On 02/07/10 13:31, Bruce Momjian wrote:
> Leonardo F wrote:
>    
>> I'm trying to find more docs that explain the "improvements" of
>> bitmap indexes in other products... but most of what I've found
>> talks about bitmapAND/OR.... which is something that is very
>> cool, but that postgres already does even with btree indexes...
>> or index creation time/size, which are, for the moment, the only
>> things that I'm pretty confident the patch would actually provide.
>>      
> I think a real limitation of on-disk bitmap indexes is that they are
> only feable for low cardinality columns, while btree handles all column
> types.
>
>    

I recall that for (some/most? of) those low cardinality cases, (on disk) 
bitmap indexes would perform better too. I think the size saving alone 
is a huge win for serious data warehousing situations. On the other hand 
problems I recall are possibly reduced UPDATE/DELETE performance and 
issues with CREATE INDEX CONCURRENTLY and also complications with VACUUM 
(altho these last two may have been sorted - I've lost touch with what 
was in the most recent patches).

regards

Mark

In response to

• Re: bitmap indexes - performance at 2010-07-02 01:31:32 from Bruce Momjian

Responses

• Re: bitmap indexes - performance at 2010-07-03 02:00:26 from Mark Kirkwood

pgsql-hackers by date

Next:	From: uwcssa	Date: 2010-07-02 11:59:56
	Subject: hello
Previous:	From: Magnus Hagander	Date: 2010-07-02 08:16:15
	Subject: Re: server authentication over Unix-domain sockets