Simplify the implementations of the to_reg* functions.

Given the soft-input-error feature, we can reduce these functions
to be just thin wrappers around a soft-error call of the
corresponding datatype input function.  This means less code and
more certainty that the to_reg* functions match the normal input
behavior.

Notably, it also means that they will accept numeric OID input,
which they didn't before.  It's not clear to me if that omission
had more than laziness behind it, but it doesn't seem like
something we need to work hard to preserve.

Discussion: https://postgr.es/m/3910031.1672095600@sss.pgh.pa.us

2 files changed, 63 insertions, 159 deletions

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 836b9254fbc..3bf8d021c3c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -24100,8 +24100,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regclass</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24118,8 +24117,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regcollation</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24136,8 +24134,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regnamespace</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24154,8 +24151,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regoper</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found or is ambiguous.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found or is ambiguous.
        </para></entry>
       </row>
 
@@ -24172,8 +24168,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regoperator</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24190,8 +24185,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regproc</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found or is ambiguous.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found or is ambiguous.
        </para></entry>
       </row>
 
@@ -24208,8 +24202,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regprocedure</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24226,8 +24219,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regrole</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
 
@@ -24244,8 +24236,7 @@ SELECT collation for ('foo' COLLATE "de_DE");
         obtained by casting the string to type <type>regtype</type> (see
         <xref linkend="datatype-oid"/>); however, this function will return
         <literal>NULL</literal> rather than throwing an error if the name is
-        not found.  Also unlike the cast, this does not accept
-        a numeric OID as input.
+        not found.
        </para></entry>
       </row>
      </tbody>
diff --git a/src/backend/utils/adt/regproc.c b/src/backend/utils/adt/regproc.c
index 14d76c856d7..3635a946330 100644
--- a/src/backend/utils/adt/regproc.c
+++ b/src/backend/utils/adt/regproc.c
@@ -118,24 +118,15 @@ Datum
 to_regproc(PG_FUNCTION_ARGS)
 {
 	char	   *pro_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	List	   *names;
-	FuncCandidateList clist;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name into components and see if it matches any pg_proc
-	 * entries in the current search path.
-	 */
-	names = stringToQualifiedNameList(pro_name, (Node *) &escontext);
-	if (names == NIL)
-		PG_RETURN_NULL();
-
-	clist = FuncnameGetCandidates(names, -1, NIL, false, false, false, true);
-
-	if (clist == NULL || clist->next != NULL)
+	if (!DirectInputFunctionCallSafe(regprocin, pro_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
-
-	PG_RETURN_OID(clist->oid);
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -287,31 +278,15 @@ Datum
 to_regprocedure(PG_FUNCTION_ARGS)
 {
 	char	   *pro_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	List	   *names;
-	int			nargs;
-	Oid			argtypes[FUNC_MAX_ARGS];
-	FuncCandidateList clist;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name and arguments, look up potential matches in the current
-	 * namespace search list, and scan to see which one exactly matches the
-	 * given argument types.    (There will not be more than one match.)
-	 */
-	if (!parseNameAndArgTypes(pro_name, false,
-							  &names, &nargs, argtypes,
-							  (Node *) &escontext))
+	if (!DirectInputFunctionCallSafe(regprocedurein, pro_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
-
-	clist = FuncnameGetCandidates(names, nargs, NIL, false, false, false, true);
-
-	for (; clist; clist = clist->next)
-	{
-		if (memcmp(clist->args, argtypes, nargs * sizeof(Oid)) == 0)
-			PG_RETURN_OID(clist->oid);
-	}
-
-	PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -552,24 +527,15 @@ Datum
 to_regoper(PG_FUNCTION_ARGS)
 {
 	char	   *opr_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	List	   *names;
-	FuncCandidateList clist;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name into components and see if it matches any pg_operator
-	 * entries in the current search path.
-	 */
-	names = stringToQualifiedNameList(opr_name, (Node *) &escontext);
-	if (names == NIL)
+	if (!DirectInputFunctionCallSafe(regoperin, opr_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
-
-	clist = OpernameGetCandidates(names, '\0', true);
-
-	if (clist == NULL || clist->next != NULL)
-		PG_RETURN_NULL();
-
-	PG_RETURN_OID(clist->oid);
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -728,31 +694,15 @@ Datum
 to_regoperator(PG_FUNCTION_ARGS)
 {
 	char	   *opr_name_or_oid = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	List	   *names;
-	int			nargs;
-	Oid			argtypes[FUNC_MAX_ARGS];
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name and arguments, look up potential matches in the current
-	 * namespace search list, and scan to see which one exactly matches the
-	 * given argument types.    (There will not be more than one match.)
-	 */
-	if (!parseNameAndArgTypes(opr_name_or_oid, true,
-							  &names, &nargs, argtypes,
-							  (Node *) &escontext))
-		PG_RETURN_NULL();
-
-	if (nargs != 2)
+	if (!DirectInputFunctionCallSafe(regoperatorin, opr_name_or_oid,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
-
-	result = OpernameGetOprid(names, argtypes[0], argtypes[1]);
-
-	if (!OidIsValid(result))
-		PG_RETURN_NULL();
-
-	PG_RETURN_OID(result);
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -975,25 +925,15 @@ Datum
 to_regclass(PG_FUNCTION_ARGS)
 {
 	char	   *class_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	List	   *names;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name into components and see if it matches any pg_class
-	 * entries in the current search path.
-	 */
-	names = stringToQualifiedNameList(class_name, (Node *) &escontext);
-	if (names == NIL)
-		PG_RETURN_NULL();
-
-	/* We might not even have permissions on this relation; don't lock it. */
-	result = RangeVarGetRelid(makeRangeVarFromNameList(names), NoLock, true);
-
-	if (OidIsValid(result))
-		PG_RETURN_OID(result);
-	else
+	if (!DirectInputFunctionCallSafe(regclassin, class_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -1128,24 +1068,15 @@ Datum
 to_regcollation(PG_FUNCTION_ARGS)
 {
 	char	   *collation_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	List	   *names;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Parse the name into components and see if it matches any pg_collation
-	 * entries in the current search path.
-	 */
-	names = stringToQualifiedNameList(collation_name, (Node *) &escontext);
-	if (names == NIL)
-		PG_RETURN_NULL();
-
-	result = get_collation_oid(names, true);
-
-	if (OidIsValid(result))
-		PG_RETURN_OID(result);
-	else
+	if (!DirectInputFunctionCallSafe(regcollationin, collation_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -1278,17 +1209,15 @@ Datum
 to_regtype(PG_FUNCTION_ARGS)
 {
 	char	   *typ_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	int32		typmod;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	/*
-	 * Invoke the full parser to deal with special cases such as array syntax.
-	 */
-	if (parseTypeString(typ_name, &result, &typmod, (Node *) &escontext))
-		PG_RETURN_OID(result);
-	else
+	if (!DirectInputFunctionCallSafe(regtypein, typ_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -1634,23 +1563,15 @@ Datum
 to_regrole(PG_FUNCTION_ARGS)
 {
 	char	   *role_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	List	   *names;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	names = stringToQualifiedNameList(role_name, (Node *) &escontext);
-	if (names == NIL)
-		PG_RETURN_NULL();
-
-	if (list_length(names) != 1)
-		PG_RETURN_NULL();
-
-	result = get_role_oid(strVal(linitial(names)), true);
-
-	if (OidIsValid(result))
-		PG_RETURN_OID(result);
-	else
+	if (!DirectInputFunctionCallSafe(regrolein, role_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*
@@ -1759,23 +1680,15 @@ Datum
 to_regnamespace(PG_FUNCTION_ARGS)
 {
 	char	   *nsp_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
-	Oid			result;
-	List	   *names;
+	Datum		result;
 	ErrorSaveContext escontext = {T_ErrorSaveContext};
 
-	names = stringToQualifiedNameList(nsp_name, (Node *) &escontext);
-	if (names == NIL)
-		PG_RETURN_NULL();
-
-	if (list_length(names) != 1)
-		PG_RETURN_NULL();
-
-	result = get_namespace_oid(strVal(linitial(names)), true);
-
-	if (OidIsValid(result))
-		PG_RETURN_OID(result);
-	else
+	if (!DirectInputFunctionCallSafe(regnamespacein, nsp_name,
+									 InvalidOid, -1,
+									 (Node *) &escontext,
+									 &result))
 		PG_RETURN_NULL();
+	PG_RETURN_DATUM(result);
 }
 
 /*