pg_lsn macro naming and type behavior revisions.

Change pg_lsn_mi so that it can return negative values when subtracting
LSNs, and clean up some perhaps ill-considered macro names.

src/backend/utils/adt/pg_lsn.c

@@ -50,13 +50,13 @@ pg_lsn_in(PG_FUNCTION_ARGS)
 	off = (uint32) strtoul(str + len1 + 1, NULL, 16);
 	result = (XLogRecPtr) ((uint64) id << 32) | off;
 
-	PG_RETURN_PG_LSN(result);
+	PG_RETURN_LSN(result);
 }
 
 Datum
 pg_lsn_out(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr	lsn = (XLogRecPtr) PG_GETARG_PG_LSN(0);
+	XLogRecPtr	lsn = (XLogRecPtr) PG_GETARG_LSN(0);
 	char		buf[MAXPG_LSNLEN + 1];
 	char	   *result;
 	uint32		id, off;
@@ -77,13 +77,13 @@ pg_lsn_recv(PG_FUNCTION_ARGS)
 	XLogRecPtr	result;
 
 	result = pq_getmsgint64(buf);
-	PG_RETURN_PG_LSN(result);
+	PG_RETURN_LSN(result);
 }
 
 Datum
 pg_lsn_send(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn = (XLogRecPtr) PG_GETARG_PG_LSN(0);
+	XLogRecPtr lsn = (XLogRecPtr) PG_GETARG_LSN(0);
 	StringInfoData buf;
 
 	pq_begintypsend(&buf);
@@ -99,8 +99,8 @@ pg_lsn_send(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_eq(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 == lsn2);
 }
@@ -108,8 +108,8 @@ pg_lsn_eq(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_ne(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 != lsn2);
 }
@@ -117,8 +117,8 @@ pg_lsn_ne(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_lt(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 < lsn2);
 }
@@ -126,8 +126,8 @@ pg_lsn_lt(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_gt(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 > lsn2);
 }
@@ -135,8 +135,8 @@ pg_lsn_gt(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_le(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 <= lsn2);
 }
@@ -144,8 +144,8 @@ pg_lsn_le(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_ge(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 
 	PG_RETURN_BOOL(lsn1 >= lsn2);
 }
@@ -158,19 +158,18 @@ pg_lsn_ge(PG_FUNCTION_ARGS)
 Datum
 pg_lsn_mi(PG_FUNCTION_ARGS)
 {
-	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_PG_LSN(0);
-	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_PG_LSN(1);
+	XLogRecPtr lsn1 = (XLogRecPtr) PG_GETARG_LSN(0);
+	XLogRecPtr lsn2 = (XLogRecPtr) PG_GETARG_LSN(1);
 	char		buf[256];
 	Datum		result;
 
-	/* Negative results are not allowed. */
+	/* Output could be as large as plus or minus 2^63 - 1. */
 	if (lsn1 < lsn2)
-		ereport(ERROR,
-				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-				 errmsg("transaction log location out of range")));
+		snprintf(buf, sizeof buf, "-" UINT64_FORMAT, lsn2 - lsn1);
+	else
+		snprintf(buf, sizeof buf, UINT64_FORMAT, lsn1 - lsn2);
 
 	/* Convert to numeric. */
-	snprintf(buf, sizeof buf, UINT64_FORMAT, lsn1 - lsn2);
 	result = DirectFunctionCall3(numeric_in,
 								 CStringGetDatum(buf),
 								 ObjectIdGetDatum(0),

src/include/fmgr.h

@@ -230,7 +230,7 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
 #define PG_GETARG_CHAR(n)	 DatumGetChar(PG_GETARG_DATUM(n))
 #define PG_GETARG_BOOL(n)	 DatumGetBool(PG_GETARG_DATUM(n))
 #define PG_GETARG_OID(n)	 DatumGetObjectId(PG_GETARG_DATUM(n))
-#define PG_GETARG_PG_LSN(n)	 DatumGetPgLsn(PG_GETARG_DATUM(n))
+#define PG_GETARG_LSN(n)	 DatumGetLSN(PG_GETARG_DATUM(n))
 #define PG_GETARG_POINTER(n) DatumGetPointer(PG_GETARG_DATUM(n))
 #define PG_GETARG_CSTRING(n) DatumGetCString(PG_GETARG_DATUM(n))
 #define PG_GETARG_NAME(n)	 DatumGetName(PG_GETARG_DATUM(n))
@@ -303,7 +303,7 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
 #define PG_RETURN_CHAR(x)	 return CharGetDatum(x)
 #define PG_RETURN_BOOL(x)	 return BoolGetDatum(x)
 #define PG_RETURN_OID(x)	 return ObjectIdGetDatum(x)
-#define PG_RETURN_PG_LSN(x)	 return PgLsnGetDatum(x)
+#define PG_RETURN_LSN(x)	 return LSNGetDatum(x)
 #define PG_RETURN_POINTER(x) return PointerGetDatum(x)
 #define PG_RETURN_CSTRING(x) return CStringGetDatum(x)
 #define PG_RETURN_NAME(x)	 return NameGetDatum(x)

src/include/postgres.h

@@ -484,18 +484,18 @@ typedef Datum *DatumPtr;
 #define ObjectIdGetDatum(X) ((Datum) SET_4_BYTES(X))
 
 /*
- * DatumGetPgLsn
+ * DatumGetLSN
  *		Returns PostgreSQL log sequence number of a datum.
  */
 
-#define DatumGetPgLsn(X) ((XLogRecPtr) GET_8_BYTES(X))
+#define DatumGetLSN(X) ((XLogRecPtr) GET_8_BYTES(X))
 
 /*
- * PG_LSNGetDatum
+ * LSNGetDatum
  *		Returns datum representation for a PostgreSQL log sequence number.
  */
 
-#define PgLsnGetDatum(X) ((Datum) SET_8_BYTES(X))
+#define LSNGetDatum(X) ((Datum) SET_8_BYTES(X))
 
 /*
  * DatumGetTransactionId

src/test/regress/expected/pg_lsn.out

@@ -53,7 +53,11 @@ SELECT '0/16AE7F8' > pg_lsn '0/16AE7F7';
 (1 row)
 
 SELECT '0/16AE7F7'::pg_lsn - '0/16AE7F8'::pg_lsn; -- No negative results
-ERROR:  transaction log location out of range
+ ?column? 
+----------
+       -1
+(1 row)
+
 SELECT '0/16AE7F8'::pg_lsn - '0/16AE7F7'::pg_lsn; -- correct
  ?column? 
 ----------