Horton

Re: COPY FROM WHEN condition

Surafel Temsgen <surafel3000@gmail.com>

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From: Surafel Temesgen <surafel3000@gmail.com>
To: dean.a.rasheed@gmail.com
Cc: tomas.vondra@2ndquadrant.com, Adam Berlin <berlin.ab@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2018-11-26T13:05:15Z
Lists: pgsql-hackers 
On Sat, Nov 24, 2018 at 12:02 PM Dean Rasheed <dean.a.rasheed@gmail.com>
wrote:

> Right now we have 2 syntaxes for filtering rows in queries, both of
> which use WHERE immediately before the condition:
>
> 1). SELECT ... FROM ... WHERE condition
>
> 2). SELECT agg_fn FILTER (WHERE condition) FROM ...
>
> I'm not a huge fan of (2), but that's the SQL standard, so we're stuck
> with it. There's a certain consistency in it's use of WHERE to
> introduce the condition, and preceding that with FILTER helps to
> distinguish it from any later WHERE clause. But what you'd be adding
> here would be a 3rd syntax
>
> 3). COPY ... FROM ... FILTER condition
>
> which IMO will just lead to confusion.
>


your case is for retrieving data but this is for deciding which data to
insert and word FILTER I think describe it more and not lead to confusion.

regards
Surafel

Commits

  1. Remove unused struct member, enforce multi_insert callback presence.

  2. Separate per-batch and per-tuple memory contexts in COPY

  3. Fix handling of volatile expressions in COPY FROM ... WHERE

  4. Allow COPY FROM to filter data using WHERE conditions

  5. Remove obsolete netbsd dynloader code