Merge "Remove deprecated 1.7 SpecialPage::addPage"

[lhc/web/wiklou.git] / includes / db / Database.php

diff --git a/includes/db/Database.php b/includes/db/Database.php
index 5344b12..5271208 100644 (file)
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -228,7 +228,10 @@ abstract class DatabaseBase implements DatabaseType {
        protected $mConn = null;
        protected $mOpened = false;
 
-       /** @var Array */
+       /**
+        * @since 1.20
+        * @var array of callable
+        */
        protected $trxIdleCallbacks = array();
 
        protected $mTablePrefix;
@@ -247,7 +250,7 @@ abstract class DatabaseBase implements DatabaseType {
        protected $delimiter = ';';
 
        /**
-        * Remembers the function name given for starting the most recent transaction via the begin() method.
+        * Remembers the function name given for starting the most recent transaction via begin().
         * Used to provide additional context for error reporting.
         *
         * @var String
@@ -255,6 +258,14 @@ abstract class DatabaseBase implements DatabaseType {
         */
        private $mTrxFname = null;
 
+       /**
+        * Record if possible write queries were done in the last transaction started
+        *
+        * @var Bool
+        * @see DatabaseBase::mTrxLevel
+        */
+       private $mTrxDoneWrites = false;
+
 # ------------------------------------------------------------------------------
 # Accessors
 # ------------------------------------------------------------------------------
@@ -845,9 +856,10 @@ abstract class DatabaseBase implements DatabaseType {
                $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 
                # If DBO_TRX is set, start a transaction
-               if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
-                       $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
-                       # avoid establishing transactions for SHOW and SET statements too -
+               if ( ( $this->mFlags & DBO_TRX ) && !$this->mTrxLevel &&
+                       $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' )
+               {
+                       # Avoid establishing transactions for SHOW and SET statements too -
                        # that would delay transaction initializations to once connection
                        # is really used by application
                        $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
@@ -860,6 +872,11 @@ abstract class DatabaseBase implements DatabaseType {
                        }
                }
 
+               # Keep track of whether the transaction has write queries pending
+               if ( $this->mTrxLevel && !$this->mTrxDoneWrites && $this->isWriteQuery( $sql ) ) {
+                       $this->mTrxDoneWrites = true;
+               }
+
                if ( $this->debug() ) {
                        static $cnt = 0;
 
@@ -2846,8 +2863,9 @@ abstract class DatabaseBase implements DatabaseType {
         *
         * This is useful for updates to different systems or separate transactions are needed.
         *
+        * @since 1.20
+        *
         * @param Closure $callback
-        * @return void
         */
        final public function onTransactionIdle( Closure $callback ) {
                if ( $this->mTrxLevel ) {
@@ -2858,7 +2876,9 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
-        * Actually run the "on transaction idle" callbacks
+        * Actually run the "on transaction idle" callbacks.
+        *
+        * @since 1.20
         */
        protected function runOnTransactionIdleCallbacks() {
                $e = null; // last exception
@@ -2878,22 +2898,50 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
-        * Begin a transaction
+        * Begin a transaction. If a transaction is already in progress, that transaction will be committed before the
+        * new transaction is started.
+        *
+        * Note that when the DBO_TRX flag is set (which is usually the case for web requests, but not for maintenance scripts),
+        * any previous database query will have started a transaction automatically.
+        *
+        * Nesting of transactions is not supported. Attempts to nest transactions will cause warnings if DBO_TRX is not set
+        * or the extsting transaction contained write operations.
         *
         * @param $fname string
         */
        final public function begin( $fname = 'DatabaseBase::begin' ) {
+               global $wgDebugDBTransactions;
+
                if ( $this->mTrxLevel ) { // implicit commit
-                       wfWarn( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
-                               " performing implicit commit!" );
+                       if ( $this->mTrxDoneWrites || ( $this->mFlags & DBO_TRX ) === 0 ) {
+                               // In theory, we should always warn about nesting BEGIN statements.
+                               // However, it is sometimes hard to avoid so we only warn if:
+                               //
+                               // a) the transaction has done writes. This gives warnings about bad transactions
+                               // that could cause partial writes but not about read queries seeing more
+                               // than one DB snapshot (when in REPEATABLE-READ) due to nested BEGINs.
+                               //
+                               // b) the DBO_TRX flag is not set. Explicit transactions should always be properly
+                               //    started and comitted.
+                               /*wfWarn( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
+                                       " performing implicit commit!" );*/
+                       } elseif ( $wgDebugDBTransactions ) {
+                               wfDebug( "$fname: Transaction already in progress (from {$this->mTrxFname}), " .
+                                       " performing implicit commit!\n" );
+                       }
+
                        $this->doCommit( $fname );
                        $this->runOnTransactionIdleCallbacks();
                }
+
                $this->doBegin( $fname );
                $this->mTrxFname = $fname;
+               $this->mTrxDoneWrites = false;
        }
 
        /**
+        * Issues the BEGIN command to the database server.
+        *
         * @see DatabaseBase::begin()
         * @param type $fname
         */
@@ -2903,7 +2951,10 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
-        * End a transaction
+        * Commits a transaction previously started using begin().
+        * If no transaction is in progress, a warning is issued.
+        *
+        * Nesting of transactions is not supported.
         *
         * @param $fname string
         */
@@ -2916,6 +2967,8 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
+        * Issues the COMMIT command to the database server.
+        *
         * @see DatabaseBase::commit()
         * @param type $fname
         */
@@ -2927,7 +2980,9 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
-        * Rollback a transaction.
+        * Rollback a transaction previously started using begin().
+        * If no transaction is in progress, a warning is issued.
+        *
         * No-op on non-transactional databases.
         *
         * @param $fname string
@@ -2941,6 +2996,8 @@ abstract class DatabaseBase implements DatabaseType {
        }
 
        /**
+        * Issues the ROLLBACK command to the database server.
+        *
         * @see DatabaseBase::rollback()
         * @param type $fname
         */