Re: [PATCHES] Bitmapscan changes

Tom Lane wrote:
> At this point I'm feeling unconvinced that we want it at all. It's
> sounding like a large increase in complexity (both implementation-wise
> and in terms of API ugliness) for a fairly narrow use-case --- just how
> much territory is going to be left for this between HOT and bitmap indexes?

I'm in a awkward situation right now. I've done my best to describe the
use cases for clustered indexes. I know the patch needs refactoring,
I've refrained from making API changes and tried to keep all the
ugliness inside the b-tree, knowing that there's changes to the indexam
API coming from the bitmap index patch as well.

I've been seeking for comments on the design since November, knowing
that this is a non-trivial change. I have not wanted to spend too much
time polishing the patch, in case I need to rewrite it from scratch
because of some major design flaw or because someone comes up with a
much better idea.

It's frustrating to have the patch dismissed at this late stage on the
grounds of "it's not worth it". As I said in February, I have the time
to work on this, but if major changes are required to the current
design, I need to know.

Just to recap the general idea: reduce index size taking advantage of
clustering in the heap.

Clustered indexes have roughly the same performance effect and use cases
as clustered indexes on MS SQL Server, and Index-Organized-Tables on
Oracle, but the way I've implemented them is significantly different. On
other DBMSs, the index and heap are combined to a single b-tree
structure. The way I've implemented them is less invasive, there's no
changes to the heap for example, and it doesn't require moving live tuples.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com