Bug 1126129 - Only enable SQLite tracing when the right environment variable is set, r=asuth.

storage/src/mozStorageConnection.cpp

@@ -647,6 +647,9 @@ Connection::initializeInternal(nsIFile* aDatabaseFile)
   if (!gStorageLog)
     gStorageLog = ::PR_NewLogModule("mozStorage");
 
+  // SQLite tracing can slow down queries (especially long queries)
+  // significantly. Don't trace unless the user is actively monitoring SQLite.
+  if (PR_LOG_TEST(gStorageLog, PR_LOG_DEBUG)) {
     ::sqlite3_trace(mDBConn, tracefunc, this);
 
     nsAutoCString leafName(":memory");
@@ -654,6 +657,7 @@ Connection::initializeInternal(nsIFile* aDatabaseFile)
       (void)aDatabaseFile->GetNativeLeafName(leafName);
     PR_LOG(gStorageLog, PR_LOG_NOTICE, ("Opening connection to '%s' (%p)",
                                         leafName.get(), this));
+  }
 #endif
 
   int64_t pageSize = Service::getDefaultPageSize();