Обсуждение: RE: [INTERFACES] 8k limit

The 8kB limit you are refering to is probably the tuple-length limit.  This
can be altered to a maximum of 64kB (I think, might only be 32kB), but you
need to recompile your server, and initdb.  This limit will not be removed
until at least version 7.
There is also a limit on the length of a query string, if you are using a
6.5.x production release.  This limit is set to twice the tuple-length
limit, so if your block-size (tuple-length) is set to 8kB, then your maximum
query string length will be 16kB.  If you recompile your server to up the
block-size to, say, 32kB, then your query string limit will automatically be
altered to 64kB.

As far as the number of los go, I'm afraid I can't help you on that one.

MikeA


>> -----Original Message-----
>> From: StOo [mailto:stuart@comodo.net]
>> Sent: Tuesday, October 26, 1999 2:45 PM
>> To: pgsql-interfaces@postgreSQL.org
>> Subject: [INTERFACES] 8k limit
>> 
>> 
>> 
>> Hello,
>>  Im trying to store a string of ascii characters greater 
>> than 8k. Is there a
>> tunable which will allow me to alter the 8k max limit? Im 
>> pretty sure this has
>> been discussed here before =). Next question is whats the 
>> max number of large
>> objects you can store? I think its about 4 billion , am i wrong?
>> 
>> 
>> 
>> +-=-=-=-=-=-=-=StOo=-=-=-=-=-=-=-+
>> 
>> Stuart Hodgkinson Software Engineer
>> stuart@comodo.net 
>> 
>> 
>> 
>> ************
>> 

"Ansley, Michael" <Michael.Ansley@intec.co.za> writes:
> The 8kB limit you are refering to is probably the tuple-length limit.  This
> can be altered to a maximum of 64kB (I think, might only be 32kB),

32k; otherwise Michael's comments are accurate.

>>> been discussed here before =). Next question is whats the 
>>> max number of large
>>> objects you can store? I think its about 4 billion , am i wrong?

Each LO results in the creation of two files in your database directory,
which means performance will get pretty horrible when you get past a
few thousand LOs (at least on most flavors of Unix, which are not
optimized for huge directories).

There has been discussion of fixing this, eg by making a subdirectory
tree for LOs, but I'd rather see us put our effort into eliminating
the tuple length limit.
        regards, tom lane

> 
> There has been discussion of fixing this, eg by making a subdirectory
> tree for LOs, but I'd rather see us put our effort into eliminating
> the tuple length limit.
> 
This would be very nice - because this also means to get SQL
statements that may really be 8k long !
Perhaps you all remember a rather complex view statement I posted here
some days ago, where postgresql said something like "rule too large" and
this seems to be a limitation for me. Actually as a user one does not know
when this limit is reached by the system.
All "we" (the users :-)) know about the 8192 byte limit of an SQL statement,
but this is not the whole truth.
Marten