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https://issues.apache.org/jira/browse/DRILL-5728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16131488#comment-16131488
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Boaz Ben-Zvi commented on DRILL-5728:
-------------------------------------
This Jira has some relation to DRILL-5588 -- we'd need to change the "values"
value vector ( *vv1* ) to a nullable value vector so it could be returned as is
with no need to iterate over the whole vector when producing an output.
> Hash Aggregate: Useless bigint value vector in the values batch
> ---------------------------------------------------------------
>
> Key: DRILL-5728
> URL: https://issues.apache.org/jira/browse/DRILL-5728
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Codegen
> Affects Versions: 1.11.0
> Reporter: Boaz Ben-Zvi
> Priority: Minor
>
> When aggregating a non-nullable column (like *sum(l_partkey)* below), the
> code generation creates an extra value vector (in addition to the actual
> "sum" vector) which is used as a "nonNullCount".
> This is useless (as the underlying column is non-nullable), and wastes
> considerable memory ( 8 * 64K = 512K per each value in a batch !!)
> Example query:
> {{select sum(l_partkey) as slpk from cp.`tpch/lineitem.parquet` group by
> l_orderkry;}}
> And as can be seen in the generated code below, the bigint value vector *vv5*
> is only used to hold a *1* flag to note "not null":
> {code}
> public void updateAggrValuesInternal(int incomingRowIdx, int htRowIdx)
> throws SchemaChangeException
> {
> {
> IntHolder out11 = new IntHolder();
> {
> out11 .value = vv8 .getAccessor().get((incomingRowIdx));
> }
> IntHolder in = out11;
> work0 .value = vv1 .getAccessor().get((htRowIdx));
> BigIntHolder value = work0;
> work4 .value = vv5 .getAccessor().get((htRowIdx));
> BigIntHolder nonNullCount = work4;
>
> SumFunctions$IntSum_add: {
> nonNullCount.value = 1;
> value.value += in.value;
> }
>
> work0 = value;
> vv1 .getMutator().set((htRowIdx), work0 .value);
> work4 = nonNullCount;
> vv5 .getMutator().set((htRowIdx), work4 .value);
> }
> }
> {code}
>
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