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Message-ID: <9f2e40a90610170439n4b670c23ld586e4f0840e943@mail.gmail.com>
Date: Tue, 17 Oct 2006 17:09:29 +0530
From: "soni de" <soni.de@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Regarding Bitmap Scan
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Hello,



I was going through the Performance Enhancements of 8.1.0, in that I have
read "Bitmap Scan"



"*Bitmap Scan:* indexes will be dynamically converted to bitmaps in memory
when appropriate, giving up to twenty times faster index performance on
complex queries against very large tables. This also helps simplify database
management by greatly reducing the need for multi-column indexes."



I didn't understand the "Bitmap Scan" and the sentence "indexes will be
dynamically converted to bitmaps in memory". What does mean by "Bitmap Scan"
in database?



Can anybody help us regarding above query?



Thanks,

Soni

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<div>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">Hello,</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&nbsp;</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">I&nbsp;was going through the&nbsp;Performance Enhancements of 8.1.0, in that I have read &quot;Bitmap Scan&quot;
</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&nbsp;</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&quot;<b><span style="FONT-WEIGHT: bold">Bitmap Scan:</span></b> indexes will be dynamically converted to bitmaps in memory when appropriate, giving up to twenty times faster index performance on complex queries against very large tables. This also helps simplify database management by greatly reducing the need for multi-column indexes.&quot;
</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&nbsp;</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">I didn't understand the&nbsp;&quot;Bitmap Scan&quot; and&nbsp;the sentence &quot;indexes will be dynamically converted to bitmaps in memory&quot;. What does mean by &quot;Bitmap Scan&quot; in database?
</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&nbsp;</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">Can anybody help us regarding above query?</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">&nbsp;</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">Thanks,</span></font></p>
<p class="MsoNormal" style="BACKGROUND: white; MARGIN: 0in 0in 0pt"><font face="Arial" size="3"><span style="FONT-SIZE: 12pt; FONT-FAMILY: Arial">Soni</span></font></p></div>

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