diff -r 4b92d79506ba doc/src/sgml/func.sgml
--- a/doc/src/sgml/func.sgml	Mon Nov 03 01:17:08 2008 +0000
+++ b/doc/src/sgml/func.sgml	Mon Nov 03 00:13:50 2008 -0800
@@ -11592,6 +11592,10 @@
    </indexterm>
 
    <indexterm>
+    <primary>pg_typeof</primary>
+   </indexterm>
+
+   <indexterm>
     <primary>pg_get_keywords</primary>
    </indexterm>
 
@@ -11660,6 +11664,11 @@
        <entry><literal><function>format_type</function>(<parameter>type_oid</parameter>, <parameter>typemod</>)</literal></entry>
        <entry><type>text</type></entry>
        <entry>get SQL name of a data type</entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_typeof</function>(<parameter>any</parameter>)</literal></entry>
+       <entry><type>regtype</type></entry>
+       <entry>get the data type of any value</entry>
       </row>
       <row>
        <entry><literal><function>pg_get_keywords</function>()</literal></entry>
@@ -11774,6 +11783,12 @@
    <function>format_type</function> returns the SQL name of a data type that
    is identified by its type OID and possibly a type modifier.  Pass NULL
    for the type modifier if no specific modifier is known.
+  </para>
+
+  <para>
+   <function>pg_typeof</function> returns the OID of the data type of any
+   value which is passed to it as an argument.  This can be helpful for
+   troubleshooting or dynamically constructing SQL queries.
   </para>
 
   <para>
diff -r 4b92d79506ba src/backend/utils/adt/misc.c
--- a/src/backend/utils/adt/misc.c	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/backend/utils/adt/misc.c	Mon Nov 03 00:13:51 2008 -0800
@@ -35,6 +35,15 @@
 
 #define atooid(x)  ((Oid) strtoul((x), NULL, 10))
 
+
+/*
+ * Return the type of the argument.
+ */
+Datum
+pg_typeof(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_OID(get_fn_expr_argtype(fcinfo->flinfo, 0));
+}
 
 /*
  * current_database()
diff -r 4b92d79506ba src/include/catalog/catversion.h
--- a/src/include/catalog/catversion.h	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/include/catalog/catversion.h	Mon Nov 03 00:13:51 2008 -0800
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200810311
+#define CATALOG_VERSION_NO	200811021
 
 #endif
diff -r 4b92d79506ba src/include/catalog/pg_proc.h
--- a/src/include/catalog/pg_proc.h	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/include/catalog/pg_proc.h	Mon Nov 03 00:13:51 2008 -0800
@@ -1085,6 +1085,9 @@
 DESCR("greater-than-or-equal");
 
 /* OIDS 800 - 899 */
+
+DATA(insert OID =  826 (  pg_typeof		   PGNSP PGUID 12 1 0 0 f f f f i 1 2206  "2276" _null_ _null_ _null_  pg_typeof _null_ _null_ _null_ ));
+DESCR("returns the type of the argument");
 
 DATA(insert OID =  846 (  cash_mul_flt4    PGNSP PGUID 12 1 0 0 f f t f i 2 790 "790 700" _null_ _null_ _null_	cash_mul_flt4 _null_ _null_ _null_ ));
 DESCR("multiply");
diff -r 4b92d79506ba src/include/utils/builtins.h
--- a/src/include/utils/builtins.h	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/include/utils/builtins.h	Mon Nov 03 00:13:51 2008 -0800
@@ -395,6 +395,7 @@
 extern Datum pg_ls_dir(PG_FUNCTION_ARGS);
 
 /* misc.c */
+extern Datum pg_typeof(PG_FUNCTION_ARGS);
 extern Datum current_database(PG_FUNCTION_ARGS);
 extern Datum current_query(PG_FUNCTION_ARGS);
 extern Datum pg_cancel_backend(PG_FUNCTION_ARGS);
diff -r 4b92d79506ba src/test/regress/expected/polymorphism.out
--- a/src/test/regress/expected/polymorphism.out	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/test/regress/expected/polymorphism.out	Mon Nov 03 00:13:51 2008 -0800
@@ -688,7 +688,6 @@
  
 (1 row)
 
-drop function concat(text, anyarray);
 -- mix variadic with anyelement
 create function formarray(anyelement, variadic anyarray) returns anyarray as $$
   select array_prepend($1, $2);
@@ -720,4 +719,52 @@
 LINE 1: select formarray(1, variadic array['x'::text]);
                ^
 HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
+-- test pg_typeof() function
+select pg_typeof(null),           -- unknown
+       pg_typeof(0),              -- integer
+       pg_typeof(0.0),            -- numeric
+       pg_typeof(1+1 = 2),        -- boolean
+       pg_typeof('x'),            -- unknown
+       pg_typeof('' || ''),       -- text
+       pg_typeof(pg_typeof(0));   -- regtype
+ pg_typeof | pg_typeof | pg_typeof | pg_typeof | pg_typeof | pg_typeof | pg_typeof 
+-----------+-----------+-----------+-----------+-----------+-----------+-----------
+ unknown   | integer   | numeric   | boolean   | unknown   | text      | regtype
+(1 row)
+
+select pg_typeof(f1), pg_typeof(sql_if(f1 > 0, bleat(f1), bleat(f1 + 1))) from int4_tbl limit 1;
+NOTICE:  bleat 1
+ pg_typeof | pg_typeof 
+-----------+-----------
+ integer   | integer
+(1 row)
+
+select pg_typeof(q2), pg_typeof(sql_if(q2 > 0, q2, q2 + 1)) from int8_tbl limit 1;
+ pg_typeof | pg_typeof 
+-----------+-----------
+ bigint    | bigint
+(1 row)
+
+select pg_typeof(myleast(10, 1, 20, 33)),
+       pg_typeof(myleast(variadic array[1.1, -5.5])),
+       pg_typeof(formarray(1,2,3,4,5)),
+       pg_typeof(formarray(1.1, variadic array[1.2,55.5])),
+       pg_typeof(concat('%', 1, 2, 3, 4, 5));
+ pg_typeof | pg_typeof | pg_typeof | pg_typeof | pg_typeof 
+-----------+-----------+-----------+-----------+-----------
+ integer   | numeric   | integer[] | numeric[] | text
+(1 row)
+
+select pg_typeof(array[1.2,55.5]),
+       pg_typeof(variadic array[1,2,33]),
+       pg_typeof(variadic array[]::int[]),
+       pg_typeof(row(1,1.1)),
+       pg_typeof(array[ row(7,7.7), row(1,1.0), row(0,0.0) ]);
+ pg_typeof | pg_typeof | pg_typeof | pg_typeof | pg_typeof 
+-----------+-----------+-----------+-----------+-----------
+ numeric[] | integer[] | integer[] | record    | record[]
+(1 row)
+
+-- cleanup
+drop function concat(text, anyarray);
 drop function formarray(anyelement, variadic anyarray);
diff -r 4b92d79506ba src/test/regress/sql/polymorphism.sql
--- a/src/test/regress/sql/polymorphism.sql	Mon Nov 03 01:17:08 2008 +0000
+++ b/src/test/regress/sql/polymorphism.sql	Mon Nov 03 00:13:51 2008 -0800
@@ -455,8 +455,6 @@
 select concat('|', variadic array[1,2,33]);
 select concat('|', variadic array[]::int[]);
 
-drop function concat(text, anyarray);
-
 -- mix variadic with anyelement
 create function formarray(anyelement, variadic anyarray) returns anyarray as $$
   select array_prepend($1, $2);
@@ -468,4 +466,27 @@
 select formarray(1, 'x'::text); -- fail, type mismatch
 select formarray(1, variadic array['x'::text]); -- fail, type mismatch
 
+-- test pg_typeof() function
+select pg_typeof(null),           -- unknown
+       pg_typeof(0),              -- integer
+       pg_typeof(0.0),            -- numeric
+       pg_typeof(1+1 = 2),        -- boolean
+       pg_typeof('x'),            -- unknown
+       pg_typeof('' || ''),       -- text
+       pg_typeof(pg_typeof(0));   -- regtype
+select pg_typeof(f1), pg_typeof(sql_if(f1 > 0, bleat(f1), bleat(f1 + 1))) from int4_tbl limit 1;
+select pg_typeof(q2), pg_typeof(sql_if(q2 > 0, q2, q2 + 1)) from int8_tbl limit 1;
+select pg_typeof(myleast(10, 1, 20, 33)),
+       pg_typeof(myleast(variadic array[1.1, -5.5])),
+       pg_typeof(formarray(1,2,3,4,5)),
+       pg_typeof(formarray(1.1, variadic array[1.2,55.5])),
+       pg_typeof(concat('%', 1, 2, 3, 4, 5));
+select pg_typeof(array[1.2,55.5]),
+       pg_typeof(variadic array[1,2,33]),
+       pg_typeof(variadic array[]::int[]),
+       pg_typeof(row(1,1.1)),
+       pg_typeof(array[ row(7,7.7), row(1,1.0), row(0,0.0) ]);
+
+-- cleanup
+drop function concat(text, anyarray);
 drop function formarray(anyelement, variadic anyarray);