Fix to_timestamp/to_date so that zero year input for Y, YY, or YYY

formats will be taken as 2000, not year zero.  Per bug report from
Aasmund Midttun Godal.  Fix from Karel Zak.

src/backend/utils/adt/formatting.c

 /* -----------------------------------------------------------------------
  * formatting.c
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/formatting.c,v 1.47 2001/12/10 15:34:05 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/formatting.c,v 1.48 2002/01/02 22:09:23 tgl Exp $
  *
  *
  *	 Portions Copyright (c) 1999-2000, PostgreSQL Global Development Group
@@ -371,10 +371,7 @@ typedef struct
 				ddd,
 				mm,
 				ms,
-				yyyy,
-				yyy,
-				yy,
-				y,
+				year,
 				bc,
 				iw,
 				ww,
@@ -393,10 +390,10 @@ typedef struct
  */
 #ifdef DEBUG_TO_FROM_CHAR
 #define DEBUG_TMFC( _X ) \
-		elog(DEBUG_elog_output, "TMFC:\nhh %d\nam %d\npm %d\nmi %d\nss %d\nssss %d\nd %d\ndd %d\nddd %d\nmm %d\nms: %d\nyyyy %d\nbc %d\niw %d\nww %d\nw %d\ncc %d\nq %d\nj %d\nus: %d", \
+		elog(DEBUG_elog_output, "TMFC:\nhh %d\nam %d\npm %d\nmi %d\nss %d\nssss %d\nd %d\ndd %d\nddd %d\nmm %d\nms: %d\nyear %d\nbc %d\niw %d\nww %d\nw %d\ncc %d\nq %d\nj %d\nus: %d", \
 			(_X)->hh, (_X)->am, (_X)->pm, (_X)->mi, (_X)->ss, \
 			(_X)->ssss, (_X)->d, (_X)->dd, (_X)->ddd, (_X)->mm, (_X)->ms, \
-			(_X)->yyyy, (_X)->bc, (_X)->iw, (_X)->ww, (_X)->w, \
+			(_X)->year, (_X)->bc, (_X)->iw, (_X)->ww, (_X)->w, \
 			(_X)->cc, (_X)->q, (_X)->j, (_X)->us);
 #define DEBUG_TM( _X ) \
 		elog(DEBUG_elog_output, "TM:\nsec %d\nyear %d\nmin %d\nwday %d\nhour %d\nyday %d\nmday %d\nnisdst %d\nmon %d\n",\
@@ -2396,8 +2393,8 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			{
 				int			cc;
 
-				sscanf(inout, "%d,%03d", &cc, &tmfc->yyyy);
-				tmfc->yyyy += (cc * 1000);
+				sscanf(inout, "%d,%03d", &cc, &tmfc->year);
+				tmfc->year += (cc * 1000);
 
 				return strdigits_len(inout) + 3 + SKIP_THth(suf);
 			}
@@ -2417,12 +2414,12 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			{
 				if (S_FM(suf) || is_next_separator(node))
 				{
-					sscanf(inout, "%d", &tmfc->yyyy);
+					sscanf(inout, "%d", &tmfc->year);
 					return strdigits_len(inout) - 1 + SKIP_THth(suf);
 				}
 				else
 				{
-					sscanf(inout, "%04d", &tmfc->yyyy);
+					sscanf(inout, "%04d", &tmfc->year);
 					return 3 + SKIP_THth(suf);
 				}
 			}
@@ -2443,7 +2440,18 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			else if (flag == FROM_CHAR)
 			{
-				sscanf(inout, "%03d", &tmfc->yyy);
+				sscanf(inout, "%03d", &tmfc->year);
+				
+				/*
+				 * 3-digit year:
+				 *	'100' ... '999' = 1100 ... 1999
+				 *	'000' ... '099' = 2000 ... 2099
+				 */
+				if (tmfc->year >= 100)
+					tmfc->year += 1000;
+				else
+					tmfc->year += 2000;
+
 				return 2 + SKIP_THth(suf);
 			}
 			break;
@@ -2463,7 +2471,18 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			else if (flag == FROM_CHAR)
 			{
-				sscanf(inout, "%02d", &tmfc->yy);
+				sscanf(inout, "%02d", &tmfc->year);
+
+				/*
+				 * 2-digit year:
+				 * '00' ... '69'  = 2000 ... 2069
+				 * '70' ... '99'  = 1970 ... 1999
+		 		 */
+				if (tmfc->year < 70)
+					tmfc->year += 2000;
+				else
+					tmfc->year += 1900;
+
 				return 1 + SKIP_THth(suf);
 			}
 			break;
@@ -2483,7 +2502,13 @@ dch_date(int arg, char *inout, int suf, int flag, FormatNode *node, void *data)
 			}
 			else if (flag == FROM_CHAR)
 			{
-				sscanf(inout, "%1d", &tmfc->y);
+				sscanf(inout, "%1d", &tmfc->year);
+				
+				/*
+				 * 1-digit year: always +2000
+				 */
+				tmfc->year += 2000;
+
 				return 0 + SKIP_THth(suf);
 			}
 			break;
@@ -3002,48 +3027,8 @@ to_timestamp(PG_FUNCTION_ARGS)
 			break;
 	}
 
-	if (tmfc.yyyy)
-		tm.tm_year = tmfc.yyyy;
-
-	else if (tmfc.y)
-	{
-		/*
-		 * 1-digit year: always +2000
-		 */
-		tm.tm_year = tmfc.y + 2000;
-	}
-	else if (tmfc.yy)
-	{
-
-		/*---------
-		 * 2-digit year:
-		 * '00' ... '69'  = 2000 ... 2069
-		 * '70' ... '99'  = 1970 ... 1999
-		 *---------
-		 */
-		tm.tm_year = tmfc.yy;
-
-		if (tm.tm_year < 70)
-			tm.tm_year += 2000;
-		else
-			tm.tm_year += 1900;
-	}
-	else if (tmfc.yyy)
-	{
-
-		/*---------
-		 * 3-digit year:
-		 *	'100' ... '999' = 1100 ... 1999
-		 *	'000' ... '099' = 2000 ... 2099
-		 *---------
-		 */
-		tm.tm_year = tmfc.yyy;
-
-		if (tm.tm_year >= 100)
-			tm.tm_year += 1000;
-		else
-			tm.tm_year += 2000;
-	}
+	if (tmfc.year)
+		tm.tm_year = tmfc.year;
 
 	if (tmfc.bc)
 	{