Add pg_typeof() function.

Brendan Jurd

doc/src/sgml/func.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.451 2008/10/27 09:37:46 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.452 2008/11/03 17:51:12 tgl Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -11643,6 +11643,10 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
     <primary>pg_tablespace_databases</primary>
    </indexterm>
 
+   <indexterm>
+    <primary>pg_typeof</primary>
+   </indexterm>
+
   <para>
    <xref linkend="functions-info-catalog-table"> lists functions that
    extract information from the system catalogs.
@@ -11766,6 +11770,11 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        <entry><type>setof oid</type></entry>
        <entry>get the set of database OIDs that have objects in the tablespace</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>
      </tbody>
     </tgroup>
    </table>
@@ -11848,6 +11857,12 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
    <structname>pg_class</> catalogs.
   </para>
 
+  <para>
+   <function>pg_typeof</function> returns the OID of the data type of the
+   value that is passed to it.  This can be helpful for troubleshooting or
+   dynamically constructing SQL queries.
+  </para>
+
    <indexterm>
     <primary>col_description</primary>
    </indexterm>

src/backend/utils/adt/misc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/misc.c,v 1.64 2008/10/05 17:33:16 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/misc.c,v 1.65 2008/11/03 17:51:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -371,3 +371,13 @@ pg_get_keywords(PG_FUNCTION_ARGS)
 
 	SRF_RETURN_DONE(funcctx);
 }
+
+
+/*
+ * Return the type of the argument.
+ */
+Datum
+pg_typeof(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_OID(get_fn_expr_argtype(fcinfo->flinfo, 0));
+}

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.500 2008/10/31 08:39:22 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.501 2008/11/03 17:51:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200810311
+#define CATALOG_VERSION_NO	200811031
 
 #endif

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.520 2008/10/14 17:12:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.521 2008/11/03 17:51:13 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -2289,7 +2289,8 @@ DESCR("result type of a function");
 
 DATA(insert OID = 1686 (  pg_get_keywords		PGNSP PGUID 12 10 400 0 f f t t s 0 2249 "" "{25,18,25}" "{o,o,o}" "{word,catcode,catdesc}" pg_get_keywords _null_ _null_ _null_ ));
 DESCR("list of SQL keywords");
-
+DATA(insert OID = 1619 (  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");
 
 /* Generic referential integrity constraint triggers */
 DATA(insert OID = 1644 (  RI_FKey_check_ins		PGNSP PGUID 12 1 0 0 f f t f v 0 2279 "" _null_ _null_ _null_ RI_FKey_check_ins _null_ _null_ _null_ ));

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.324 2008/10/13 16:25:20 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.325 2008/11/03 17:51:13 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -404,6 +404,7 @@ extern Datum pg_tablespace_databases(PG_FUNCTION_ARGS);
 extern Datum pg_rotate_logfile(PG_FUNCTION_ARGS);
 extern Datum pg_sleep(PG_FUNCTION_ARGS);
 extern Datum pg_get_keywords(PG_FUNCTION_ARGS);
+extern Datum pg_typeof(PG_FUNCTION_ARGS);
 
 /* oid.c */
 extern Datum oidin(PG_FUNCTION_ARGS);

src/test/regress/expected/polymorphism.out

@@ -721,3 +721,58 @@ 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.
 drop function formarray(anyelement, variadic anyarray);
+-- test pg_typeof() function
+select pg_typeof(null);           -- unknown
+ pg_typeof 
+-----------
+ unknown
+(1 row)
+
+select pg_typeof(0);              -- integer
+ pg_typeof 
+-----------
+ integer
+(1 row)
+
+select pg_typeof(0.0);            -- numeric
+ pg_typeof 
+-----------
+ numeric
+(1 row)
+
+select pg_typeof(1+1 = 2);        -- boolean
+ pg_typeof 
+-----------
+ boolean
+(1 row)
+
+select pg_typeof('x');            -- unknown
+ pg_typeof 
+-----------
+ unknown
+(1 row)
+
+select pg_typeof('' || '');       -- text
+ pg_typeof 
+-----------
+ text
+(1 row)
+
+select pg_typeof(pg_typeof(0));   -- regtype
+ pg_typeof 
+-----------
+ regtype
+(1 row)
+
+select pg_typeof(array[1.2,55.5]); -- numeric[]
+ pg_typeof 
+-----------
+ numeric[]
+(1 row)
+
+select pg_typeof(myleast(10, 1, 20, 33));  -- polymorphic input
+ pg_typeof 
+-----------
+ integer
+(1 row)
+

src/test/regress/sql/polymorphism.sql

@@ -469,3 +469,14 @@ select formarray(1, 'x'::text); -- fail, type mismatch
 select formarray(1, variadic array['x'::text]); -- fail, type mismatch
 
 drop function formarray(anyelement, variadic anyarray);
+
+-- test pg_typeof() function
+select pg_typeof(null);           -- unknown
+select pg_typeof(0);              -- integer
+select pg_typeof(0.0);            -- numeric
+select pg_typeof(1+1 = 2);        -- boolean
+select pg_typeof('x');            -- unknown
+select pg_typeof('' || '');       -- text
+select pg_typeof(pg_typeof(0));   -- regtype
+select pg_typeof(array[1.2,55.5]); -- numeric[]
+select pg_typeof(myleast(10, 1, 20, 33));  -- polymorphic input