jenkins-bot has submitted this change and it was merged.
Change subject: Added DatabaseBase::startAtomic and endAtomic
......................................................................
Added DatabaseBase::startAtomic and endAtomic
Added new functions to ensure certain groups of statements
are atomic without having to go through the trouble of
starting a new transaction if one has already been opened.
Change-Id: I5328fb337e5544bf28ea282860ef8f81e19ac43c
---
M includes/db/Database.php
1 file changed, 85 insertions(+), 1 deletion(-)
Approvals:
Aaron Schulz: Looks good to me, approved
jenkins-bot: Verified
diff --git a/includes/db/Database.php b/includes/db/Database.php
index c3850b9..ee17904 100644
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -282,6 +282,20 @@
private $mTrxAutomatic = false;
/**
+ * Array of levels of atomicity within transactions
+ *
+ * @var SplStack
+ */
+ private $mTrxAtomicLevels;
+
+ /**
+ * Record if the current transaction was started implicitly by
DatabaseBase::startAtomic
+ *
+ * @var Bool
+ */
+ private $mTrxAutomaticAtomic = false;
+
+ /**
* @since 1.21
* @var file handle for upgrade
*/
@@ -687,6 +701,7 @@
) {
global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
+ $this->mTrxAtomicLevels = new SplStack;
$this->mFlags = $flags;
if ( $this->mFlags & DBO_DEFAULT ) {
@@ -3185,6 +3200,39 @@
}
/**
+ * Begin an atomic section of statements
+ *
+ * If a transaction has been started already, just keep track of the
given
+ * section name to make sure the transaction is not committed
pre-maturely.
+ * This function can be used in layers (with sub-sections), so use a
stack
+ * to keep track of the different atomic sections. If there is no
transaction,
+ * start one implicitly.
+ *
+ * The goal of this function is to create an atomic section of SQL
queries
+ * without having to start a new transaction if it already exists.
+ *
+ * Atomic sections are more strict than transactions. With transactions,
+ * attempting to begin a new transaction when one is already running
results
+ * in MediaWiki issuing a brief warning and doing an implicit commit.
All
+ * atomic levels *must* be explicitly closed using
DatabaseBase::endAtomic(),
+ * and any database transactions cannot be began or committed until all
atomic
+ * levels are closed. There is no such thing as implicitly opening or
closing
+ * an atomic section.
+ *
+ * @since 1.23
+ * @param string $fname
+ */
+ final public function startAtomic( $fname = __METHOD__ ) {
+ if ( !$this->mTrxLevel ) {
+ $this->begin( $fname );
+ $this->mTrxAutomatic = true;
+ $this->mTrxAutomaticAtomic = true;
+ }
+
+ $this->mTrxAtomicLevels->push( $fname );
+ }
+
+ /**
* Begin a transaction. If a transaction is already in progress, that
transaction will be committed before the
* new transaction is started.
*
@@ -3200,7 +3248,13 @@
global $wgDebugDBTransactions;
if ( $this->mTrxLevel ) { // implicit commit
- if ( !$this->mTrxAutomatic ) {
+ if ( !$this->mTrxAtomicLevels->isEmpty() ) {
+ // If the current transaction was an automatic
atomic one, then we definitely have
+ // a problem. Same if there is any unclosed
atomic level.
+ throw new DBUnexpectedError( $this,
+ "Attempted to start explicit
transaction when atomic levels are still open."
+ );
+ } elseif ( !$this->mTrxAutomatic ) {
// We want to warn about inadvertently nested
begin/commit pairs, but not about
// auto-committing implicit transactions that
were started by query() via DBO_TRX
$msg = "$fname: Transaction already in progress
(from {$this->mTrxFname}), " .
@@ -3229,6 +3283,8 @@
$this->mTrxFname = $fname;
$this->mTrxDoneWrites = false;
$this->mTrxAutomatic = false;
+ $this->mTrxAutomaticAtomic = false;
+ $this->mTrxAtomicLevels = new SplStack;
}
/**
@@ -3240,6 +3296,28 @@
protected function doBegin( $fname ) {
$this->query( 'BEGIN', $fname );
$this->mTrxLevel = 1;
+ }
+
+ /**
+ * Ends an atomic section of SQL statements
+ *
+ * Ends the next section of atomic SQL statements and commits the
transaction
+ * if necessary.
+ *
+ * @since 1.23
+ * @see DatabaseBase::startAtomic
+ * @param string $fname
+ */
+ final public function endAtomic( $fname = __METHOD__ ) {
+ if ( $this->mTrxAtomicLevels->isEmpty() ||
+ $this->mTrxAtomicLevels->pop() !== $fname
+ ) {
+ throw new DBUnexpectedError( $this, 'Invalid atomic
section ended.' );
+ }
+
+ if ( $this->mTrxAtomicLevels->isEmpty() &&
$this->mTrxAutomaticAtomic ) {
+ $this->commit( $fname, 'flush' );
+ }
}
/**
@@ -3255,6 +3333,11 @@
* that it is safe to ignore these warnings in your context.
*/
final public function commit( $fname = __METHOD__, $flush = '' ) {
+ if ( !$this->mTrxAtomicLevels->isEmpty() ) {
+ // There are still atomic sections open. This cannot be
ignored
+ throw new DBUnexpectedError( $this, "Attempted to
commit transaction while atomic sections are still open" );
+ }
+
if ( $flush != 'flush' ) {
if ( !$this->mTrxLevel ) {
wfWarn( "$fname: No transaction to commit,
something got out of sync!" );
@@ -3305,6 +3388,7 @@
$this->doRollback( $fname );
$this->mTrxIdleCallbacks = array(); // cancel
$this->mTrxPreCommitCallbacks = array(); // cancel
+ $this->mTrxAtomicLevels = new SplStack;
if ( $this->mTrxDoneWrites ) {
Profiler::instance()->transactionWritingOut(
$this->mServer, $this->mDBname );
}
--
To view, visit https://gerrit.wikimedia.org/r/90856
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: merged
Gerrit-Change-Id: I5328fb337e5544bf28ea282860ef8f81e19ac43c
Gerrit-PatchSet: 2
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Parent5446 <[email protected]>
Gerrit-Reviewer: Aaron Schulz <[email protected]>
Gerrit-Reviewer: Parent5446 <[email protected]>
Gerrit-Reviewer: jenkins-bot
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