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Re: type unknown - how important is it?

From: Shachar Shemesh <psql(at)shemesh(dot)biz>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: type unknown - how important is it?
Date: 2004-09-28 20:17:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Joshua D. Drake wrote:

> Shachar Shemesh wrote:
>> I have a complaint from an OLE DB user that when he does "select 
>> 'a'", he gets an "unhanded type" error. Since OLE DB uses a binary 
>> interface, it has to know about all variable types that pass through it.
>> The debug information for the problem show that the returned type is 
>> 705, which is "unknown". My question is - what is "unknown" used for? 
>> Is it important to support binary send and receives with this type? 
>> Does postgresql know how to convert it to other types?
>> I was under the impression that 'a' would be "text". Why is "unknown" 
>> used instead?
> Try casting a to varchar. Which is binary compatible but understood by 

Hmm, I did not explain myself clearly enough.

I maintain the OLE DB provider. My question was not that. My question 
was whether I should add support to unknown? If so, what type should it 
be represented to outside applications?

If unknown is binary compatible to text, I can just pass it on as text 
and have it done with. The question is whether that makes sense, whether 
it makes more sense to pull and error if that happens, or whether there 
is something else which I should do.



Shachar Shemesh
Lingnu Open Source Consulting ltd.

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