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< * Allow star join optimizations
<
<   While our bitmap scan allows multiple indexes to be joined to get
<   to heap rows, a star joins allows multiple dimension _tables_ to
<   be joined to index into a larger main fact table.  The join is
<   usually performed by either creating a cartesian product of all
<   the dimmension tables and doing a single join on that product or
<   using subselects to create bitmaps of each dimmension table match
<   and merge the bitmaps to perform the join on the fact table.  Some
<   of these algorithms might be patented.
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Bruce Momjian
2005-12-17 19:03:24 +00:00
parent 3282b6338b
commit 25af534ea1
2 changed files with 2 additions and 22 deletions
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@ -2,7 +2,7 @@
PostgreSQL TODO List
====================
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
Last updated: Sat Dec 17 13:06:57 EST 2005
Last updated: Sat Dec 17 14:03:20 EST 2005
The most recent version of this document can be viewed at
http://www.postgresql.org/docs/faqs.TODO.html.
@ -1029,16 +1029,6 @@ Optimizer / Executor
* Log statements where the optimizer row estimates were dramatically
different from the number of rows actually found?
* Allow star join optimizations
While our bitmap scan allows multiple indexes to be joined to get
to heap rows, a star joins allows multiple dimension _tables_ to
be joined to index into a larger main fact table. The join is
usually performed by either creating a cartesian product of all
the dimmension tables and doing a single join on that product or
using subselects to create bitmaps of each dimmension table match
and merge the bitmaps to perform the join on the fact table. Some
of these algorithms might be patented.
Miscellaneous Performance