Re: MySQL search query is not executing in Postgres DB

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Bruce Momjian <bruce(at)momjian(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, premanand <kottiprem(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: MySQL search query is not executing in Postgres DB
Date: 2012-11-27 09:59:04
Message-ID: 1354010344.10198.188.camel@jdavis-laptop
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On Wed, 2012-11-21 at 15:27 +0000, Simon Riggs wrote:
> It would be useful if we issued a NOTICE when an ambiguity is
> introduced, rather than when using it.
> Like Bison's reporting of reduce conflicts.

This brings up a very important point, which is that a lot of the code
is frozen in applications yet invisible at DDL time. So we have to be
careful that DDL changes have a reasonable impact on the ability to
continue to compile and execute the previously-working SQL received from
the applications.

In other words, as I said in another reply, we want to avoid cases where
something seemingly innocuous (like creating a function) causes
previously-working SQL to fail due to ambiguity.

As Tom said, detecting the ambiguity at DDL time is not easy, so I'm not
suggesting that. And I know that creating a function can already cause
previously-working SQL to fail. I'm just saying we should be careful of
these situations and not make them more likely than necessary.

Jeff Davis

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