On Thu, Aug 25, 2011 at 07:05:34PM +0000, Noah Hamerslough wrote:
>
> The following bug has been logged online:
>
> Bug reference: 6178
> Logged by: Noah Hamerslough
> Email address: n...@pcc.com
> PostgreSQL version: 8.4
> Operating system: Windows Vista
> Description: date_trunc : interval units "week" not supported
> contradicts documentation
> Details:
>
> http://www.postgresql.org/docs/8.4/static/functions-datetime.html#FUNCTIONS-
> DATETIME-TRUNC
>
> The documentation for date_trunc('field', source) lists 'week' in the as a
> valid value for 'field' However, if the source is an interval, 'week' is not
> supported.
>
> select date_trunc('week', '1 month 15 days'::interval);
>
> ERROR: interval units "week" not supported
> SQL state: 0A000
>
> Either 'week' should be supported or the documentation should be updated to
> reflect that it is not.
Turns out the reason we don't support this is because there are usually
a fractional number of weeks in a month, so there is no good way to do
this for intervals. I have applied the attached patch to PG 9.3 which
will explain why this is not supported. I saw this as better than a
documentation mention.
--
Bruce Momjian <br...@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
new file mode 100644
index 8593b6b..2adc178
*** a/src/backend/utils/adt/timestamp.c
--- b/src/backend/utils/adt/timestamp.c
*************** interval_trunc(PG_FUNCTION_ARGS)
*** 3710,3719 ****
break;
default:
! ereport(ERROR,
! (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
! errmsg("interval units \"%s\" not supported",
! lowunits)));
}
if (tm2interval(tm, fsec, result) != 0)
--- 3710,3726 ----
break;
default:
! if (val == DTK_WEEK)
! ereport(ERROR,
! (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
! errmsg("interval units \"%s\" not supported "
! "because months usually have fractional weeks",
! lowunits)));
! else
! ereport(ERROR,
! (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
! errmsg("interval units \"%s\" not supported",
! lowunits)));
}
if (tm2interval(tm, fsec, result) != 0)
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