Fix handling of BC years in to_date/to_timestamp.

Previously, a conversion such as
	to_date('-44-02-01','YYYY-MM-DD')
would result in '0045-02-01 BC', as the code attempted to interpret
the negative year as BC, but failed to apply the correction needed
for our internal handling of BC years.  Fix the off-by-one problem.

Also, arrange for the combination of a negative year and an
explicit "BC" marker to cancel out and produce AD.  This is how
the negative-century case works, so it seems sane to do likewise.

Continue to read "year 0000" as 1 BC.  Oracle would throw an error,
but we've accepted that case for a long time so I'm hesitant to
change it in a back-patch.

Per bug #16419 from Saeed Hubaishan.  Back-patch to all supported
branches.

Dar Alathar-Yemen and Tom Lane

Discussion: https://postgr.es/m/16419-d8d9db0a7553f01b@postgresql.org

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index dcda4525102478511c8513069df1944dd3879aff..a698f424dee661736ef3920342913ca5884bc7d2 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6692,6 +6692,15 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
       
      
 
+     
+      
+       In to_timestamp and to_date,
+       negative years are treated as signifying BC.  If you write both a
+       negative year and an explicit BC field, you get AD
+       again.  An input of year zero is treated as 1 BC.
+      
+     
+
      
       
        In to_timestamp and to_date,

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 4cdcc16f722d2a008e9ed17a1fb160db1354fe79..5c54823efde9117d778207139c8a1d108418f3e8 100644 (file)
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -3881,8 +3881,11 @@ do_to_timestamp(text *date_txt, text *fmt,
        {
            /* If a 4-digit year is provided, we use that and ignore CC. */
            tm->tm_year = tmfc.year;
-           if (tmfc.bc && tm->tm_year > 0)
-               tm->tm_year = -(tm->tm_year - 1);
+           if (tmfc.bc)
+               tm->tm_year = -tm->tm_year;
+           /* correct for our representation of BC years */
+           if (tm->tm_year < 0)
+               tm->tm_year++;
        }
        fmask |= DTK_M(YEAR);
    }

diff --git a/src/test/regress/expected/horology.out b/src/test/regress/expected/horology.out
index 2e2e3790bbfdae352d9bbfc3e57395b2667d5f13..5f619891c5d6b34b2ccf36e3369759231c6e6f14 100644 (file)
--- a/src/test/regress/expected/horology.out
+++ b/src/test/regress/expected/horology.out
@@ -2837,6 +2837,45 @@ SELECT to_date('2458872', 'J');
  01-23-2020
 (1 row)
 
+--
+-- Check handling of BC dates
+--
+SELECT to_date('44-02-01 BC','YYYY-MM-DD BC');
+    to_date    
+---------------
+ 02-01-0044 BC
+(1 row)
+
+SELECT to_date('-44-02-01','YYYY-MM-DD');
+    to_date    
+---------------
+ 02-01-0044 BC
+(1 row)
+
+SELECT to_date('-44-02-01 BC','YYYY-MM-DD BC');
+  to_date   
+------------
+ 02-01-0044
+(1 row)
+
+SELECT to_timestamp('44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+          to_timestamp           
+---------------------------------
+ Fri Feb 01 11:12:13 0044 PST BC
+(1 row)
+
+SELECT to_timestamp('-44-02-01 11:12:13','YYYY-MM-DD HH24:MI:SS');
+          to_timestamp           
+---------------------------------
+ Fri Feb 01 11:12:13 0044 PST BC
+(1 row)
+
+SELECT to_timestamp('-44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+         to_timestamp         
+------------------------------
+ Mon Feb 01 11:12:13 0044 PST
+(1 row)
+
 --
 -- Check handling of multiple spaces in format and/or input
 --
@@ -3096,6 +3135,12 @@ SELECT to_date('2016 366', 'YYYY DDD');  -- ok
 
 SELECT to_date('2016 367', 'YYYY DDD');
 ERROR:  date/time field value out of range: "2016 367"
+SELECT to_date('0000-02-01','YYYY-MM-DD');  -- allowed, though it shouldn't be
+    to_date    
+---------------
+ 02-01-0001 BC
+(1 row)
+
 --
 -- Check behavior with SQL-style fixed-GMT-offset time zone (cf bug #8572)
 --

diff --git a/src/test/regress/sql/horology.sql b/src/test/regress/sql/horology.sql
index fbad8dea9f17907c74db3d7e1d0f3381715aae19..a9495718288ddd2cb50296cbea20772b2425d4a7 100644 (file)
--- a/src/test/regress/sql/horology.sql
+++ b/src/test/regress/sql/horology.sql
@@ -417,6 +417,17 @@ SELECT to_date('1 4 1902', 'Q MM YYYY');  -- Q is ignored
 SELECT to_date('3 4 21 01', 'W MM CC YY');
 SELECT to_date('2458872', 'J');
 
+--
+-- Check handling of BC dates
+--
+
+SELECT to_date('44-02-01 BC','YYYY-MM-DD BC');
+SELECT to_date('-44-02-01','YYYY-MM-DD');
+SELECT to_date('-44-02-01 BC','YYYY-MM-DD BC');
+SELECT to_timestamp('44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+SELECT to_timestamp('-44-02-01 11:12:13','YYYY-MM-DD HH24:MI:SS');
+SELECT to_timestamp('-44-02-01 11:12:13 BC','YYYY-MM-DD HH24:MI:SS BC');
+
 --
 -- Check handling of multiple spaces in format and/or input
 --
@@ -500,6 +511,7 @@ SELECT to_date('2015 366', 'YYYY DDD');
 SELECT to_date('2016 365', 'YYYY DDD');  -- ok
 SELECT to_date('2016 366', 'YYYY DDD');  -- ok
 SELECT to_date('2016 367', 'YYYY DDD');
+SELECT to_date('0000-02-01','YYYY-MM-DD');  -- allowed, though it shouldn't be
 
 --
 -- Check behavior with SQL-style fixed-GMT-offset time zone (cf bug #8572)