mirrors/postgres
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Add some documentation about handling of fractions in interval input.

Browse Source 
(It's always worked like this, but we never documented it before.)
This commit is contained in:
Tom Lane 2008-11-09 17:09:48 +00:00
parent df7641e25a
commit dbf57d31f8
1 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
doc/src/sgml/datatype.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.232 2008/11/09 00:28:34 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.233 2008/11/09 17:09:48 tgl Exp $ -->
<chapter id="datatype">
<title id="datatype-title">Data Types</title>
@ -2413,13 +2413,26 @@ January 8 04:05:06 1999 PST
Internally <type>interval</> values are stored as months, days,
and seconds. This is done because the number of days in a month
varies, and a day can have 23 or 25 hours if a daylight savings
time adjustment is involved. Because intervals are usually created
from constant strings or <type>timestamp</> subtraction, this
storage method works well in most cases. Functions
time adjustment is involved. The months and days fields are integers
while the seconds field can store fractions. Because intervals are
usually created from constant strings or <type>timestamp</> subtraction,
this storage method works well in most cases. Functions
<function>justify_days</> and <function>justify_hours</> are
available for adjusting days and hours that overflow their normal
ranges.
</para>
<para>
In the verbose input format, and in some fields of the more compact
input formats, field values can have fractional parts; for example
<literal>'1.5 week'</> or <literal>'01:02:03.45'</>. Such input is
converted to the appropriate number of months, days, and seconds
for storage. When this would result in a fractional number of
months or days, the fraction is added to the lower-order fields
using the conversion factors 1 month = 30 days and 1 day = 24 hours.
For example, <literal>'1.5 month'</> becomes 1 month and 15 days.
Only seconds will ever be shown as fractional on output.
</para>
</sect2>
<sect2 id="datatype-interval-output">