Re: More then 1600 columns?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Clark C(dot) Evans" <cce(at)clarkevans(dot)com>
Cc: "Mark Mitchell" <mmitchell(at)riccagroup(dot)com>, "'Dmitriy Igrishin'" <dmitigr(at)gmail(dot)com>, "'Dann Corbit'" <DCorbit(at)connx(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: More then 1600 columns?
Date: 2010-11-13 03:49:35
Message-ID: 8914.1289620175@sss.pgh.pa.us
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"Clark C. Evans" <cce(at)clarkevans(dot)com> writes:
> What would be most helpful though is if the answer to
> this question stop being an attack on the business
> requirement analysis, database design skills, and/or
> sanity of the requester. It's a limitation of
> PostgreSQL's implementation; a deliberate performance
> trade-off that is infeasible to change.

Just for the record: I don't think its *infeasible* to change it.
What I'm saying is that it would be a bad tradeoff for the vast
majority of users.

I could imagine accepting a patch that provides a compile-time option
to change the limit. The core of it would be something like

+ #ifdef SUPPORT_RIDICULOUSLY_MANY_COLUMNS
+ uint16 t_hoff; /* sizeof header incl. bitmap, padding */
+ #else
uint8 t_hoff; /* sizeof header incl. bitmap, padding */
+ #endif

plus whatever other fallout ensues elsewhere. But somebody would have
to step up to develop and test such a patch, and keep on testing it to
ensure no bit-rot sets in, because it seems very unlikely that any
mainstream distributions would ever choose to enable the option.
I don't think any of the core developers have any interest in hacking
on this; we have bigger fish to fry. So it'd be a matter of someone
scratching their own itch.

regards, tom lane

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