[
https://issues.apache.org/jira/browse/CALCITE-4264?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17203325#comment-17203325
]
Thomas Rebele commented on CALCITE-4264:
----------------------------------------
I implemented the proposal and run the tests. It improves some plans slightly.
The order of a sort and project is arranged in a way, so that the sort is
applied to the input with the fewest columns. This is because the CPU cost of
sort takes the number of columns into account. A pull request is available.
> The query planner should take CPU cost into account
> ---------------------------------------------------
>
> Key: CALCITE-4264
> URL: https://issues.apache.org/jira/browse/CALCITE-4264
> Project: Calcite
> Issue Type: Improvement
> Reporter: Thomas Rebele
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Calcite only takes the row count into account when optimizing the queries.
> See [the relevant lines in
> VolcanoCost|https://github.com/apache/calcite/blob/52a57078ba081b24b9d086ed363c715485d1a519/core/src/main/java/org/apache/calcite/plan/volcano/VolcanoCost.java#L98-L116].
> However, two plans might have the same row count, but differ greatly in CPU
> cost. This happens for example when the limit sort rule
> ([CALCITE-3920|https://issues.apache.org/jira/browse/CALCITE-3920]) is
> activated. The row cost is the same, the EnumerableLimitSort only sorts the
> input partially, so has a lower CPU cost.
> Low impact proposal: Compare first the row cost, and only if the row cost is
> equal, compare by CPU cost.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
