[
https://issues.apache.org/jira/browse/CALCITE-4514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17291978#comment-17291978
]
Julian Hyde commented on CALCITE-4514:
--------------------------------------
I missed it first time around: you are dealing with the subtle (and somewhat
infrequent) case of a cycle of length 1. It's worth calling out in the comment.
Computing child sets, and whether set is parent of set2, is a little expensive,
so I would cache in variables.
I stand by my previous remarks that when neither is parent of the other, it is
worth choosing by popularity first, size second, and lastly age.
> Prefer merge new relset into old relset when they are parent set of each other
> ------------------------------------------------------------------------------
>
> Key: CALCITE-4514
> URL: https://issues.apache.org/jira/browse/CALCITE-4514
> Project: Calcite
> Issue Type: Improvement
> Reporter: Botong Huang
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> When merging two relsets, we have two preferences:
> 1. Merge parent relset into child relset
> 2. Merge newer relset into older relset
> Currently, when the two relsets are parent set of each other, we randomly
> pick a merge order without checking the second condition above. For
> performance reasons, we should, to avoid unnecessary churn.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
