Re: [HACKERS] [BUGS] BUG #3431: age() gets the days wrong
I don't see this as applied yet.
---
Tom Lane wrote:
Pelle Johansson [EMAIL PROTECTED] writes:
The age() function seem to work by first counting months until less than a
month remains to to the second argument, then counting days left. This
doesn't give the correct result, as shown by this example:
# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 29 days | 2007-01-31 00:00:00
(2 rows)
I took another look at this example. I believe what is actually going
wrong here is that when timestamp_age converts a month into an
equivalent number of days, it uses the number of days in the first
month of the interval it's dealing with (ie, the month containing
the earlier of the two dates). This is just wrong, because interval
addition adds months first and then days. The appropriate conversion
to use is actually the length of the next-to-last month of the interval.
As an example, 8.2 and CVS HEAD produce
regression=# select age('2007-03-14', '2007-02-15');
age
-
27 days
(1 row)
which is reasonable, but
regression=# select age('2007-04-14', '2007-02-15');
age
---
1 mon 27 days
(1 row)
is not so reasonable, nor is
regression=# select age('2007-03-14', '2007-01-15');
age
---
1 mon 30 days
(1 row)
If we change the code to use the next-to-last month of the interval
then these two cases produce '1 mon 30 days' and '1 mon 27 days'
respectively.
Another problem is that the code isn't doing the propagate-to-next-field
bit for negative fractional seconds. Hence it produces
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:00.4');
age
--
30 days -00:00:00.40
(1 row)
which is maybe not incorrect, but certainly fairly inconsistent with
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:01');
age
--
29 days 23:59:59
(1 row)
Hence I propose the attached patch. This does not change any existing
regression test outputs, but it does change the example given in the
documentation: age(timestamp '2001-04-10', timestamp '1957-06-13')
will now produce '43 years 9 mons 28 days' not 27 days. Which actually
is correct if you try to add back the result to timestamp '1957-06-13'.
It also appears to fix Palle's example:
regression=# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 30 days | 2007-02-01 00:00:00
(2 rows)
As I said earlier, I'm worried about changing the behavior of a function
that's been around for so long, so I'm disinclined to back-patch this.
But it seems like a reasonable change to make in 8.3. Comments?
regards, tom lane
--
Bruce Momjian [EMAIL PROTECTED] http://momjian.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
---(end of broadcast)---
TIP 7: You can help support the PostgreSQL project by donating at
http://www.postgresql.org/about/donate
Re: [HACKERS] [BUGS] BUG #3431: age() gets the days wrong
Sorry, I see there was later discussion.
---
Tom Lane wrote:
Pelle Johansson [EMAIL PROTECTED] writes:
The age() function seem to work by first counting months until less than a
month remains to to the second argument, then counting days left. This
doesn't give the correct result, as shown by this example:
# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 29 days | 2007-01-31 00:00:00
(2 rows)
I took another look at this example. I believe what is actually going
wrong here is that when timestamp_age converts a month into an
equivalent number of days, it uses the number of days in the first
month of the interval it's dealing with (ie, the month containing
the earlier of the two dates). This is just wrong, because interval
addition adds months first and then days. The appropriate conversion
to use is actually the length of the next-to-last month of the interval.
As an example, 8.2 and CVS HEAD produce
regression=# select age('2007-03-14', '2007-02-15');
age
-
27 days
(1 row)
which is reasonable, but
regression=# select age('2007-04-14', '2007-02-15');
age
---
1 mon 27 days
(1 row)
is not so reasonable, nor is
regression=# select age('2007-03-14', '2007-01-15');
age
---
1 mon 30 days
(1 row)
If we change the code to use the next-to-last month of the interval
then these two cases produce '1 mon 30 days' and '1 mon 27 days'
respectively.
Another problem is that the code isn't doing the propagate-to-next-field
bit for negative fractional seconds. Hence it produces
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:00.4');
age
--
30 days -00:00:00.40
(1 row)
which is maybe not incorrect, but certainly fairly inconsistent with
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:01');
age
--
29 days 23:59:59
(1 row)
Hence I propose the attached patch. This does not change any existing
regression test outputs, but it does change the example given in the
documentation: age(timestamp '2001-04-10', timestamp '1957-06-13')
will now produce '43 years 9 mons 28 days' not 27 days. Which actually
is correct if you try to add back the result to timestamp '1957-06-13'.
It also appears to fix Palle's example:
regression=# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 30 days | 2007-02-01 00:00:00
(2 rows)
As I said earlier, I'm worried about changing the behavior of a function
that's been around for so long, so I'm disinclined to back-patch this.
But it seems like a reasonable change to make in 8.3. Comments?
regards, tom lane
Content-Description: age.patch
Index: timestamp.c
===
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.179
diff -c -r1.179 timestamp.c
*** timestamp.c 6 Jul 2007 04:15:59 - 1.179
--- timestamp.c 8 Jul 2007 19:45:04 -
***
*** 3044,3050
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! fsec = (fsec1 - fsec2);
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
--- 3044,3051
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! /* form the symbolic difference */
! fsec = fsec1 - fsec2;
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
***
*** 3064,3069
--- 3065,3081
tm-tm_year = -tm-tm_year;
}
+ /* propagate any negative fields into the next higher field */
+ while (fsec 0)
+ {
+ #ifdef HAVE_INT64_TIMESTAMP
+ fsec += USECS_PER_SEC;
+ #else
+ fsec += 1.0;
+ #endif
+ tm-tm_sec--;
+ }
+
Re: [HACKERS] [BUGS] BUG #3431: age() gets the days wrong
Pelle Johansson [EMAIL PROTECTED] writes:
The age() function seem to work by first counting months until less than a
month remains to to the second argument, then counting days left. This
doesn't give the correct result, as shown by this example:
# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 29 days | 2007-01-31 00:00:00
(2 rows)
I took another look at this example. I believe what is actually going
wrong here is that when timestamp_age converts a month into an
equivalent number of days, it uses the number of days in the first
month of the interval it's dealing with (ie, the month containing
the earlier of the two dates). This is just wrong, because interval
addition adds months first and then days. The appropriate conversion
to use is actually the length of the next-to-last month of the interval.
As an example, 8.2 and CVS HEAD produce
regression=# select age('2007-03-14', '2007-02-15');
age
-
27 days
(1 row)
which is reasonable, but
regression=# select age('2007-04-14', '2007-02-15');
age
---
1 mon 27 days
(1 row)
is not so reasonable, nor is
regression=# select age('2007-03-14', '2007-01-15');
age
---
1 mon 30 days
(1 row)
If we change the code to use the next-to-last month of the interval
then these two cases produce '1 mon 30 days' and '1 mon 27 days'
respectively.
Another problem is that the code isn't doing the propagate-to-next-field
bit for negative fractional seconds. Hence it produces
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:00.4');
age
--
30 days -00:00:00.40
(1 row)
which is maybe not incorrect, but certainly fairly inconsistent with
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:01');
age
--
29 days 23:59:59
(1 row)
Hence I propose the attached patch. This does not change any existing
regression test outputs, but it does change the example given in the
documentation: age(timestamp '2001-04-10', timestamp '1957-06-13')
will now produce '43 years 9 mons 28 days' not 27 days. Which actually
is correct if you try to add back the result to timestamp '1957-06-13'.
It also appears to fix Palle's example:
regression=# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 30 days | 2007-02-01 00:00:00
(2 rows)
As I said earlier, I'm worried about changing the behavior of a function
that's been around for so long, so I'm disinclined to back-patch this.
But it seems like a reasonable change to make in 8.3. Comments?
regards, tom lane
Index: timestamp.c
===
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.179
diff -c -r1.179 timestamp.c
*** timestamp.c 6 Jul 2007 04:15:59 - 1.179
--- timestamp.c 8 Jul 2007 19:45:04 -
***
*** 3044,3050
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! fsec = (fsec1 - fsec2);
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
--- 3044,3051
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! /* form the symbolic difference */
! fsec = fsec1 - fsec2;
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
***
*** 3064,3069
--- 3065,3081
tm-tm_year = -tm-tm_year;
}
+ /* propagate any negative fields into the next higher field */
+ while (fsec 0)
+ {
+ #ifdef HAVE_INT64_TIMESTAMP
+ fsec += USECS_PER_SEC;
+ #else
+ fsec += 1.0;
+ #endif
+ tm-tm_sec--;
+ }
+
while (tm-tm_sec 0)
{
tm-tm_sec += SECS_PER_MINUTE;
***
*** 3082,3097
tm-tm_mday--;
}
! while (tm-tm_mday 0)
{
Re: [HACKERS] [BUGS] BUG #3431: age() gets the days wrong
Pelle Johansson [EMAIL PROTECTED] writes: If you were to use the result for subtracting from the first value, instead of adding to the second, the conditions are reversed. It's not really as obvious as I first thought whether there's 2 months and 29 days or 2 months and 30 days between 2006-11-02 and 2007-02-01... Hmm, that's a really good point; perhaps the original author was thinking of it in those terms, in which case using the first month of the interval is indeed sane. (Almost: I believe that the loop can iterate more than once, and then you need to look to the second month etc. The code's not doing that, so there's still a corner-case bug, plus the fsec issue.) Other than that corner case, it seems the behavior we currently have is if x y, age() produces a positive interval such that x - age(x, y) = y if x y, age() produces a negative interval such that y + age(x, y) = x Are we satisfied with just documenting that, or do we want to change it, and if so to what? As the code currently stands, we have the symmetry property age(x,y) = - age(y,x) for all x,y. I don't think we can preserve that if we try to simplify the relationship to interval addition/subtraction. Comments? regards, tom lane ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [HACKERS] [BUGS] BUG #3431: age() gets the days wrong
Hi Tom,
I only have one remark really, which I first thought of after sending
the report.
If you were to use the result for subtracting from the first value,
instead of adding to the second, the conditions are reversed. It's
not really as obvious as I first thought whether there's 2 months and
29 days or 2 months and 30 days between 2006-11-02 and 2007-02-01...
If one want mathematical correctness, it will have to be defined
precisely.
--
Pelle Johansson
8 jul 2007 kl. 22.07 skrev Tom Lane:
Pelle Johansson [EMAIL PROTECTED] writes:
The age() function seem to work by first counting months until
less than a
month remains to to the second argument, then counting days left.
This
doesn't give the correct result, as shown by this example:
# select column1, age(column1, '2006-11-02'), date '2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 29 days | 2007-01-31 00:00:00
(2 rows)
I took another look at this example. I believe what is actually going
wrong here is that when timestamp_age converts a month into an
equivalent number of days, it uses the number of days in the first
month of the interval it's dealing with (ie, the month containing
the earlier of the two dates). This is just wrong, because interval
addition adds months first and then days. The appropriate conversion
to use is actually the length of the next-to-last month of the
interval.
As an example, 8.2 and CVS HEAD produce
regression=# select age('2007-03-14', '2007-02-15');
age
-
27 days
(1 row)
which is reasonable, but
regression=# select age('2007-04-14', '2007-02-15');
age
---
1 mon 27 days
(1 row)
is not so reasonable, nor is
regression=# select age('2007-03-14', '2007-01-15');
age
---
1 mon 30 days
(1 row)
If we change the code to use the next-to-last month of the interval
then these two cases produce '1 mon 30 days' and '1 mon 27 days'
respectively.
Another problem is that the code isn't doing the propagate-to-next-
field
bit for negative fractional seconds. Hence it produces
regression=# select age('2007-02-14 01:00:00', '2007-01-15
01:00:00.4');
age
--
30 days -00:00:00.40
(1 row)
which is maybe not incorrect, but certainly fairly inconsistent with
regression=# select age('2007-02-14 01:00:00', '2007-01-15 01:00:01');
age
--
29 days 23:59:59
(1 row)
Hence I propose the attached patch. This does not change any existing
regression test outputs, but it does change the example given in the
documentation: age(timestamp '2001-04-10', timestamp '1957-06-13')
will now produce '43 years 9 mons 28 days' not 27 days. Which
actually
is correct if you try to add back the result to timestamp
'1957-06-13'.
It also appears to fix Palle's example:
regression=# select column1, age(column1, '2006-11-02'), date
'2006-11-02' +
age(column1, '2006-11-02') from (values ('2007-01-31'::date),
('2007-02-01')) as alias;
column1 | age | ?column?
++-
2007-01-31 | 2 mons 29 days | 2007-01-31 00:00:00
2007-02-01 | 2 mons 30 days | 2007-02-01 00:00:00
(2 rows)
As I said earlier, I'm worried about changing the behavior of a
function
that's been around for so long, so I'm disinclined to back-patch this.
But it seems like a reasonable change to make in 8.3. Comments?
regards, tom lane
Index: timestamp.c
===
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.179
diff -c -r1.179 timestamp.c
*** timestamp.c 6 Jul 2007 04:15:59 - 1.179
--- timestamp.c 8 Jul 2007 19:45:04 -
***
*** 3044,3050
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! fsec = (fsec1 - fsec2);
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
--- 3044,3051
if (timestamp2tm(dt1, NULL, tm1, fsec1, NULL, NULL) == 0
timestamp2tm(dt2, NULL, tm2, fsec2, NULL, NULL) == 0)
{
! /* form the symbolic difference */
! fsec = fsec1 - fsec2;
tm-tm_sec = tm1-tm_sec - tm2-tm_sec;
tm-tm_min = tm1-tm_min - tm2-tm_min;
tm-tm_hour = tm1-tm_hour - tm2-tm_hour;
***
*** 3064,3069
--- 3065,3081
tm-tm_year = -tm-tm_year;
}
+ /* propagate any negative fields into the next higher field */
+ while (fsec 0)
+
