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From "ASF GitHub Bot (Jira)" <j...@apache.org>
Subject [jira] [Work logged] (HIVE-24221) Use vectorizable expression to combine multiple columns in semijoin bloom filters
Date Wed, 14 Oct 2020 08:11:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-24221?focusedWorklogId=500527&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-500527
]

ASF GitHub Bot logged work on HIVE-24221:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 14/Oct/20 08:10
            Start Date: 14/Oct/20 08:10
    Worklog Time Spent: 10m 
      Work Description: kgyrtkirk commented on a change in pull request #1544:
URL: https://github.com/apache/hive/pull/1544#discussion_r504482010



##########
File path: ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeDescUtils.java
##########
@@ -233,6 +235,23 @@ public static ExprNodeGenericFuncDesc and(List<ExprNodeDesc> exps)
{
     return new ExprNodeGenericFuncDesc(TypeInfoFactory.booleanTypeInfo, new GenericUDFOPAnd(),
"and", flatExps);
   }
 
+  /**
+   * Create an expression for computing a hash by recursively hashing given expressions by
two:
+   * <pre>
+   * Input: HASH(A, B, C, D)
+   * Output: HASH(HASH(HASH(A,B),C),D)
+   * </pre>
+   */
+  public static ExprNodeGenericFuncDesc hash(List<ExprNodeDesc> exps) {
+    assert exps.size() >= 2;
+    ExprNodeDesc hashExp = exps.get(0);
+    for (int i = 1; i < exps.size(); i++) {
+      List<ExprNodeDesc> hArgs = Arrays.asList(hashExp, exps.get(i));
+      hashExp = new ExprNodeGenericFuncDesc(TypeInfoFactory.intTypeInfo, new GenericUDFMurmurHash(),
"hash", hArgs);

Review comment:
       it seems like we have some inconsistency in `GenericUDFMurmurHash` which is registered
as `murmur_hash` in the `FunctionRegistry` ; however in the UDF's annotation it only has `hash`
- and here as well we use simply "hash".
   a change like this will most likely cause a lot of q.out changes - could you file a follow-up
ticket?
   




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Issue Time Tracking
-------------------

    Worklog Id:     (was: 500527)
    Time Spent: 20m  (was: 10m)

> Use vectorizable expression to combine multiple columns in semijoin bloom filters
> ---------------------------------------------------------------------------------
>
>                 Key: HIVE-24221
>                 URL: https://issues.apache.org/jira/browse/HIVE-24221
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>         Environment: 
>            Reporter: Stamatis Zampetakis
>            Assignee: Stamatis Zampetakis
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Currently, multi-column semijoin reducers use an n-ary call to GenericUDFMurmurHash to
combine multiple values into one, which is used as an entry to the bloom filter. However,
there are no vectorized operators that treat n-ary inputs. The same goes for the vectorized
implementation of GenericUDFMurmurHash introduced in HIVE-23976. 
> The goal of this issue is to choose an alternative way to combine multiple values into
one to pass in the bloom filter comprising only vectorized operators.



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