[jira] [Commented] (CALCITE-1337) Lazy evaluate RexCall digests

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15403271#comment-15403271 ] 

Julian Hyde commented on CALCITE-1337:
--------------------------------------

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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