Finish initial markup of cvs.sgml, and include it in the programmer's guide
and the integrated doc. Clean up other markup.
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Thomas G. Lockhart
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From - Mon May 10 15:59:27 1999
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Date: Wed, 14 Apr 1999 17:39:34 +0200
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||||
CC: hackers <pgsql-hackers@postgresql.org>,
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||||
general <pgsql-general@postgresql.org>
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Subject: Re: [GENERAL] Re: [HACKERS] Gregorian Calendar
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References: <3711B1E5.80213DF6@sferacarta.com> <37135951.88FDB948@alumni.caltech.edu>
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<!--
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||||
$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.2 1999/05/22 02:27:23 thomas Exp $
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Date/time details
|
||||
|
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Hi Thomas,
|
||||
$Log: datetime.sgml,v $
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||||
Revision 2.2 1999/05/22 02:27:23 thomas
|
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Finish initial markup of cvs.sgml, and include it in the programmer's guide
|
||||
and the integrated doc. Clean up other markup.
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||||
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Thomas Lockhart ha scritto:
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-->
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||||
> > I have a question about dates.
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> > The Gregorian reform of calendar skiped 10 days on Oct, 1582.
|
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> > This reform was accepted by Great Britain and Dominions (including
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> > what is now the USA) only in 1752.
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> > If I insert a date that doesn't exist PostgreSQL accepts it.
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> > Should it be considered normal ?
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>
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> As Peter says, this is tricky.
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>
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> Date conventions before the 19th century make for interesting reading,
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> but are not imho consistant enough to warrant coding into a date/time
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> handler.
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||||
>
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> As you probably have noticed, we use Julian date calculations for our
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> date/time support.
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<appendix label="UG1" id="datetime-append">
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<title>Date/Time Support</title>
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I suppose you refer to Julian Day invented by the French scholar
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Joseph Justus Scaliger (1540-1609)
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that probably takes its name from the Scaliger's father,
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the Italian scholar Julius Caesar Scaliger (1484-1558).
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Astronomers have used the Julian period to assign a unique number to
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||||
every day since 1 January 4713 BC. This is the so-called Julian Day
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||||
(JD). JD 0 designates the 24 hours from noon UTC on 1 January 4713 BC
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to noon UTC on 2 January 4713 BC.
|
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<sect1>
|
||||
<title>Time Zones</title>
|
||||
|
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Julian Day is different from Julian Date
|
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<para>
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<table tocentry="1">
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<title><productname>Postgres</productname> Recognized Time Zones</title>
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<titleabbrev>Time Zones</titleabbrev>
|
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Time Zone</entry>
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<entry>Offset from UTC</entry>
|
||||
<entry>Description</entry>
|
||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry>NZDT</entry>
|
||||
<entry>+13:00</entry>
|
||||
<entry>New Zealand Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>IDLE</entry>
|
||||
<entry>+12:00</entry>
|
||||
<entry>International Date Line, East</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NZST</entry>
|
||||
<entry>+12:00</entry>
|
||||
<entry>New Zealand Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NZT</entry>
|
||||
<entry>+12:00</entry>
|
||||
<entry>New Zealand Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AESST</entry>
|
||||
<entry>+11:00 </entry>
|
||||
<entry>Australia Eastern Summer Std Time</entry>
|
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</row>
|
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<row>
|
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<entry>ACSST</entry>
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<entry>+10:30 </entry>
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||||
<entry>Central Australia Summer Std Time</entry>
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</row>
|
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<row>
|
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<entry>CADT</entry>
|
||||
<entry>+10:30 </entry>
|
||||
<entry>Central Australia Daylight Savings Time</entry>
|
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</row>
|
||||
<row>
|
||||
<entry>SADT</entry>
|
||||
<entry>+10:30</entry>
|
||||
<entry>South Australian Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AEST</entry>
|
||||
<entry>+10:00 </entry>
|
||||
<entry>Australia Eastern Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>EAST</entry>
|
||||
<entry>+10:00 </entry>
|
||||
<entry>East Australian Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>GST</entry>
|
||||
<entry>+10:00</entry>
|
||||
<entry>Guam Std Time, USSR Zone 9</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>LIGT</entry>
|
||||
<entry>+10:00</entry>
|
||||
<entry>Melbourne, Australia</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>ACST</entry>
|
||||
<entry>+09:30 </entry>
|
||||
<entry>Central Australia Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CAST</entry>
|
||||
<entry>+09:30 </entry>
|
||||
<entry>Central Australia Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>SAT</entry>
|
||||
<entry>+9:30</entry>
|
||||
<entry>South Australian Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AWSST</entry>
|
||||
<entry>+9:00 </entry>
|
||||
<entry>Australia Western Summer Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>JST</entry>
|
||||
<entry>+9:00</entry>
|
||||
<entry>Japan Std Time,USSR Zone 8</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>KST</entry>
|
||||
<entry>+9:00</entry>
|
||||
<entry>Korea Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WDT</entry>
|
||||
<entry>+9:00</entry>
|
||||
<entry>West Australian Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MT</entry>
|
||||
<entry>+8:30</entry>
|
||||
<entry>Moluccas Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AWST</entry>
|
||||
<entry>+8:00 </entry>
|
||||
<entry>Australia Western Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CCT</entry>
|
||||
<entry>+8:00 </entry>
|
||||
<entry>China Coastal Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WADT</entry>
|
||||
<entry>+8:00</entry>
|
||||
<entry>West Australian Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WST</entry>
|
||||
<entry>+8:00</entry>
|
||||
<entry>West Australian Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>JT</entry>
|
||||
<entry>+7:30</entry>
|
||||
<entry>Java Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WAST</entry>
|
||||
<entry>+7:00</entry>
|
||||
<entry>West Australian Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>IT</entry>
|
||||
<entry>+3:30</entry>
|
||||
<entry>Iran Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>BT</entry>
|
||||
<entry>+3:00 </entry>
|
||||
<entry>Baghdad Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>EETDST</entry>
|
||||
<entry>+3:00 </entry>
|
||||
<entry>Eastern Europe Daylight Savings Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CETDST</entry>
|
||||
<entry>+2:00 </entry>
|
||||
<entry>Central European Daylight Savings Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>EET</entry>
|
||||
<entry>+2:00 </entry>
|
||||
<entry>Eastern Europe, USSR Zone 1</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>FWT</entry>
|
||||
<entry>+2:00</entry>
|
||||
<entry>French Winter Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>IST</entry>
|
||||
<entry>+2:00</entry>
|
||||
<entry>Israel Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MEST</entry>
|
||||
<entry>+2:00</entry>
|
||||
<entry>Middle Europe Summer Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>METDST</entry>
|
||||
<entry>+2:00</entry>
|
||||
<entry>Middle Europe Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>SST</entry>
|
||||
<entry>+2:00</entry>
|
||||
<entry>Swedish Summer Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>BST</entry>
|
||||
<entry>+1:00 </entry>
|
||||
<entry>British Summer Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CET</entry>
|
||||
<entry>+1:00 </entry>
|
||||
<entry>Central European Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>DNT</entry>
|
||||
<entry>+1:00 </entry>
|
||||
<entry>Dansk Normal Tid</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>DST</entry>
|
||||
<entry>+1:00 </entry>
|
||||
<entry>Dansk Standard Time (?)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>FST</entry>
|
||||
<entry>+1:00 </entry>
|
||||
<entry>French Summer Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MET</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Middle Europe Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MEWT</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Middle Europe Winter Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MEZ</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Middle Europe Zone</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NOR</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Norway Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>SET</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Seychelles Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>SWT</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Swedish Winter Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WETDST</entry>
|
||||
<entry>+1:00</entry>
|
||||
<entry>Western Europe Daylight Savings Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>GMT</entry>
|
||||
<entry>0:00</entry>
|
||||
<entry>Greenwish Mean Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WET</entry>
|
||||
<entry>0:00</entry>
|
||||
<entry>Western Europe</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>WAT</entry>
|
||||
<entry>-1:00</entry>
|
||||
<entry>West Africa Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NDT</entry>
|
||||
<entry>-2:30</entry>
|
||||
<entry>Newfoundland Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>ADT</entry>
|
||||
<entry>-03:00 </entry>
|
||||
<entry>Atlantic Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NFT</entry>
|
||||
<entry>-3:30</entry>
|
||||
<entry>Newfoundland Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NST</entry>
|
||||
<entry>-3:30</entry>
|
||||
<entry>Newfoundland Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AST</entry>
|
||||
<entry>-4:00 </entry>
|
||||
<entry>Atlantic Std Time (Canada)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>EDT</entry>
|
||||
<entry>-4:00 </entry>
|
||||
<entry>Eastern Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>ZP4</entry>
|
||||
<entry>-4:00</entry>
|
||||
<entry>GMT +4 hours</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CDT</entry>
|
||||
<entry>-5:00 </entry>
|
||||
<entry>Central Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>EST</entry>
|
||||
<entry>-5:00 </entry>
|
||||
<entry>Eastern Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>ZP5</entry>
|
||||
<entry>-5:00</entry>
|
||||
<entry>GMT +5 hours</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CST</entry>
|
||||
<entry>-6:00 </entry>
|
||||
<entry>Central Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MDT</entry>
|
||||
<entry>-6:00</entry>
|
||||
<entry>Mountain Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>ZP6</entry>
|
||||
<entry>-6:00</entry>
|
||||
<entry>GMT +6 hours</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>MST</entry>
|
||||
<entry>-7:00</entry>
|
||||
<entry>Mountain Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>PDT</entry>
|
||||
<entry>-7:00</entry>
|
||||
<entry>Pacific Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>PST</entry>
|
||||
<entry>-8:00</entry>
|
||||
<entry>Pacific Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>YDT</entry>
|
||||
<entry>-8:00</entry>
|
||||
<entry>Yukon Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>HDT</entry>
|
||||
<entry>-9:00</entry>
|
||||
<entry>Hawaii/Alaska Daylight Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>YST</entry>
|
||||
<entry>-9:00</entry>
|
||||
<entry>Yukon Standard Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>AHST</entry>
|
||||
<entry>-10:00 </entry>
|
||||
<entry>Alaska-Hawaii Std Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>CAT</entry>
|
||||
<entry>-10:00 </entry>
|
||||
<entry>Central Alaska Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>NT</entry>
|
||||
<entry>-11:00</entry>
|
||||
<entry>Nome Time</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>IDLW</entry>
|
||||
<entry>-12:00</entry>
|
||||
<entry>International Date Line, West</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
<note>
|
||||
<para>
|
||||
If the compiler option USE_AUSTRALIAN_RULES is set
|
||||
then <literal>EST</literal> refers to Australia Eastern Std Time,
|
||||
which has an offset of +10:00 hours from UTC.
|
||||
</para>
|
||||
</note>
|
||||
</para>
|
||||
|
||||
The Julian calendar was introduced by Julius Caesar in 45 BC. It was
|
||||
in common use until the 1582, when countries started changing to the
|
||||
Gregorian calendar.
|
||||
<para>
|
||||
Australian time zones and their naming variants
|
||||
account for fully one quarter of all time zones in the
|
||||
<productname>Postgres</productname> time zone lookup table.
|
||||
</para>
|
||||
|
||||
In the Julian calendar, the tropical year is approximated as 365 1/4
|
||||
days = 365.25 days. This gives an error of 1 day in approximately 128
|
||||
<procedure>
|
||||
<title>Date/Time Input Interpretation</title>
|
||||
|
||||
and this is why pope Gregory XIII in accordance with instructions
|
||||
from the Council of Trent reformed the calendar to correct this error.
|
||||
<para>
|
||||
The date/time types are all decoded using a common set of routines.
|
||||
</para>
|
||||
|
||||
In the Gregorian calendar, the tropical year is approximated as
|
||||
365 + 97 / 400 days = 365.2425 days. Thus it takes approximately 3300
|
||||
years for the tropical year to shift one day with respect to the
|
||||
Gregorian calendar.
|
||||
<step>
|
||||
<para>
|
||||
Break the input string into tokens and categorize each token as
|
||||
a string, time, time zone, or number.
|
||||
</para>
|
||||
|
||||
The approximation 365+97/400 is achieved by having 97 leap years
|
||||
every 400 years.
|
||||
<substeps>
|
||||
<step>
|
||||
<para>
|
||||
If the token contains a colon (":"), this is a time string.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
The Gregorian calendar has 97 leap years every 400 years:
|
||||
<step>
|
||||
<para>
|
||||
If the token contains a dash ("-"), slash ("/"), or dot ("."),
|
||||
this is a date string which may have a text month.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If the token is numeric only, then it is either a single field
|
||||
or an ISO-8601 concatenated date (e.g. "19990113" for January 13, 1999)
|
||||
or time (e.g. 141516 for 14:15:16).
|
||||
</para>
|
||||
</step>
|
||||
<step>
|
||||
<para>
|
||||
If the token starts with a plus ("+") or minus ("-"),
|
||||
then it is either a time zone or a special field.
|
||||
</para>
|
||||
</step>
|
||||
</substeps>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If the token is a text string, match up with possible strings.
|
||||
</para>
|
||||
|
||||
<substeps>
|
||||
<step>
|
||||
<para>
|
||||
Do a binary-search table lookup for the token
|
||||
as either a special string (e.g. <literal>today</literal>),
|
||||
day (e.g. <literal>Thursday</literal>),
|
||||
month (e.g. <literal>January</literal>), or noise word (e.g. <literal>on</literal>).
|
||||
</para>
|
||||
<para>
|
||||
Set field values and bit mask for fields.
|
||||
For example, set year, month, day for <literal>today</literal>, and additionally
|
||||
hour, minute, second for <literal>now</literal>.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If not found, do a similar binary-search table lookup to match
|
||||
the token with a time zone.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If not found, throw an error.
|
||||
</para>
|
||||
</step>
|
||||
</substeps>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
The token is a number or number field.
|
||||
If there are more than 4 digits,
|
||||
and if no other date fields have been previously read, then interpret
|
||||
as a "concatenated date" (e.g. <literal>19990118</literal>).
|
||||
</para>
|
||||
|
||||
<substeps>
|
||||
<step>
|
||||
<para>
|
||||
If there are more than 4 digits,
|
||||
and if no other date fields have been previously read, then interpret
|
||||
as a "concatenated date" (e.g. <literal>19990118</literal>).
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If three digits and a year has already been decoded, then interpret as day of year.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If longer than two digits, then interpret as a year.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If in European date mode, and if the day field has not yet been read,
|
||||
and if the value is less than or equal to 31, then interpret as a day.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If in non-European (US) date mode, and if the month field has not yet been read,
|
||||
and if the value is less than or equal to 12, then interpret as a month.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If the day field has not yet been read,
|
||||
and if the value is less than or equal to 31, then interpret as a month.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If the month field has not yet been read,
|
||||
and if the value is less than or equal to 12, then interpret as a month.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
Otherwise, interpret as a year.
|
||||
</para>
|
||||
</step>
|
||||
</substeps>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If BC has been specified, negate the year and offset by one
|
||||
(there is no year zero in the Gregorian calendar).
|
||||
</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<para>
|
||||
If BC was not specified, and if the year field was two digits in length, then
|
||||
adjust the year to 4 digits. If the field was less than 70, then add 2000;
|
||||
otherwise, add 1900.
|
||||
</para>
|
||||
</step>
|
||||
|
||||
</procedure>
|
||||
</sect1>
|
||||
|
||||
<sect1>
|
||||
<title>History</title>
|
||||
|
||||
<note>
|
||||
<para>
|
||||
Contributed by
|
||||
<ulink url="jose@sferacarta.com">José Soares</ulink>.
|
||||
</para>
|
||||
</note>
|
||||
|
||||
<para>
|
||||
The Julian Day invented by the French scholar
|
||||
Joseph Justus Scaliger (1540-1609)
|
||||
and which probably takes its name from the Scaliger's father,
|
||||
the Italian scholar Julius Caesar Scaliger (1484-1558).
|
||||
Astronomers have used the Julian period to assign a unique number to
|
||||
every day since 1 January 4713 BC. This is the so-called Julian Day
|
||||
(JD). JD 0 designates the 24 hours from noon UTC on 1 January 4713 BC
|
||||
to noon UTC on 2 January 4713 BC.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Julian Day is different from Julian Date.
|
||||
|
||||
The Julian calendar was introduced by Julius Caesar in 45 BC. It was
|
||||
in common use until the 1582, when countries started changing to the
|
||||
Gregorian calendar.
|
||||
|
||||
In the Julian calendar, the tropical year is approximated as 365 1/4
|
||||
days = 365.25 days. This gives an error of 1 day in approximately
|
||||
128 days.
|
||||
The accumulating calendar error prompted pope Gregory XIII
|
||||
to reform the calendar in accordance with instructions
|
||||
from the Council of Trent.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
In the Gregorian calendar, the tropical year is approximated as
|
||||
365 + 97 / 400 days = 365.2425 days. Thus it takes approximately 3300
|
||||
years for the tropical year to shift one day with respect to the
|
||||
Gregorian calendar.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The approximation 365+97/400 is achieved by having 97 leap years
|
||||
every 400 years, using the following rules:
|
||||
|
||||
<simplelist>
|
||||
<member>
|
||||
Every year divisible by 4 is a leap year.
|
||||
</member>
|
||||
<member>
|
||||
However, every year divisible by 100 is not a leap year.
|
||||
</member>
|
||||
<member>
|
||||
However, every year divisible by 400 is a leap year after all.
|
||||
</member>
|
||||
</simplelist>
|
||||
|
||||
So, 1700, 1800, 1900, 2100, and 2200 are not leap years. But 1600,
|
||||
2000, and 2400 are leap years.
|
||||
So, 1700, 1800, 1900, 2100, and 2200 are not leap years. But 1600,
|
||||
2000, and 2400 are leap years.
|
||||
|
||||
instead in the Julian calendar only years divisible by 4 are leap years.
|
||||
By contrast, in the older Julian calendar only years divisible by 4 are leap years.
|
||||
</para>
|
||||
|
||||
The papal bull of February 1582 decreed that 10 days should be dropped
|
||||
from October 1582 so that 15 October should follow immediately after
|
||||
4 October.
|
||||
This was observed in Italy, Poland, Portugal, and Spain. Other Catholic
|
||||
countries followed shortly after, but Protestant countries were
|
||||
reluctant to change, and the Greek orthodox countries didn't change
|
||||
until the start of this century.
|
||||
<para>
|
||||
The papal bull of February 1582 decreed that 10 days should be dropped
|
||||
from October 1582 so that 15 October should follow immediately after
|
||||
4 October.
|
||||
This was observed in Italy, Poland, Portugal, and Spain. Other Catholic
|
||||
countries followed shortly after, but Protestant countries were
|
||||
reluctant to change, and the Greek orthodox countries didn't change
|
||||
until the start of this century.
|
||||
|
||||
The reform was observed by Great Britain and Dominions (including what is
|
||||
now the USA)
|
||||
in 1752.
|
||||
The 2 Sep 1752 was followed by 14 Sep 1752.
|
||||
The reform was observed by Great Britain and Dominions (including what is
|
||||
now the USA) in 1752.
|
||||
Thus 2 Sep 1752 was followed by 14 Sep 1752.
|
||||
|
||||
This is why unix has the cal 9 1752 like this:
|
||||
This is why Unix systems have <application>cal</application>
|
||||
produce the following:
|
||||
|
||||
<programlisting>
|
||||
% cal 9 1752
|
||||
September 1752
|
||||
S M Tu W Th F S
|
||||
1 2 14 15 16
|
||||
1 2 14 15 16
|
||||
17 18 19 20 21 22 23
|
||||
24 25 26 27 28 29 30
|
||||
</programlisting>
|
||||
</para>
|
||||
|
||||
My question is:
|
||||
^^^^^^^^^^^^
|
||||
|
||||
If SQL92 says:
|
||||
|
||||
(Second Informal Review Draft) ISO/IEC 9075:1992, Database
|
||||
Language SQL- July 30, 1992
|
||||
|
||||
5.3 literals
|
||||
22)Within the definition of a <datetime literal>, the <datetime
|
||||
value>s are constrained by the natural rules for dates and
|
||||
times
|
||||
according to the Gregorian calendar.
|
||||
^^^^^^^^^^^^^^^
|
||||
|
||||
Dates between 1752-09-03 and 1752-09-13.
|
||||
Are they valid dates?
|
||||
^^^^^^^^^^^^^^^^
|
||||
|
||||
> They have the nice property of correctly
|
||||
> predicting/calculating any date more recent than something like 4013BC
|
||||
> to far into the future, using the assumption that the length of the
|
||||
> year is 365.25 days. This is a very recently adopted convention
|
||||
> (sometime in the 1800s I had thought, but perhaps it was during the
|
||||
> same "reform" in 1752).
|
||||
>
|
||||
> I've toyed with the idea of implementing a Chinese dynastic calendar,
|
||||
> since it seems to be more predictable than historical European
|
||||
> calendars.
|
||||
|
||||
People's Republic of China uses the Gregorian calendar
|
||||
for civil purposes. Chinese calendar is used for determining
|
||||
festivals.
|
||||
|
||||
The beginnings of the Chinese calendar can be traced back to the 14th
|
||||
century BC. Legend has it that the Emperor Huangdi invented the
|
||||
calendar in 2637 B
|
||||
|
||||
José
|
||||
<note>
|
||||
<para>
|
||||
SQL92 states that
|
||||
<quote>Within the definition of a <sgmltag>datetime literal</sgmltag>,
|
||||
the <sgmltag>datetime value</sgmltag>s are constrained by the
|
||||
natural rules for dates and times
|
||||
according to the Gregorian calendar</quote>.
|
||||
Dates between 1752-09-03 and 1752-09-13, although eliminated in
|
||||
some countries by Papal fiat, conform to
|
||||
<quote>natural rules</quote> and are hence valid dates.
|
||||
</para>
|
||||
</note>
|
||||
|
||||
<para>
|
||||
Different calendars have been developed in various parts of the
|
||||
world, many predating the Gregorian system.
|
||||
|
||||
For example,
|
||||
the beginnings of the Chinese calendar can be traced back to the 14th
|
||||
century BC. Legend has it that the Emperor Huangdi invented the
|
||||
calendar in 2637 BC.
|
||||
|
||||
The People's Republic of China uses the Gregorian calendar
|
||||
for civil purposes. Chinese calendar is used for determining
|
||||
festivals.
|
||||
</para>
|
||||
</sect1>
|
||||
</appendix>
|
||||
|
||||
<!-- Keep this comment at the end of the file
|
||||
Local variables:
|
||||
mode: sgml
|
||||
sgml-omittag:nil
|
||||
sgml-shorttag:t
|
||||
sgml-minimize-attributes:nil
|
||||
sgml-always-quote-attributes:t
|
||||
sgml-indent-step:1
|
||||
sgml-indent-data:t
|
||||
sgml-parent-document:nil
|
||||
sgml-default-dtd-file:"./reference.ced"
|
||||
sgml-exposed-tags:nil
|
||||
sgml-local-catalogs:"/usr/lib/sgml/catalog"
|
||||
sgml-local-ecat-files:nil
|
||||
End:
|
||||
-->
|
||||
|
|
|
|||
|
|
@ -1,4 +1,4 @@
|
|||
<Chapter Id="pg-options">
|
||||
<Chapter Id="pg-options-dev">
|
||||
<DocInfo>
|
||||
<AuthorGroup>
|
||||
<Author>
|
||||
|
|
|
|||
|
|
@ -1,11 +1,15 @@
|
|||
<!--
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/postgres.sgml,v 1.22 1999/05/20 05:39:27 thomas Exp $
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/postgres.sgml,v 1.23 1999/05/22 02:27:24 thomas Exp $
|
||||
|
||||
Postgres integrated documentation.
|
||||
Other subset docs should be copied and shrunk from here.
|
||||
thomas 1998-02-23
|
||||
|
||||
$Log: postgres.sgml,v $
|
||||
Revision 1.23 1999/05/22 02:27:24 thomas
|
||||
Finish initial markup of cvs.sgml, and include it in the programmer's guide
|
||||
and the integrated doc. Clean up other markup.
|
||||
|
||||
Revision 1.22 1999/05/20 05:39:27 thomas
|
||||
Rearrange and consolidate the Admin Guide.
|
||||
Add reference pages for utilities and remove standalone chapters for same.
|
||||
|
|
@ -90,6 +94,7 @@ Move SQL reference pages up into the User's Guide.
|
|||
<!entity advanced SYSTEM "advanced.sgml">
|
||||
<!entity array SYSTEM "array.sgml">
|
||||
<!entity datatype SYSTEM "datatype.sgml">
|
||||
<!entity datetime SYSTEM "datetime.sgml">
|
||||
<!entity environ SYSTEM "environ.sgml">
|
||||
<!entity func SYSTEM "func.sgml">
|
||||
<!entity inherit SYSTEM "inherit.sgml">
|
||||
|
|
@ -351,8 +356,11 @@ Your name here...
|
|||
Additional related information.
|
||||
</Para>
|
||||
</PartIntro>
|
||||
&docguide;
|
||||
&datetime;
|
||||
&docguide;
|
||||
<!--
|
||||
&contacts;
|
||||
-->
|
||||
&biblio;
|
||||
</Part>
|
||||
|
||||
|
|
|
|||
|
|
@ -1,10 +1,14 @@
|
|||
<!--
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/programmer.sgml,v 1.14 1999/05/20 05:39:27 thomas Exp $
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/programmer.sgml,v 1.15 1999/05/22 02:27:24 thomas Exp $
|
||||
|
||||
Postgres Programmer's Guide.
|
||||
- thomas 1998-10-27
|
||||
|
||||
$Log: programmer.sgml,v $
|
||||
Revision 1.15 1999/05/22 02:27:24 thomas
|
||||
Finish initial markup of cvs.sgml, and include it in the programmer's guide
|
||||
and the integrated doc. Clean up other markup.
|
||||
|
||||
Revision 1.14 1999/05/20 05:39:27 thomas
|
||||
Rearrange and consolidate the Admin Guide.
|
||||
Add reference pages for utilities and remove standalone chapters for same.
|
||||
|
|
@ -94,6 +98,7 @@ Bigger updates to the installation instructions (install and config).
|
|||
<!entity bki SYSTEM "bki.sgml">
|
||||
<!entity compiler SYSTEM "compiler.sgml">
|
||||
<!entity contacts SYSTEM "contacts.sgml">
|
||||
<!entity cvs SYSTEM "cvs.sgml">
|
||||
<!entity docguide SYSTEM "docguide.sgml">
|
||||
<!entity geqo SYSTEM "geqo.sgml">
|
||||
<!entity options SYSTEM "pg_options.sgml">
|
||||
|
|
@ -216,6 +221,7 @@ Disable it until we put in some info.
|
|||
|
||||
<!-- appendices -->
|
||||
|
||||
&cvs;
|
||||
&docguide;
|
||||
<!--
|
||||
&contacts;
|
||||
|
|
|
|||
|
|
@ -158,9 +158,6 @@ COPY INTO weather FROM '/home/user/weather.txt'
|
|||
</para>
|
||||
</sect1>
|
||||
|
||||
</Para>
|
||||
</sect1>
|
||||
|
||||
<Sect1>
|
||||
<Title>Querying a Class</Title>
|
||||
|
||||
|
|
|
|||
|
|
@ -288,7 +288,7 @@ attributes are taken from. We often write a relation scheme as
|
|||
<parameter>D<subscript>i</subscript></parameter>,
|
||||
for each attribute
|
||||
<parameter>A<subscript>i</subscript></parameter>,
|
||||
1 <&equal; <literal>i</literal> <&equal; <literal>k</literal>,
|
||||
1 <= <literal>i</literal> <= <literal>k</literal>,
|
||||
where the values of the attributes are taken from. We often write
|
||||
a relation scheme as
|
||||
<literal>R(<parameter>A<subscript>1</subscript></parameter>,
|
||||
|
|
@ -325,11 +325,11 @@ attributes are taken from. We often write a relation scheme as
|
|||
integers. We define this by assigning a data type to each
|
||||
attribute. The type of <classname>SNAME</classname> will be
|
||||
<type>VARCHAR(20)</type> (this is the <acronym>SQL</acronym> type
|
||||
for character strings of length <&equal; 20),
|
||||
for character strings of length <= 20),
|
||||
the type of <classname>SNO</classname> will be
|
||||
<type>INTEGER</type>. With the assignment of a data type we also have selected
|
||||
a domain for an attribute. The domain of <classname>SNAME</classname> is the set of all
|
||||
character strings of length <&equal; 20,
|
||||
character strings of length <= 20,
|
||||
the domain of <classname>SNO</classname> is the set of
|
||||
all integer numbers.
|
||||
</para>
|
||||
|
|
|
|||
|
|
@ -1,11 +1,15 @@
|
|||
<!--
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/user.sgml,v 1.9 1999/05/20 05:39:29 thomas Exp $
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/user.sgml,v 1.10 1999/05/22 02:27:25 thomas Exp $
|
||||
|
||||
Postgres User's Manual.
|
||||
Derived from postgres.sgml.
|
||||
thomas 1998-02-24
|
||||
|
||||
$Log: user.sgml,v $
|
||||
Revision 1.10 1999/05/22 02:27:25 thomas
|
||||
Finish initial markup of cvs.sgml, and include it in the programmer's guide
|
||||
and the integrated doc. Clean up other markup.
|
||||
|
||||
Revision 1.9 1999/05/20 05:39:29 thomas
|
||||
Rearrange and consolidate the Admin Guide.
|
||||
Add reference pages for utilities and remove standalone chapters for same.
|
||||
|
|
@ -49,6 +53,7 @@ Move SQL reference pages up into the User's Guide.
|
|||
<!entity array SYSTEM "array.sgml">
|
||||
<!entity biblio SYSTEM "biblio.sgml">
|
||||
<!entity datatype SYSTEM "datatype.sgml">
|
||||
<!entity datetime SYSTEM "datetime.sgml">
|
||||
<!entity environ SYSTEM "environ.sgml">
|
||||
<!entity func SYSTEM "func.sgml">
|
||||
<!entity inherit SYSTEM "inherit.sgml">
|
||||
|
|
@ -149,7 +154,8 @@ Your name here...
|
|||
&manage;
|
||||
&storage;
|
||||
&commands;
|
||||
|
||||
|
||||
&datetime;
|
||||
<!--
|
||||
&contacts;
|
||||
-->
|
||||
|
|
|
|||
|
|
@ -186,7 +186,7 @@ SELECT (a + b) AS c FROM test_complex;
|
|||
<para>
|
||||
Providing NEGATOR is very helpful to the query optimizer since
|
||||
it allows expressions like NOT (x = y) to be simplified into
|
||||
x <> y. This comes up more often than you might think, because
|
||||
x <> y. This comes up more often than you might think, because
|
||||
NOTs can be inserted as a consequence of other rearrangements.
|
||||
</para>
|
||||
|
||||
|
|
@ -225,21 +225,21 @@ SELECT (a + b) AS c FROM test_complex;
|
|||
These are the standard restriction estimators:
|
||||
<ProgramListing>
|
||||
eqsel for =
|
||||
neqsel for <>
|
||||
intltsel for < or <=
|
||||
intgtsel for > or >=
|
||||
neqsel for <>
|
||||
intltsel for < or <=
|
||||
intgtsel for > or >=
|
||||
</ProgramListing>
|
||||
It might seem a little odd that these are the categories, but they
|
||||
make sense if you think about it. '=' will typically accept only
|
||||
a small fraction of the rows in a table; '<>' will typically reject
|
||||
only a small fraction. '<' will accept a fraction that depends on
|
||||
a small fraction of the rows in a table; '<>' will typically reject
|
||||
only a small fraction. '<' will accept a fraction that depends on
|
||||
where the given constant falls in the range of values for that table
|
||||
column (which, it just so happens, is information collected by
|
||||
VACUUM ANALYZE and made available to the selectivity estimator).
|
||||
'<=' will accept a slightly larger fraction than '<' for the same
|
||||
'<=' will accept a slightly larger fraction than '<' for the same
|
||||
comparison constant, but they're close enough to not be worth
|
||||
distinguishing, especially since we're not likely to do better than a
|
||||
rough guess anyhow. Similar remarks apply to '>' and '>='.
|
||||
rough guess anyhow. Similar remarks apply to '>' and '>='.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
|
|
@ -249,48 +249,48 @@ SELECT (a + b) AS c FROM test_complex;
|
|||
matching operators (~, ~*, etc) use eqsel on the assumption that they'll
|
||||
usually only match a small fraction of the entries in a table.
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
<title>JOIN</title>
|
||||
<sect2>
|
||||
<title>JOIN</title>
|
||||
|
||||
<para>
|
||||
The JOIN clause, if provided, names a join selectivity
|
||||
estimation function for the operator (note that this is a function
|
||||
name, not an operator name). JOIN clauses only make sense for
|
||||
binary operators that return boolean. The idea behind a join
|
||||
selectivity estimator is to guess what fraction of the rows in a
|
||||
pair of tables will satisfy a WHERE-clause condition of the form
|
||||
<ProgramListing>
|
||||
<para>
|
||||
The JOIN clause, if provided, names a join selectivity
|
||||
estimation function for the operator (note that this is a function
|
||||
name, not an operator name). JOIN clauses only make sense for
|
||||
binary operators that return boolean. The idea behind a join
|
||||
selectivity estimator is to guess what fraction of the rows in a
|
||||
pair of tables will satisfy a WHERE-clause condition of the form
|
||||
<ProgramListing>
|
||||
table1.field1 OP table2.field2
|
||||
</ProgramListing>
|
||||
for the current operator. As with the RESTRICT clause, this helps
|
||||
the optimizer very substantially by letting it figure out which
|
||||
of several possible join sequences is likely to take the least work.
|
||||
</para>
|
||||
</ProgramListing>
|
||||
for the current operator. As with the RESTRICT clause, this helps
|
||||
the optimizer very substantially by letting it figure out which
|
||||
of several possible join sequences is likely to take the least work.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
As before, this chapter will make no attempt to explain how to write
|
||||
a join selectivity estimator function, but will just suggest that
|
||||
you use one of the standard estimators if one is applicable:
|
||||
<ProgramListing>
|
||||
<para>
|
||||
As before, this chapter will make no attempt to explain how to write
|
||||
a join selectivity estimator function, but will just suggest that
|
||||
you use one of the standard estimators if one is applicable:
|
||||
<ProgramListing>
|
||||
eqjoinsel for =
|
||||
neqjoinsel for <>
|
||||
intltjoinsel for < or <=
|
||||
intgtjoinsel for > or >=
|
||||
</ProgramListing>
|
||||
</para>
|
||||
neqjoinsel for <>
|
||||
intltjoinsel for < or <=
|
||||
intgtjoinsel for > or >=
|
||||
</ProgramListing>
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
</sect2>
|
||||
<sect2>
|
||||
<title>HASHES</title>
|
||||
|
||||
<sect2>
|
||||
<title>HASHES</title>
|
||||
|
||||
<para>
|
||||
The HASHES clause, if present, tells the system that it is OK to
|
||||
use the hash join method for a join based on this operator. HASHES
|
||||
only makes sense for binary operators that return boolean --- and
|
||||
in practice, the operator had better be equality for some data type.
|
||||
</para>
|
||||
<para>
|
||||
The HASHES clause, if present, tells the system that it is OK to
|
||||
use the hash join method for a join based on this operator. HASHES
|
||||
only makes sense for binary operators that return boolean --- and
|
||||
in practice, the operator had better be equality for some data type.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The assumption underlying hash join is that the join operator can
|
||||
|
|
|
|||
Loading…
Reference in New Issue