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

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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 16:38:14
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers

On 02/21/2011 11:23 AM, Tom Lane wrote:
> 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?

Well, I thought the motivation was to allow easy construction of parsers 
for the data, since creating a parser for those formats is pretty trivial.

Anyway, if we don't care about validation that's fine. I just didn't 
want us to make that decision unconsciously.



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