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https://issues.apache.org/jira/browse/CALCITE-3981?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Haisheng Yuan updated CALCITE-3981:
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Fix Version/s: 1.24.0
> Volcano.register should not return stale/merged subset
> ------------------------------------------------------
>
> Key: CALCITE-3981
> URL: https://issues.apache.org/jira/browse/CALCITE-3981
> Project: Calcite
> Issue Type: Bug
> Reporter: Botong Huang
> Priority: Major
> Fix For: 1.24.0
>
> Time Spent: 1h 20m
> Remaining Estimate: 0h
>
> When a subset is registered, registerImpl() and registerSubset() currently
> simply returns the subset itself. The problem is that subset can become stale
> when relSets get merged (for example in ensureRegistered() and
> registerSubset() "merge(set, subset.set)"). As a result, a stale/merged
> subset might be returned from registerImpl, and the newly registering subtree
> might get registered recursively on top of the stale subset (see
> AbstractRelNode.onRegister()). This is a leak because once a relSet/subset is
> merged into others and becomes stale, it should not be used to connect new
> relNodes.
> With CALCITE-3755, subsets can now be directly matched by rules. This opens
> another source of stale subset leak: (1) An active subset gets matched, the
> RuleMatch gets queued in RuleQueue. (2) The subset becomes stale due to
> relSet merge. (3) The rule match in (1) is popped from queue and fired. (4)
> In OnMatch the rule gets the stale subset, builds new rels on top of it and
> regsiter the new rels. In this case, the entire new rel subtree will be
> registered on top of the stale subset as is.
> Rather than returning the registering subset itself, register should always
> use canonize() to find and return the equivalent active subset instead.
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