Improved DB handling in LCStoreDB

* Only do the DB inserts in finishWrite(). Previously this would
  COMMIT there but would spread out queries throughout the set()
  calls. This pushes all the contention down to the last step.

Change-Id: Ia8afb79a8328c18a7d8a386bcd15a5074007d52e

diff --git a/includes/cache/LocalisationCache.php b/includes/cache/LocalisationCache.php
index 1153fd2..ec36cfb 100644 (file)
--- a/includes/cache/LocalisationCache.php
+++ b/includes/cache/LocalisationCache.php
@@ -1155,11 +1155,11 @@ class LCStoreDB implements LCStore {
        private $currentLang;
        private $writesDone = false;
 
-       /**
-        * @var DatabaseBase
-        */
+       /** @var DatabaseBase */
        private $dbw;
-       private $batch;
+       /** @var Array */
+       private $batch = array();
+
        private $readOnly = false;
 
        public function get( $code, $key ) {
@@ -1180,26 +1180,11 @@ class LCStoreDB implements LCStore {
        public function startWrite( $code ) {
                if ( $this->readOnly ) {
                        return;
-               }
-
-               if ( !$code ) {
+               } elseif ( !$code ) {
                        throw new MWException( __METHOD__ . ": Invalid language \"$code\"" );
                }
 
                $this->dbw = wfGetDB( DB_MASTER );
-               try {
-                       $this->dbw->begin( __METHOD__ );
-                       $this->dbw->delete( 'l10n_cache', array( 'lc_lang' => $code ), __METHOD__ );
-               } catch ( DBQueryError $e ) {
-                       if ( $this->dbw->wasReadOnlyError() ) {
-                               $this->readOnly = true;
-                               $this->dbw->rollback( __METHOD__ );
-
-                               return;
-                       } else {
-                               throw $e;
-                       }
-               }
 
                $this->currentLang = $code;
                $this->batch = array();
@@ -1208,37 +1193,42 @@ class LCStoreDB implements LCStore {
        public function finishWrite() {
                if ( $this->readOnly ) {
                        return;
+               } elseif ( is_null( $this->currentLang ) ) {
+                       throw new MWException( __CLASS__ . ': must call startWrite() before finishWrite()' );
                }
 
-               if ( $this->batch ) {
-                       $this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
+               $this->dbw->begin( __METHOD__ );
+               try {
+                       $this->dbw->delete( 'l10n_cache',
+                               array( 'lc_lang' => $this->currentLang ), __METHOD__ );
+                       foreach ( array_chunk( $this->batch, 500 ) as $rows ) {
+                               $this->dbw->insert( 'l10n_cache', $rows, __METHOD__ );
+                       }
+                       $this->writesDone = true;
+               } catch ( DBQueryError $e ) {
+                       if ( $this->dbw->wasReadOnlyError() ) {
+                               $this->readOnly = true; // just avoid site down time
+                       } else {
+                               throw $e;
+                       }
                }
-
                $this->dbw->commit( __METHOD__ );
+
                $this->currentLang = null;
-               $this->dbw = null;
                $this->batch = array();
-               $this->writesDone = true;
        }
 
        public function set( $key, $value ) {
                if ( $this->readOnly ) {
                        return;
-               }
-
-               if ( is_null( $this->currentLang ) ) {
-                       throw new MWException( __CLASS__ . ': must call startWrite() before calling set()' );
+               } elseif ( is_null( $this->currentLang ) ) {
+                       throw new MWException( __CLASS__ . ': must call startWrite() before set()' );
                }
 
                $this->batch[] = array(
                        'lc_lang' => $this->currentLang,
                        'lc_key' => $key,
                        'lc_value' => $this->dbw->encodeBlob( serialize( $value ) ) );
-
-               if ( count( $this->batch ) >= 100 ) {
-                       $this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
-                       $this->batch = array();
-               }
        }
 }