Re: Adjusting index special storage for pg_filedump's convenience

Gavin Sherry <swm@alcove.com.au> writes:
> On Mon, 9 Apr 2007, Tom Lane wrote:
>> ... I don't see any way to make it completely bulletproof
>> without enlarging the special space, which seems an unreasonable price
>> to pay.  But even one chance in 16K is way better than the current
>> situation.

> Sounds like the only workable approach.

Actually, I realized after writing that that it *is* possible to make it
bulletproof: all we have to do is make the BTCycleId wrap around at a
little less than 64K, which adds about one line of code and doesn't
materially change its reliability.  That leaves a few bitpatterns free
for IDs of other index types with no chance of collision.  I made hash
use 0xFF80 and gist 0xFF81; please use 0xFF82 for bitmaps.  (GIN turns
out not to need a code because its special space is a different size,
so we can tell it apart anyway.)

See patch already committed here:
http://archives.postgresql.org/pgsql-committers/2007-04/msg00125.php
        regards, tom lane