From 8f9fe6edce358f7904e0db119416b4d1080a83aa Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 21 Jun 2011 22:15:24 -0400
Subject: Add notion of a "transform function" that can simplify function
 calls.

Initially, we use this only to eliminate calls to the varchar()
function in cases where the length is not being reduced and, therefore,
the function call is equivalent to a RelabelType operation.  The most
significant effect of this is that we can avoid a table rewrite when
changing a varchar(X) column to a varchar(Y) column, where Y > X.

Noah Misch, reviewed by me and Alexey Klyukin
---
 doc/src/sgml/catalogs.sgml | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'doc/src')

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 24d7d98722a..7a380ce2f94 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -4337,6 +4337,13 @@
        or zero if the function does not have a variadic parameter</entry>
      </row>
 
+     <row>
+      <entry><structfield>protransform</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Calls to function can be simplified by this other function</entry>
+     </row>
+
      <row>
       <entry><structfield>proisagg</structfield></entry>
       <entry><type>bool</type></entry>
-- 
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