<?php
/**
* Meta API: WP_Meta_Query class
*
* @package WordPress
* @subpackage Meta
* @since 4.4.0
*/

/**
* Core class used to implement meta queries for the Meta API.
*
* Used for generating SQL clauses that filter a primary query according to metadata keys and values.
*
* WP_Meta_Query is a helper that allows primary query classes, such as WP_Query and WP_User_Query,
*
* to filter their results by object metadata, by generating `JOIN` and `WHERE` subclauses to be attached
* to the primary SQL query string.
*
* @since 3.2.0
*/
#[AllowDynamicProperties]
class WP_Meta_Query {
/**
* Array of metadata queries.
*
* See WP_Meta_Query::__construct() for information on meta query arguments.
*
* @since 3.2.0
* @var array
*/
public $queries = array();

/**
* The relation between the queries. Can be one of 'AND' or 'OR'.
*
* @since 3.2.0
* @var string
*/
public $relation;

/**
* Database table to query for the metadata.
*
* @since 4.1.0
* @var string
*/
public $meta_table;

/**
* Column in meta_table that represents the ID of the object the metadata belongs to.
*
* @since 4.1.0
* @var string
*/
public $meta_id_column;

/**
* Database table that where the metadata's objects are stored (eg $wpdb->users).
*
* @since 4.1.0
* @var string
*/
public $primary_table;

/**
* Column in primary_table that represents the ID of the object.
*
* @since 4.1.0
* @var string
*/
public $primary_id_column;

/**
* A flat list of table aliases used in JOIN clauses.
*
* @since 4.1.0
* @var array
*/
protected $table_aliases = array();

/**
* A flat list of clauses, keyed by clause 'name'.
*
* @since 4.2.0
* @var array
*/
protected $clauses = array();

/**
* Whether the query contains any OR relations.
*
* @since 4.3.0
* @var bool
*/
protected $has_or_relation = false;

/**
* Constructor.
*
* @since 3.2.0
* @since 4.2.0 Introduced support for naming query clauses by associative array keys.
* @since 5.1.0 Introduced `$compare_key` clause parameter, which enables LIKE key matches.
* @since 5.3.0 Increased the number of operators available to `$compare_key`. Introduced `$type_key`,
* which enables the `$key` to be cast to a new data type for comparisons.
*
* @param array $meta_query {
* Array of meta query clauses. When first-order clauses or sub-clauses use strings as
* their array keys, they may be referenced in the 'orderby' parameter of the parent query.
*
* @type string $relation Optional. The MySQL keyword used to join the clauses of the query.
* Accepts 'AND' or 'OR'. Default 'AND'.
* @type array ...$0 {
* Optional. An array of first-order clause parameters, or another fully-formed meta query.
*
* @type string|string[] $key Meta key or keys to filter by.
* @type string $compare_key MySQL operator used for comparing the $key. Accepts:
* - '='
* - '!='
* - 'LIKE'
* - 'NOT LIKE'
* - 'IN'
* - 'NOT IN'
* - 'REGEXP'
* - 'NOT REGEXP'
* - 'RLIKE'
* - 'EXISTS' (alias of '=')
* - 'NOT EXISTS' (alias of '!=')
* Default is 'IN' when `$key` is an array, '=' otherwise.
* @type string $type_key MySQL data type that the meta_key column will be CAST to for
* comparisons. Accepts 'BINARY' for case-sensitive regular expression
* comparisons. Default is ''.
* @type string|string[] $value Meta value or values to filter by.
* @type string $compare MySQL operator used for comparing the $value. Accepts:
* - '='
* - '!='
* - '>'
* - '>='
* - '<'
* - '<='
* - 'LIKE'
* - 'NOT LIKE'
* - 'IN'
* - 'NOT IN'
* - 'BETWEEN'
* - 'NOT BETWEEN'
* - 'REGEXP'
* - 'NOT REGEXP'
* - 'RLIKE'
* - 'EXISTS'
* - 'NOT EXISTS'
* Default is 'IN' when `$value` is an array, '=' otherwise.
* @type string $type MySQL data type that the meta_value column will be CAST to for
* comparisons. Accepts:
* - 'NUMERIC'
* - 'BINARY'
* - 'CHAR'
* - 'DATE'
* - 'DATETIME'
* - 'DECIMAL'
* - 'SIGNED'
* - 'TIME'
* - 'UNSIGNED'
* Default is 'CHAR'.
* }
* }
*/
public function __construct( $meta_query = false ) {
if ( ! $meta_query ) {
return;
}

if ( isset( $meta_query['relation'] ) && 'OR' === strtoupper( $meta_query['relation'] ) ) {
$this->relation = 'OR';
} else {
$this->relation = 'AND';
}

$this->queries = $this->sanitize_query( $meta_query );
}

/**
* Ensures the 'meta_query' argument passed to the class constructor is well-formed.
*
* Eliminates empty items and ensures that a 'relation' is set.
*
* @since 4.1.0
*
* @param array $queries Array of query clauses.
* @return array Sanitized array of query clauses.
*/
public function sanitize_query( $queries ) {
$clean_queries = array();

if ( ! is_array( $queries ) ) {
return $clean_queries;
}

foreach ( $queries as $key => $query ) {
if ( 'relation' === $key ) {
$relation = $query;

} elseif ( ! is_array( $query ) ) {
continue;

// First-order clause.
} elseif ( $this->is_first_order_clause( $query ) ) {
if ( isset( $query['value'] ) && array() === $query['value'] ) {
unset( $query['value'] );
}

$clean_queries[ $key ] = $query;

// Otherwise, it's a nested query, so we recurse.
} else {
$cleaned_query = $this->sanitize_query( $query );

if ( ! empty( $cleaned_query ) ) {
$clean_queries[ $key ] = $cleaned_query;
}
}
}

if ( empty( $clean_queries ) ) {
return $clean_queries;
}

// Sanitize the 'relation' key provided in the query.
if ( isset( $relation ) && 'OR' === strtoupper( $relation ) ) {
$clean_queries['relation'] = 'OR';
$this->has_or_relation = true;

/*
* If there is only a single clause, call the relation 'OR'.
* This value will not actually be used to join clauses, but it
* simplifies the logic around combining key-only queries.
*/
} elseif ( 1 === count( $clean_queries ) ) {
$clean_queries['relation'] = 'OR';

// Default to AND.
} else {
$clean_queries['relation'] = 'AND';
}

return $clean_queries;
}

/**
* Determines whether a query clause is first-order.
*
* A first-order meta query clause is one that has either a 'key' or
* a 'value' array key.
*
* @since 4.1.0
*
* @param array $query Meta query arguments.
* @return bool Whether the query clause is a first-order clause.
*/
protected function is_first_order_clause( $query ) {
return isset( $query['key'] ) || isset( $query['value'] );
}

/**
* Constructs a meta query based on 'meta_*' query vars
*
* @since 3.2.0
*
* @param array $qv The query variables.
*/
public function parse_query_vars( $qv ) {
$meta_query = array();

/*
* For orderby=meta_value to work correctly, simple query needs to be
* first (so that its table join is against an unaliased meta table) and
* needs to be its own clause (so it doesn't interfere with the logic of
* the rest of the meta_query).
*/
$primary_meta_query = array();
foreach ( array( 'key', 'compare', 'type', 'compare_key', 'type_key' ) as $key ) {
if ( ! empty( $qv[ "meta_$key" ] ) ) {
$primary_meta_query[ $key ] = $qv[ "meta_$key" ];
}
}

// WP_Query sets 'meta_value' = '' by default.
if ( isset( $qv['meta_value'] ) && '' !== $qv['meta_value'] && ( ! is_array( $qv['meta_value'] ) || $qv['meta_value'] ) ) {
$primary_meta_query['value'] = $qv['meta_value'];
}

$existing_meta_query = isset( $qv['meta_query'] ) && is_array( $qv['meta_query'] ) ? $qv['meta_query'] : array();

if ( ! empty( $primary_meta_query ) && ! empty( $existing_meta_query ) ) {
$meta_query = array(
'relation' => 'AND',
$primary_meta_query,
$existing_meta_query,
);
} elseif ( ! empty( $primary_meta_query ) ) {
$meta_query = array(
$primary_meta_query,
);
} elseif ( ! empty( $existing_meta_query ) ) {
$meta_query = $existing_meta_query;
}

$this->__construct( $meta_query );
}

/**
* Returns the appropriate alias for the given meta type if applicable.
*
* @since 3.7.0
*
* @param string $type MySQL type to cast meta_value.
* @return string MySQL type.
*/
public function get_cast_for_type( $type = '' ) {
if ( empty( $type ) ) {
return 'CHAR';
}

$meta_type = strtoupper( $type );

if ( ! preg_match( '/^(?:BINARY|CHAR|DATE|DATETIME|SIGNED|UNSIGNED|TIME|NUMERIC(?:\(\d+(?:,\s?\d+)?\))?|DECIMAL(?:\(\d+(?:,\s?\d+)?\))?)$/', $meta_type ) ) {
return 'CHAR';
}

if ( 'NUMERIC' === $meta_type ) {
$meta_type = 'SIGNED';
}

return $meta_type;
}

/**
* Generates SQL clauses to be appended to a main query.
*
* @since 3.2.0
*
* @param string $type Type of meta. Possible values include but are not limited
* to 'post', 'comment', 'blog', 'term', and 'user'.
* @param string $primary_table Database table where the object being filtered is stored (eg wp_users).
* @param string $primary_id_column ID column for the filtered object in $primary_table.
* @param object $context Optional. The main query object that corresponds to the type, for
* example a `WP_Query`, `WP_User_Query`, or `WP_Site_Query`.
* Default null.
* @return string[]|false {
* Array containing JOIN and WHERE SQL clauses to append to the main query,
* or false if no table exists for the requested meta type.
*
* @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( $type, $primary_table, $primary_id_column, $context = null ) {
$meta_table = _get_meta_table( $type );
if ( ! $meta_table ) {
return false;
}

$this->table_aliases = array();

$this->meta_table = $meta_table;
$this->meta_id_column = sanitize_key( $type . '_id' );

$this->primary_table = $primary_table;
$this->primary_id_column = $primary_id_column;

$sql = $this->get_sql_clauses();

/*
* If any JOINs are LEFT JOINs (as in the case of NOT EXISTS), then all JOINs should
* be LEFT. Otherwise posts with no metadata will be excluded from results.
*/
if ( str_contains( $sql['join'], 'LEFT JOIN' ) ) {
$sql['join'] = str_replace( 'INNER JOIN', 'LEFT JOIN', $sql['join'] );
}

/**
* Filters the meta query's generated SQL.
*
* @since 3.1.0
*
* @param string[] $sql Array containing the query's JOIN and WHERE clauses.
* @param array $queries Array of meta queries.
* @param string $type Type of meta. Possible values include but are not limited
* to 'post', 'comment', 'blog', 'term', and 'user'.
* @param string $primary_table Primary table.
* @param string $primary_id_column Primary column ID.
* @param object $context The main query object that corresponds to the type, for
* example a `WP_Query`, `WP_User_Query`, or `WP_Site_Query`.
*/
return apply_filters_ref_array( 'get_meta_sql', array( $sql, $this->queries, $type, $primary_table, $primary_id_column, $context ) );
}

/**
* Generates SQL clauses to be appended to a main query.
*
* Called by the public WP_Meta_Query::get_sql(), this method is abstracted
* out to maintain parity with the other Query classes.
*
* @since 4.1.0
*
* @return string[] {
* Array containing JOIN and WHERE SQL clauses to append to the main 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.
* }
*/
protected function get_sql_clauses() {
/*
* $queries are passed by reference to get_sql_for_query() for recursion.
* To keep $this->queries unaltered, pass a copy.
*/
$queries = $this->queries;
$sql = $this->get_sql_for_query( $queries );

if ( ! empty( $sql['where'] ) ) {
$sql['where'] = ' AND ' . $sql['where'];
}

return $sql;
}

/**
* Generates 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
*
* @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 string[] {
* 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'];
} elseif ( 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, $key );

$where_count = count( $clause_sql['where'] );
if ( ! $where_count ) {
$sql_chunks['where'][] = '';
} elseif ( 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;
}

/**
* Generates 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
*
* @global wpdb $wpdb WordPress database abstraction object.
*
* @param array $clause Query clause (passed by reference).
* @param array $parent_query Parent query array.
* @param string $clause_key Optional. The array key used to name the clause in the original `$meta_query`
* parameters. If not provided, a key will be generated automatically.
* Default empty string.
* @return array {
* Array containing JOIN and WHERE SQL clauses to append to a first-order query.
*
* @type string[] $join Array of SQL fragments to append to the main JOIN clause.
* @type string[] $where Array of SQL fragments to append to the main WHERE clause.
* }
*/
public function get_sql_for_clause( &$clause, $parent_query, $clause_key = '' ) {
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' : '=';
}

$non_numeric_operators = array(
'=',
'!=',
'LIKE',
'NOT LIKE',
'IN',
'NOT IN',
'EXISTS',
'NOT EXISTS',
'RLIKE',
'REGEXP',
'NOT REGEXP',
);

$numeric_operators = array(
'>',
'>=',
'<',
'<=',
'BETWEEN',
'NOT BETWEEN',
);

if ( ! in_array( $clause['compare'], $non_numeric_operators, true ) && ! in_array( $clause['compare'], $numeric_operators, true ) ) {
$clause['compare'] = '=';
}

if ( isset( $clause['compare_key'] ) ) {
$clause['compare_key'] = strtoupper( $clause['compare_key'] );
} else {
$clause['compare_key'] = isset( $clause['key'] ) && is_array( $clause['key'] ) ? 'IN' : '=';
}

if ( ! in_array( $clause['compare_key'], $non_numeric_operators, true ) ) {
$clause['compare_key'] = '=';
}

$meta_compare = $clause['compare'];
$meta_compare_key = $clause['compare_key'];

// 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" : '';

if ( 'LIKE' === $meta_compare_key ) {
$join .= $wpdb->prepare( " ON ( $this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key LIKE %s )", '%' . $wpdb->esc_like( $clause['key'] ) . '%' );
} else {
$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;

// Determine the data type.
$_meta_type = isset( $clause['type'] ) ? $clause['type'] : '';
$meta_type = $this->get_cast_for_type( $_meta_type );
$clause['cast'] = $meta_type;

// Fallback for clause keys is the table alias. Key must be a string.
if ( is_int( $clause_key ) || ! $clause_key ) {
$clause_key = $clause['alias'];
}

// Ensure unique clause keys, so none are overwritten.
$iterator = 1;
$clause_key_base = $clause_key;
while ( isset( $this->clauses[ $clause_key ] ) ) {
$clause_key = $clause_key_base . '-' . $iterator;
++$iterator;
}

// Store the clause in our flat array.
$this->clauses[ $clause_key ] =& $clause;

// 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 {
/**
* In joined clauses negative operators have to be nested into a
* NOT EXISTS clause and flipped, to avoid returning records with
* matching post IDs but different meta keys. Here we prepare the
* nested clause.
*/
if ( in_array( $meta_compare_key, array( '!=', 'NOT IN', 'NOT LIKE', 'NOT EXISTS', 'NOT REGEXP' ), true ) ) {
// Negative clauses may be reused.
$i = count( $this->table_aliases );
$subquery_alias = $i ? 'mt' . $i : $this->meta_table;
$this->table_aliases[] = $subquery_alias;

$meta_compare_string_start = 'NOT EXISTS (';
$meta_compare_string_start .= "SELECT 1 FROM $wpdb->postmeta $subquery_alias ";
$meta_compare_string_start .= "WHERE $subquery_alias.post_ID = $alias.post_ID ";
$meta_compare_string_end = 'LIMIT 1';
$meta_compare_string_end .= ')';
}

switch ( $meta_compare_key ) {
case '=':
case 'EXISTS':
$where = $wpdb->prepare( "$alias.meta_key = %s", trim( $clause['key'] ) ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
break;
case 'LIKE':
$meta_compare_value = '%' . $wpdb->esc_like( trim( $clause['key'] ) ) . '%';
$where = $wpdb->prepare( "$alias.meta_key LIKE %s", $meta_compare_value ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
break;
case 'IN':
$meta_compare_string = "$alias.meta_key IN (" . substr( str_repeat( ',%s', count( $clause['key'] ) ), 1 ) . ')';
$where = $wpdb->prepare( $meta_compare_string, $clause['key'] ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
break;
case 'RLIKE':
case 'REGEXP':
$operator = $meta_compare_key;
if ( isset( $clause['type_key'] ) && 'BINARY' === strtoupper( $clause['type_key'] ) ) {
$cast = 'BINARY';
$meta_key = "CAST($alias.meta_key AS BINARY)";
} else {
$cast = '';
$meta_key = "$alias.meta_key";
}
$where = $wpdb->prepare( "$meta_key $operator $cast %s", trim( $clause['key'] ) ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
break;

case '!=':
case 'NOT EXISTS':
$meta_compare_string = $meta_compare_string_start . "AND $subquery_alias.meta_key = %s " . $meta_compare_string_end;
$where = $wpdb->prepare( $meta_compare_string, $clause['key'] ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
break;
case 'NOT LIKE':
$meta_compare_string = $meta_compare_string_start . "AND $subquery_alias.meta_key LIKE %s " . $meta_compare_string_end;

$meta_compare_value = '%' . $wpdb->esc_like( trim( $clause['key'] ) ) . '%';
$where = $wpdb->prepare( $meta_compare_string, $meta_compare_value ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
break;
case 'NOT IN':
$array_subclause = '(' . substr( str_repeat( ',%s', count( $clause['key'] ) ), 1 ) . ') ';
$meta_compare_string = $meta_compare_string_start . "AND $subquery_alias.meta_key IN " . $array_subclause . $meta_compare_string_end;
$where = $wpdb->prepare( $meta_compare_string, $clause['key'] ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
break;
case 'NOT REGEXP':
$operator = $meta_compare_key;
if ( isset( $clause['type_key'] ) && 'BINARY' === strtoupper( $clause['type_key'] ) ) {
$cast = 'BINARY';
$meta_key = "CAST($subquery_alias.meta_key AS BINARY)";
} else {
$cast = '';
$meta_key = "$subquery_alias.meta_key";
}

$meta_compare_string = $meta_compare_string_start . "AND $meta_key REGEXP $cast %s " . $meta_compare_string_end;
$where = $wpdb->prepare( $meta_compare_string, $clause['key'] ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
break;
}

$sql_chunks['where'][] = $where;
}
}

// meta_value.
if ( array_key_exists( 'value', $clause ) ) {
$meta_value = $clause['value'];

if ( in_array( $meta_compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ), true ) ) {
if ( ! is_array( $meta_value ) ) {
$meta_value = preg_split( '/[,\s]+/', $meta_value );
}
} elseif ( is_string( $meta_value ) ) {
$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':
$where = $wpdb->prepare( '%s AND %s', $meta_value[0], $meta_value[1] );
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 ) {
if ( 'CHAR' === $meta_type ) {
$sql_chunks['where'][] = "$alias.meta_value {$meta_compare} {$where}";
} else {
$sql_chunks['where'][] = "CAST($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;
}

/**
* Gets a flattened list of sanitized meta clauses.
*
* This array should be used for clause lookup, as when the table alias and CAST type must be determined for
* a value of 'orderby' corresponding to a meta clause.
*
* @since 4.2.0
*
* @return array Meta clauses.
*/
public function get_clauses() {
return $this->clauses;
}

/**
* Identifies 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 WP_Meta_Query, this only applies to 'IN' clauses that are
* connected by the relation 'OR'.
*
* @since 4.1.0
*
* @param array $clause Query clause.
* @param array $parent_query Parent query of $clause.
* @return string|false 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.
} elseif ( 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, true ) && in_array( $sibling_compare, $compatible_compares, true ) ) {
$alias = preg_replace( '/\W/', '_', $sibling['alias'] );
break;
}
}

/**
* Filters the table alias identified as compatible with the current clause.
*
* @since 4.1.0
*
* @param string|false $alias Table alias, or false if none was found.
* @param array $clause First-order query clause.
* @param array $parent_query Parent of $clause.
* @param WP_Meta_Query $query WP_Meta_Query object.
*/
return apply_filters( 'meta_query_find_compatible_table_alias', $alias, $clause, $parent_query, $this );
}

/**
* Checks whether the current query has any OR relations.
*
* In some cases, the presence of an OR relation somewhere in the query will require
* the use of a `DISTINCT` or `GROUP BY` keyword in the `SELECT` clause. The current
* method can be used in these cases to determine whether such a clause is necessary.
*
* @since 4.3.0
*
* @return bool True if the query contains any `OR` relations, otherwise false.
*/
public function has_or_relation() {
return $this->has_or_relation;
}
}