[jira] [Updated] (IMPALA-3884) Enable codegen for TIMESTAMP in hash table.

["Alex Rodoni (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-3884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alex Rodoni updated IMPALA-3884:
--------------------------------
    Docs Text:   (was: Before this fix, codegen was disable for joins on timestamps, GROUP BY on timestamps, and select distinct of timestamp columns. With this fix, affected aggregations are significantly faster (e.g. 5x).)

> Enable codegen for TIMESTAMP in hash table.
> -------------------------------------------
>
>                 Key: IMPALA-3884
>                 URL: https://issues.apache.org/jira/browse/IMPALA-3884
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 2.5.0, Impala 2.4.0, Impala 2.6.0
>            Reporter: Alexander Behm
>            Assignee: Michael Ho
>            Priority: Major
>              Labels: codegen, compute-stats, performance
>             Fix For: Impala 2.8.0
>
>
> Referencing TIMESTAMP columns in joins and aggrregations prevents those exec nodes from being codegen, leading to a severe performance hit. This may impact queries with group-by or join on timestamp column.
> See this snippet from HashTableCtx::CodegenEvalRow() in hash-table.cc:
> {code}
>   // TODO: CodegenAssignNullValue() can't handle TYPE_TIMESTAMP or TYPE_DECIMAL yet
>   const vector<ExprContext*>& ctxs = build ? build_expr_ctxs_ : probe_expr_ctxs_;
>   for (int i = 0; i < ctxs.size(); ++i) {
>     PrimitiveType type = ctxs[i]->root()->type().type;
>     if (type == TYPE_TIMESTAMP || type == TYPE_CHAR) {
>       return Status(Substitute("HashTableCtx::CodegenEvalRow(): type $0 NYI",
>           TypeToString(type)));
>     }
>   }
> {code}



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