Honor to_char() "FM" specification in YYY, YY, and Y; it was already

honored by YYYY.  Also document Oracle "toggle" FM behavior.

Per report from Guy Rouillier

doc/src/sgml/func.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.502 2010/02/12 17:33:19 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.503 2010/02/16 21:18:01 momjian Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -5174,7 +5174,11 @@ SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
       <para>
        <literal>FM</literal> suppresses leading zeroes and trailing blanks
        that would otherwise be added to make the output of a pattern be
-       fixed-width.
+       fixed-width.  In <productname>PostgreSQL</productname>,
+       <literal>FM</literal> modifies only the next specification, while in
+       Oracle <literal>FM</literal> affects all subsequent
+       specifications, and repeated <literal>FM</literal> modifiers
+       toggle fill mode on and off.
       </para>
      </listitem>
 

src/backend/utils/adt/formatting.c

 /* -----------------------------------------------------------------------
  * formatting.c
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/formatting.c,v 1.162 2010/01/02 16:57:53 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/formatting.c,v 1.163 2010/02/16 21:18:01 momjian Exp $
  *
  *
  *	 Portions Copyright (c) 1999-2010, PostgreSQL Global Development Group
@@ -515,6 +515,7 @@ do { \
 #define S_th(_s)	(((_s) & DCH_S_th) ? 1 : 0)
 #define S_TH_TYPE(_s)	(((_s) & DCH_S_TH) ? TH_UPPER : TH_LOWER)
 
+/* Oracle toggles FM behavior, we don't; see docs. */
 #define S_FM(_s)	(((_s) & DCH_S_FM) ? 1 : 0)
 #define S_SP(_s)	(((_s) & DCH_S_SP) ? 1 : 0)
 #define S_TM(_s)	(((_s) & DCH_S_TM) ? 1 : 0)
@@ -2411,28 +2412,30 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out)
 				break;
 			case DCH_YYY:
 			case DCH_IYY:
-				snprintf(buff, sizeof(buff), "%03d",
+				snprintf(buff, sizeof(buff), "%0*d",
+						 S_FM(n->suffix) ? 0 : 3,
 						 n->key->id == DCH_YYY ?
 						 ADJUST_YEAR(tm->tm_year, is_interval) :
 						 ADJUST_YEAR(date2isoyear(tm->tm_year,
 												  tm->tm_mon, tm->tm_mday),
 									 is_interval));
 				i = strlen(buff);
-				strcpy(s, buff + (i - 3));
+				strcpy(s, buff + (i > 3 ? i - 3 : 0));
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);
 				break;
 			case DCH_YY:
 			case DCH_IY:
-				snprintf(buff, sizeof(buff), "%02d",
+				snprintf(buff, sizeof(buff), "%0*d",
+						 S_FM(n->suffix) ? 0 : 2,
 						 n->key->id == DCH_YY ?
 						 ADJUST_YEAR(tm->tm_year, is_interval) :
 						 ADJUST_YEAR(date2isoyear(tm->tm_year,
 												  tm->tm_mon, tm->tm_mday),
 									 is_interval));
 				i = strlen(buff);
-				strcpy(s, buff + (i - 2));
+				strcpy(s, buff + (i > 2 ? i - 2 : 0));
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);
@@ -2446,7 +2449,7 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out)
 												  tm->tm_mon, tm->tm_mday),
 									 is_interval));
 				i = strlen(buff);
-				strcpy(s, buff + (i - 1));
+				strcpy(s, buff + (i > 1 ? i - 1 : 0));
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);

src/test/regress/expected/timestamp.out

@@ -1063,8 +1063,8 @@ SELECT '' AS to_char_4, to_char(d1, 'FMY,YYY FMYYYY FMYYY FMYY FMY FMCC FMQ FMMM
            | 1,997 1997 997 97 7 20 1 2 7 45 14 6 2450494
            | 1,997 1997 997 97 7 20 1 2 7 46 15 7 2450495
            | 1,997 1997 997 97 7 20 1 2 7 47 16 1 2450496
-           | 0,097 97 097 97 7 1 1 2 7 47 16 3 1686042
-           | 0,097 97 097 97 7 1 1 2 7 47 16 7 1756536
+           | 0,097 97 97 97 7 1 1 2 7 47 16 3 1686042
+           | 0,097 97 97 97 7 1 1 2 7 47 16 7 1756536
            | 0,597 597 597 97 7 6 1 2 7 47 16 5 1939157
            | 1,097 1097 097 97 7 11 1 2 7 47 16 3 2121778
            | 1,697 1697 697 97 7 17 1 2 7 47 16 7 2340924
@@ -1561,8 +1561,8 @@ SELECT '' AS to_char_11, to_char(d1, 'FMIYYY FMIYY FMIY FMI FMIW FMIDDD FMID')
             | 1997 997 97 7 7 47 5
             | 1997 997 97 7 7 48 6
             | 1997 997 97 7 7 49 7
-            | 97 097 97 7 7 44 2
-            | 97 097 97 7 7 48 6
+            | 97 97 97 7 7 44 2
+            | 97 97 97 7 7 48 6
             | 597 597 97 7 7 46 4
             | 1097 097 97 7 7 44 2
             | 1697 697 97 7 7 48 6

src/test/regress/expected/timestamptz.out

@@ -1148,8 +1148,8 @@ SELECT '' AS to_char_4, to_char(d1, 'FMY,YYY FMYYYY FMYYY FMYY FMY FMCC FMQ FMMM
            | 1,997 1997 997 97 7 20 1 2 7 45 14 6 2450494
            | 1,997 1997 997 97 7 20 1 2 7 46 15 7 2450495
            | 1,997 1997 997 97 7 20 1 2 7 47 16 1 2450496
-           | 0,097 97 097 97 7 1 1 2 7 47 16 3 1686042
-           | 0,097 97 097 97 7 1 1 2 7 47 16 7 1756536
+           | 0,097 97 97 97 7 1 1 2 7 47 16 3 1686042
+           | 0,097 97 97 97 7 1 1 2 7 47 16 7 1756536
            | 0,597 597 597 97 7 6 1 2 7 47 16 5 1939157
            | 1,097 1097 097 97 7 11 1 2 7 47 16 3 2121778
            | 1,697 1697 697 97 7 17 1 2 7 47 16 7 2340924
@@ -1655,8 +1655,8 @@ SELECT '' AS to_char_11, to_char(d1, 'FMIYYY FMIYY FMIY FMI FMIW FMIDDD FMID')
             | 1997 997 97 7 7 47 5
             | 1997 997 97 7 7 48 6
             | 1997 997 97 7 7 49 7
-            | 97 097 97 7 7 44 2
-            | 97 097 97 7 7 48 6
+            | 97 97 97 7 7 44 2
+            | 97 97 97 7 7 48 6
             | 597 597 97 7 7 46 4
             | 1097 097 97 7 7 44 2
             | 1697 697 97 7 7 48 6