[jira] [Comment Edited] (CALCITE-3952) Improve SortRemoveRule to remove Sort based on rowcount

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

    [ https://issues.apache.org/jira/browse/CALCITE-3952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17091050#comment-17091050 ] 

Julian Hyde edited comment on CALCITE-3952 at 4/24/20, 12:23 AM:
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The SQL {{select * from (values 1) as t\(x) order by x fetch 1 offset 10}} should return zero rows. After you remove the Sort it will return 1 row.

I don't think we need a boolean flag and two rule instances. One rule that checks both conditions.

Yes, I think it's worth doing the RelBuilder thing as well. 3 lines in RelBuilder and a simple test in RelBuilderTest. (I know it's a bit belt-and-braces.)


was (Author: julianhyde):
The SQL {{select * from (values 1) as t(x) order by x fetch 1 offset 10}} should return zero rows. After you remove the Sort it will return 1 row.

I don't think we need a boolean flag and two rule instances. One rule that checks both conditions.

Yes, I think it's worth doing the RelBuilder thing as well. 3 lines in RelBuilder and a simple test in RelBuilderTest. (I know it's a bit belt-and-braces.)

> Improve SortRemoveRule to remove Sort based on rowcount
> -------------------------------------------------------
>
>                 Key: CALCITE-3952
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3952
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>            Priority: Major
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> If a query is guaranteed to produce maximum one row it is safe to remove Sort (along with limit). 
> Example:
> {code:sql}
> select count(*) cs from store_sales where ss_ext_sales_price > 100.00 order by cs limit 100
> {code}
> Although logically equivalent this can greatly benefit physical plans by removing extra operator and avoiding unnecessary data transfer.



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