';
+ }
+
+ $sql_chunks['join'] = array_merge( $sql_chunks['join'], $clause_sql['join'] );
+ // This is a subquery, so we recurse.
+ } else {
+ $clause_sql = $this->get_sql_for_query( $clause, $depth + 1 );
+
+ $sql_chunks['where'][] = $clause_sql['where'];
+ $sql_chunks['join'][] = $clause_sql['join'];
+ }
+ }
+ }
+
+ // Filter to remove empties.
+ $sql_chunks['join'] = array_filter( $sql_chunks['join'] );
+ $sql_chunks['where'] = array_filter( $sql_chunks['where'] );
+
+ if ( empty( $relation ) ) {
+ $relation = 'AND';
+ }
+
+ // Filter duplicate JOIN clauses and combine into a single string.
+ if ( ! empty( $sql_chunks['join'] ) ) {
+ $sql['join'] = implode( ' ', array_unique( $sql_chunks['join'] ) );
+ }
+
+ // Generate a single WHERE clause with proper brackets and indentation.
+ if ( ! empty( $sql_chunks['where'] ) ) {
+ $sql['where'] = '( ' . "\n " . $indent . implode( ' ' . "\n " . $indent . $relation . ' ' . "\n " . $indent, $sql_chunks['where'] ) . "\n" . $indent . ')';
+ }
+
+ return $sql;
+ }
+
+ /**
+ * Generate SQL JOIN and WHERE clauses for a first-order query clause.
+ *
+ * "First-order" means that it's an array with a 'key' or 'value'.
+ *
+ * @since 4.1.0
+ * @access public
+ *
+ * @param array $clause Query clause, passed by reference.
+ * @param array $parent_query Parent query array.
+ * @return array {
+ * Array containing JOIN and WHERE SQL clauses to append to a first-order query.
+ *
+ * @type string $join SQL fragment to append to the main JOIN clause.
+ * @type string $where SQL fragment to append to the main WHERE clause.
+ * }
+ */
+ public function get_sql_for_clause( &$clause, $parent_query ) {
+ global $wpdb;
+
+ $sql_chunks = array(
+ 'where' => array(),
+ 'join' => array(),
+ );
+
+ if ( isset( $clause['compare'] ) ) {
+ $clause['compare'] = strtoupper( $clause['compare'] );
+ } else {
+ $clause['compare'] = isset( $clause['value'] ) && is_array( $clause['value'] ) ? 'IN' : '=';
+ }
+
+ if ( ! in_array( $clause['compare'], array(
+ '=', '!=', '>', '>=', '<', '<=',
+ 'LIKE', 'NOT LIKE',
+ 'IN', 'NOT IN',
+ 'BETWEEN', 'NOT BETWEEN',
+ 'EXISTS', 'NOT EXISTS',
+ 'REGEXP', 'NOT REGEXP', 'RLIKE'
+ ) ) ) {
+ $clause['compare'] = '=';
+ }
+
+ $meta_compare = $clause['compare'];
+
+ // First build the JOIN clause, if one is required.
+ $join = '';
+
+ // We prefer to avoid joins if possible. Look for an existing join compatible with this clause.
+ $alias = $this->find_compatible_table_alias( $clause, $parent_query );
+ if ( false === $alias ) {
+ $i = count( $this->table_aliases );
+ $alias = $i ? 'mt' . $i : $this->meta_table;
+
+ // JOIN clauses for NOT EXISTS have their own syntax.
+ if ( 'NOT EXISTS' === $meta_compare ) {
+ $join .= " LEFT JOIN $this->meta_table";
+ $join .= $i ? " AS $alias" : '';
+ $join .= $wpdb->prepare( " ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key = %s )", $clause['key'] );
+
+ // All other JOIN clauses.
+ } else {
+ $join .= " INNER JOIN $this->meta_table";
+ $join .= $i ? " AS $alias" : '';
+ $join .= " ON ( $this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column )";
+ }
+
+ $this->table_aliases[] = $alias;
+ $sql_chunks['join'][] = $join;
+ }
+
+ // Save the alias to this clause, for future siblings to find.
+ $clause['alias'] = $alias;
+
+ // Next, build the WHERE clause.
+
+ // meta_key.
+ if ( array_key_exists( 'key', $clause ) ) {
+ if ( 'NOT EXISTS' === $meta_compare ) {
+ $sql_chunks['where'][] = $alias . '.' . $this->meta_id_column . ' IS NULL';
+ } else {
+ $sql_chunks['where'][] = $wpdb->prepare( "$alias.meta_key = %s", trim( $clause['key'] ) );
+ }
+ }
+
+ // meta_value.
+ if ( array_key_exists( 'value', $clause ) ) {
+ $meta_value = $clause['value'];
+ $meta_type = $this->get_cast_for_type( isset( $clause['type'] ) ? $clause['type'] : '' );
+
+ if ( in_array( $meta_compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ) ) ) {
+ if ( ! is_array( $meta_value ) ) {
+ $meta_value = preg_split( '/[,\s]+/', $meta_value );
+ }
+ } else {
+ $meta_value = trim( $meta_value );
+ }
+
+ switch ( $meta_compare ) {
+ case 'IN' :
+ case 'NOT IN' :
+ $meta_compare_string = '(' . substr( str_repeat( ',%s', count( $meta_value ) ), 1 ) . ')';
+ $where = $wpdb->prepare( $meta_compare_string, $meta_value );
+ break;
+
+ case 'BETWEEN' :
+ case 'NOT BETWEEN' :
+ $meta_value = array_slice( $meta_value, 0, 2 );
+ $where = $wpdb->prepare( '%s AND %s', $meta_value );
+ break;
+
+ case 'LIKE' :
+ case 'NOT LIKE' :
+ $meta_value = '%' . $wpdb->esc_like( $meta_value ) . '%';
+ $where = $wpdb->prepare( '%s', $meta_value );
+ break;
+
+ // EXISTS with a value is interpreted as '='.
+ case 'EXISTS' :
+ $meta_compare = '=';
+ $where = $wpdb->prepare( '%s', $meta_value );
+ break;
+
+ // 'value' is ignored for NOT EXISTS.
+ case 'NOT EXISTS' :
+ $where = '';
+ break;
+
+ default :
+ $where = $wpdb->prepare( '%s', $meta_value );
+ break;
+
+ }
+
+ if ( $where ) {
+ $sql_chunks['where'][] = "CAST($alias.meta_value AS {$meta_type}) {$meta_compare} {$where}";
+ }
+ }
+
+ /*
+ * Multiple WHERE clauses (for meta_key and meta_value) should
+ * be joined in parentheses.
+ */
+ if ( 1 < count( $sql_chunks['where'] ) ) {
+ $sql_chunks['where'] = array( '( ' . implode( ' AND ', $sql_chunks['where'] ) . ' )' );
+ }
+
+ return $sql_chunks;
+ }
+
+ /**
+ * Identify an existing table alias that is compatible with the current
+ * query clause.
+ *
+ * We avoid unnecessary table joins by allowing each clause to look for
+ * an existing table alias that is compatible with the query that it
+ * needs to perform.
+ *
+ * An existing alias is compatible if (a) it is a sibling of `$clause`
+ * (ie, it's under the scope of the same relation), and (b) the combination
+ * of operator and relation between the clauses allows for a shared table join.
+ * In the case of {@see WP_Meta_Query}, this only applies to 'IN' clauses that
+ * are connected by the relation 'OR'.
+ *
+ * @since 4.1.0
+ * @access protected
+ *
+ * @param array $clause Query clause.
+ * @param array $parent_query Parent query of $clause.
+ * @return string|bool Table alias if found, otherwise false.
+ */
+ protected function find_compatible_table_alias( $clause, $parent_query ) {
+ $alias = false;
+
+ foreach ( $parent_query as $sibling ) {
+ // If the sibling has no alias yet, there's nothing to check.
+ if ( empty( $sibling['alias'] ) ) {
+ continue;
+ }
+
+ // We're only interested in siblings that are first-order clauses.
+ if ( ! is_array( $sibling ) || ! $this->is_first_order_clause( $sibling ) ) {
+ continue;
+ }
+
+ $compatible_compares = array();
+
+ // Clauses connected by OR can share joins as long as they have "positive" operators.
+ if ( 'OR' === $parent_query['relation'] ) {
+ $compatible_compares = array( '=', 'IN', 'BETWEEN', 'LIKE', 'REGEXP', 'RLIKE', '>', '>=', '<', '<=' );
+
+ // Clauses joined by AND with "negative" operators share a join only if they also share a key.
+ } else if ( isset( $sibling['key'] ) && isset( $clause['key'] ) && $sibling['key'] === $clause['key'] ) {
+ $compatible_compares = array( '!=', 'NOT IN', 'NOT LIKE' );
+ }
+
+ $clause_compare = strtoupper( $clause['compare'] );
+ $sibling_compare = strtoupper( $sibling['compare'] );
+ if ( in_array( $clause_compare, $compatible_compares ) && in_array( $sibling_compare, $compatible_compares ) ) {
+ $alias = $sibling['alias'];
+ break;
+ }
+ }
+
+ /**
+ * Filter the table alias identified as compatible with the current clause.
+ *
+ * @since 4.1.0
+ *
+ * @param string|bool $alias Table alias, or false if none was found.
+ * @param array $clause First-order query clause.
+ * @param array $parent_query Parent of $clause.
+ * @param object $this WP_Meta_Query object.
+ */
+ return apply_filters( 'meta_query_find_compatible_table_alias', $alias, $clause, $parent_query, $this ) ;
+ }