Log.php

<?php

namespace Drupal\Core\Database;


/**
 * Database query logger.
 *
 * We log queries in a separate object rather than in the connection object
 * because we want to be able to see all queries sent to a given database, not
 * database target. If we logged the queries in each connection object we
 * would not be able to track what queries went to which target.
 *
 * Every connection has one and only one logging object on it for all targets
 * and logging keys.
 */
class Log {
    
    /**
     * Cache of logged queries. This will only be used if the query logger is enabled.
     *
     * The structure for the logging array is as follows:
     *
     * array(
     *   $logging_key = array(
     *     array('query' => '', 'args' => array(), 'caller' => '', 'target' => '', 'time' => 0),
     *     array('query' => '', 'args' => array(), 'caller' => '', 'target' => '', 'time' => 0),
     *   ),
     * );
     *
     * @var array
     */
    protected $queryLog = [];
    
    /**
     * The connection key for which this object is logging.
     *
     * @var string
     */
    protected $connectionKey = 'default';
    
    /**
     * Constructor.
     *
     * @param $key
     *   The database connection key for which to enable logging.
     */
    public function __construct($key = 'default') {
        $this->connectionKey = $key;
    }
    
    /**
     * Begin logging queries to the specified connection and logging key.
     *
     * If the specified logging key is already running this method does nothing.
     *
     * @param $logging_key
     *   The identification key for this log request. By specifying different
     *   logging keys we are able to start and stop multiple logging runs
     *   simultaneously without them colliding.
     */
    public function start($logging_key) {
        if (empty($this->queryLog[$logging_key])) {
            $this->clear($logging_key);
        }
    }
    
    /**
     * Retrieve the query log for the specified logging key so far.
     *
     * @param $logging_key
     *   The logging key to fetch.
     *
     * @return
     *   An indexed array of all query records for this logging key.
     */
    public function get($logging_key) {
        return $this->queryLog[$logging_key];
    }
    
    /**
     * Empty the query log for the specified logging key.
     *
     * This method does not stop logging, it simply clears the log. To stop
     * logging, use the end() method.
     *
     * @param $logging_key
     *   The logging key to empty.
     */
    public function clear($logging_key) {
        $this->queryLog[$logging_key] = [];
    }
    
    /**
     * Stop logging for the specified logging key.
     *
     * @param $logging_key
     *   The logging key to stop.
     */
    public function end($logging_key) {
        unset($this->queryLog[$logging_key]);
    }
    
    /**
     * Log a query to all active logging keys.
     *
     * @param $statement
     *   The prepared statement object to log.
     * @param $args
     *   The arguments passed to the statement object.
     * @param $time
     *   The time in milliseconds the query took to execute.
     */
    public function log(StatementInterface $statement, $args, $time) {
        foreach (array_keys($this->queryLog) as $key) {
            $this->queryLog[$key][] = [
                'query' => $statement->getQueryString(),
                'args' => $args,
                'target' => $statement->dbh
                    ->getTarget(),
                'caller' => $this->findCaller(),
                'time' => $time,
            ];
        }
    }
    
    /**
     * Determine the routine that called this query.
     *
     * We define "the routine that called this query" as the first entry in
     * the call stack that is not inside the includes/Drupal/Database directory,
     * does not begin with db_ and does have a file (which excludes
     * call_user_func_array(), anonymous functions and similar). That makes the
     * climbing logic very simple, and handles the variable stack depth caused by
     * the query builders.
     *
     * See the @link http://php.net/debug_backtrace debug_backtrace() @endlink
     * function.
     *
     * @return
     *   This method returns a stack trace entry similar to that generated by
     *   debug_backtrace(). However, it flattens the trace entry and the trace
     *   entry before it so that we get the function and args of the function that
     *   called into the database system, not the function and args of the
     *   database call itself.
     */
    public function findCaller() {
        $stack = debug_backtrace();
        for ($i = 0, $stack_count = count($stack); $i < $stack_count; ++$i) {
            // If the call was made from a function, 'class' will be empty. It's
            // just easier to give it a default value than to try and integrate
            // that into the if statement below.
            if (empty($stack[$i + 1]['class'])) {
                $stack[$i + 1]['class'] = '';
            }
            if (strpos($stack[$i + 1]['class'], __NAMESPACE__) === FALSE && strpos($stack[$i + 1]['function'], 'db_') === FALSE && !empty($stack[$i]['file'])) {
                $stack[$i] += [
                    'file' => '?',
                    'line' => '?',
                    'args' => [],
                ];
                return [
                    'file' => $stack[$i]['file'],
                    'line' => $stack[$i]['line'],
                    'function' => $stack[$i + 1]['function'],
                    'class' => $stack[$i + 1]['class'],
                    'type' => isset($stack[$i + 1]['type']) ? $stack[$i + 1]['type'] : NULL,
                    'args' => $stack[$i + 1]['args'],
                ];
            }
        }
    }

}