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, 1 insertions, 54 deletions

diff --git a/src/backend/utils/adt/mac.c b/src/backend/utils/adt/mac.c
index fa13abe4618..aa13589b8a6 100644
--- a/src/backend/utils/adt/mac.c
+++ b/src/backend/utils/adt/mac.c
@@ -1,7 +1,7 @@
 /*
  *	PostgreSQL type definitions for MAC addresses.
  *
- *	$PostgreSQL: pgsql/src/backend/utils/adt/mac.c,v 1.37 2007/02/27 23:48:08 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/utils/adt/mac.c,v 1.38 2007/06/05 21:31:06 tgl Exp $
  */
 
 #include "postgres.h"
@@ -145,59 +145,6 @@ macaddr_send(PG_FUNCTION_ARGS)
 
 
 /*
- * Convert macaddr to text data type.
- */
-
-Datum
-macaddr_text(PG_FUNCTION_ARGS)
-{
-	/* Input is a macaddr, but may as well leave it in Datum form */
-	Datum		addr = PG_GETARG_DATUM(0);
-	text	   *result;
-	char	   *str;
-	int			len;
-
-	str = DatumGetCString(DirectFunctionCall1(macaddr_out, addr));
-
-	len = (strlen(str) + VARHDRSZ);
-
-	result = palloc(len);
-
-	SET_VARSIZE(result, len);
-	memcpy(VARDATA(result), str, (len - VARHDRSZ));
-
-	pfree(str);
-
-	PG_RETURN_TEXT_P(result);
-}
-
-/*
- * Convert text to macaddr data type.
- */
-
-Datum
-text_macaddr(PG_FUNCTION_ARGS)
-{
-	text	   *addr = PG_GETARG_TEXT_P(0);
-	Datum		result;
-	char		str[100];
-	int			len;
-
-	len = (VARSIZE(addr) - VARHDRSZ);
-	if (len >= sizeof(str))
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-				 errmsg("text too long to convert to MAC address")));
-
-	memcpy(str, VARDATA(addr), len);
-	*(str + len) = '\0';
-
-	result = DirectFunctionCall1(macaddr_in, CStringGetDatum(str));
-
-	return result;
-}
-
-/*
  *	Comparison function for sorting:
  */