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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4743) HashJoin's not fully parallelized in query plan
Date Tue, 12 Jul 2016 18:32:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15373414#comment-15373414
] 

ASF GitHub Bot commented on DRILL-4743:
---------------------------------------

Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/534#discussion_r70495124
  
    --- Diff: exec/java-exec/src/test/java/org/apache/drill/TestOptions.java ---
    @@ -0,0 +1,79 @@
    +/**
    + * 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.drill;
    +
    +import org.apache.drill.common.util.TestTools;
    +import org.junit.Test;
    +
    +import static org.junit.Assert.assertEquals;
    +
    +public class TestOptions extends BaseTestQuery {
    +    static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(TestOptions.class);
    +
    +    static final String WORKING_PATH = TestTools.getWorkingPath();
    +    static final String TEST_RES_PATH = WORKING_PATH + "/src/test/resources";
    +    private static final String EXPLAIN_PREFIX = "EXPLAIN PLAN FOR ";
    --- End diff --
    
    Not used anywhere ?


> HashJoin's not fully parallelized in query plan
> -----------------------------------------------
>
>                 Key: DRILL-4743
>                 URL: https://issues.apache.org/jira/browse/DRILL-4743
>             Project: Apache Drill
>          Issue Type: Bug
>    Affects Versions: 1.5.0
>            Reporter: Gautam Kumar Parai
>            Assignee: Gautam Kumar Parai
>              Labels: doc-impacting
>
> The underlying problem is filter selectivity under-estimate for a query with complicated
predicates e.g. deeply nested and/or predicates. This leads to under parallelization of the
major fragment doing the join. 
> To really resolve this problem we need table/column statistics to correctly estimate
the selectivity. However, in the absence of statistics OR even when existing statistics are
insufficient to get a correct estimate of selectivity this will serve as a workaround.



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