Обсуждение: 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.

Ocie Mitchell

>
> 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


--
Bruce Momjian                          |  830 Blythe Avenue
maillist@candle.pha.pa.us              |  Drexel Hill, Pennsylvania 19026
  +  If your life is a hard drive,     |  (610) 353-9879(w)
  +  Christ can be your backup.        |  (610) 853-3000(h)