Re: Insert Documentation - Returning Clause and Order

From: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
To: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Cc: Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Insert Documentation - Returning Clause and Order
Date: 2020-12-11 22:31:04
Message-ID: CAKFQuwZc3YPKDBrAnxXo8Ad+21kWf0hXuZNEXtJqXKX1FwkoUw@mail.gmail.com
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On Fri, Dec 11, 2020 at 6:24 AM Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
wrote:

> On Thu, Dec 10, 2020 at 7:49 PM David G. Johnston
> <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
> > Yeah, the ongoing work on parallel inserts would seem to be an issue.
> We should probably document that though. And maybe as part of parallel
> inserts patch provide a user-specifiable way to ask for such a guarantee if
> needed. ‘Insert returning ordered”
>
> I am curious about the usecase which needs that guarantee? Don't you
> have a column on which you can ORDER BY so that it returns the same
> order as INSERT?
>

This comes up periodically in the context of auto-generated keys being
returned - specifically on the JDBC project list (maybe elsewhere...). If
one adds 15 VALUES entries to an insert and then sends them in bulk to the
server it would be helpful if the generated keys could be matched up
one-to-one with the keyless objects in the client. Basically "pipelining"
the client and server.

David J.

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