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  1. Calcite
  2. CALCITE-2974

Timestamp conversion performance can be improved

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    Details

    • Type: Improvement
    • Status: Reopened
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: 1.19.0
    • Fix Version/s: next
    • Component/s: core

      Description

      RexSimplify.simplifyCast() is slow when converting a string to SQL Timestamp value. The slowness is caused by this line:

      executor.reduce(rexBuilder, ImmutableList.of(e), reducedValues);
      

      Debugging this code line with my team showed that for timestamp conversion it loads a pre-compiled conversion code, which makes it slow. My team proposes to replace this line with the following code that greately improves performance:

      if (typeName == SqlTypeName.CHAR && e.getType().getSqlTypeName() == SqlTypeName.TIMESTAMP_WITH_LOCAL_TIME_ZONE) {
          if (literal.getValue() instanceof NlsString) {
              String timestampStr = ((NlsString) literal.getValue()).getValue();
              Long timestampLong = SqlFunctions.toTimestampWithLocalTimeZone(timestampStr);
              reducedValues.add(rexBuilder.makeLiteral(timestampLong, e.getType(), true));
          }
      }
      
      if (reducedValues.isEmpty()) {
          executor.reduce(rexBuilder, ImmutableList.of(e), reducedValues);
      }
      

      Let us know if we can submit a pull request with this code change or if we've missed anything. Do you know the reason behind using a pre-compiled code for timestamp conversion?

        Attachments

        1. Proposed.txt
          25 kB
          Valeriy Trofimov
        2. Current.txt
          32 kB
          Valeriy Trofimov

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              • Assignee:
                Unassigned
                Reporter:
                ValTrofFuture Valeriy Trofimov
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