I was playing around with my latest compile and tried to make a unique
index on two columns, using a hash method.  Both of these (more than
one column and unique) are currently not allowed for hash indexes.

I thought about this for a bit and realized that making a NESTED hash
index (index on a and b also serves as an index on a) would be a
trick, but allowing the unique clause should not be a problem.

Therefore, I would like to try implementing unique constraints on hash
indexes.  Has this come up before?  Are there any reasons not to
support this?  As far as I understand, specifying an index method is
non standard (above and beyond standard) to begin with.

Ocie Mitchell


Mon, 16 Mar 1998 17:45:15 -0800 (PST)
ocie@paracel.com
Unique index using hash?
> 
> I was playing around with my latest compile and tried to make a unique
> index on two columns, using a hash method.  Both of these (more than
> one column and unique) are currently not allowed for hash indexes.
> 
> I thought about this for a bit and realized that making a NESTED hash
> index (index on a and b also serves as an index on a) would be a
> trick, but allowing the unique clause should not be a problem.
> 
> Therefore, I would like to try implementing unique constraints on hash
> indexes.  Has this come up before?  Are there any reasons not to
> support this?  As far as I understand, specifying an index method is
> non standard (above and beyond standard) to begin with.
> 

It is on the TODO list:

	* add UNIQUE capability to non-btree indexes


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Mon, 16 Mar 1998 22:02:49 -0500 (EST)
Bruce Momjian <maillist@candle.pha.pa.us>
Re: [HACKERS] Unique index using hash?