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https://issues.apache.org/jira/browse/CALCITE-1290?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15327947#comment-15327947
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Julian Hyde commented on CALCITE-1290:
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The bound could be in terms of number of leaves (counting a leaf twice if it
occurs in two expressions) or in terms of nodes (leaves plus interior nodes). I
don't mind which... either would be effective, and one might be easier to
compute efficiently as the CNF is being built.
> When converting to CNF, fail if the expression exceeds a threshold
> ------------------------------------------------------------------
>
> Key: CALCITE-1290
> URL: https://issues.apache.org/jira/browse/CALCITE-1290
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> When converting to conjunctive normal form (CNF), fail if the expression
> exceeds a threshold. CNF can explode exponentially in the size of the input
> expression, but rarely does so in practice. Add a {{maxNodeCount}} parameter
> to {{RexUtil.toCnf}} and throw or return null if it is exceeded.
> I don't believe it is possible to predict the size of the CNF from the input
> expression (especially if there are duplicate terms) but I might be wrong.
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