Fix_Century_V1_PG.patch

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index aba1145..ad42126 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -989,6 +989,7 @@ static DCHCacheEntry *DCH_cache_getnew(char *str);
 static NUMCacheEntry *NUM_cache_search(char *str);
 static NUMCacheEntry *NUM_cache_getnew(char *str);
 static void NUM_cache_remove(NUMCacheEntry *ent);
+static int DecideCentury(int *in, int len);
 
 
 /* ----------
@@ -2733,21 +2734,14 @@ DCH_from_char(FormatNode *node, char *in, TmFromChar *out)
 			case DCH_IYYY:
 				from_char_parse_int(&out->year, &s, n);
 				out->yysz = 4;
+				DecideCentury(&out->year, out->yysz);
 				s += SKIP_THth(n->suffix);
 				break;
 			case DCH_YYY:
 			case DCH_IYY:
 				from_char_parse_int(&out->year, &s, n);
 				out->yysz = 3;
-
-				/*
-				 * 3-digit year: '100' ... '999' = 1100 ... 1999 '000' ...
-				 * '099' = 2000 ... 2099
-				 */
-				if (out->year >= 100)
-					out->year += 1000;
-				else
-					out->year += 2000;
+				DecideCentury(&out->year, out->yysz);
 				s += SKIP_THth(n->suffix);
 				break;
 			case DCH_YY:
@@ -2755,14 +2749,7 @@ DCH_from_char(FormatNode *node, char *in, TmFromChar *out)
 				from_char_parse_int(&out->year, &s, n);
 				out->yysz = 2;
 
-				/*
-				 * 2-digit year: '00' ... '69'	= 2000 ... 2069 '70' ... '99'
-				 * = 1970 ... 1999
-				 */
-				if (out->year < 70)
-					out->year += 2000;
-				else
-					out->year += 1900;
+				DecideCentury(&out->year, out->yysz);
 				s += SKIP_THth(n->suffix);
 				break;
 			case DCH_Y:
@@ -2770,10 +2757,7 @@ DCH_from_char(FormatNode *node, char *in, TmFromChar *out)
 				from_char_parse_int(&out->year, &s, n);
 				out->yysz = 1;
 
-				/*
-				 * 1-digit year: always +2000
-				 */
-				out->year += 2000;
+				DecideCentury(&out->year, out->yysz);
 				s += SKIP_THth(n->suffix);
 				break;
 			case DCH_RM:
@@ -5161,3 +5145,63 @@ float8_to_char(PG_FUNCTION_ARGS)
 	NUM_TOCHAR_finish;
 	PG_RETURN_TEXT_P(result);
 }
+
+/*
+ * In case of different Inputs & different Year formats, engine itself
+ * has to decide the century for the given year. This function will take
+ * care of the input & accordingly append the century their if not provided.
+ *
+ *   Input 	=	Transformed output
+ * 0 ... 9 		= 2000 ... 2009
+ * 00 ... 69 	= 2000 ... 2069
+ * 70 ... 99 	= 1900 ... 1999
+ * 000 ... 999 	= 2000 ... 2999
+ *
+ * In case input is greater than 9999 it throws an error. The basic rule of
+ * the function is " If the format is lesser than the actual value, then it
+ * should throw an error. Only in case of 'YY', we need not throw an error,
+ * unless the year is later than 9999".
+ */
+
+static int DecideCentury(int *in, int len)
+{
+	if (len == 1)
+	{
+		if (*in > 0 && *in < 9)
+			*in += 2000;
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_DATETIME_FORMAT),
+					 errmsg("date format picture ends before converting entire input string %d ", len)));
+	}
+	else if (len == 2)
+	{
+		if (*in > 0 && *in < 69)
+			*in += 2000;
+		else if (*in > 70 && *in < 99)
+			*in += 1900;
+		else if (*in > 9999)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_DATETIME_FORMAT),
+					 errmsg("date format picture ends before converting entire input string %d ", len)));
+
+	}
+	else if (len == 3)
+	{
+		if (*in > 0 && *in < 999)
+			*in += 2000;
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_DATETIME_FORMAT),
+					 errmsg("date format picture ends before converting entire input string %d ", len)));
+	}
+	else if (len == 4)
+	{
+		if (*in > 9999)
+			ereport(ERROR,
+				(errcode(ERRCODE_INVALID_DATETIME_FORMAT),
+				 errmsg("date format picture ends before converting entire input string %d ", len)));
+	}
+
+	return 0;
+}