Re: patch: function xmltable

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: patch: function xmltable
Date: 2017-01-31 13:57:07
Message-ID: 20170131135707.b433fy2ph2v5lp4k@alvherre.pgsql
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Pavel Stehule wrote:
> 2017-01-24 21:38 GMT+01:00 Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>:

> > I think it would be good to have a more complex test case in regress --
> > let's say there is a table with some simple XML values, then we use
> > XMLFOREST (or maybe one of the table_to_xml functions) to generate a
> > large document, and then XMLTABLE uses that document as input document.
>
> I have a 16K lines long real XML 6.MB. Probably we would not to append it
> to regress tests.
>
> It is really fast - original customer implementation 20min, nested our
> xpath implementation 10 sec, PLPython xml reader 5 sec, xmltable 400ms

That's great numbers, kudos for the hard work here. That will make for
a nice headline in pg10 PR materials. But what I was getting at is that
I would like to exercise a bit more of the expression handling in
xmltable execution, to make sure it doesn't handle just string literals.

> I have a plan to create tests based on pg_proc and CTE - if all works, then
> the query must be empty
>
> with x as (select proname, proowner, procost, pronargs,
> array_to_string(proargnames,',') as proargnames,
> array_to_string(proargtypes,',') as proargtypes from pg_proc), y as (select
> xmlelement(name proc, xmlforest(proname, proowner, procost, pronargs,
> proargnames, proargtypes)) as proc from x), z as (select xmltable.* from y,
> lateral xmltable('/proc' passing proc columns proname name, proowner oid,
> procost float, pronargs int, proargnames text, proargtypes text)) select *
> from z except select * from x;

Nice one :-)

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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