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https://issues.apache.org/jira/browse/CALCITE-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15403271#comment-15403271
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Julian Hyde commented on CALCITE-1337:
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Is {{RexCall.toString()}} called often? (Not counting the case where tracing is
enabled.) If it is, we have a performance bug that we should definitely fix.
If we have large expressions, then there is considerable duplication of
strings. For example, in {{0 + 1 + 2 + ... + 999999}}, the string "99998 +
999999" will occur in all digests but one. Maybe a
[rope|http://ahmadsoft.org/ropes/] would be a better data structure.
> Lazy evaluate RexCall digests
> -----------------------------
>
> Key: CALCITE-1337
> URL: https://issues.apache.org/jira/browse/CALCITE-1337
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Ted Xu
> Assignee: Julian Hyde
> Fix For: 1.8.0
>
>
> Currently RexCall compute digests eagerly in its constructor, also, it
> compute digest every time when toString invoked. It may cause performance
> issue when the RexCall tree is very large.
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