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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.
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‎doc/TODO‎

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

‎doc/src/FAQ/TODO.html‎

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<body bgcolor="#FFFFFF" text="#000000" link="#FF0000" vlink="#A00000" alink="#0000FF">
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<h1><a name="section_1">PostgreSQL TODO List</a></h1>
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<p>Current maintainer: Bruce Momjian (<a href="mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</a>)<br/>
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Last updated: Thu Apr 21 00:09:27 EDT 2005
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Last updated: Thu Apr 21 11:20:13 EDT 2005
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</p>
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<p>The most recent version of this document can be viewed at the PostgreSQL web<br/>
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site, <a href="http://www.PostgreSQL.org">http://www.PostgreSQL.org</a>.
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before accessing the heap rows.
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</p>
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</li><li>Allow non-bitmap indexes to be combined by creating bitmaps in memory
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<p> Bitmap indexes index single columns that can be combined with other bitmap
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indexes to dynamically create a composite index to match a specific query.
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Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
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combined. They can index by tid or can be lossy requiring a scan of the
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heap page to find matching rows, or perhaps use a mixed solution where
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tids are recorded for pages with only a few matches and per-page bitmaps
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are used for more dense pages. Another idea is to use a 32-bit bitmap
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for every page and set a bit based on the item number mod(32).
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<p> This feature allows separate indexes to be ANDed or ORed together. This
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is particularly useful for data warehousing applications that need to
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query the database in an many permutations. This feature scans an index
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and creates an in-memory bitmap, and allows that bitmap to be combined
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with other bitmap created in a similar way. The bitmap can either index
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all TIDs, or be lossy, meaning it records just page numbers and each
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page tuple has to be checked for validity in a separate pass.
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</p>
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</li><li>Allow the creation of on-disk bitmap indexes which can be quickly
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combined with other bitmap indexes

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