d in conjunction with startTransaction.
	 *
	 * @since 4.0.0
	 */
	public function commit() {
		$this->db->query( 'COMMIT' );
	}

	/**
	 * This will rollback a MySQL transaction. Used in conjunction with startTransaction.
	 *
	 * @since 4.0.0
	 */
	public function rollback() {
		$this->db->query( 'ROLLBACK' );
	}

	/**
	 * Fast way to execute raw queries.
	 * NOTE: When using this method, all arguments must be sanitized manually!
	 *
	 * @since 4.0.0
	 *
	 * @param  string $sql      The sql query to execute.
	 * @param  bool   $results  Whether to return the results or not.
	 * @param  bool   $useCache Whether to use the cache or not.
	 * @return mixed            Could be an array or object depending on the result set.
	 */
	public function execute( $sql, $results = false, $useCache = false ) {
		$this->lastQuery = $sql;
		$queryHash       = sha1( $sql );
		$cacheTableName  = $this->getCacheTableName();

		// Pull the result from the in-memory cache if everything checks out.
		if (
			$useCache &&
			! $this->shouldResetCache &&
			isset( $this->cache[ $cacheTableName ][ $queryHash ] )
		) {
			if ( $results ) {
				$this->result = $this->cache[ $cacheTableName ][ $queryHash ];
			}

			return $this;
		}

		if ( $results ) {
			$this->result = $this->db->get_results( $sql, $this->output );

			if ( $useCache ) {
				$this->cache[ $cacheTableName ][ $queryHash ] = $this->result;

				// Reset the cache trigger for the next run.
				$this->shouldResetCache = false;
			}

			return $this;
		}

		return $this->db->query( $sql );
	}

	/**
	 * Escape a value for safe use in SQL queries.
	 *
	 * @param string   $value   The value to be escaped.
	 * @param int|null $options The escape options.
	 * @return string           The escaped SQL value.
	 */
	public function escape( $value, $options = null ) {
		if ( is_array( $value ) ) {
			foreach ( $value as &$val ) {
				$val = $this->escape( $val, $options );
			}

			return $value;
		}

		$options = ( is_null( $options ) ) ? $this->getEscapeOptions() : $options;
		if ( ( $options & self::ESCAPE_STRIP_HTML ) !== 0 && isset( $this->stripTags ) && true === $this->stripTags ) {
			$value = wp_strip_all_tags( $value );
		}

		if (
			( ( $options & self::ESCAPE_FORCE ) !== 0 || php_sapi_name() === 'cli' ) ||
			( ( $options & self::ESCAPE_QUOTE ) !== 0 && ! is_int( $value ) )
		) {
			$value = esc_sql( $value );
			if ( ! is_int( $value ) ) {
				$value = "'$value'";
			}
		}

		return $value;
	}

	/**
	 * Returns the current escape options value.
	 *
	 * @since 4.0.0
	 *
	 * @return int The current escape options value.
	 */
	public function getEscapeOptions() {
		return $this->escapeOptions;
	}


	/**
	 * Sets the current escape options value.
	 *
	 * @since 4.0.0
	 *
	 * @param int $options The escape options value.
	 */
	public function setEscapeOptions( $options ) {
		$this->escapeOptions = $options;
	}

	/**
	 * Backtick-escapes an array of column and/or table names.
	 *
	 * @since 4.0.0
	 *
	 * @param  array $cols An array of column names to be escaped.
	 * @return array       An array of escaped column names.
	 */
	private function escapeColNames( $cols ) {
		if ( ! is_array( $cols ) ) {
			$cols = [ $cols ];
		}

		foreach ( $cols as &$col ) {
			if ( false === stripos( $col, '(' ) && false === stripos( $col, ' ' ) && false === stripos( $col, '*' ) ) {
				if ( stripos( $col, '.' ) ) {
					list( $table, $c ) = explode( '.', $col );
					$col = "`$table`.`$c`";
					continue;
				}

				$col = "`$col`";
			}
		}

		return $cols;
	}

	/**
	 * Gets a variable list of function arguments and reformats them as needed for many of the functions of this class.
	 *
	 * @since 4.0.0
	 *
	 * @param  mixed $values This could be anything, but if used properly it usually is a string or an array.
	 * @return mixed         If the preparation was successful, it will return an array of arguments. Otherwise it could be anything.
	 */
	private function prepArgs( $values ) {
		$values = (array) $values;
		if ( ! is_array( $values[0] ) && count( $values ) === 2 ) {
			$values = [ $values[0] => $values[1] ];
		} elseif ( is_array( $values[0] ) && count( $values ) === 1 ) {
			$values = $values[0];
		}

		return $values;
	}

	/**
	 * Resets all the variables that make up the query.
	 *
	 * @since 4.0.0
	 *
	 * @param  array    $what Set which properties you want to reset. All are selected by default.
	 * @return Database       Returns the Database instance.
	 */
	public function reset(
		$what = [
			'table',
			'statement',
			'limit',
			'group',
			'order',
			'select',
			'set',
			'onDuplicate',
			'ignore',
			'where',
			'union',
			'distinct',
			'orderDirection',
			'query',
			'output',
			'stripTags',
			'models',
			'join'
		]
	) {
		// If we are not running a select query, let's bust the cache for this table.
		$selectStatements = [ 'SELECT', 'SELECT DISTINCT' ];
		if (
			! empty( $this->statement ) &&
			! in_array( $this->statement, $selectStatements, true )
		) {
			$this->bustCache( $this->getCacheTableName() );
		}

		foreach ( (array) $what as $var ) {
			switch ( $var ) {
				case 'group':
				case 'order':
				case 'select':
				case 'set':
				case 'onDuplicate':
				case 'where':
				case 'union':
				case 'join':
					$this->$var = [];
					break;
				case 'orderDirection':
					$this->$var = 'ASC';
					break;
				case 'ignore':
				case 'stripTags':
					$this->$var = false;
					break;
				case 'output':
					$this->$var = 'OBJECT';
					break;
				default:
					if ( isset( $this->$var ) ) {
						$this->$var = null;
					}
					break;
			}
		}

		return $this;
	}

	/**
	 * Returns the current value of one or more query properties.
	 *
	 * @since 4.0.0
	 *
	 * @param  string|array  $what You can pass in an array of options to retrieve. By default it selects all if them.
	 * @return string|array       Returns the value of whichever variables are passed in.
	 */
	public function getQueryProperty(
		$what = [
			'table',
			'statement',
			'limit',
			'group',
			'order',
			'select',
			'set',
			'onDuplicate',
			'where',
			'union',
			'distinct',
			'orderDirection',
			'query',
			'output',
			'result'
		]
	) {
		if ( is_array( $what ) ) {
			$return = [];
			foreach ( (array) $what as $which ) {
				$return[ $which ] = $this->$which;
			}

			return $return;
		}

		return $this->$what;
	}

	/**
	 * Get a table name for the cache key.
	 *
	 * @since 4.1.6
	 *
	 * @param  string $cacheTableName The table name to check against.
	 * @return string                 The cache key table name.
	 */
	private function getCacheTableName( $cacheTableName = '' ) {
		$cacheTableName = empty( $cacheTableName ) ? $this->table : $cacheTableName;

		foreach ( $this->customTables as $tableName ) {
			if ( false !== stripos( (string) $cacheTableName, $this->prefix . $tableName ) ) {
				$cacheTableName = $tableName;
				break;
			}
		}

		return $cacheTableName;
	}

	/**
	 * Busts the cache for the given table name.
	 *
	 * @since 4.1.6
	 *
	 * @param  string $tableName The table name.
	 * @return void
	 */
	public function bustCache( $tableName = '' ) {
		if ( ! $tableName ) {
			// Bust all the cache.
			$this->cache = [];

			return;
		}

		unset( $this->cache[ $tableName ] );
	}

	/**
	 * In order to not have a conflict, we need to return a clone.
	 *
	 * @since 4.1.0
	 *
	 * @return Database The cloned Database instance.
	 */
	public function noConflict() {
		return clone $this;
	}

	/**
	 * Checks whether the given index exists on the given table.
	 *
	 * @since 4.4.8
	 *
	 * @param  string $tableName      The table name.
	 * @param  string $indexName      The index name.
	 * @param  bool   $includesPrefix Whether the table name includes the WordPress prefix or not.
	 * @return bool                   Whether the index exists or not.
	 */
	public function indexExists( $tableName, $indexName, $includesPrefix = false ) {
		$prefix    = $includesPrefix ? '' : $this->prefix;
		$tableName = strtolower( $prefix . $tableName );
		$indexName = strtolower( $indexName );

		$indexes = $this->db->get_results( "SHOW INDEX FROM `$tableName`" );
		foreach ( $indexes as $index ) {
			if ( empty( $index->Key_name ) ) {
				continue;
			}

			if ( strtolower( $index->Key_name ) === $indexName ) {
				return true;
			}
		}

		return false;
	}
}