From: Ian Barwick <barwick@gmx.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Patch for DBD::Pg pg_relcheck problem
Date: Tue, 10 Dec 2002 00:34:31 +0100
References: <200212091631.00125.barwick@gmx.net>
	<8159.1039449832@sss.pgh.pa.us>
In-Reply-To: <8159.1039449832@sss.pgh.pa.us>
Cc: dbi-dev@perl.org, pgsql-interfaces@postgresql.org
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On Monday 09 December 2002 17:03, Tom Lane wrote:
> Ian Barwick <barwick@gmx.net> writes:
> > To avoid voodoo with PostgreSQL version numbers
> > a check is made whether pg_relcheck exists and
> > the appropriate query (either 7.3 or pre 7.3)
> > executed.
>
> I would think that looking at version number (select version())
> would be a much cleaner approach.  Or do you think that direct
> examination of pg_class is a version-independent operation?

No, but I was hoping it will remain stable for long enough
for what is basically a temporary work around until a revised version of=20
DBD::Pg can be produced. It doesn't make any more assumptions=20
about pg_class than are made elsewhere in the current Pg.pm.

> This inquiry into pg_relcheck's existence is already arguably wrong
> in 7.3 (since it's not taking account of which schema pg_relcheck
> might be found in) and it can only go downhill in future versions.

Doh. Knew I had to be missing something obvious. (Of course,
anyone using current DBD::Pg with 7.3 as is will have to take
extra care with system tables and schema namespaces anyway.)

So out with the candle wax and pins ;-). Am I right
in thinking that the string returned by SELECT version()
starts with the word "PostgreSQL" followed by:
  a space;=20
  a single digit indicating the major version number;
  a full stop / decimal point;
  a single digit indicating the minor version number;
and either "interim release" number (e.g. ".1" in the case of 7.3.1), or
"devel", "rc1" etc. ?
And that this has been true since 6.x and will continue for the forseeable=
=20
future (i.e. far far longer than the intended lifespan of attached patch)?


Ian Barwick
barwick@gmx.net

Attached: revised patch


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619c619,629
<             my ($constraint) = $dbh->selectrow_array("select rcsrc from pg_relcheck where rcname = '${table}_$col_name'");
---
>             # Note: as of PostgreSQL 7.3 pg_relcheck has been replaced
>             # by pg_constraint. To maintain compatibility, check 
>             # version number and execute appropriate query.
> 	
>             my ($version) = $dbh->selectrow_array("SELECT version()");
>             $version =~ /^PostgreSQL (\d)\.(\d)/;
>             
>             my $con_query = $1.$2 < 73
>              ? "SELECT rcsrc FROM pg_relcheck WHERE rcname = '${table}_$col_name'"
>              : "SELECT consrc FROM pg_catalog.pg_constraint WHERE contype = 'c' AND conname = '${table}_$col_name'";
>             my ($constraint) = $dbh->selectrow_array($con_query);

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