MySQLPlatform.php

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<?php
namespace Wikimedia\Rdbms\Platform;
 
use Wikimedia\Rdbms\DBLanguageError;
use Wikimedia\Rdbms\Query;
 
class MySQLPlatform extends SQLPlatform {
    protected function getIdentifierQuoteChar() {
        return '`';
    }
 
    public function buildStringCast( $field ) {
        return "CAST( $field AS BINARY )";
    }
 
    public function buildIntegerCast( $field ) {
        return 'CAST( ' . $field . ' AS SIGNED )';
    }
 
    protected function normalizeJoinType( string $joinType ) {
        switch ( strtoupper( $joinType ) ) {
            case 'STRAIGHT_JOIN':
            case 'STRAIGHT JOIN':
                return 'STRAIGHT_JOIN';
 
            default:
                return parent::normalizeJoinType( $joinType );
        }
    }
 
    public function useIndexClause( $index ) {
        return "FORCE INDEX (" . $index . ")";
    }
 
    public function ignoreIndexClause( $index ) {
        return "IGNORE INDEX (" . $index . ")";
    }
 
    public function deleteJoinSqlText( $delTable, $joinTable, $delVar, $joinVar, $conds ) {
        if ( !$conds ) {
            throw new DBLanguageError( __METHOD__ . ' called with empty $conds' );
        }
 
        $delTable = $this->tableName( $delTable );
        $joinTable = $this->tableName( $joinTable );
        $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
 
        if ( $conds != '*' ) {
            $sql .= ' AND ' . $this->makeList( $conds, self::LIST_AND );
        }
 
        return $sql;
    }
 
    public function isTransactableQuery( Query $sql ) {
        return parent::isTransactableQuery( $sql ) &&
            // TODO: Use query verb
            !preg_match( '/^SELECT\s+(GET|RELEASE|IS_FREE)_LOCK\‍(/', $sql->getSQL() );
    }
 
    public function buildExcludedValue( $column ) {
        /* @see DatabaseMySQL::upsert() */
        // Within "INSERT INTO ON DUPLICATE KEY UPDATE" statements:
        //   - MySQL>= 8.0.20 supports and prefers "VALUES ... AS".
        //   - MariaDB >= 10.3.3 supports and prefers VALUE().
        //   - Both support the old VALUES() function
        // https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html
        // https://mariadb.com/kb/en/insert-on-duplicate-key-update/
        return "VALUES($column)";
    }
 
    public function lockSQLText( $lockName, $timeout ) {
        $encName = $this->quoter->addQuotes( $this->makeLockName( $lockName ) );
        // Unlike NOW(), SYSDATE() gets the time at invocation rather than query start.
        // The precision argument is silently ignored for MySQL < 5.6 and MariaDB < 5.3.
        // https://dev.mysql.com/doc/refman/5.6/en/date-and-time-functions.html#function_sysdate
        // https://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html
        return "SELECT IF(GET_LOCK($encName,$timeout),UNIX_TIMESTAMP(SYSDATE(6)),NULL) AS acquired";
    }
 
    public function lockIsFreeSQLText( $lockName ) {
        $encName = $this->quoter->addQuotes( $this->makeLockName( $lockName ) );
        return "SELECT IS_FREE_LOCK($encName) AS unlocked";
    }
 
    public function unlockSQLText( $lockName ) {
        $encName = $this->quoter->addQuotes( $this->makeLockName( $lockName ) );
        return "SELECT RELEASE_LOCK($encName) AS released";
    }
 
    public function makeLockName( $lockName ) {
        // https://dev.mysql.com/doc/refman/5.7/en/locking-functions.html#function_get-lock
        // MySQL 5.7+ enforces a 64 char length limit.
        return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
    }
}