From 3ab0c7d4d7b5b788b2f57a95408e5984d83f0c51 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 22 Dec 2015 18:18:59 -0800
Subject: [PATCH] Added IDatabase::doAtomicSection() convenience method

This can replace startAtomic/endAtomic pairs.

Bug: T122115
Change-Id: I01c8e4773ec2b42dbe87a5508a10b997be103c11
---
 includes/db/DBConnRef.php          |  4 +++
 includes/db/Database.php           | 15 ++++++++++
 includes/db/IDatabase.php          | 28 +++++++++++++++++
 includes/specialpage/QueryPage.php | 48 +++++++++++++++++++-----------
 4 files changed, 78 insertions(+), 17 deletions(-)

diff --git a/includes/db/DBConnRef.php b/includes/db/DBConnRef.php
index 5443eeb902..3cac22a13c 100644
--- a/includes/db/DBConnRef.php
+++ b/includes/db/DBConnRef.php
@@ -429,6 +429,10 @@ class DBConnRef implements IDatabase {
 		return $this->__call( __FUNCTION__, func_get_args() );
 	}
 
+	public function doAtomicSection( $fname, $callback ) {
+		return $this->__call( __FUNCTION__, func_get_args() );
+	}
+
 	public function begin( $fname = __METHOD__ ) {
 		return $this->__call( __FUNCTION__, func_get_args() );
 	}
diff --git a/includes/db/Database.php b/includes/db/Database.php
index 31e26531d8..abd4e3af59 100644
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -3446,6 +3446,21 @@ abstract class DatabaseBase implements IDatabase {
 		}
 	}
 
+	final public function doAtomicSection( $fname, $callback ) {
+		if ( !is_callable( $callback ) ) {
+			throw new UnexpectedValueException( "Invalid callback." );
+		};
+
+		$this->startAtomic( $fname );
+		try {
+			call_user_func_array( $callback, array( $this, $fname ) );
+		} catch ( Exception $e ) {
+			$this->rollback( $fname );
+			throw $e;
+		}
+		$this->endAtomic( $fname );
+	}
+
 	/**
 	 * Begin a transaction. If a transaction is already in progress,
 	 * that transaction will be committed before the new transaction is started.
diff --git a/includes/db/IDatabase.php b/includes/db/IDatabase.php
index 4674c17bed..31b2758c33 100644
--- a/includes/db/IDatabase.php
+++ b/includes/db/IDatabase.php
@@ -1268,6 +1268,34 @@ interface IDatabase {
 	 */
 	public function endAtomic( $fname = __METHOD__ );
 
+	/**
+	 * Run a callback to do an atomic set of updates for this database
+	 *
+	 * The $callback takes the following arguments:
+	 *   - This database object
+	 *   - The value of $fname
+	 *
+	 * If any exception occurs in the callback, then rollback() will be called and the error will
+	 * be re-thrown. It may also be that the rollback itself fails with an exception before then.
+	 * In any case, such errors are expected to terminate the request, without any outside caller
+	 * attempting to catch errors and commit anyway. Note that any rollback undoes all prior
+	 * atomic section and uncommitted updates, which trashes the current request, requiring an
+	 * error to be displayed.
+	 *
+	 * This can be an alternative to explicit startAtomic()/endAtomic() calls.
+	 *
+	 * @see DatabaseBase::startAtomic
+	 * @see DatabaseBase::endAtomic
+	 *
+	 * @param string $fname Caller name (usually __METHOD__)
+	 * @param callable $callback Callback that issues DB updates
+	 * @throws DBError
+	 * @throws RuntimeException
+	 * @throws UnexpectedValueException
+	 * @since 1.27
+	 */
+	public function doAtomicSection( $fname, $callback );
+
 	/**
 	 * Begin a transaction. If a transaction is already in progress,
 	 * that transaction will be committed before the new transaction is started.
diff --git a/includes/specialpage/QueryPage.php b/includes/specialpage/QueryPage.php
index 9755e8e0e0..2d25710614 100644
--- a/includes/specialpage/QueryPage.php
+++ b/includes/specialpage/QueryPage.php
@@ -325,25 +325,39 @@ abstract class QueryPage extends SpecialPage {
 						$value = 0;
 					}
 
-					$vals[] = array( 'qc_type' => $this->getName(),
-							'qc_namespace' => $row->namespace,
-							'qc_title' => $row->title,
-							'qc_value' => $value );
+					$vals[] = array(
+						'qc_type' => $this->getName(),
+						'qc_namespace' => $row->namespace,
+						'qc_title' => $row->title,
+						'qc_value' => $value
+					);
 				}
 
-				$dbw->startAtomic( __METHOD__ );
-				# Clear out any old cached data
-				$dbw->delete( 'querycache', array( 'qc_type' => $this->getName() ), $fname );
-				# Save results into the querycache table on the master
-				if ( count( $vals ) ) {
-					$dbw->insert( 'querycache', $vals, __METHOD__ );
-				}
-				# Update the querycache_info record for the page
-				$dbw->delete( 'querycache_info', array( 'qci_type' => $this->getName() ), $fname );
-				$dbw->insert( 'querycache_info',
-					array( 'qci_type' => $this->getName(), 'qci_timestamp' => $dbw->timestamp() ),
-					$fname );
-				$dbw->endAtomic( __METHOD__ );
+				$that = $this;
+				$dbw->doAtomicSection(
+					__METHOD__,
+					function ( IDatabase $dbw, $fname ) use ( $that, $vals ) {
+						# Clear out any old cached data
+						$dbw->delete( 'querycache',
+							array( 'qc_type' => $that->getName() ),
+							$fname
+						);
+						# Save results into the querycache table on the master
+						if ( count( $vals ) ) {
+							$dbw->insert( 'querycache', $vals, $fname );
+						}
+						# Update the querycache_info record for the page
+						$dbw->delete( 'querycache_info',
+							array( 'qci_type' => $that->getName() ),
+							$fname
+						);
+						$dbw->insert( 'querycache_info',
+							array( 'qci_type' => $that->getName(),
+								'qci_timestamp' => $dbw->timestamp() ),
+							$fname
+						);
+					}
+				);
 			}
 		} catch ( DBError $e ) {
 			if ( !$ignoreErrors ) {
-- 
2.20.1