Index: doc/src/sgml/spi.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/spi.sgml,v
retrieving revision 1.42
diff -u -r1.42 spi.sgml
--- doc/src/sgml/spi.sgml	29 Jul 2005 13:00:03 -0000	1.42
+++ doc/src/sgml/spi.sgml	13 Aug 2005 19:10:54 -0000
@@ -29,6 +29,14 @@
   </para>
  </note>
 
+ <note>
+  <para>
+   SPI can not be used in functions called prior to the start of query
+   execution because there is no current snapshot at that point. Examples of
+   this include type input functions and cost estimation functions.
+  </para>
+ </note>
+
  <para>
   To avoid misunderstanding we'll use the term <quote>function</quote>
   when we speak of <acronym>SPI</acronym> interface functions and
Index: doc/src/sgml/xfunc.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/xfunc.sgml,v
retrieving revision 1.103
diff -u -r1.103 xfunc.sgml
--- doc/src/sgml/xfunc.sgml	30 May 2005 23:09:07 -0000	1.103
+++ doc/src/sgml/xfunc.sgml	13 Aug 2005 19:10:55 -0000
@@ -2778,6 +2778,16 @@
      as an alternative to <function>get_fn_expr_rettype</>.
     </para>
 
+    <footnote>
+     <para>
+      Information about argument and return types is generally available if
+      you are executing a normal function within a normal query. However, it
+      can be missing for implicitly used functions, such as type
+      input/output functions that are called directly by the planner before
+      the query starts.
+     </para>
+    </footnote>
+
     <para>
      For example, suppose we want to write a function to accept a single
      element of any type, and return a one-dimensional array of that type: