ext being searched.
			 * @param WP_User_Query $query          The current WP_User_Query instance.
			 */
			$search_columns = apply_filters( 'user_search_columns', $search_columns, $search, $this );

			$this->query_where .= $this->get_search_sql( $search, $search_columns, $wild );
		}

		if ( ! empty( $include ) ) {
			// Sanitized earlier.
			$ids                = implode( ',', $include );
			$this->query_where .= " AND $wpdb->users.ID IN ($ids)";
		} elseif ( ! empty( $qv['exclude'] ) ) {
			$ids                = implode( ',', wp_parse_id_list( $qv['exclude'] ) );
			$this->query_where .= " AND $wpdb->users.ID NOT IN ($ids)";
		}

		// Date queries are allowed for the user_registered field.
		if ( ! empty( $qv['date_query'] ) && is_array( $qv['date_query'] ) ) {
			$date_query         = new WP_Date_Query( $qv['date_query'], 'user_registered' );
			$this->query_where .= $date_query->get_sql();
		}

		/**
		 * Fires after the WP_User_Query has been parsed, and before
		 * the query is executed.
		 *
		 * The passed WP_User_Query object contains SQL parts formed
		 * from parsing the given query.
		 *
		 * @since 3.1.0
		 *
		 * @param WP_User_Query $query Current instance of WP_User_Query (passed by reference).
		 */
		do_action_ref_array( 'pre_user_query', array( &$this ) );
	}

	/**
	 * Executes the query, with the current variables.
	 *
	 * @since 3.1.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 */
	public function query() {
		global $wpdb;

		$qv =& $this->query_vars;

		/**
		 * Filters the users array before the query takes place.
		 *
		 * Return a non-null value to bypass WordPress' default user queries.
		 *
		 * Filtering functions that require pagination information are encouraged to set
		 * the `total_users` property of the WP_User_Query object, passed to the filter
		 * by reference. If WP_User_Query does not perform a database query, it will not
		 * have enough information to generate these values itself.
		 *
		 * @since 5.1.0
		 *
		 * @param array|null    $results Return an array of user data to short-circuit WP's user query
		 *                               or null to allow WP to run its normal queries.
		 * @param WP_User_Query $query   The WP_User_Query instance (passed by reference).
		 */
		$this->results = apply_filters_ref_array( 'users_pre_query', array( null, &$this ) );

		if ( null === $this->results ) {
			$this->request = "
				SELECT {$this->query_fields}
				{$this->query_from}
				{$this->query_where}
				{$this->query_orderby}
				{$this->query_limit}
			";

			if ( is_array( $qv['fields'] ) || 'all' === $qv['fields'] ) {
				$this->results = $wpdb->get_results( $this->request );
			} else {
				$this->results = $wpdb->get_col( $this->request );
			}

			if ( isset( $qv['count_total'] ) && $qv['count_total'] ) {
				/**
				 * Filters SELECT FOUND_ROWS() query for the current WP_User_Query instance.
				 *
				 * @since 3.2.0
				 * @since 5.1.0 Added the `$this` parameter.
				 *
				 * @global wpdb $wpdb WordPress database abstraction object.
				 *
				 * @param string        $sql   The SELECT FOUND_ROWS() query for the current WP_User_Query.
				 * @param WP_User_Query $query The current WP_User_Query instance.
				 */
				$found_users_query = apply_filters( 'found_users_query', 'SELECT FOUND_ROWS()', $this );

				$this->total_users = (int) $wpdb->get_var( $found_users_query );
			}
		}

		if ( ! $this->results ) {
			return;
		}
		if (
			is_array( $qv['fields'] ) &&
			isset( $this->results[0]->ID )
		) {
			foreach ( $this->results as $result ) {
				$result->id = $result->ID;
			}
		} elseif ( 'all_with_meta' === $qv['fields'] ) {
			cache_users( $this->results );

			$r = array();
			foreach ( $this->results as $userid ) {
				$r[ $userid ] = new WP_User( $userid, '', $qv['blog_id'] );
			}

			$this->results = $r;
		} elseif ( 'all' === $qv['fields'] ) {
			foreach ( $this->results as $key => $user ) {
				$this->results[ $key ] = new WP_User( $user, '', $qv['blog_id'] );
			}
		}
	}

	/**
	 * Retrieves query variable.
	 *
	 * @since 3.5.0
	 *
	 * @param string $query_var Query variable key.
	 * @return mixed
	 */
	public function get( $query_var ) {
		if ( isset( $this->query_vars[ $query_var ] ) ) {
			return $this->query_vars[ $query_var ];
		}

		return null;
	}

	/**
	 * Sets query variable.
	 *
	 * @since 3.5.0
	 *
	 * @param string $query_var Query variable key.
	 * @param mixed  $value     Query variable value.
	 */
	public function set( $query_var, $value ) {
		$this->query_vars[ $query_var ] = $value;
	}

	/**
	 * Used internally to generate an SQL string for searching across multiple columns.
	 *
	 * @since 3.1.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string   $search  Search string.
	 * @param string[] $columns Array of columns to search.
	 * @param bool     $wild    Whether to allow wildcard searches. Default is false for Network Admin, true for single site.
	 *                          Single site allows leading and trailing wildcards, Network Admin only trailing.
	 * @return string
	 */
	protected function get_search_sql( $search, $columns, $wild = false ) {
		global $wpdb;

		$searches      = array();
		$leading_wild  = ( 'leading' === $wild || 'both' === $wild ) ? '%' : '';
		$trailing_wild = ( 'trailing' === $wild || 'both' === $wild ) ? '%' : '';
		$like          = $leading_wild . $wpdb->esc_like( $search ) . $trailing_wild;

		foreach ( $columns as $column ) {
			if ( 'ID' === $column ) {
				$searches[] = $wpdb->prepare( "$column = %s", $search );
			} else {
				$searches[] = $wpdb->prepare( "$column LIKE %s", $like );
			}
		}

		return ' AND (' . implode( ' OR ', $searches ) . ')';
	}

	/**
	 * Returns the list of users.
	 *
	 * @since 3.1.0
	 *
	 * @return array Array of results.
	 */
	public function get_results() {
		return $this->results;
	}

	/**
	 * Returns the total number of users for the current query.
	 *
	 * @since 3.1.0
	 *
	 * @return int Number of total users.
	 */
	public function get_total() {
		return $this->total_users;
	}

	/**
	 * Parses and sanitizes 'orderby' keys passed to the user query.
	 *
	 * @since 4.2.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string $orderby Alias for the field to order by.
	 * @return string Value to used in the ORDER clause, if `$orderby` is valid.
	 */
	protected function parse_orderby( $orderby ) {
		global $wpdb;

		$meta_query_clauses = $this->meta_query->get_clauses();

		$_orderby = '';
		if ( in_array( $orderby, array( 'login', 'nicename', 'email', 'url', 'registered' ), true ) ) {
			$_orderby = 'user_' . $orderby;
		} elseif ( in_array( $orderby, array( 'user_login', 'user_nicename', 'user_email', 'user_url', 'user_registered' ), true ) ) {
			$_orderby = $orderby;
		} elseif ( 'name' === $orderby || 'display_name' === $orderby ) {
			$_orderby = 'display_name';
		} elseif ( 'post_count' === $orderby ) {
			// @todo Avoid the JOIN.
			$where             = get_posts_by_author_sql( 'post' );
			$this->query_from .= " LEFT OUTER JOIN (
				SELECT post_author, COUNT(*) as post_count
				FROM $wpdb->posts
				$where
				GROUP BY post_author
			) p ON ({$wpdb->users}.ID = p.post_author)
			";
			$_orderby          = 'post_count';
		} elseif ( 'ID' === $orderby || 'id' === $orderby ) {
			$_orderby = 'ID';
		} elseif ( 'meta_value' === $orderby || $this->get( 'meta_key' ) == $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value";
		} elseif ( 'meta_value_num' === $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value+0";
		} elseif ( 'include' === $orderby && ! empty( $this->query_vars['include'] ) ) {
			$include     = wp_parse_id_list( $this->query_vars['include'] );
			$include_sql = implode( ',', $include );
			$_orderby    = "FIELD( $wpdb->users.ID, $include_sql )";
		} elseif ( 'nicename__in' === $orderby ) {
			$sanitized_nicename__in = array_map( 'esc_sql', $this->query_vars['nicename__in'] );
			$nicename__in           = implode( "','", $sanitized_nicename__in );
			$_orderby               = "FIELD( user_nicename, '$nicename__in' )";
		} elseif ( 'login__in' === $orderby ) {
			$sanitized_login__in = array_map( 'esc_sql', $this->query_vars['login__in'] );
			$login__in           = implode( "','", $sanitized_login__in );
			$_orderby            = "FIELD( user_login, '$login__in' )";
		} elseif ( isset( $meta_query_clauses[ $orderby ] ) ) {
			$meta_clause = $meta_query_clauses[ $orderby ];
			$_orderby    = sprintf( 'CAST(%s.meta_value AS %s)', esc_sql( $meta_clause['alias'] ), esc_sql( $meta_clause['cast'] ) );
		}

		return $_orderby;
	}

	/**
	 * Parses an 'order' query variable and casts it to ASC or DESC as necessary.
	 *
	 * @since 4.2.0
	 *
	 * @param string $order The 'order' query variable.
	 * @return string The sanitized 'order' query variable.
	 */
	protected function parse_order( $order ) {
		if ( ! is_string( $order ) || empty( $order ) ) {
			return 'DESC';
		}

		if ( 'ASC' === strtoupper( $order ) ) {
			return 'ASC';
		} else {
			return 'DESC';
		}
	}

	/**
	 * Makes private properties readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to get.
	 * @return mixed Property.
	 */
	public function __get( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return $this->$name;
		}
	}

	/**
	 * Makes private properties settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name  Property to check if set.
	 * @param mixed  $value Property value.
	 * @return mixed Newly-set property.
	 */
	public function __set( $name, $value ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return $this->$name = $value;
		}
	}

	/**
	 * Makes private properties checkable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to check if set.
	 * @return bool Whether the property is set.
	 */
	public function __isset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return isset( $this->$name );
		}
	}

	/**
	 * Makes private properties un-settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to unset.
	 */
	public function __unset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			unset( $this->$name );
		}
	}

	/**
	 * Makes private/protected methods readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name      Method to call.
	 * @param array  $arguments Arguments to pass when calling.
	 * @return mixed Return value of the callback, false otherwise.
	 */
	public function __call( $name, $arguments ) {
		if ( 'get_search_sql' === $name ) {
			return $this->get_search_sql( ...$arguments );
		}
		return false;
	}
}