Add support for user-defined I/O conversion casts.

Author: hlinnaka

doc/src/sgml/catalogs.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.179 2008/10/17 22:10:29 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.180 2008/10/31 08:39:19 heikki Exp $ -->
 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
  -->
@@ -1415,9 +1415,10 @@
    cannot be deduced from some generic rule.  For example, casting between a
    domain and its base type is not explicitly represented in
    <structname>pg_cast</structname>.  Another important exception is that
-   <quote>I/O conversion casts</>, those performed using a data type's own
-   I/O functions to convert to or from <type>text</> or other string types,
-   are not explicitly represented in <structname>pg_cast</structname>.
+   <quote>automatic I/O conversion casts</>, those performed using a data
+   type's own I/O functions to convert to or from <type>text</> or other
+   string types, are not explicitly represented in
+   <structname>pg_cast</structname>.
   </para>
 
   <table>
@@ -1454,8 +1455,7 @@
       <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
       <entry>
        The OID of the function to use to perform this cast.  Zero is
-       stored if the data types are binary coercible (that is, no
-       run-time operation is needed to perform the cast)
+       stored if the cast method doesn't require a function.
       </entry>
      </row>
 
@@ -1473,6 +1473,17 @@
        other cases
       </entry>
      </row>
+     <row>
+      <entry><structfield>castmethod</structfield></entry>
+      <entry><type>char</type></entry>
+      <entry></entry>
+      <entry>
+       Indicates how the cast is performed.
+       <literal>f</> means that the function specified in the <structfield>castfunc</> field is used.
+       <literal>i</> means that the input/output functions are used.
+       <literal>b</> means that the types are binary-coercible, thus no conversion is required
+      </entry>
+     </row>
     </tbody>
    </tgroup>
   </table>

doc/src/sgml/ref/create_cast.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.29 2008/07/30 21:23:17 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.30 2008/10/31 08:39:20 heikki Exp $ -->
 
 <refentry id="SQL-CREATECAST">
  <refmeta>
@@ -24,6 +24,10 @@ CREATE CAST (<replaceable>sourcetype</replaceable> AS <replaceable>targettype</r
 CREATE CAST (<replaceable>sourcetype</replaceable> AS <replaceable>targettype</replaceable>)
     WITHOUT FUNCTION
     [ AS ASSIGNMENT | AS IMPLICIT ]
+
+CREATE CAST (<replaceable>sourcetype</replaceable> AS <replaceable>targettype</replaceable>)
+    WITH INOUT
+    [ AS ASSIGNMENT | AS IMPLICIT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -58,6 +62,13 @@ SELECT CAST(42 AS float8);
    binary compatible.)
   </para>
 
+  <para>
+   You can define a cast as an <firstterm>I/O conversion cast</> using
+   the <literal>WITH INOUT</literal> syntax. An I/O conversion cast is
+   performed by invoking the output function of the source data type, and
+   passing the result to the input function of the target data type.
+  </para>
+
   <para>
    By default, a cast can be invoked only by an explicit cast request,
    that is an explicit <literal>CAST(<replaceable>x</> AS
@@ -199,6 +210,18 @@ SELECT CAST ( 2 AS numeric ) + 4.0;
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>WITH INOUT</literal></term>
+
+     <listitem>
+      <para>
+       Indicates that the cast is an I/O conversion cast, performed by
+       invoking the output function of the source data type, and passing the
+       result to the input function of the target data type.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>AS ASSIGNMENT</literal></term>
 
@@ -284,15 +307,12 @@ SELECT CAST ( 2 AS numeric ) + 4.0;
    It is normally not necessary to create casts between user-defined types
    and the standard string types (<type>text</>, <type>varchar</>, and
    <type>char(<replaceable>n</>)</type>, as well as user-defined types that
-   are defined to be in the string category).  <productname>PostgreSQL</> will
-   automatically handle a cast to a string type by invoking the other
-   type's output function, or conversely handle a cast from a string type
-   by invoking the other type's input function.  These
-   automatically-provided casts are known as <firstterm>I/O conversion
-   casts</>.  I/O conversion casts to string types are treated as
-   assignment casts, while I/O conversion casts from string types are
+   are defined to be in the string category).  <productname>PostgreSQL</>
+   provides automatic I/O conversion casts for that. The automatic casts to
+   string types are treated as assignment casts, while the automatic casts
+   from string types are
    explicit-only.  You can override this behavior by declaring your own
-   cast to replace an I/O conversion cast, but usually the only reason to
+   cast to replace an automatic cast, but usually the only reason to
    do so is if you want the conversion to be more easily invokable than the
    standard assignment-only or explicit-only setting.  Another possible
    reason is that you want the conversion to behave differently from the

src/backend/commands/functioncmds.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.99 2008/10/21 10:38:51 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/functioncmds.c,v 1.100 2008/10/31 08:39:20 heikki Exp $
  *
  * DESCRIPTION
  *	  These routines take the parse tree and pick out the
@@ -1383,6 +1383,7 @@ CreateCast(CreateCastStmt *stmt)
 	Oid			funcid;
 	int			nargs;
 	char		castcontext;
+	char		castmethod;
 	Relation	relation;
 	HeapTuple	tuple;
 	Datum		values[Natts_pg_cast];
@@ -1415,7 +1416,15 @@ CreateCast(CreateCastStmt *stmt)
 						format_type_be(sourcetypeid),
 						format_type_be(targettypeid))));
 
+	/* Detemine the cast method */
 	if (stmt->func != NULL)
+		castmethod = COERCION_METHOD_FUNCTION;
+	else if(stmt->inout)
+		castmethod = COERCION_METHOD_INOUT;
+	else
+		castmethod = COERCION_METHOD_BINARY;
+
+	if (castmethod == COERCION_METHOD_FUNCTION)
 	{
 		Form_pg_proc procstruct;
 
@@ -1475,6 +1484,12 @@ CreateCast(CreateCastStmt *stmt)
 		ReleaseSysCache(tuple);
 	}
 	else
+	{
+		funcid = InvalidOid;
+		nargs = 0;
+	}
+
+	if (castmethod == COERCION_METHOD_BINARY)
 	{
 		int16		typ1len;
 		int16		typ2len;
@@ -1483,10 +1498,6 @@ CreateCast(CreateCastStmt *stmt)
 		char		typ1align;
 		char		typ2align;
 
-		/* indicates binary coercibility */
-		funcid = InvalidOid;
-		nargs = 0;
-
 		/*
 		 * Must be superuser to create binary-compatible casts, since
 		 * erroneous casts can easily crash the backend.
@@ -1562,6 +1573,7 @@ CreateCast(CreateCastStmt *stmt)
 	values[Anum_pg_cast_casttarget - 1] = ObjectIdGetDatum(targettypeid);
 	values[Anum_pg_cast_castfunc - 1] = ObjectIdGetDatum(funcid);
 	values[Anum_pg_cast_castcontext - 1] = CharGetDatum(castcontext);
+	values[Anum_pg_cast_castmethod - 1] = CharGetDatum(castmethod);
 
 	MemSet(nulls, ' ', Natts_pg_cast);
 

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.409 2008/10/21 20:42:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.410 2008/10/31 08:39:20 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3042,6 +3042,7 @@ _copyCreateCastStmt(CreateCastStmt *from)
 	COPY_NODE_FIELD(targettype);
 	COPY_NODE_FIELD(func);
 	COPY_SCALAR_FIELD(context);
+	COPY_SCALAR_FIELD(inout);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.334 2008/10/21 20:42:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.335 2008/10/31 08:39:20 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1666,6 +1666,7 @@ _equalCreateCastStmt(CreateCastStmt *a, CreateCastStmt *b)
 	COMPARE_NODE_FIELD(targettype);
 	COMPARE_NODE_FIELD(func);
 	COMPARE_SCALAR_FIELD(context);
+	COMPARE_SCALAR_FIELD(inout);
 
 	return true;
 }

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.632 2008/10/29 11:24:53 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.633 2008/10/31 08:39:20 heikki Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -4590,6 +4590,7 @@ CreateCastStmt: CREATE CAST '(' Typename AS Typename ')'
 					n->targettype = $6;
 					n->func = $10;
 					n->context = (CoercionContext) $11;
+					n->inout = false;
 					$$ = (Node *)n;
 				}
 			| CREATE CAST '(' Typename AS Typename ')'
@@ -4600,6 +4601,18 @@ CreateCastStmt: CREATE CAST '(' Typename AS Typename ')'
 					n->targettype = $6;
 					n->func = NULL;
 					n->context = (CoercionContext) $10;
+					n->inout = false;
+					$$ = (Node *)n;
+				}
+			| CREATE CAST '(' Typename AS Typename ')'
+					WITH INOUT cast_context
+				{
+					CreateCastStmt *n = makeNode(CreateCastStmt);
+					n->sourcetype = $4;
+					n->targettype = $6;
+					n->func = NULL;
+					n->context = (CoercionContext) $10;
+					n->inout = true;
 					$$ = (Node *)n;
 				}
 		;

src/backend/parser/parse_coerce.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.170 2008/10/25 17:19:09 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_coerce.c,v 2.171 2008/10/31 08:39:21 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1909,11 +1909,23 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
 		/* Rely on ordering of enum for correct behavior here */
 		if (ccontext >= castcontext)
 		{
-			*funcid = castForm->castfunc;
-			if (OidIsValid(*funcid))
-				result = COERCION_PATH_FUNC;
-			else
-				result = COERCION_PATH_RELABELTYPE;
+			switch (castForm->castmethod)
+			{
+				case COERCION_METHOD_FUNCTION:
+					result = COERCION_PATH_FUNC;
+					*funcid = castForm->castfunc;
+					break;
+				case COERCION_METHOD_INOUT:
+					result = COERCION_PATH_COERCEVIAIO;
+					break;
+				case COERCION_METHOD_BINARY:
+					result = COERCION_PATH_RELABELTYPE;
+					break;
+				default:
+					elog(ERROR, "unrecognized castmethod: %d",
+						 (int) castForm->castmethod);
+					break;
+			}
 		}
 
 		ReleaseSysCache(tuple);

src/bin/pg_dump/pg_dump.c

@@ -12,7 +12,7 @@
  *	by PostgreSQL
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.502 2008/09/24 19:33:15 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.503 2008/10/31 08:39:21 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -36,6 +36,7 @@ int			optreset;
 
 #include "access/attnum.h"
 #include "access/sysattr.h"
+#include "catalog/pg_cast.h"
 #include "catalog/pg_class.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_trigger.h"
@@ -4410,21 +4411,31 @@ getCasts(int *numCasts)
 	int			i_casttarget;
 	int			i_castfunc;
 	int			i_castcontext;
+	int			i_castmethod;
 
 	/* Make sure we are in proper schema */
 	selectSourceSchema("pg_catalog");
 
-	if (g_fout->remoteVersion >= 70300)
+	if (g_fout->remoteVersion >= 80400)
+	{
+		appendPQExpBuffer(query, "SELECT tableoid, oid, "
+						  "castsource, casttarget, castfunc, castcontext, "
+						  "castmethod "
+						  "FROM pg_cast ORDER BY 3,4");
+	}
+	else if (g_fout->remoteVersion >= 70300)
 	{
 		appendPQExpBuffer(query, "SELECT tableoid, oid, "
-						  "castsource, casttarget, castfunc, castcontext "
+						  "castsource, casttarget, castfunc, castcontext, "
+						  "CASE WHEN castfunc = 0 THEN 'b' ELSE 'f' END AS castmethod "
 						  "FROM pg_cast ORDER BY 3,4");
 	}
 	else
 	{
 		appendPQExpBuffer(query, "SELECT 0 as tableoid, p.oid, "
 						  "t1.oid as castsource, t2.oid as casttarget, "
-						  "p.oid as castfunc, 'e' as castcontext "
+						  "p.oid as castfunc, 'e' as castcontext, "
+						  "'f' as castmethod "
 						  "FROM pg_type t1, pg_type t2, pg_proc p "
 						  "WHERE p.pronargs = 1 AND "
 						  "p.proargtypes[0] = t1.oid AND "
@@ -4447,6 +4458,7 @@ getCasts(int *numCasts)
 	i_casttarget = PQfnumber(res, "casttarget");
 	i_castfunc = PQfnumber(res, "castfunc");
 	i_castcontext = PQfnumber(res, "castcontext");
+	i_castmethod = PQfnumber(res, "castmethod");
 
 	for (i = 0; i < ntups; i++)
 	{
@@ -4462,6 +4474,7 @@ getCasts(int *numCasts)
 		castinfo[i].casttarget = atooid(PQgetvalue(res, i, i_casttarget));
 		castinfo[i].castfunc = atooid(PQgetvalue(res, i, i_castfunc));
 		castinfo[i].castcontext = *(PQgetvalue(res, i, i_castcontext));
+		castinfo[i].castmethod = *(PQgetvalue(res, i, i_castmethod));
 
 		/*
 		 * Try to name cast as concatenation of typnames.  This is only used
@@ -7188,18 +7201,26 @@ dumpCast(Archive *fout, CastInfo *cast)
 					  getFormattedTypeName(cast->castsource, zeroAsNone),
 					  getFormattedTypeName(cast->casttarget, zeroAsNone));
 
-	if (!OidIsValid(cast->castfunc))
-		appendPQExpBuffer(defqry, "WITHOUT FUNCTION");
-	else
+	switch(cast->castmethod)
 	{
-		/*
-		 * Always qualify the function name, in case it is not in pg_catalog
-		 * schema (format_function_signature won't qualify it).
-		 */
-		appendPQExpBuffer(defqry, "WITH FUNCTION %s.",
-						  fmtId(funcInfo->dobj.namespace->dobj.name));
-		appendPQExpBuffer(defqry, "%s",
-						  format_function_signature(funcInfo, true));
+		case COERCION_METHOD_BINARY:
+			appendPQExpBuffer(defqry, "WITHOUT FUNCTION");
+			break;
+		case COERCION_METHOD_INOUT:
+			appendPQExpBuffer(defqry, "WITH INOUT");
+			break;
+		case COERCION_METHOD_FUNCTION:
+			/*
+			 * Always qualify the function name, in case it is not in
+			 * pg_catalog schema (format_function_signature won't qualify it).
+			 */
+			appendPQExpBuffer(defqry, "WITH FUNCTION %s.",
+							  fmtId(funcInfo->dobj.namespace->dobj.name));
+			appendPQExpBuffer(defqry, "%s",
+							  format_function_signature(funcInfo, true));
+			break;
+		default:
+			write_msg(NULL, "WARNING: bogus value in pg_cast.castmethod field\n");
 	}
 
 	if (cast->castcontext == 'a')