Add calcluation of bitmap storage capacity.

bmomjian · bmomjian · commit 9322a04759c2 · 2005-12-02T04:28:19.000Z
&lt;   be cleared when a heap tuple is expired.  Another idea is to maintain
&lt;   a bitmap of heap pages where all rows are visible to all backends,
&lt;   and allow index lookups to reference that bitmap to avoid heap
&lt;   lookups, perhaps the same bitmap we might add someday to determine
&lt;   which heap pages need vacuuming.
&gt;   be cleared when a heap tuple is expired.
&gt;
&gt;   Another idea is to maintain a bitmap of heap pages where all rows
&gt;   are visible to all backends, and allow index lookups to reference
&gt;   that bitmap to avoid heap lookups, perhaps the same bitmap we might
&gt;   add someday to determine which heap pages need vacuuming.  Frequently
&gt;   accessed bitmaps would have to be stored in shared memory.  One 8k
&gt;   page of bitmaps could track 512MB of heap pages.
diff --git 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 Dec  1 17:30:23 EST 2005
+Last updated:		Thu Dec  1 23:28:03 EST 2005
 
 The most recent version of this document can be viewed at
 http://www.postgresql.org/docs/faqs.TODO.html.
@@ -862,11 +862,14 @@ Cache Usage
   the heap.  One way to allow this is to set a bit on index tuples 
   to indicate if a tuple is currently visible to all transactions 
   when the first valid heap lookup happens.  This bit would have to 
-  be cleared when a heap tuple is expired.  Another idea is to maintain
-  a bitmap of heap pages where all rows are visible to all backends,
-  and allow index lookups to reference that bitmap to avoid heap
-  lookups, perhaps the same bitmap we might add someday to determine 
-  which heap pages need vacuuming.
+  be cleared when a heap tuple is expired.  
+
+  Another idea is to maintain a bitmap of heap pages where all rows
+  are visible to all backends, and allow index lookups to reference 
+  that bitmap to avoid heap lookups, perhaps the same bitmap we might
+  add someday to determine which heap pages need vacuuming.  Frequently
+  accessed bitmaps would have to be stored in shared memory.  One 8k
+  page of bitmaps could track 512MB of heap pages.
 
 * Consider automatic caching of queries at various levels:
 
diff --git 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 Dec  1 17:30:23 EST 2005
+Last updated:           Thu Dec  1 23:28:03 EST 2005
 </p>
 <p>The most recent version of this document can be viewed at<br/>
 <a href="http://www.postgresql.org/docs/faqs.TODO.html">http://www.postgresql.org/docs/faqs.TODO.html</a>.
@@ -781,11 +781,14 @@ <h1><a name="section_15">Cache Usage</a></h1>
   the heap.  One way to allow this is to set a bit on index tuples 
   to indicate if a tuple is currently visible to all transactions 
   when the first valid heap lookup happens.  This bit would have to 
-  be cleared when a heap tuple is expired.  Another idea is to maintain
-  a bitmap of heap pages where all rows are visible to all backends,
-  and allow index lookups to reference that bitmap to avoid heap
-  lookups, perhaps the same bitmap we might add someday to determine 
-  which heap pages need vacuuming.
+  be cleared when a heap tuple is expired.  
+</p>
+<p>  Another idea is to maintain a bitmap of heap pages where all rows
+  are visible to all backends, and allow index lookups to reference 
+  that bitmap to avoid heap lookups, perhaps the same bitmap we might
+  add someday to determine which heap pages need vacuuming.  Frequently
+  accessed bitmaps would have to be stored in shared memory.  One 8k
+  page of bitmaps could track 512MB of heap pages.
 </p>
   </li><li>Consider automatic caching of queries at various levels:
   <ul>
