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  1. IMPALA
  2. IMPALA-3884

Enable codegen for TIMESTAMP in hash table.

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      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:

        // 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)));
          }
        }
      

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              kwho Michael Ho
              alex.behm Alexander Behm
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