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Updated text for bitmaps:

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<   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.
This commit is contained in:
Bruce Momjian 2005-04-21 15:20:39 +00:00
parent 631e03145f
commit c6221db3c0
2 changed files with 16 additions and 18 deletions
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17
doc/TODO
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@ -2,7 +2,7 @@
PostgreSQL TODO List PostgreSQL TODO List
==================== ====================
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) 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 The most recent version of this document can be viewed at the PostgreSQL web
site, http://www.PostgreSQL.org. site, http://www.PostgreSQL.org.
@ -300,14 +300,13 @@ Indexes
* Allow non-bitmap indexes to be combined by creating bitmaps in memory * Allow non-bitmap indexes to be combined by creating bitmaps in memory
Bitmap indexes index single columns that can be combined with other bitmap This feature allows separate indexes to be ANDed or ORed together. This
indexes to dynamically create a composite index to match a specific query. is particularly useful for data warehousing applications that need to
Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be query the database in an many permutations. This feature scans an index
combined. They can index by tid or can be lossy requiring a scan of the and creates an in-memory bitmap, and allows that bitmap to be combined
heap page to find matching rows, or perhaps use a mixed solution where with other bitmap created in a similar way. The bitmap can either index
tids are recorded for pages with only a few matches and per-page bitmaps all TIDs, or be lossy, meaning it records just page numbers and each
are used for more dense pages. Another idea is to use a 32-bit bitmap page tuple has to be checked for validity in a separate pass.
for every page and set a bit based on the item number mod(32).
* Allow the creation of on-disk bitmap indexes which can be quickly * Allow the creation of on-disk bitmap indexes which can be quickly
combined with other bitmap indexes combined with other bitmap indexes

17
doc/src/FAQ/TODO.html
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@ -8,7 +8,7 @@
<body bgcolor="#FFFFFF" text="#000000" link="#FF0000" vlink="#A00000" alink="#0000FF"> <body bgcolor="#FFFFFF" text="#000000" link="#FF0000" vlink="#A00000" alink="#0000FF">
<h1><a name="section_1">PostgreSQL TODO List</a></h1> <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/> <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>
<p>The most recent version of this document can be viewed at the PostgreSQL web<br/> <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>. site, <a href="http://www.PostgreSQL.org">http://www.PostgreSQL.org</a>.
@ -277,14 +277,13 @@ first.
before accessing the heap rows. before accessing the heap rows.
</p> </p>
</li><li>Allow non-bitmap indexes to be combined by creating bitmaps in memory </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 <p> This feature allows separate indexes to be ANDed or ORed together. This
indexes to dynamically create a composite index to match a specific query. is particularly useful for data warehousing applications that need to
Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be query the database in an many permutations. This feature scans an index
combined. They can index by tid or can be lossy requiring a scan of the and creates an in-memory bitmap, and allows that bitmap to be combined
heap page to find matching rows, or perhaps use a mixed solution where with other bitmap created in a similar way. The bitmap can either index
tids are recorded for pages with only a few matches and per-page bitmaps all TIDs, or be lossy, meaning it records just page numbers and each
are used for more dense pages. Another idea is to use a 32-bit bitmap page tuple has to be checked for validity in a separate pass.
for every page and set a bit based on the item number mod(32).
</p> </p>
</li><li>Allow the creation of on-disk bitmap indexes which can be quickly </li><li>Allow the creation of on-disk bitmap indexes which can be quickly
combined with other bitmap indexes combined with other bitmap indexes