Done!

bmomjian · bmomjian · commit 19d561cbd00f · 2007-02-09T03:37:45.000Z
&lt; * Merge xmin/xmax/cmin/cmax back into three header fields
&lt;
&lt;   Before subtransactions, there used to be only three fields needed to
&lt;   store these four values. This was possible because only the current
&lt;   transaction looks at the cmin/cmax values. If the current transaction
&lt;   created and expired the row the fields stored where xmin (same as
&lt;   xmax), cmin, cmax, and if the transaction was expiring a row from a
&lt;   another transaction, the fields stored were xmin (cmin was not
&lt;   needed), xmax, and cmax. Such a system worked because a transaction
&lt;   could only see rows from another completed transaction. However,
&lt;   subtransactions can see rows from outer transactions, and once the
&lt;   subtransaction completes, the outer transaction continues, requiring
&lt;   the storage of all four fields. With subtransactions, an outer
&lt;   transaction can create a row, a subtransaction expire it, and when the
&lt;   subtransaction completes, the outer transaction still has to have
&lt;   proper visibility of the row's cmin, for example, for cursors.
&lt;
&lt;   One possible solution is to create a phantom cid which represents a
&lt;   cmin/cmax pair and is stored in local memory.  Another idea is to
&lt;   store both cmin and cmax only in local memory.
&lt;
&gt; * -Merge xmin/xmax/cmin/cmax back into three header fields
diff --git a/doc/TODO b/doc/TODO
@@ -2,7 +2,7 @@
 PostgreSQL TODO List
 ====================
 Current maintainer:	Bruce Momjian (bruce@momjian.us)
-Last updated:		Thu Feb  8 20:29:43 EST 2007
+Last updated:		Thu Feb  8 22:37:41 EST 2007
 
 The most recent version of this document can be viewed at
 http://www.postgresql.org/docs/faqs.TODO.html.
@@ -1329,27 +1329,7 @@ Miscellaneous Performance
   could hit disk before WAL is written.
 
 * Add a script to ask system configuration questions and tune postgresql.conf
-* Merge xmin/xmax/cmin/cmax back into three header fields
-
-  Before subtransactions, there used to be only three fields needed to
-  store these four values. This was possible because only the current
-  transaction looks at the cmin/cmax values. If the current transaction
-  created and expired the row the fields stored where xmin (same as
-  xmax), cmin, cmax, and if the transaction was expiring a row from a
-  another transaction, the fields stored were xmin (cmin was not
-  needed), xmax, and cmax. Such a system worked because a transaction
-  could only see rows from another completed transaction. However,
-  subtransactions can see rows from outer transactions, and once the
-  subtransaction completes, the outer transaction continues, requiring
-  the storage of all four fields. With subtransactions, an outer
-  transaction can create a row, a subtransaction expire it, and when the
-  subtransaction completes, the outer transaction still has to have
-  proper visibility of the row's cmin, for example, for cursors.
-
-  One possible solution is to create a phantom cid which represents a
-  cmin/cmax pair and is stored in local memory.  Another idea is to
-  store both cmin and cmax only in local memory.
-
+* -Merge xmin/xmax/cmin/cmax back into three header fields
 * Consider ways of storing rows more compactly on disk
 
 	o Support a smaller header for short variable-length fields?
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:bruce@momjian.us">bruce@momjian.us</a>)<br/>
-Last updated:           Thu Feb  8 20:29:43 EST 2007
+Last updated:           Thu Feb  8 22:37:41 EST 2007
 </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>.
@@ -1189,26 +1189,7 @@ <h1><a name="section_20">Miscellaneous Performance</a></h1>
   could hit disk before WAL is written.
 </p>
   </li><li>Add a script to ask system configuration questions and tune postgresql.conf
-  </li><li>Merge xmin/xmax/cmin/cmax back into three header fields
-<p>  Before subtransactions, there used to be only three fields needed to
-  store these four values. This was possible because only the current
-  transaction looks at the cmin/cmax values. If the current transaction
-  created and expired the row the fields stored where xmin (same as
-  xmax), cmin, cmax, and if the transaction was expiring a row from a
-  another transaction, the fields stored were xmin (cmin was not
-  needed), xmax, and cmax. Such a system worked because a transaction
-  could only see rows from another completed transaction. However,
-  subtransactions can see rows from outer transactions, and once the
-  subtransaction completes, the outer transaction continues, requiring
-  the storage of all four fields. With subtransactions, an outer
-  transaction can create a row, a subtransaction expire it, and when the
-  subtransaction completes, the outer transaction still has to have
-  proper visibility of the row's cmin, for example, for cursors.
-</p>
-<p>  One possible solution is to create a phantom cid which represents a
-  cmin/cmax pair and is stored in local memory.  Another idea is to
-  store both cmin and cmax only in local memory.
-</p>
+  </li><li>-<em>Merge xmin/xmax/cmin/cmax back into three header fields</em>
   </li><li>Consider ways of storing rows more compactly on disk
   <ul>
     <li>Support a smaller header for short variable-length fields?
