On Mon, 26 Dec 2005, Tom Lane wrote:
...snip...
Thanks, it's a very good explanation!
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TIP 6: explain analyze is your friend
Ivan Voras [EMAIL PROTECTED] writes:
This is PostgreSQL 8.1.0.
- what does Bitmap Heap Scan phase do?
A plain indexscan fetches one tuple-pointer at a time from the index,
and immediately visits that tuple in the table. A bitmap scan fetches
all the tuple-pointers from the index in one go,
PFC wrote:
There's a great deal about this in the list archives (probably more in
pgsql-hackers than in -performance). Most of the current interest has
to do with building in-memory bitmaps on the fly, as a way of decoupling
index and heap scan processing. Which is not quite what you're
PFC wrote:
contrib/intarray has an index type which could be what you need.
I've used intarray for a site that requires that I match multiple low
cardinality attributes with multiple search criteria. Here's an
(abridged) example:
The table:
\d person_attributes
Table
[EMAIL PROTECTED] (Alex Turner) writes:
I was wondering about index types. Oracle has an index type called a
'bitmap' index. They describe this as an index for low cardinality
fields, where only the cardinal values are indexed in a b-tree, and
then it uses a bitmap below that to describe
