Follow up r87630. The file cache is now checked at reportHTML() which overrides the...

[mediawiki.git] / includes / db / DatabaseIbm_db2.php

<?php
/**
 * This is the IBM DB2 database abstraction layer.
 * See maintenance/ibm_db2/README for development notes
 * and other specific information
 *
 * @file
 * @ingroup Database
 * @author leo.petr+mediawiki@gmail.com
 */

/**
 * This represents a column in a DB2 database
 * @ingroup Database
 */
class IBM_DB2Field implements Field {
        private $name = '';
        private $tablename = '';
        private $type = '';
        private $nullable = false;
        private $max_length = 0;

        /**
         * Builder method for the class
         * @param $db DatabaseIbm_db2: Database interface
         * @param $table String: table name
         * @param $field String: column name
         * @return IBM_DB2Field
         */
        static function fromText( $db, $table, $field ) {
                global $wgDBmwschema;

                $q = <<<SQL
SELECT
lcase( coltype ) AS typname,
nulls AS attnotnull, length AS attlen
FROM sysibm.syscolumns
WHERE tbcreator=%s AND tbname=%s AND name=%s;
SQL;
                $res = $db->query(
                        sprintf( $q,
                                $db->addQuotes( $wgDBmwschema ),
                                $db->addQuotes( $table ),
                                $db->addQuotes( $field )
                        )
                );
                $row = $db->fetchObject( $res );
                if ( !$row ) {
                        return null;
                }
                $n = new IBM_DB2Field;
                $n->type = $row->typname;
                $n->nullable = ( $row->attnotnull == 'N' );
                $n->name = $field;
                $n->tablename = $table;
                $n->max_length = $row->attlen;
                return $n;
        }
        /**
         * Get column name
         * @return string column name
         */
        function name() { return $this->name; }
        /**
         * Get table name
         * @return string table name
         */
        function tableName() { return $this->tablename; }
        /**
         * Get column type
         * @return string column type
         */
        function type() { return $this->type; }
        /**
         * Can column be null?
         * @return bool true or false
         */
        function isNullable() { return $this->nullable; }
        /**
         * How much can you fit in the column per row?
         * @return int length
         */
        function maxLength() { return $this->max_length; }
}

/**
 * Wrapper around binary large objects
 * @ingroup Database
 */
class IBM_DB2Blob {
        private $mData;

        public function __construct( $data ) {
                $this->mData = $data;
        }

        public function getData() {
                return $this->mData;
        }

        public function __toString() {
                return $this->mData;
        }
}

/**
 * Primary database interface
 * @ingroup Database
 */
class DatabaseIbm_db2 extends DatabaseBase {
        /*
         * Inherited members
        protected $mLastQuery = '';
        protected $mPHPError = false;

        protected $mServer, $mUser, $mPassword, $mConn = null, $mDBname;
        protected $mOpened = false;

        protected $mTablePrefix;
        protected $mFlags;
        protected $mTrxLevel = 0;
        protected $mErrorCount = 0;
        protected $mLBInfo = array();
        protected $mFakeSlaveLag = null, $mFakeMaster = false;
         *
         */

        /** Database server port */
        protected $mPort = null;
        /** Schema for tables, stored procedures, triggers */
        protected $mSchema = null;
        /** Whether the schema has been applied in this session */
        protected $mSchemaSet = false;
        /** Result of last query */
        protected $mLastResult = null;
        /** Number of rows affected by last INSERT/UPDATE/DELETE */
        protected $mAffectedRows = null;
        /** Number of rows returned by last SELECT */
        protected $mNumRows = null;

        /** Connection config options - see constructor */
        public $mConnOptions = array();
        /** Statement config options -- see constructor */
        public $mStmtOptions = array();

        /** Default schema */
        const USE_GLOBAL = 'get from global';

        /** Option that applies to nothing */
        const NONE_OPTION = 0x00;
        /** Option that applies to connection objects */
        const CONN_OPTION = 0x01;
        /** Option that applies to statement objects */
        const STMT_OPTION = 0x02;

        /** Regular operation mode -- minimal debug messages */
        const REGULAR_MODE = 'regular';
        /** Installation mode -- lots of debug messages */
        const INSTALL_MODE = 'install';

        /** Controls the level of debug message output */
        protected $mMode = self::REGULAR_MODE;

        /** Last sequence value used for a primary key */
        protected $mInsertId = null;

        ######################################
        # Getters and Setters
        ######################################

        /**
         * Returns true if this database supports (and uses) cascading deletes
         */
        function cascadingDeletes() {
                return true;
        }

        /**
         * Returns true if this database supports (and uses) triggers (e.g. on the
         *  page table)
         */
        function cleanupTriggers() {
                return true;
        }

        /**
         * Returns true if this database is strict about what can be put into an
         *  IP field.
         * Specifically, it uses a NULL value instead of an empty string.
         */
        function strictIPs() {
                return true;
        }

        /**
         * Returns true if this database uses timestamps rather than integers
        */
        function realTimestamps() {
                return true;
        }

        /**
         * Returns true if this database does an implicit sort when doing GROUP BY
         */
        function implicitGroupby() {
                return false;
        }

        /**
         * Returns true if this database does an implicit order by when the column
         *  has an index
         * For example: SELECT page_title FROM page LIMIT 1
         */
        function implicitOrderby() {
                return false;
        }

        /**
         * Returns true if this database can do a native search on IP columns
         * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
         */
        function searchableIPs() {
                return true;
        }

        /**
         * Returns true if this database can use functional indexes
         */
        function functionalIndexes() {
                return true;
        }

        /**
         * Returns a unique string representing the wiki on the server
         */
        function getWikiID() {
                if( $this->mSchema ) {
                        return "{$this->mDBname}-{$this->mSchema}";
                } else {
                        return $this->mDBname;
                }
        }

        function getType() {
                return 'ibm_db2';
        }

        /**
         *
         * @param $server String: hostname of database server
         * @param $user String: username
         * @param $password String: password
         * @param $dbName String: database name on the server
         * @param $flags Integer: database behaviour flags (optional, unused)
         * @param $schema String
         */
        public function __construct( $server = false, $user = false,
                                                        $password = false,
                                                        $dbName = false, $flags = 0,
                                                        $schema = self::USE_GLOBAL )
        {
                global $wgDBmwschema;

                if ( $schema == self::USE_GLOBAL ) {
                        $this->mSchema = $wgDBmwschema;
                } else {
                        $this->mSchema = $schema;
                }

                // configure the connection and statement objects
                /*
                $this->setDB2Option( 'cursor', 'DB2_SCROLLABLE',
                        self::CONN_OPTION | self::STMT_OPTION );
                */
                $this->setDB2Option( 'db2_attr_case', 'DB2_CASE_LOWER',
                        self::CONN_OPTION | self::STMT_OPTION );
                $this->setDB2Option( 'deferred_prepare', 'DB2_DEFERRED_PREPARE_ON',
                        self::STMT_OPTION );
                $this->setDB2Option( 'rowcount', 'DB2_ROWCOUNT_PREFETCH_ON',
                        self::STMT_OPTION );

                parent::__construct( $server, $user, $password, $dbName, DBO_TRX | $flags );
        }

        /**
         * Enables options only if the ibm_db2 extension version supports them
         * @param $name String: name of the option in the options array
         * @param $const String: name of the constant holding the right option value
         * @param $type Integer: whether this is a Connection or Statement otion
         */
        private function setDB2Option( $name, $const, $type ) {
                if ( defined( $const ) ) {
                        if ( $type & self::CONN_OPTION ) {
                                $this->mConnOptions[$name] = constant( $const );
                        }
                        if ( $type & self::STMT_OPTION ) {
                                $this->mStmtOptions[$name] = constant( $const );
                        }
                } else {
                        $this->installPrint(
                                "$const is not defined. ibm_db2 version is likely too low." );
                }
        }

        /**
         * Outputs debug information in the appropriate place
         * @param $string String: the relevant debug message
         */
        private function installPrint( $string ) {
                wfDebug( "$string\n" );
                if ( $this->mMode == self::INSTALL_MODE ) {
                        print "<li><pre>$string</pre></li>";
                        flush();
                }
        }

        /**
         * Opens a database connection and returns it
         * Closes any existing connection
         *
         * @param $server String: hostname
         * @param $user String
         * @param $password String
         * @param $dbName String: database name
         * @return a fresh connection
         */
        public function open( $server, $user, $password, $dbName ) {
                wfProfileIn( __METHOD__ );

                # Load IBM DB2 driver if missing
                wfDl( 'ibm_db2' );

                # Test for IBM DB2 support, to avoid suppressed fatal error
                if ( !function_exists( 'db2_connect' ) ) {
                        throw new DBConnectionError( $this, "DB2 functions missing, have you enabled the ibm_db2 extension for PHP?" );
                }

                global $wgDBport;

                // Close existing connection
                $this->close();
                // Cache conn info
                $this->mServer = $server;
                $this->mPort = $port = $wgDBport;
                $this->mUser = $user;
                $this->mPassword = $password;
                $this->mDBname = $dbName;

                $this->openUncataloged( $dbName, $user, $password, $server, $port );

                if ( !$this->mConn ) {
                        $this->installPrint( "DB connection error\n" );
                        $this->installPrint(
                                "Server: $server, Database: $dbName, User: $user, Password: "
                                . substr( $password, 0, 3 ) . "...\n" );
                        $this->installPrint( $this->lastError() . "\n" );
                        wfProfileOut( __METHOD__ );
                        wfDebug( "DB connection error\n" );
                        wfDebug( "Server: $server, Database: $dbName, User: $user, Password: " . substr( $password, 0, 3 ) . "...\n" );
                        wfDebug( $this->lastError() . "\n" );
                        throw new DBConnectionError( $this, $this->lastError() );
                }

                // Apply connection config
                db2_set_option( $this->mConn, $this->mConnOptions, 1 );
                // Some MediaWiki code is still transaction-less (?).
                // The strategy is to keep AutoCommit on for that code
                //  but switch it off whenever a transaction is begun.
                db2_autocommit( $this->mConn, DB2_AUTOCOMMIT_ON );

                $this->mOpened = true;
                $this->applySchema();

                wfProfileOut( __METHOD__ );
                return $this->mConn;
        }

        /**
         * Opens a cataloged database connection, sets mConn
         */
        protected function openCataloged( $dbName, $user, $password ) {
                @$this->mConn = db2_pconnect( $dbName, $user, $password );
        }

        /**
         * Opens an uncataloged database connection, sets mConn
         */
        protected function openUncataloged( $dbName, $user, $password, $server, $port )
        {
                $dsn = "DRIVER={IBM DB2 ODBC DRIVER};DATABASE=$dbName;CHARSET=UTF-8;HOSTNAME=$server;PORT=$port;PROTOCOL=TCPIP;UID=$user;PWD=$password;";
                @$this->mConn = db2_pconnect($dsn, "", "", array());
        }

        /**
         * Closes a database connection, if it is open
         * Returns success, true if already closed
         */
        public function close() {
                $this->mOpened = false;
                if ( $this->mConn ) {
                        if ( $this->trxLevel() > 0 ) {
                                $this->commit();
                        }
                        return db2_close( $this->mConn );
                } else {
                        return true;
                }
        }

        /**
         * Retrieves the most current database error
         * Forces a database rollback
         */
        public function lastError() {
                $connerr = db2_conn_errormsg();
                if ( $connerr ) {
                        //$this->rollback();
                        return $connerr;
                }
                $stmterr = db2_stmt_errormsg();
                if ( $stmterr ) {
                        //$this->rollback();
                        return $stmterr;
                }

                return false;
        }

        /**
         * Get the last error number
         * Return 0 if no error
         * @return integer
         */
        public function lastErrno() {
                $connerr = db2_conn_error();
                if ( $connerr ) {
                        return $connerr;
                }
                $stmterr = db2_stmt_error();
                if ( $stmterr ) {
                        return $stmterr;
                }
                return 0;
        }

        /**
         * Is a database connection open?
         * @return
         */
        public function isOpen() { return $this->mOpened; }

        /**
         * The DBMS-dependent part of query()
         * @param  $sql String: SQL query.
         * @return object Result object for fetch functions or false on failure
         * @access private
         */
        /*private*/
        public function doQuery( $sql ) {
                $this->applySchema();
                
                // Needed to handle any UTF-8 encoding issues in the raw sql
                // Note that we fully support prepared statements for DB2
                // prepare() and execute() should be used instead of doQuery() whenever possible
                $sql = utf8_decode($sql);
                
                $ret = db2_exec( $this->mConn, $sql, $this->mStmtOptions );
                if( $ret == false ) {
                        $error = db2_stmt_errormsg();
                        
                        $this->installPrint( "<pre>$sql</pre>" );
                        $this->installPrint( $error );
                        throw new DBUnexpectedError( $this, 'SQL error: '
                                . htmlspecialchars( $error ) );
                }
                $this->mLastResult = $ret;
                $this->mAffectedRows = null; // Not calculated until asked for
                return $ret;
        }

        /**
         * @return string Version information from the database
         */
        public function getServerVersion() {
                $info = db2_server_info( $this->mConn );
                return $info->DBMS_VER;
        }

        /**
         * Queries whether a given table exists
         * @return boolean
         */
        public function tableExists( $table ) {
                $schema = $this->mSchema;
                
                $sql = "SELECT COUNT( * ) FROM SYSIBM.SYSTABLES ST WHERE ST.NAME = '" . 
                        strtoupper( $table ) .
                        "' AND ST.CREATOR = '" .
                        strtoupper( $schema ) . "'";
                $res = $this->query( $sql );
                if ( !$res ) {
                        return false;
                }

                // If the table exists, there should be one of it
                @$row = $this->fetchRow( $res );
                $count = $row[0];
                if ( $count == '1' || $count == 1 ) {
                        return true;
                }

                return false;
        }

        /**
         * Fetch the next row from the given result object, in object form.
         * Fields can be retrieved with $row->fieldname, with fields acting like
         * member variables.
         *
         * @param $res SQL result object as returned from Database::query(), etc.
         * @return DB2 row object
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        public function fetchObject( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                @$row = db2_fetch_object( $res );
                if( $this->lastErrno() ) {
                        throw new DBUnexpectedError( $this, 'Error in fetchObject(): '
                                . htmlspecialchars( $this->lastError() ) );
                }
                return $row;
        }

        /**
         * Fetch the next row from the given result object, in associative array
         * form. Fields are retrieved with $row['fieldname'].
         *
         * @param $res SQL result object as returned from Database::query(), etc.
         * @return DB2 row object
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        public function fetchRow( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                if ( db2_num_rows( $res ) > 0) {
                        @$row = db2_fetch_array( $res );
                        if ( $this->lastErrno() ) {
                                throw new DBUnexpectedError( $this, 'Error in fetchRow(): '
                                        . htmlspecialchars( $this->lastError() ) );
                        }
                        return $row;
                }
                return false;
        }

        /**
         * Create tables, stored procedures, and so on
         */
        public function setup_database() {
                try {
                        // TODO: switch to root login if available

                        // Switch into the correct namespace
                        $this->applySchema();
                        $this->begin();

                        $res = $this->sourceFile( "../maintenance/ibm_db2/tables.sql" );
                        if ( $res !== true ) {
                                print ' <b>FAILED</b>: ' . htmlspecialchars( $res ) . '</li>';
                        } else {
                                print ' done</li>';
                        }
                        $res = $this->sourceFile( "../maintenance/ibm_db2/foreignkeys.sql" );
                        if ( $res !== true ) {
                                print ' <b>FAILED</b>: ' . htmlspecialchars( $res ) . '</li>';
                        } else {
                                print '<li>Foreign keys done</li>';
                        }

                        // TODO: populate interwiki links

                        if ( $this->lastError() ) {
                                $this->installPrint(
                                        'Errors encountered during table creation -- rolled back' );
                                $this->installPrint( 'Please install again' );
                                $this->rollback();
                        } else {
                                $this->commit();
                        }
                } catch ( MWException $mwe ) {
                        print "<br><pre>$mwe</pre><br>";
                }
        }

        /**
         * Escapes strings
         * Doesn't escape numbers
         *
         * @param $s String: string to escape
         * @return escaped string
         */
        public function addQuotes( $s ) {
                //$this->installPrint( "DB2::addQuotes( $s )\n" );
                if ( is_null( $s ) ) {
                        return 'NULL';
                } elseif ( $s instanceof Blob ) {
                        return "'" . $s->fetch( $s ) . "'";
                } elseif ( $s instanceof IBM_DB2Blob ) {
                        return "'" . $this->decodeBlob( $s ) . "'";
                }
                $s = $this->strencode( $s );
                if ( is_numeric( $s ) ) {
                        return $s;
                } else {
                        return "'$s'";
                }
        }

        /**
         * Verifies that a DB2 column/field type is numeric
         *
         * @param $type String: DB2 column type
         * @return Boolean: true if numeric
         */
        public function is_numeric_type( $type ) {
                switch ( strtoupper( $type ) ) {
                        case 'SMALLINT':
                        case 'INTEGER':
                        case 'INT':
                        case 'BIGINT':
                        case 'DECIMAL':
                        case 'REAL':
                        case 'DOUBLE':
                        case 'DECFLOAT':
                                return true;
                }
                return false;
        }

        /**
         * Alias for addQuotes()
         * @param $s String: string to escape
         * @return escaped string
         */
        public function strencode( $s ) {
                // Bloody useless function
                //  Prepends backslashes to \x00, \n, \r, \, ', " and \x1a.
                //  But also necessary
                $s = db2_escape_string( $s );
                // Wide characters are evil -- some of them look like '
                $s = utf8_encode( $s );
                // Fix its stupidity
                $from = array(  "\\\\", "\\'",  '\\n',  '\\t',  '\\"',  '\\r' );
                $to = array(            "\\",           "''",           "\n",           "\t",           '"',            "\r" );
                $s = str_replace( $from, $to, $s ); // DB2 expects '', not \' escaping
                return $s;
        }

        /**
         * Switch into the database schema
         */
        protected function applySchema() {
                if ( !( $this->mSchemaSet ) ) {
                        $this->mSchemaSet = true;
                        $this->begin();
                        $this->doQuery( "SET SCHEMA = $this->mSchema" );
                        $this->commit();
                }
        }

        /**
         * Start a transaction (mandatory)
         */
        public function begin( $fname = 'DatabaseIbm_db2::begin' ) {
                // BEGIN is implicit for DB2
                // However, it requires that AutoCommit be off.

                // Some MediaWiki code is still transaction-less (?).
                // The strategy is to keep AutoCommit on for that code
                //  but switch it off whenever a transaction is begun.
                db2_autocommit( $this->mConn, DB2_AUTOCOMMIT_OFF );

                $this->mTrxLevel = 1;
        }

        /**
         * End a transaction
         * Must have a preceding begin()
         */
        public function commit( $fname = 'DatabaseIbm_db2::commit' ) {
                db2_commit( $this->mConn );

                // Some MediaWiki code is still transaction-less (?).
                // The strategy is to keep AutoCommit on for that code
                //  but switch it off whenever a transaction is begun.
                db2_autocommit( $this->mConn, DB2_AUTOCOMMIT_ON );

                $this->mTrxLevel = 0;
        }

        /**
         * Cancel a transaction
         */
        public function rollback( $fname = 'DatabaseIbm_db2::rollback' ) {
                db2_rollback( $this->mConn );
                // turn auto-commit back on
                // not sure if this is appropriate
                db2_autocommit( $this->mConn, DB2_AUTOCOMMIT_ON );
                $this->mTrxLevel = 0;
        }

        /**
         * Makes an encoded list of strings from an array
         * $mode:
         *   LIST_COMMA         - comma separated, no field names
         *   LIST_AND           - ANDed WHERE clause (without the WHERE)
         *   LIST_OR            - ORed WHERE clause (without the WHERE)
         *   LIST_SET           - comma separated with field names, like a SET clause
         *   LIST_NAMES         - comma separated field names
         *   LIST_SET_PREPARED  - like LIST_SET, except with ? tokens as values
         */
        function makeList( $a, $mode = LIST_COMMA ) {
                if ( !is_array( $a ) ) {
                        throw new DBUnexpectedError( $this,
                                'DatabaseIbm_db2::makeList called with incorrect parameters' );
                }

                // if this is for a prepared UPDATE statement
                // (this should be promoted to the parent class
                //  once other databases use prepared statements)
                if ( $mode == LIST_SET_PREPARED ) {
                        $first = true;
                        $list = '';
                        foreach ( $a as $field => $value ) {
                                if ( !$first ) {
                                        $list .= ", $field = ?";
                                } else {
                                        $list .= "$field = ?";
                                        $first = false;
                                }
                        }
                        $list .= '';

                        return $list;
                }

                // otherwise, call the usual function
                return parent::makeList( $a, $mode );
        }

        /**
         * Construct a LIMIT query with optional offset
         * This is used for query pages
         *
         * @param $sql string SQL query we will append the limit too
         * @param $limit integer the SQL limit
         * @param $offset integer the SQL offset (default false)
         */
        public function limitResult( $sql, $limit, $offset=false ) {
                if( !is_numeric( $limit ) ) {
                        throw new DBUnexpectedError( $this,
                                "Invalid non-numeric limit passed to limitResult()\n" );
                }
                if( $offset ) {
                        if ( stripos( $sql, 'where' ) === false ) {
                                return "$sql AND ( ROWNUM BETWEEN $offset AND $offset+$limit )";
                        } else {
                                return "$sql WHERE ( ROWNUM BETWEEN $offset AND $offset+$limit )";
                        }
                }
                return "$sql FETCH FIRST $limit ROWS ONLY ";
        }

        /**
         * Handle reserved keyword replacement in table names
         *
         * @param $name Object
         * @param $name Boolean
         * @return String
         */
        public function tableName( $name, $quoted = true ) {
                // we want maximum compatibility with MySQL schema
                return $name;
        }

        /**
         * Generates a timestamp in an insertable format
         *
         * @param $ts timestamp
         * @return String: timestamp value
         */
        public function timestamp( $ts = 0 ) {
                // TS_MW cannot be easily distinguished from an integer
                return wfTimestamp( TS_DB2, $ts );
        }

        /**
         * Return the next in a sequence, save the value for retrieval via insertId()
         * @param $seqName String: name of a defined sequence in the database
         * @return next value in that sequence
         */
        public function nextSequenceValue( $seqName ) {
                // Not using sequences in the primary schema to allow for easier migration
                //  from MySQL
                // Emulating MySQL behaviour of using NULL to signal that sequences
                // aren't used
                /*
                $safeseq = preg_replace( "/'/", "''", $seqName );
                $res = $this->query( "VALUES NEXTVAL FOR $safeseq" );
                $row = $this->fetchRow( $res );
                $this->mInsertId = $row[0];
                return $this->mInsertId;
                */
                return null;
        }

        /**
         * This must be called after nextSequenceVal
         * @return Last sequence value used as a primary key
         */
        public function insertId() {
                return $this->mInsertId;
        }

        /**
         * Updates the mInsertId property with the value of the last insert
         *  into a generated column
         *
         * @param $table      String: sanitized table name
         * @param $primaryKey Mixed: string name of the primary key
         * @param $stmt       Resource: prepared statement resource
         *  of the SELECT primary_key FROM FINAL TABLE ( INSERT ... ) form
         */
        private function calcInsertId( $table, $primaryKey, $stmt ) {
                if ( $primaryKey ) {
                        $this->mInsertId = db2_last_insert_id( $this->mConn );
                }
        }

        /**
         * INSERT wrapper, inserts an array into a table
         *
         * $args may be a single associative array, or an array of arrays
         *  with numeric keys, for multi-row insert
         *
         * @param $table   String: Name of the table to insert to.
         * @param $args    Array: Items to insert into the table.
         * @param $fname   String: Name of the function, for profiling
         * @param $options String or Array. Valid options: IGNORE
         *
         * @return bool Success of insert operation. IGNORE always returns true.
         */
        public function insert( $table, $args, $fname = 'DatabaseIbm_db2::insert',
                $options = array() )
        {
                if ( !count( $args ) ) {
                        return true;
                }
                // get database-specific table name (not used)
                $table = $this->tableName( $table );
                // format options as an array
                $options = IBM_DB2Helper::makeArray( $options );
                // format args as an array of arrays
                if ( !( isset( $args[0] ) && is_array( $args[0] ) ) ) {
                        $args = array( $args );
                }

                // prevent insertion of NULL into primary key columns
                list( $args, $primaryKeys ) = $this->removeNullPrimaryKeys( $table, $args );
                // if there's only one primary key
                // we'll be able to read its value after insertion
                $primaryKey = false;
                if ( count( $primaryKeys ) == 1 ) {
                        $primaryKey = $primaryKeys[0];
                }

                // get column names
                $keys = array_keys( $args[0] );
                $key_count = count( $keys );

                // If IGNORE is set, we use savepoints to emulate mysql's behavior
                $ignore = in_array( 'IGNORE', $options ) ? 'mw' : '';

                // assume success
                $res = true;
                // If we are not in a transaction, we need to be for savepoint trickery
                if ( !$this->mTrxLevel ) {
                        $this->begin();
                }

                $sql = "INSERT INTO $table ( " . implode( ',', $keys ) . ' ) VALUES ';
                if ( $key_count == 1 ) {
                        $sql .= '( ? )';
                } else {
                        $sql .= '( ?' . str_repeat( ',?', $key_count-1 ) . ' )';
                }
                $this->installPrint( "Preparing the following SQL:" );
                $this->installPrint( "$sql" );
                $this->installPrint( print_r( $args, true ));
                $stmt = $this->prepare( $sql );

                // start a transaction/enter transaction mode
                $this->begin();

                if ( !$ignore ) {
                        //$first = true;
                        foreach ( $args as $row ) {
                                //$this->installPrint( "Inserting " . print_r( $row, true ));
                                // insert each row into the database
                                $res = $res & $this->execute( $stmt, $row );
                                if ( !$res ) {
                                        $this->installPrint( 'Last error:' );
                                        $this->installPrint( $this->lastError() );
                                }
                                // get the last inserted value into a generated column
                                $this->calcInsertId( $table, $primaryKey, $stmt );
                        }
                } else {
                        $olde = error_reporting( 0 );
                        // For future use, we may want to track the number of actual inserts
                        // Right now, insert (all writes) simply return true/false
                        $numrowsinserted = 0;

                        // always return true
                        $res = true;

                        foreach ( $args as $row ) {
                                $overhead = "SAVEPOINT $ignore ON ROLLBACK RETAIN CURSORS";
                                db2_exec( $this->mConn, $overhead, $this->mStmtOptions );

                                $res2 = $this->execute( $stmt, $row );

                                if ( !$res2 ) {
                                        $this->installPrint( 'Last error:' );
                                        $this->installPrint( $this->lastError() );
                                }
                                // get the last inserted value into a generated column
                                $this->calcInsertId( $table, $primaryKey, $stmt );

                                $errNum = $this->lastErrno();
                                if ( $errNum ) {
                                        db2_exec( $this->mConn, "ROLLBACK TO SAVEPOINT $ignore",
                                                $this->mStmtOptions );
                                } else {
                                        db2_exec( $this->mConn, "RELEASE SAVEPOINT $ignore",
                                                $this->mStmtOptions );
                                        $numrowsinserted++;
                                }
                        }

                        $olde = error_reporting( $olde );
                        // Set the affected row count for the whole operation
                        $this->mAffectedRows = $numrowsinserted;
                }
                // commit either way
                $this->commit();
                $this->freePrepared( $stmt );

                return $res;
        }

        /**
         * Given a table name and a hash of columns with values
         * Removes primary key columns from the hash where the value is NULL
         *
         * @param $table String: name of the table
         * @param $args Array of hashes of column names with values
         * @return Array: tuple( filtered array of columns, array of primary keys )
         */
        private function removeNullPrimaryKeys( $table, $args ) {
                $schema = $this->mSchema;
                
                // find out the primary keys
                $keyres = $this->doQuery( "SELECT NAME FROM SYSIBM.SYSCOLUMNS WHERE TBNAME = '" 
                  . strtoupper( $table ) 
                  . "' AND TBCREATOR = '" 
                  . strtoupper( $schema ) 
                  . "' AND KEYSEQ > 0" );
                
                $keys = array();
                for (
                        $row = $this->fetchRow( $keyres );
                        $row != null;
                        $row = $this->fetchRow( $keyres )
                )
                {
                        $keys[] = strtolower( $row[0] );
                }
                // remove primary keys
                foreach ( $args as $ai => $row ) {
                        foreach ( $keys as $key ) {
                                if ( $row[$key] == null ) {
                                        unset( $row[$key] );
                                }
                        }
                        $args[$ai] = $row;
                }
                // return modified hash
                return array( $args, $keys );
        }

        /**
         * UPDATE wrapper, takes a condition array and a SET array
         *
         * @param $table  String: The table to UPDATE
         * @param $values An array of values to SET
         * @param $conds  An array of conditions ( WHERE ). Use '*' to update all rows.
         * @param $fname  String: The Class::Function calling this function
         *                ( for the log )
         * @param $options An array of UPDATE options, can be one or
         *                 more of IGNORE, LOW_PRIORITY
         * @return Boolean
         */
        public function update( $table, $values, $conds, $fname = 'DatabaseIbm_db2::update',
                $options = array() )
        {
                $table = $this->tableName( $table );
                $opts = $this->makeUpdateOptions( $options );
                $sql = "UPDATE $opts $table SET "
                        . $this->makeList( $values, LIST_SET_PREPARED );
                if ( $conds != '*' ) {
                        $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
                }
                $stmt = $this->prepare( $sql );
                $this->installPrint( 'UPDATE: ' . print_r( $values, true ) );
                // assuming for now that an array with string keys will work
                // if not, convert to simple array first
                $result = $this->execute( $stmt, $values );
                $this->freePrepared( $stmt );

                return $result;
        }

        /**
         * DELETE query wrapper
         *
         * Use $conds == "*" to delete all rows
         */
        public function delete( $table, $conds, $fname = 'DatabaseIbm_db2::delete' ) {
                if ( !$conds ) {
                        throw new DBUnexpectedError( $this,
                                'DatabaseIbm_db2::delete() called with no conditions' );
                }
                $table = $this->tableName( $table );
                $sql = "DELETE FROM $table";
                if ( $conds != '*' ) {
                        $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
                }
                $result = $this->query( $sql, $fname );

                return $result;
        }

        /**
         * Returns the number of rows affected by the last query or 0
         * @return Integer: the number of rows affected by the last query
         */
        public function affectedRows() {
                if ( !is_null( $this->mAffectedRows ) ) {
                        // Forced result for simulated queries
                        return $this->mAffectedRows;
                }
                if( empty( $this->mLastResult ) ) {
                        return 0;
                }
                return db2_num_rows( $this->mLastResult );
        }

        /**
         * Simulates REPLACE with a DELETE followed by INSERT
         * @param $table Object
         * @param $uniqueIndexes Array consisting of indexes and arrays of indexes
         * @param $rows Array: rows to insert
         * @param $fname String: name of the function for profiling
         * @return nothing
         */
        function replace( $table, $uniqueIndexes, $rows,
                $fname = 'DatabaseIbm_db2::replace' )
        {
                $table = $this->tableName( $table );

                if ( count( $rows )==0 ) {
                        return;
                }

                # Single row case
                if ( !is_array( reset( $rows ) ) ) {
                        $rows = array( $rows );
                }

                foreach( $rows as $row ) {
                        # Delete rows which collide
                        if ( $uniqueIndexes ) {
                                $sql = "DELETE FROM $table WHERE ";
                                $first = true;
                                foreach ( $uniqueIndexes as $index ) {
                                        if ( $first ) {
                                                $first = false;
                                                $sql .= '( ';
                                        } else {
                                                $sql .= ' ) OR ( ';
                                        }
                                        if ( is_array( $index ) ) {
                                                $first2 = true;
                                                foreach ( $index as $col ) {
                                                        if ( $first2 ) {
                                                                $first2 = false;
                                                        } else {
                                                                $sql .= ' AND ';
                                                        }
                                                        $sql .= $col . '=' . $this->addQuotes( $row[$col] );
                                                }
                                        } else {
                                                $sql .= $index . '=' . $this->addQuotes( $row[$index] );
                                        }
                                }
                                $sql .= ' )';
                                $this->query( $sql, $fname );
                        }

                        # Now insert the row
                        $this->insert($table, $row);
                }
        }

        /**
         * Returns the number of rows in the result set
         * Has to be called right after the corresponding select query
         * @param $res Object result set
         * @return Integer: number of rows
         */
        public function numRows( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                
                if ( $this->mNumRows ) {
                        return $this->mNumRows;
                } else {
                        return 0;
                }
        }

        /**
         * Moves the row pointer of the result set
         * @param $res Object: result set
         * @param $row Integer: row number
         * @return success or failure
         */
        public function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return db2_fetch_row( $res, $row );
        }

        ###
        # Fix notices in Block.php
        ###

        /**
         * Frees memory associated with a statement resource
         * @param $res Object: statement resource to free
         * @return Boolean success or failure
         */
        public function freeResult( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                if ( !@db2_free_result( $res ) ) {
                        throw new DBUnexpectedError( $this, "Unable to free DB2 result\n" );
                }
        }

        /**
         * Returns the number of columns in a resource
         * @param $res Object: statement resource
         * @return Number of fields/columns in resource
         */
        public function numFields( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return db2_num_fields( $res );
        }

        /**
         * Returns the nth column name
         * @param $res Object: statement resource
         * @param $n Integer: Index of field or column
         * @return String name of nth column
         */
        public function fieldName( $res, $n ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return db2_field_name( $res, $n );
        }

        /**
         * SELECT wrapper
         *
         * @param $table   Array or string, table name(s) (prefix auto-added)
         * @param $vars    Array or string, field name(s) to be retrieved
         * @param $conds   Array or string, condition(s) for WHERE
         * @param $fname   String: calling function name (use __METHOD__)
         *                 for logs/profiling
         * @param $options Associative array of options
         *                 (e.g. array('GROUP BY' => 'page_title')),
         *                 see Database::makeSelectOptions code for list of
         *                 supported stuff
         * @param $join_conds Associative array of table join conditions (optional)
         *                    (e.g. array( 'page' => array('LEFT JOIN',
         *                    'page_latest=rev_id') )
         * @return Mixed: database result resource for fetch functions or false
         *                 on failure
         */
        public function select( $table, $vars, $conds = '', $fname = 'DatabaseIbm_db2::select', $options = array(), $join_conds = array() )
        {
                $res = parent::select( $table, $vars, $conds, $fname, $options,
                        $join_conds );

                // We must adjust for offset
                if ( isset( $options['LIMIT'] ) && isset ( $options['OFFSET'] ) ) {
                        $limit = $options['LIMIT'];
                        $offset = $options['OFFSET'];
                }

                // DB2 does not have a proper num_rows() function yet, so we must emulate
                // DB2 9.5.4 and the corresponding ibm_db2 driver will introduce
                //  a working one
                // TODO: Yay!

                // we want the count
                $vars2 = array( 'count( * ) as num_rows' );
                // respecting just the limit option
                $options2 = array();
                if ( isset( $options['LIMIT'] ) ) {
                        $options2['LIMIT'] = $options['LIMIT'];
                }
                // but don't try to emulate for GROUP BY
                if ( isset( $options['GROUP BY'] ) ) {
                        return $res;
                }

                $res2 = parent::select( $table, $vars2, $conds, $fname, $options2,
                        $join_conds );
                $obj = $this->fetchObject( $res2 );
                $this->mNumRows = $obj->num_rows;

                return $res;
        }

        /**
         * Handles ordering, grouping, and having options ('GROUP BY' => colname)
         * Has limited support for per-column options (colnum => 'DISTINCT')
         *
         * @private
         *
         * @param $options Associative array of options to be turned into
         *              an SQL query, valid keys are listed in the function.
         * @return Array
         */
        function makeSelectOptions( $options ) {
                $preLimitTail = $postLimitTail = '';
                $startOpts = '';

                $noKeyOptions = array();
                foreach ( $options as $key => $option ) {
                        if ( is_numeric( $key ) ) {
                                $noKeyOptions[$option] = true;
                        }
                }

                if ( isset( $options['GROUP BY'] ) ) {
                        $preLimitTail .= " GROUP BY {$options['GROUP BY']}";
                }
                if ( isset( $options['HAVING'] ) ) {
                        $preLimitTail .= " HAVING {$options['HAVING']}";
                }
                if ( isset( $options['ORDER BY'] ) ) {
                        $preLimitTail .= " ORDER BY {$options['ORDER BY']}";
                }

                if ( isset( $noKeyOptions['DISTINCT'] )
                        || isset( $noKeyOptions['DISTINCTROW'] ) )
                {
                        $startOpts .= 'DISTINCT';
                }

                return array( $startOpts, '', $preLimitTail, $postLimitTail );
        }

        /**
         * Returns link to IBM DB2 free download
         * @return String: wikitext of a link to the server software's web site
         */
        public static function getSoftwareLink() {
                return '[http://www.ibm.com/db2/express/ IBM DB2]';
        }

        /**
         * Get search engine class. All subclasses of this
         * need to implement this if they wish to use searching.
         *
         * @return String
         */
        public function getSearchEngine() {
                return 'SearchIBM_DB2';
        }

        /**
         * Did the last database access fail because of deadlock?
         * @return Boolean
         */
        public function wasDeadlock() {
                // get SQLSTATE
                $err = $this->lastErrno();
                switch( $err ) {
                        // This is literal port of the MySQL logic and may be wrong for DB2
                        case '40001':   // sql0911n, Deadlock or timeout, rollback
                        case '57011':   // sql0904n, Resource unavailable, no rollback
                        case '57033':   // sql0913n, Deadlock or timeout, no rollback
                        $this->installPrint( "In a deadlock because of SQLSTATE $err" );
                        return true;
                }
                return false;
        }

        /**
         * Ping the server and try to reconnect if it there is no connection
         * The connection may be closed and reopened while this happens
         * @return Boolean: whether the connection exists
         */
        public function ping() {
                // db2_ping() doesn't exist
                // Emulate
                $this->close();
                $this->mConn = $this->openUncataloged( $this->mDBName, $this->mUser,
                        $this->mPassword, $this->mServer, $this->mPort );

                return false;
        }
        ######################################
        # Unimplemented and not applicable
        ######################################
        /**
         * Not implemented
         * @return string ''
         */
        public function getStatus( $which = '%' ) {
                $this->installPrint( 'Not implemented for DB2: getStatus()' );
                return '';
        }
        /**
         * Not implemented
         * @return string $sql
         */
        public function limitResultForUpdate( $sql, $num ) {
                $this->installPrint( 'Not implemented for DB2: limitResultForUpdate()' );
                return $sql;
        }

        /**
         * Only useful with fake prepare like in base Database class
         * @return      string
         */
        public function fillPreparedArg( $matches ) {
                $this->installPrint( 'Not useful for DB2: fillPreparedArg()' );
                return '';
        }

        ######################################
        # Reflection
        ######################################

        /**
         * Returns information about an index
         * If errors are explicitly ignored, returns NULL on failure
         * @param $table String: table name
         * @param $index String: index name
         * @param $fname String: function name for logging and profiling
         * @return Object query row in object form
         */
        public function indexInfo( $table, $index,
                $fname = 'DatabaseIbm_db2::indexExists' )
        {
                $table = $this->tableName( $table );
                $sql = <<<SQL
SELECT name as indexname
FROM sysibm.sysindexes si
WHERE si.name='$index' AND si.tbname='$table'
AND sc.tbcreator='$this->mSchema'
SQL;
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return null;
                }
                $row = $this->fetchObject( $res );
                if ( $row != null ) {
                        return $row;
                } else {
                        return false;
                }
        }

        /**
         * Returns an information object on a table column
         * @param $table String: table name
         * @param $field String: column name
         * @return IBM_DB2Field
         */
        public function fieldInfo( $table, $field ) {
                return IBM_DB2Field::fromText( $this, $table, $field );
        }

        /**
         * db2_field_type() wrapper
         * @param $res Object: result of executed statement
         * @param $index Mixed: number or name of the column
         * @return String column type
         */
        public function fieldType( $res, $index ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return db2_field_type( $res, $index );
        }

        /**
         * Verifies that an index was created as unique
         * @param $table String: table name
         * @param $index String: index name
         * @param $fname function name for profiling
         * @return Bool
         */
        public function indexUnique ( $table, $index,
                $fname = 'DatabaseIbm_db2::indexUnique' )
        {
                $table = $this->tableName( $table );
                $sql = <<<SQL
SELECT si.name as indexname
FROM sysibm.sysindexes si
WHERE si.name='$index' AND si.tbname='$table'
AND sc.tbcreator='$this->mSchema'
AND si.uniquerule IN ( 'U', 'P' )
SQL;
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return null;
                }
                if ( $this->fetchObject( $res ) ) {
                        return true;
                }
                return false;

        }

        /**
         * Returns the size of a text field, or -1 for "unlimited"
         * @param $table String: table name
         * @param $field String: column name
         * @return Integer: length or -1 for unlimited
         */
        public function textFieldSize( $table, $field ) {
                $table = $this->tableName( $table );
                $sql = <<<SQL
SELECT length as size
FROM sysibm.syscolumns sc
WHERE sc.name='$field' AND sc.tbname='$table'
AND sc.tbcreator='$this->mSchema'
SQL;
                $res = $this->query( $sql );
                $row = $this->fetchObject( $res );
                $size = $row->size;
                return $size;
        }

        /**
         * DELETE where the condition is a join
         * @param $delTable String: deleting from this table
         * @param $joinTable String: using data from this table
         * @param $delVar String: variable in deleteable table
         * @param $joinVar String: variable in data table
         * @param $conds Array: conditionals for join table
         * @param $fname String: function name for profiling
         */
        public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar,
                $conds, $fname = "DatabaseIbm_db2::deleteJoin" )
        {
                if ( !$conds ) {
                        throw new DBUnexpectedError( $this,
                                'DatabaseIbm_db2::deleteJoin() called with empty $conds' );
                }

                $delTable = $this->tableName( $delTable );
                $joinTable = $this->tableName( $joinTable );
                $sql = <<<SQL
DELETE FROM $delTable
WHERE $delVar IN (
        SELECT $joinVar FROM $joinTable

SQL;
                if ( $conds != '*' ) {
                        $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
                }
                $sql .= ' )';

                $this->query( $sql, $fname );
        }

        /**
         * Description is left as an exercise for the reader
         * @param $b Mixed: data to be encoded
         * @return IBM_DB2Blob
         */
        public function encodeBlob( $b ) {
                return new IBM_DB2Blob( $b );
        }

        /**
         * Description is left as an exercise for the reader
         * @param $b IBM_DB2Blob: data to be decoded
         * @return mixed
         */
        public function decodeBlob( $b ) {
                return "$b";
        }

        /**
         * Convert into a list of string being concatenated
         * @param $stringList Array: strings that need to be joined together
         *                    by the SQL engine
         * @return String: joined by the concatenation operator
         */
        public function buildConcat( $stringList ) {
                // || is equivalent to CONCAT
                // Sample query: VALUES 'foo' CONCAT 'bar' CONCAT 'baz'
                return implode( ' || ', $stringList );
        }

        /**
         * Generates the SQL required to convert a DB2 timestamp into a Unix epoch
         * @param $column String: name of timestamp column
         * @return String: SQL code
         */
        public function extractUnixEpoch( $column ) {
                // TODO
                // see SpecialAncientpages
        }

        ######################################
        # Prepared statements
        ######################################

        /**
         * Intended to be compatible with the PEAR::DB wrapper functions.
         * http://pear.php.net/manual/en/package.database.db.intro-execute.php
         *
         * ? = scalar value, quoted as necessary
         * ! = raw SQL bit (a function for instance)
         * & = filename; reads the file and inserts as a blob
         *     (we don't use this though...)
         * @param $sql String: SQL statement with appropriate markers
         * @param $func String: Name of the function, for profiling
         * @return resource a prepared DB2 SQL statement
         */
        public function prepare( $sql, $func = 'DB2::prepare' ) {
                $stmt = db2_prepare( $this->mConn, $sql, $this->mStmtOptions );
                return $stmt;
        }

        /**
         * Frees resources associated with a prepared statement
         * @return Boolean success or failure
         */
        public function freePrepared( $prepared ) {
                return db2_free_stmt( $prepared );
        }

        /**
         * Execute a prepared query with the various arguments
         * @param $prepared String: the prepared sql
         * @param $args Mixed: either an array here, or put scalars as varargs
         * @return Resource: results object
         */
        public function execute( $prepared, $args = null ) {
                if( !is_array( $args ) ) {
                        # Pull the var args
                        $args = func_get_args();
                        array_shift( $args );
                }
                $res = db2_execute( $prepared, $args );
                if ( !$res ) {
                        $this->installPrint( db2_stmt_errormsg() );
                }
                return $res;
        }

        /**
         * Prepare & execute an SQL statement, quoting and inserting arguments
         * in the appropriate places.
         * @param $query String
         * @param $args ...
         */
        public function safeQuery( $query, $args = null ) {
                // copied verbatim from Database.php
                $prepared = $this->prepare( $query, 'DB2::safeQuery' );
                if( !is_array( $args ) ) {
                        # Pull the var args
                        $args = func_get_args();
                        array_shift( $args );
                }
                $retval = $this->execute( $prepared, $args );
                $this->freePrepared( $prepared );
                return $retval;
        }

        /**
         * For faking prepared SQL statements on DBs that don't support
         * it directly.
         * @param $preparedQuery String: a 'preparable' SQL statement
         * @param $args Array of arguments to fill it with
         * @return String: executable statement
         */
        public function fillPrepared( $preparedQuery, $args ) {
                reset( $args );
                $this->preparedArgs =& $args;

                foreach ( $args as $i => $arg ) {
                        db2_bind_param( $preparedQuery, $i+1, $args[$i] );
                }

                return $preparedQuery;
        }

        /**
         * Switches module between regular and install modes
         */
        public function setMode( $mode ) {
                $old = $this->mMode;
                $this->mMode = $mode;
                return $old;
        }

        /**
         * Bitwise negation of a column or value in SQL
         * Same as (~field) in C
         * @param $field String
         * @return String
         */
        function bitNot( $field ) {
                // expecting bit-fields smaller than 4bytes
                return "BITNOT( $field )";
        }

        /**
         * Bitwise AND of two columns or values in SQL
         * Same as (fieldLeft & fieldRight) in C
         * @param $fieldLeft String
         * @param $fieldRight String
         * @return String
         */
        function bitAnd( $fieldLeft, $fieldRight ) {
                return "BITAND( $fieldLeft, $fieldRight )";
        }

        /**
         * Bitwise OR of two columns or values in SQL
         * Same as (fieldLeft | fieldRight) in C
         * @param $fieldLeft String
         * @param $fieldRight String
         * @return String
         */
        function bitOr( $fieldLeft, $fieldRight ) {
                return "BITOR( $fieldLeft, $fieldRight )";
        }
}

class IBM_DB2Helper {
        public static function makeArray( $maybeArray ) {
                if ( !is_array( $maybeArray ) ) {
                        return array( $maybeArray );
                }

                return $maybeArray;
        }
}