Changes between Version 16 and Version 17 of MapGuideRfc86

Timestamp:

09/24/09 20:08:50 (15 years ago)

Author:

leaf

Comment:

--

MapGuideRfc86

@@ -28 +28 @@
 
 Currently MapGuide Server maintains an FDO connection pool in order to improve performance. Once MapGuide Server receives a request to access data in a feature source, it will try to find an available FDO connection in FDO connection pool. It avoids exhausting FDO connections to the underlying RDBMS and improves performance of MapGuide Server when many users use MapGuide Server in the same time. However, it means that one user session may use the different FDO connection for the same feature source at the different time. Sometimes, it will result in some unexpected errors. Let’s take a look at one example.
+
+{{{
+    featureService.ExecuteSqlQuery(featureSourceId, "SAVEPOINT X", null, null);
+    try
+    {
+        MgSqlDataReader reader1 = featureService.ExecuteSqlQuery(featureSourceId, "SELECT FID FROM DUMMY", null, null);
+        featureService..ExecuteSqlNonQuery(featureSourceId, "SAVEPOINT Y", null, null);
+        try
+        {
+            featureService.ExecuteSqlNonQuery(featureSourceId, "INSERT INTO TEST2 (FID) VALUES (1)", null, null);
+        }
+        catch (System.Exception)
+        {
+            featureService.ExecuteSqlQuery(featureSourceId, "ROLLBACK TO Y", null, null);
+        }
+
+        while (reader1.ReadNext())
+        {
+            MgParameterCollection parameters = new MgParameterCollection();
+            MgInt32Property inFid = new MgInt32Property("myInput", r1.GetInt32("FID"));
+            MgParameter inParameter = new MgParameter(inFid, MgParameterDirection.Input);
+            parameters.Add(inParameter);
+            featureService.ExecuteSqlNonQuery(featureSourceId, "INSERT INTO TEST(FID) VALUES(:myInput)", parameters, null);
+        }
+        r1.Close();
+        r1.Dispose();
+    }
+    catch (System.Exception)
+    {
+        featureService.ExecuteSqlQuery(featureSourceId, "ROLLBACK TO X", null, null);
+    }
+    featureService.ExecuteSqlQuery(featureSourceId, "COMMIT", null, null);
+}}}
 
 In the example above, it is possible that FDO connections used by executing SQL statements "SAVEPOINT X", "ROLLBACK TO X" and "COMMIT" are completely different FDO connections. If so, it will result in an error when executing SQL statement "ROLLBACK TO X" or "COMMIT".