Downgrade implicit casts to text to be assignment-only, except for the ones

from the other string-category types; this eliminates a lot of surprising
interpretations that the parser could formerly make when there was no directly
applicable operator.

Create a general mechanism that supports casts to and from the standard string
types (text,varchar,bpchar) for *every* datatype, by invoking the datatype's
I/O functions.  These new casts are assignment-only in the to-string direction,
explicit-only in the other, and therefore should create no surprising behavior.
Remove a bunch of thereby-obsoleted datatype-specific casting functions.

The "general mechanism" is a new expression node type CoerceViaIO that can
actually convert between *any* two datatypes if their external text
representations are compatible.  This is more general than needed for the
immediate feature, but might be useful in plpgsql or other places in future.

This commit does nothing about the issue that applying the concatenation
operator || to non-text types will now fail, often with strange error messages
due to misinterpreting the operator as array concatenation.  Since it often
(not always) worked before, we should either make it succeed or at least give
a more user-friendly error; but details are still under debate.

Peter Eisentraut and Tom Lane

1 files changed, 48 insertions, 106 deletions

diff --git a/src/backend/utils/adt/enum.c b/src/backend/utils/adt/enum.c
index 635d232912e..a5506a0c1b3 100644
--- a/src/backend/utils/adt/enum.c
+++ b/src/backend/utils/adt/enum.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *    $PostgreSQL: pgsql/src/backend/utils/adt/enum.c,v 1.2 2007/04/02 22:14:17 adunstan Exp $
+ *    $PostgreSQL: pgsql/src/backend/utils/adt/enum.c,v 1.3 2007/06/05 21:31:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,8 +21,6 @@
 #include "utils/syscache.h"
 
 
-static Oid	cstring_enum(char *name, Oid enumtypoid);
-static char *enum_cstring(Oid enumval);
 static ArrayType *enum_range_internal(Oid enumtypoid, Oid lower, Oid upper);
 static int	enum_elem_cmp(const void *left, const void *right);
 
@@ -32,75 +30,60 @@ static int	enum_elem_cmp(const void *left, const void *right);
 Datum
 enum_in(PG_FUNCTION_ARGS)
 {
-    char *name = PG_GETARG_CSTRING(0);
-    Oid enumtypoid = PG_GETARG_OID(1);
-
-    PG_RETURN_OID(cstring_enum(name, enumtypoid));
-}
-
-/* guts of enum_in and text-to-enum */
-static Oid
-cstring_enum(char *name, Oid enumtypoid)
-{
-	HeapTuple tup;
+	char *name = PG_GETARG_CSTRING(0);
+	Oid enumtypoid = PG_GETARG_OID(1);
 	Oid enumoid;
+	HeapTuple tup;
 
 	/* must check length to prevent Assert failure within SearchSysCache */
-
 	if (strlen(name) >= NAMEDATALEN)
-        ereport(ERROR,
-                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-                 errmsg("invalid input value for enum %s: \"%s\"",
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+				 errmsg("invalid input value for enum %s: \"%s\"",
 						format_type_be(enumtypoid),
-                        name)));
+						name)));
 
 	tup = SearchSysCache(ENUMTYPOIDNAME,
 						 ObjectIdGetDatum(enumtypoid),
 						 CStringGetDatum(name),
 						 0, 0);
-    if (tup == NULL)
-        ereport(ERROR,
-                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-                 errmsg("invalid input value for enum %s: \"%s\"",
+	if (!HeapTupleIsValid(tup))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+				 errmsg("invalid input value for enum %s: \"%s\"",
 						format_type_be(enumtypoid),
-                        name)));
+						name)));
 
 	enumoid = HeapTupleGetOid(tup);
 
 	ReleaseSysCache(tup);
-	return enumoid;
+
+	PG_RETURN_OID(enumoid);
 }
 
 Datum
 enum_out(PG_FUNCTION_ARGS)
 {
-    Oid enumoid = PG_GETARG_OID(0);
-
-    PG_RETURN_CSTRING(enum_cstring(enumoid));
-}
-
-/* guts of enum_out and enum-to-text */
-static char *
-enum_cstring(Oid enumval)
-{
+	Oid enumval = PG_GETARG_OID(0);
+	char *result;
 	HeapTuple tup;
 	Form_pg_enum en;
-	char *label;
 
 	tup = SearchSysCache(ENUMOID,
 						 ObjectIdGetDatum(enumval),
 						 0, 0, 0);
-    if (tup == NULL)
-        ereport(ERROR,
-                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
-                 errmsg("invalid internal value for enum: %u",
-                        enumval)));
+	if (!HeapTupleIsValid(tup))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
+				 errmsg("invalid internal value for enum: %u",
+						enumval)));
 	en = (Form_pg_enum) GETSTRUCT(tup);
 
-	label = pstrdup(NameStr(en->enumlabel));
+	result = pstrdup(NameStr(en->enumlabel));
 
 	ReleaseSysCache(tup);
-	return label;
+
+	PG_RETURN_CSTRING(result);
 }
 
 /* Comparison functions and related */
@@ -191,47 +174,6 @@ enum_cmp(PG_FUNCTION_ARGS)
 		PG_RETURN_INT32(-1);
 }
 
-/* Casts between text and enum */
-
-Datum
-enum_text(PG_FUNCTION_ARGS)
-{
-	Oid enumval = PG_GETARG_OID(0);
-	text *result;
-	char *cstr;
-	int len;
-
-	cstr = enum_cstring(enumval);
-	len = strlen(cstr);
-	result = (text *) palloc(VARHDRSZ + len);
-	SET_VARSIZE(result, VARHDRSZ + len);
-	memcpy(VARDATA(result), cstr, len);
-	pfree(cstr);
-	PG_RETURN_TEXT_P(result);
-}
-
-Datum
-text_enum(PG_FUNCTION_ARGS)
-{
-	text *textval = PG_GETARG_TEXT_P(0);
-	Oid enumtypoid;
-	char *str;
-
-	/*
-	 * We rely on being able to get the specific enum type from the calling
-	 * expression tree.
-	 */
-	enumtypoid = get_fn_expr_rettype(fcinfo->flinfo);
-	if (enumtypoid == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("could not determine actual enum type")));
-
-	str = DatumGetCString(DirectFunctionCall1(textout,
-											  PointerGetDatum(textval)));
-    PG_RETURN_OID(cstring_enum(str, enumtypoid));
-}
-
 /* Enum programming support functions */
 
 Datum
@@ -266,7 +208,7 @@ enum_first(PG_FUNCTION_ARGS)
 
 	ReleaseCatCacheList(list);
 
-    if (!OidIsValid(min))		/* should not happen */
+	if (!OidIsValid(min))		/* should not happen */
 		elog(ERROR, "no values found for enum %s",
 			 format_type_be(enumtypoid));
 
@@ -276,10 +218,10 @@ enum_first(PG_FUNCTION_ARGS)
 Datum
 enum_last(PG_FUNCTION_ARGS)
 {
-    Oid enumtypoid;
-    Oid max = InvalidOid;
-    CatCList *list;
-    int num, i;
+	Oid enumtypoid;
+	Oid max = InvalidOid;
+	CatCList *list;
+	int num, i;
 
 	/*
 	 * We rely on being able to get the specific enum type from the calling
@@ -292,24 +234,24 @@ enum_last(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("could not determine actual enum type")));
 
-    list = SearchSysCacheList(ENUMTYPOIDNAME, 1,
-                              ObjectIdGetDatum(enumtypoid),
+	list = SearchSysCacheList(ENUMTYPOIDNAME, 1,
+							  ObjectIdGetDatum(enumtypoid),
 							  0, 0, 0);
-    num = list->n_members;
-    for (i = 0; i < num; i++)
-    {
+	num = list->n_members;
+	for (i = 0; i < num; i++)
+	{
 		Oid valoid = HeapTupleHeaderGetOid(list->members[i]->tuple.t_data);
-        if(!OidIsValid(max) || valoid > max)
-            max = valoid;
-    }
+		if (!OidIsValid(max) || valoid > max)
+			max = valoid;
+	}
 
 	ReleaseCatCacheList(list);
 
-    if (!OidIsValid(max))		/* should not happen */
+	if (!OidIsValid(max))		/* should not happen */
 		elog(ERROR, "no values found for enum %s",
 			 format_type_be(enumtypoid));
 
-    PG_RETURN_OID(max);
+	PG_RETURN_OID(max);
 }
 
 /* 2-argument variant of enum_range */
@@ -368,26 +310,26 @@ static ArrayType *
 enum_range_internal(Oid enumtypoid, Oid lower, Oid upper)
 {
 	ArrayType *result;
-    CatCList *list;
-    int total, i, j;
-    Datum *elems;
+	CatCList *list;
+	int total, i, j;
+	Datum *elems;
 
 	list = SearchSysCacheList(ENUMTYPOIDNAME, 1,
-                              ObjectIdGetDatum(enumtypoid),
+							  ObjectIdGetDatum(enumtypoid),
 							  0, 0, 0);
 	total = list->n_members;
 
 	elems = (Datum *) palloc(total * sizeof(Datum));
 
 	j = 0;
-    for (i = 0; i < total; i++)
-    {
+	for (i = 0; i < total; i++)
+	{
 		Oid val = HeapTupleGetOid(&(list->members[i]->tuple));
 
 		if ((!OidIsValid(lower) || lower <= val) &&
 			(!OidIsValid(upper) || val <= upper))
-            elems[j++] = ObjectIdGetDatum(val);
-    }
+			elems[j++] = ObjectIdGetDatum(val);
+	}
 
 	/* shouldn't need the cache anymore */
 	ReleaseCatCacheList(list);