Modify all callers of datatype input and receive functions so that if these

functions are not strict, they will be called (passing a NULL first parameter)
during any attempt to input a NULL value of their datatype.  Currently, all
our input functions are strict and so this commit does not change any
behavior.  However, this will make it possible to build domain input functions
that centralize checking of domain constraints, thereby closing numerous holes
in our domain support, as per previous discussion.

While at it, I took the opportunity to introduce convenience functions
InputFunctionCall, OutputFunctionCall, etc to use in code that calls I/O
functions.  This eliminates a lot of grotty-looking casts, but the main
motivation is to make it easier to grep for these places if we ever need
to touch them again.

src/backend/utils/fmgr/fmgr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.99 2006/03/05 15:58:46 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.100 2006/04/04 19:35:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1682,6 +1682,172 @@ OidFunctionCall9(Oid functionId, Datum arg1, Datum arg2,
 }
 
 
+/*
+ * Special cases for convenient invocation of datatype I/O functions.
+ */
+
+/*
+ * Call a previously-looked-up datatype input function.
+ *
+ * "str" may be NULL to indicate we are reading a NULL.  In this case
+ * the caller should assume the result is NULL, but we'll call the input
+ * function anyway if it's not strict.  So this is almost but not quite
+ * the same as FunctionCall3.
+ */
+Datum
+InputFunctionCall(FmgrInfo *flinfo, char *str, Oid typioparam, int32 typmod)
+{
+	FunctionCallInfoData fcinfo;
+	Datum		result;
+
+	if (str == NULL && flinfo->fn_strict)
+		return (Datum) 0;		/* just return null result */
+
+	InitFunctionCallInfoData(fcinfo, flinfo, 3, NULL, NULL);
+
+	fcinfo.arg[0] = CStringGetDatum(str);
+	fcinfo.arg[1] = ObjectIdGetDatum(typioparam);
+	fcinfo.arg[2] = Int32GetDatum(typmod);
+	fcinfo.argnull[0] = (str == NULL);
+	fcinfo.argnull[1] = false;
+	fcinfo.argnull[2] = false;
+
+	result = FunctionCallInvoke(&fcinfo);
+
+	/* Should get null result if and only if str is NULL */
+	if (str == NULL)
+	{
+		if (!fcinfo.isnull)
+			elog(ERROR, "input function %u returned non-NULL",
+				 fcinfo.flinfo->fn_oid);
+	}
+	else
+	{
+		if (fcinfo.isnull)
+			elog(ERROR, "input function %u returned NULL",
+				 fcinfo.flinfo->fn_oid);
+	}
+
+	return result;
+}
+
+/*
+ * Call a previously-looked-up datatype output function.
+ *
+ * Do not call this on NULL datums.
+ *
+ * This is mere window dressing for FunctionCall1, but its use is recommended
+ * anyway so that code invoking output functions can be identified easily.
+ */
+char *
+OutputFunctionCall(FmgrInfo *flinfo, Datum val)
+{
+	return DatumGetCString(FunctionCall1(flinfo, val));
+}
+
+/*
+ * Call a previously-looked-up datatype binary-input function.
+ *
+ * "buf" may be NULL to indicate we are reading a NULL.  In this case
+ * the caller should assume the result is NULL, but we'll call the receive
+ * function anyway if it's not strict.  So this is almost but not quite
+ * the same as FunctionCall3.
+ */
+Datum
+ReceiveFunctionCall(FmgrInfo *flinfo, StringInfo buf,
+					Oid typioparam, int32 typmod)
+{
+	FunctionCallInfoData fcinfo;
+	Datum		result;
+
+	if (buf == NULL && flinfo->fn_strict)
+		return (Datum) 0;		/* just return null result */
+
+	InitFunctionCallInfoData(fcinfo, flinfo, 3, NULL, NULL);
+
+	fcinfo.arg[0] = PointerGetDatum(buf);
+	fcinfo.arg[1] = ObjectIdGetDatum(typioparam);
+	fcinfo.arg[2] = Int32GetDatum(typmod);
+	fcinfo.argnull[0] = (buf == NULL);
+	fcinfo.argnull[1] = false;
+	fcinfo.argnull[2] = false;
+
+	result = FunctionCallInvoke(&fcinfo);
+
+	/* Should get null result if and only if buf is NULL */
+	if (buf == NULL)
+	{
+		if (!fcinfo.isnull)
+			elog(ERROR, "receive function %u returned non-NULL",
+				 fcinfo.flinfo->fn_oid);
+	}
+	else
+	{
+		if (fcinfo.isnull)
+			elog(ERROR, "receive function %u returned NULL",
+				 fcinfo.flinfo->fn_oid);
+	}
+
+	return result;
+}
+
+/*
+ * Call a previously-looked-up datatype binary-output function.
+ *
+ * Do not call this on NULL datums.
+ *
+ * This is little more than window dressing for FunctionCall1, but its use is
+ * recommended anyway so that code invoking output functions can be identified
+ * easily.  Note however that it does guarantee a non-toasted result.
+ */
+bytea *
+SendFunctionCall(FmgrInfo *flinfo, Datum val)
+{
+	return DatumGetByteaP(FunctionCall1(flinfo, val));
+}
+
+/*
+ * As above, for I/O functions identified by OID.  These are only to be used
+ * in seldom-executed code paths.  They are not only slow but leak memory.
+ */
+Datum
+OidInputFunctionCall(Oid functionId, char *str, Oid typioparam, int32 typmod)
+{
+	FmgrInfo	flinfo;
+
+	fmgr_info(functionId, &flinfo);
+	return InputFunctionCall(&flinfo, str, typioparam, typmod);
+}
+
+char *
+OidOutputFunctionCall(Oid functionId, Datum val)
+{
+	FmgrInfo	flinfo;
+
+	fmgr_info(functionId, &flinfo);
+	return OutputFunctionCall(&flinfo, val);
+}
+
+Datum
+OidReceiveFunctionCall(Oid functionId, StringInfo buf,
+					   Oid typioparam, int32 typmod)
+{
+	FmgrInfo	flinfo;
+
+	fmgr_info(functionId, &flinfo);
+	return ReceiveFunctionCall(&flinfo, buf, typioparam, typmod);
+}
+
+bytea *
+OidSendFunctionCall(Oid functionId, Datum val)
+{
+	FmgrInfo	flinfo;
+
+	fmgr_info(functionId, &flinfo);
+	return SendFunctionCall(&flinfo, val);
+}
+
+
 /*
  * !!! OLD INTERFACE !!!
  *