PostgreSQL TODO List
====================
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
-Last updated: Thu Apr 21 00:09:27 EDT 2005
+Last updated: Thu Apr 21 11:20:13 EDT 2005
The most recent version of this document can be viewed at the PostgreSQL web
site, http://www.PostgreSQL.org.
* Allow non-bitmap indexes to be combined by creating bitmaps in memory
- Bitmap indexes index single columns that can be combined with other bitmap
- indexes to dynamically create a composite index to match a specific query.
- Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
- combined. They can index by tid or can be lossy requiring a scan of the
- heap page to find matching rows, or perhaps use a mixed solution where
- tids are recorded for pages with only a few matches and per-page bitmaps
- are used for more dense pages. Another idea is to use a 32-bit bitmap
- for every page and set a bit based on the item number mod(32).
+ This feature allows separate indexes to be ANDed or ORed together. This
+ is particularly useful for data warehousing applications that need to
+ query the database in an many permutations. This feature scans an index
+ and creates an in-memory bitmap, and allows that bitmap to be combined
+ with other bitmap created in a similar way. The bitmap can either index
+ all TIDs, or be lossy, meaning it records just page numbers and each
+ page tuple has to be checked for validity in a separate pass.
* Allow the creation of on-disk bitmap indexes which can be quickly
combined with other bitmap indexes
<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: Thu Apr 21 00:09:27 EDT 2005
+Last updated: Thu Apr 21 11:20:13 EDT 2005
</p>
<p>The most recent version of this document can be viewed at the PostgreSQL web<br/>
site, <a href="http://www.PostgreSQL.org">http://www.PostgreSQL.org</a>.
before accessing the heap rows.
</p>
</li><li>Allow non-bitmap indexes to be combined by creating bitmaps in memory
-<p> Bitmap indexes index single columns that can be combined with other bitmap
- indexes to dynamically create a composite index to match a specific query.
- Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
- combined. They can index by tid or can be lossy requiring a scan of the
- heap page to find matching rows, or perhaps use a mixed solution where
- tids are recorded for pages with only a few matches and per-page bitmaps
- are used for more dense pages. Another idea is to use a 32-bit bitmap
- for every page and set a bit based on the item number mod(32).
+<p> This feature allows separate indexes to be ANDed or ORed together. This
+ is particularly useful for data warehousing applications that need to
+ query the database in an many permutations. This feature scans an index
+ and creates an in-memory bitmap, and allows that bitmap to be combined
+ with other bitmap created in a similar way. The bitmap can either index
+ all TIDs, or be lossy, meaning it records just page numbers and each
+ page tuple has to be checked for validity in a separate pass.
</p>
</li><li>Allow the creation of on-disk bitmap indexes which can be quickly
combined with other bitmap indexes
OSDN Git Service
