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Re: [HACKERS] ODBC and palloc ...

From: Byron Nikolaidis <byronn(at)insightdist(dot)com>
To: Davide Libenzi <dlibenzi(at)maticad(dot)it>
Cc: pgsql-hackers(at)postgreSQL(dot)org, "pgsql-interfaces(at)postgreSQL(dot)org" <pgsql-interfaces(at)postgreSQL(dot)org>, David Hartwig <daveh(at)insightdist(dot)com>
Subject: Re: [HACKERS] ODBC and palloc ...
Date: 1998-07-23 17:30:42
Message-ID: 35B77342.6558C42B@insightdist.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-interfaces
Davide Libenzi wrote:
> 
> After a lot of changes I've compiled,linked and tested (regression) my
> PostgreSQL installation no HPUX 9.*.
> 
> I've also built and installed the ODBC driver and I get Ms Access error
> which the PostgresSQL server log in "palloc failure : memory exausted".
> 
> Is this a server bug or ODBC driver bug ?
> 

I am assuming you have a fairly new odbc driver (6.30.0248 is the
latest) and not the old postodbc.  BTW, on our website
(www.insightdist.com/psqlodbc) we have the DLL and a full install EXE
for win32 so you wouldn't have to build it yourself from the source code
if you didn't want to.

The palloc failure usually occurs because Access uses the multiple OR
query (select ... where a=1 OR a=2 OR a=3...) to access the recordset.
The backend does not handle this very well and it is already well known
on the TODO list.

There are several possibilities to get past this:
1. Use a non-updateable table (by setting the driver readonly option, or
by not specifying any unique identifiers).
2. For a query, use a snapshot recordset in the query properties.
3. Show the OID column in the drivers advanced datasource options and
use that alone to index on.  You should create an index on it too.  This
is still slow, but at least shouldn't crash.

Other possibilities:

In house, Dave made a patch to postgres which rewrites the multiple OR
query into a UNION query, which works great and its fast!  We may make
this patch available evntually on our website.

Byron

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