Avoid breaking DB transactions in SqlBagOStuff

* Callers still sees some decent time ordering since writes block
  until committed. This will not blindly flush transactions though.
* Basically reverts 59e8032

Change-Id: Ib9a91ac023f8e3fafb0bf0eef9dca6e31b867be9

diff --git a/includes/objectcache/SqlBagOStuff.php b/includes/objectcache/SqlBagOStuff.php
index 8b0b738..0c91dab 100644 (file)
--- a/includes/objectcache/SqlBagOStuff.php
+++ b/includes/objectcache/SqlBagOStuff.php
@@ -238,7 +238,12 @@ class SqlBagOStuff extends BagOStuff {
                                        $res = $db->select( $tableName,
                                                array( 'keyname', 'value', 'exptime' ),
                                                array( 'keyname' => $tableKeys ),
-                                               __METHOD__ );
+                                               __METHOD__,
+                                               // Approximate write-on-the-fly BagOStuff API via blocking.
+                                               // This approximation fails if a ROLLBACK happens (which is rare).
+                                               // We do not want to flush the TRX as that can break callers.
+                                               $db->trxLevel() ? array( 'LOCK IN SHARE MODE' ) : array()
+                                       );
                                        foreach ( $res as $row ) {
                                                $row->serverIndex = $serverIndex;
                                                $row->tableName = $tableName;
@@ -258,13 +263,11 @@ class SqlBagOStuff extends BagOStuff {
                                        $db = $this->getDB( $row->serverIndex );
                                        if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
                                                $this->debug( "get: key has expired, deleting" );
-                                               $db->commit( __METHOD__, 'flush' );
                                                # Put the expiry time in the WHERE condition to avoid deleting a
                                                # newly-inserted value
                                                $db->delete( $row->tableName,
                                                        array( 'keyname' => $key, 'exptime' => $row->exptime ),
                                                        __METHOD__ );
-                                               $db->commit( __METHOD__, 'flush' );
                                        } else { // HIT
                                                $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
                                        }
@@ -327,14 +330,12 @@ class SqlBagOStuff extends BagOStuff {
                                }
 
                                try {
-                                       $db->commit( __METHOD__, 'flush' );
                                        $db->replace(
                                                $tableName,
                                                array( 'keyname' ),
                                                $rows,
                                                __METHOD__
                                        );
-                                       $db->commit( __METHOD__, 'flush' );
                                } catch ( DBError $e ) {
                                        $this->handleWriteError( $e, $serverIndex );
                                        $result = false;
@@ -374,7 +375,6 @@ class SqlBagOStuff extends BagOStuff {
 
                                $encExpiry = $db->timestamp( $exptime );
                        }
-                       $db->commit( __METHOD__, 'flush' );
                        // (bug 24425) use a replace if the db supports it instead of
                        // delete/insert to avoid clashes with conflicting keynames
                        $db->replace(
@@ -385,7 +385,6 @@ class SqlBagOStuff extends BagOStuff {
                                        'value' => $db->encodeBlob( $this->serialize( $value ) ),
                                        'exptime' => $encExpiry
                                ), __METHOD__ );
-                       $db->commit( __METHOD__, 'flush' );
                } catch ( DBError $e ) {
                        $this->handleWriteError( $e, $serverIndex );
                        return false;
@@ -419,7 +418,6 @@ class SqlBagOStuff extends BagOStuff {
                                }
                                $encExpiry = $db->timestamp( $exptime );
                        }
-                       $db->commit( __METHOD__, 'flush' );
                        // (bug 24425) use a replace if the db supports it instead of
                        // delete/insert to avoid clashes with conflicting keynames
                        $db->update(
@@ -435,7 +433,6 @@ class SqlBagOStuff extends BagOStuff {
                                ),
                                __METHOD__
                        );
-                       $db->commit( __METHOD__, 'flush' );
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e, $serverIndex );
 
@@ -454,12 +451,10 @@ class SqlBagOStuff extends BagOStuff {
                list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
                try {
                        $db = $this->getDB( $serverIndex );
-                       $db->commit( __METHOD__, 'flush' );
                        $db->delete(
                                $tableName,
                                array( 'keyname' => $key ),
                                __METHOD__ );
-                       $db->commit( __METHOD__, 'flush' );
                } catch ( DBError $e ) {
                        $this->handleWriteError( $e, $serverIndex );
                        return false;
@@ -478,7 +473,6 @@ class SqlBagOStuff extends BagOStuff {
                try {
                        $db = $this->getDB( $serverIndex );
                        $step = intval( $step );
-                       $db->commit( __METHOD__, 'flush' );
                        $row = $db->selectRow(
                                $tableName,
                                array( 'value', 'exptime' ),
@@ -487,14 +481,12 @@ class SqlBagOStuff extends BagOStuff {
                                array( 'FOR UPDATE' ) );
                        if ( $row === false ) {
                                // Missing
-                               $db->commit( __METHOD__, 'flush' );
 
                                return null;
                        }
                        $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
                        if ( $this->isExpired( $db, $row->exptime ) ) {
                                // Expired, do not reinsert
-                               $db->commit( __METHOD__, 'flush' );
 
                                return null;
                        }
@@ -512,7 +504,6 @@ class SqlBagOStuff extends BagOStuff {
                                // Race condition. See bug 28611
                                $newValue = null;
                        }
-                       $db->commit( __METHOD__, 'flush' );
                } catch ( DBError $e ) {
                        $this->handleWriteError( $e, $serverIndex );
                        return null;
@@ -603,7 +594,6 @@ class SqlBagOStuff extends BagOStuff {
                                                        $maxExpTime = $row->exptime;
                                                }
 
-                                               $db->commit( __METHOD__, 'flush' );
                                                $db->delete(
                                                        $this->getTableNameByShard( $i ),
                                                        array(
@@ -612,7 +602,6 @@ class SqlBagOStuff extends BagOStuff {
                                                                'keyname' => $keys
                                                        ),
                                                        __METHOD__ );
-                                               $db->commit( __METHOD__, 'flush' );
 
                                                if ( $progressCallback ) {
                                                        if ( intval( $totalSeconds ) === 0 ) {
@@ -645,9 +634,7 @@ class SqlBagOStuff extends BagOStuff {
                        try {
                                $db = $this->getDB( $serverIndex );
                                for ( $i = 0; $i < $this->shards; $i++ ) {
-                                       $db->commit( __METHOD__, 'flush' );
                                        $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
-                                       $db->commit( __METHOD__, 'flush' );
                                }
                        } catch ( DBError $e ) {
                                $this->handleWriteError( $e, $serverIndex );
@@ -775,12 +762,10 @@ class SqlBagOStuff extends BagOStuff {
                        }
 
                        for ( $i = 0; $i < $this->shards; $i++ ) {
-                               $db->commit( __METHOD__, 'flush' );
                                $db->query(
                                        'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
                                        ' LIKE ' . $db->tableName( 'objectcache' ),
                                        __METHOD__ );
-                               $db->commit( __METHOD__, 'flush' );
                        }
                }
        }