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https://issues.apache.org/jira/browse/CALCITE-2974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16816836#comment-16816836
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Danny Chan commented on CALCITE-2974:
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Well, i also think the code consistent is very important even though we have a
plugin RexExecutor, BTW, does this problem significantly reduce usability of
your production query ? After all, the total time for simplifying is not that
much, for me it does not make that much sense to get double the performance
boost, cause the constants reduction takes very little part of time for query
planning, the most time consuming part is the Volcano possibilities boost when
we compute the lowest cost.
> 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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