Re: FETCH FIRST clause PERCENT option

From: Surafel Temesgen <surafel3000(at)gmail(dot)com>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: vik(dot)fearing(at)2ndquadrant(dot)com, Mark Dilger <hornschnorter(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, andrew(at)tao11(dot)riddles(dot)org(dot)uk
Subject: Re: FETCH FIRST clause PERCENT option
Date: 2019-01-24 09:57:08
Message-ID: CALAY4q8NDVwv6ZbB63nL4B4zVwTsaDeu+BRDnLzQO-eT4pN7hA@mail.gmail.com
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On Wed, Jan 9, 2019 at 8:18 PM Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
wrote:

>
> See the attached patch, which recomputes the count regularly. I don't
> claim the patch is committable or that it has no other bugs, but
> hopefully it shows what I meant.
>
>

I got only one issue it is not work well with cursor

postgres=# START TRANSACTION;

START TRANSACTION

postgres=# create table t as select i from generate_series(1,1000) s(i);

SELECT 1000

postgres=# declare c cursor for select * from t fetch first 5 percent rows
only;

DECLARE CURSOR

postgres=# fetch all in c;

ERROR: trying to store a minimal tuple into wrong type of slot

I am looking at it .

meanwhile i fix row estimation and cost and make create_ordered_paths
creation with no LIMIT consideration in PERCENTAGE case

regards

Surafel

Attachment Content-Type Size
percent-incremental-v2.patch text/x-patch 31.8 KB

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