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Fix extraction of week and quarter fields from intervals.

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"EXTRACT(WEEK FROM interval_value)" formerly threw an error.
Define it as "tm->tm_mday / 7".  (With C99 division semantics,
this gives consistent results for negative intervals.)

"EXTRACT(QUARTER FROM interval_value)" has been implemented
all along, but it formerly gave extremely strange results for
negative intervals.  Fix it so that the output for -N months
is the negative of the output for N months.

Per bug #18348 from Michael Bondarenko and subsequent discussion.

Discussion: https://postgr.es/m/18348-b097a3587dfde8a4@postgresql.org
This commit is contained in:
Tom Lane
2024-08-16 12:35:50 -04:00
parent 108d2adb9e
commit 6be39d77a7
4 changed files with 94 additions and 16 deletions
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13
doc/src/sgml/func.sgml
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@ -10432,12 +10432,16 @@ SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months');
<term><literal>quarter</literal></term>
<listitem>
<para>
The quarter of the year (1&ndash;4) that the date is in
The quarter of the year (1&ndash;4) that the date is in;
for <type>interval</type> values, the month field divided by 3
plus 1
</para>
<screen>
SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
SELECT EXTRACT(QUARTER FROM INTERVAL '1 year 6 months');
<lineannotation>Result: </lineannotation><computeroutput>3</computeroutput>
</screen>
</listitem>
</varlistentry>
@ -10508,9 +10512,16 @@ SELECT EXTRACT(SECOND FROM TIME '17:12:28.5');
<literal>week</literal> to get consistent results.
</para>
<para>
For <type>interval</type> values, the week field is simply the number
of integral days divided by 7.
</para>
<screen>
SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>7</computeroutput>
SELECT EXTRACT(WEEK FROM INTERVAL '13 days 24 hours');
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
</screen>
</listitem>
</varlistentry>