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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.
This commit is contained in:
Bruce Momjian 2005-12-17 16:43:11 +00:00
parent 927f57687f
commit 9e9a844f55
2 changed files with 20 additions and 2 deletions
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11
doc/TODO
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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 09:18:30 EST 2005
Last updated: Sat Dec 17 11:43:02 EST 2005
The most recent version of this document can be viewed at
http://www.postgresql.org/docs/faqs.TODO.html.
@ -1028,6 +1028,15 @@ 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.
Miscellaneous Performance

11
doc/src/FAQ/TODO.html
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@ -8,7 +8,7 @@
<body bgcolor="#FFFFFF" text="#000000" link="#FF0000" vlink="#A00000" alink="#0000FF">
<h1><a name="section_1">PostgreSQL TODO List</a></h1>
<p>Current maintainer: Bruce Momjian (<a href="mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</a>)<br/>
Last updated: Sat Dec 17 09:18:30 EST 2005
Last updated: Sat Dec 17 11:43:02 EST 2005
</p>
<p>The most recent version of this document can be viewed at<br/>
<a href="http://www.postgresql.org/docs/faqs.TODO.html">http://www.postgresql.org/docs/faqs.TODO.html</a>.
@ -933,6 +933,15 @@ first.
</p>
</li><li>Log statements where the optimizer row estimates were dramatically
different from the number of rows actually found?
</li><li>Allow star join optimizations
<p> 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.
</p>
</li></ul>
<h1><a name="section_21">Miscellaneous Performance</a></h1>