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https://issues.apache.org/jira/browse/TAJO-751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14497778#comment-14497778
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ASF GitHub Bot commented on TAJO-751:
-------------------------------------
Github user blrunner commented on a diff in the pull request:
https://github.com/apache/tajo/pull/459#discussion_r28492503
--- Diff:
tajo-client/src/main/java/org/apache/tajo/jdbc/WaitingResultSet.java ---
@@ -0,0 +1,71 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.tajo.jdbc;
+
+import com.google.protobuf.ServiceException;
+import org.apache.tajo.QueryId;
+import org.apache.tajo.TajoProtos;
+import org.apache.tajo.catalog.CatalogUtil;
+import org.apache.tajo.catalog.Schema;
+import org.apache.tajo.catalog.TableDesc;
+import org.apache.tajo.client.QueryClient;
+import org.apache.tajo.client.QueryStatus;
+import org.apache.tajo.client.TajoClientUtil;
+import org.apache.tajo.ipc.ClientProtos;
+
+import java.sql.SQLException;
+
+/**
+ * Blocks on schema retrieval if it's not ready
+ */
+public class WaitingResultSet extends FetchResultSet {
+
+ public WaitingResultSet(QueryClient tajoClient, QueryId queryId, int
fetchRowNum)
+ throws SQLException {
+ super(tajoClient, null, queryId, fetchRowNum);
+ }
+
+ @Override
+ public boolean next() throws SQLException {
+ getSchema();
+ return super.next();
+ }
+
+ @Override
+ protected Schema getSchema() throws SQLException {
+ return schema == null ? schema = waitOnResult() : schema;
--- End diff --
Could you explain why you check schema?
> JDBC driver should support cancel() method.
> -------------------------------------------
>
> Key: TAJO-751
> URL: https://issues.apache.org/jira/browse/TAJO-751
> Project: Tajo
> Issue Type: Improvement
> Reporter: Hyoungjun Kim
> Assignee: Navis
> Priority: Minor
>
> Some OLAP or ETL tool call JDBC's cancel() function when a query is too late.
> So Tajo's JDBC should support cancel() function in Statement or
> PreparedStatement class.
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