From c6221db3c0f7049b804391d59aeadcfbd1f51800 Mon Sep 17 00:00:00 2001 From: Bruce Momjian <bruce@momjian.us> Date: Thu, 21 Apr 2005 15:20:39 +0000 Subject: [PATCH] Updated text for bitmaps: < 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. --- doc/TODO | 17 ++++++++--------- doc/src/FAQ/TODO.html | 17 ++++++++--------- 2 files changed, 16 insertions(+), 18 deletions(-) diff --git a/doc/TODO b/doc/TODO index 9c28981a3b7..6e42de72b1c 100644 --- a/doc/TODO +++ b/doc/TODO @@ -2,7 +2,7 @@ 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. @@ -300,14 +300,13 @@ Indexes * 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 diff --git a/doc/src/FAQ/TODO.html b/doc/src/FAQ/TODO.html index 70c1e257069..725e7c312e3 100644 --- a/doc/src/FAQ/TODO.html +++ b/doc/src/FAQ/TODO.html @@ -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: 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>. @@ -277,14 +277,13 @@ first. 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 -- GitLab