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  1. IMPALA
  2. IMPALA-4865

Limit size of literal values from constant folding

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: Impala 2.8.0
    • Fix Version/s: Impala 3.3.0
    • Component/s: Frontend
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      Description

      Consider (from test_insert.py) the following query:

      create table foo as select repeat('AZ', 128 * 1024 * 1024) as s

      repeat() gets constant-folded into a 256MB expression payload, which is then transmitted to every fragment instance that evaluates the expression. This can lead to timeouts.

      The workaround is ENABLE_EXPR_REWRITES=0.

      It's not obvious what the answer is - should the FE be aware of the serialized size of an expression when deciding whether to constant fold it?

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              • Assignee:
                fangyurao Fang-Yu Rao
                Reporter:
                henryr Henry Robinson
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                  Updated:
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