Subject: "large" classes

From: [email-masked] (Chris Hermansen )
Date: Fri, 3 Apr 92 20:47:50 -0800

Gee, I joined the list yesterday and no flood of postings!  Not like the other
two lists I'm on... :-)

Anyway, for the question:  I have been messing around with Postquel trying to
learn a bit about it.  My DBMS experience comes primarily from an SQL (Ok, so
it's probably taboo to use the S-word here, sorry) product we use for a lot
of ad-hoc query and data analysis; Postquel seems more flexible and concise
so I thought I'd try it out on some of our "real" data.

Now, I don't typically normalize the daylights out of things, especially for
throwaway datasets that I often use.  So, my tables are often very wide.  Upon
trying such a wide monster with Postquel, I run into problems; the "copy from"
command seems to load the table with garbage, "append" seems to go off into
the ozone, etc.  So, I normalized the original data somewhat (outside of
Postquel) and tried again, and presto, things worked.  So OK, I now have a
more elegant design, but the question lingers: is there some obvious limit
to the number of attributes within a class?  Is there a good place in the
docs/src to look for things like this, or should I spend late hours searching
the entrails of the code for clues?  Or am I way off base?

I should hasten to add that I've given the docs and Postgres papers a hasty
read, but I'd be the first to admit I could have easily missed something.

And oh yes, this is version 3.0.

Thanks for the attention;

Just another Postgres rookie,

Chris Hermansen                         Timberline Forest Inventory Consultants
Voice: 1 604 733 0731                   302 - 958 West 8th Avenue
FAX:   1 604 733 0634                   Vancouver B.C. CANADA
[email-masked]                          V5Z 1E5

C'est ma facon de parler.

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From: postarch (Postgres Mailing Archive)
Date: Mon, 06 Apr 92 15:57:08 PDT

> the entrails of the code for clues?  Or am I way off base?

If you were to "spend late hours searching the entrails of the code for clues"
you would find that the hardwired limit is defined by:

	#define MaxHeapAttributeNumber  1600            /* 8 * 200 */

But I can guarantee you that this limit is not well tested.  Another
limit is that each tuple must fit within a single page (8k), unless you use
the large object interface.  It sounds to me like you may have come across
a bug.  I would be interested to see the schema definition to find out what's
really going on.

Jeff Meredith
[email-masked]