From: Matthew Nuzum (matt.followers_at_gmail.com)
Date: Thu 28 Apr 2005 - 15:49:59 BST
> >>Sadly, Postgres is missing these important features;
> >> - bitmap indexes
> >> - OLAP query re-writing
I'm a big postgres fan and closely follow the performance mailing list.
These features sound intriguing so I'm going to enquire about their status.
Interestingly, I've heard recent discussions about both bitmap indexes and
materialized views and my belief was that many people on the list are using
materialized views now, though I'm not sure if that is provided by a
contributed module.
I'm not trying to convince you to switch to PG, I'm just curious if these
features are available to me. BTW, one interesting feature that Oracle has
is the ability to store hierarchical data in a flat db table and pull it out
in one query. For example:
It can take this data: And sort it *correctly* like this:
Id Parent Name Id Name
0 Home 0 Home
1 0 Documents 1 Documents
2 0 Applications 4 Work
3 0 Pictures 5 Personal
4 1 Work 2 Applications
5 1 Personal 6 Photoshop
6 2 Photoshop 7 OpenOffice.org
7 2 OpenOffice.org 3 Pictures
8 3 Family 8 Family
This takes several queries in PostgreSQL.
[Pause (always Google before you post)]
Oh, I knew bitmaps were fresh in my memory:
http://sql-info.de/postgresql/news/weekly-news_2005-04-24.html
"... Victor Y. Yegorov's on-disk bitmap indexes, which are a new index type
intended to allow indexing low-cardinality attributes on large tables. The
two features together should greatly improve performance of descision
support / business intelligence workloads."
And:
http://jonathangardner.net/PostgreSQL/materialized_views/matviews.html
"Materialized views are certainly possible in PostgreSQL. Because of
PostgreSQL's powerful PL/pgSQL language, and the functional trigger system,
materialized views are somewhat easy to implement."
Thanks for describing these features; they look like areas where I can
improve some aspects of my application.
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