From 9b93ddf6af8d65450d835fb285bfb1879fabdfcf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Vr=C3=A1til?= <daniel.vratil@kdab.com>
Date: Wed, 4 Jan 2017 11:32:51 +0100
Subject: [PATCH 37/40] Break down the transaction in DELETE to multiple
 smaller trxs

The recursive deletion of Collections triggers bunch of subqueries and
also generates change notifications to clients, which in turn will try
to query more details about the change, which can possibly lead to a
transaction deadlock/lock timeout.

This change replaces the one huge transaction that wrapped the whole
deletion by smaller per-collection transactions.
---
 server/src/handler/delete.cpp | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/server/src/handler/delete.cpp b/server/src/handler/delete.cpp
index de3ac4ef5..d601c7dcb 100644
--- a/server/src/handler/delete.cpp
+++ b/server/src/handler/delete.cpp
@@ -52,7 +52,14 @@ bool Delete::deleteRecursive( Collection &col )
     }
   }
   DataStore *db = connection()->storageBackend();
-  return db->cleanupCollection( col );
+  Transaction transaction( db );
+  if (!db->cleanupCollection( col )) {
+      return false;
+  }
+  if ( !transaction.commit() ) {
+      return failureResponse( "Unable to commit transaction" );
+  }
+  return true;
 }
 
 bool Delete::parseStream()
@@ -74,7 +81,6 @@ bool Delete::parseStream()
 
   // check if collection exists
   DataStore *db = connection()->storageBackend();
-  Transaction transaction( db );
 
   Collection collection = collections.first();
   if ( !collection.isValid() ) {
@@ -93,10 +99,6 @@ bool Delete::parseStream()
     return failureResponse( "Unable to delete collection" );
   }
 
-  if ( !transaction.commit() ) {
-    return failureResponse( "Unable to commit transaction." );
-  }
-
   Response response;
   response.setTag( tag() );
   response.setString( "DELETE completed" );
-- 
2.14.1