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https://issues.apache.org/jira/browse/CALCITE-2974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16812942#comment-16812942
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Chunwei Lei edited comment on CALCITE-2974 at 4/9/19 2:31 AM:
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[~ValTrofFuture], Thanks for raising this.
Though your proposal greatly improves performance, I think we should not use
implementation in SqlFunctions in RexSimplify which may be not user's expect
behavior. Besides, it may cause different behavior between
RexSimplify.simplifyCast and ReduceExpressionRule if users has provided an own
executor.
was (Author: chunwei lei):
[~ValTrofFuture], Thanks for raising this.
Though your proposal greatly improves performance, I think we should not use
implementation in SqlFunctions in RexSimplify which may be not user's expect
behavior. Besides, it may cause different behavior between
RexSimplify.simplifyCast and ReduceExpressionRule if users has provide an own
executor.
> Timestamp conversion performance can be improved
> ------------------------------------------------
>
> Key: CALCITE-2974
> URL: https://issues.apache.org/jira/browse/CALCITE-2974
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.19.0
> Reporter: Valeriy Trofimov
> Priority: Major
> Labels: easyfix, performance
> Fix For: next
>
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> RexSimplify.simplifyCast() is slow when converting a string to SQL Timestamp
> value. The slowness is caused by this line:
> {code:java}
> executor.reduce(rexBuilder, ImmutableList.of(e), reducedValues);
> {code}
> 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:
> {code:java}
> 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);
> }
> {code}
> 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?
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