Re: FDW API: don't like the EXPLAIN mechanism

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Shigeru HANADA <hanada(at)metrosystems(dot)co(dot)jp>, Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: FDW API: don't like the EXPLAIN mechanism
Date: 2011-02-21 16:23:36
Message-ID: 14889.1298305416@sss.pgh.pa.us
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Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> On 02/19/2011 11:07 PM, Tom Lane wrote:
>> However, it occurs to me that as long as we're passing the function the
>> ExplainState, it has what it needs to add arbitrary EXPLAIN result
>> fields.

> If we allow the invention of new explain states we'll never be able to
> publish an authoritative schema definition of the data. That's not
> necessarily an argument against doing it, just something to be aware of.
> Maybe we don't care about having EXPLAIN XML output validated.

I thought one of the principal arguments for outputting XML/etc formats
was exactly that we'd be able to add fields without breaking readers.
If that's not the case, why did we bother?

regards, tom lane

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