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Make to_timestamp() and to_date() range-check fields of their input.

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Historically, something like to_date('2009-06-40','YYYY-MM-DD') would
return '2009-07-10' because there was no prohibition on out-of-range
month or day numbers.  This has been widely panned, and it also turns
out that Oracle throws an error in such cases.  Since these functions
are nominally Oracle-compatibility features, let's change that.

There's no particular restriction on year (modulo the fact that the
scanner may not believe that more than 4 digits are year digits,
a matter to be addressed separately if at all).  But we now check month,
day, hour, minute, second, and fractional-second fields, as well as
day-of-year and second-of-day fields if those are used.

Currently, no checks are made on ISO-8601-style week numbers or day
numbers; it's not very clear what the appropriate rules would be there,
and they're probably so little used that it's not worth sweating over.

Artur Zakirov, reviewed by Amul Sul, further adjustments by me

Discussion: <1873520224.1784572.1465833145330.JavaMail.yahoo@mail.yahoo.com>
See-Also: <57786490.9010201@wars-nicht.de>
This commit is contained in:
Tom Lane
2016-09-28 14:36:04 -04:00
parent 967ed9205b
commit d3cd36a133
4 changed files with 239 additions and 66 deletions
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85
doc/src/sgml/func.sgml
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@ -5832,6 +5832,17 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
</para>
</note>
<tip>
<para>
<function>to_timestamp</function> and <function>to_date</function>
exist to handle input formats that cannot be converted by
simple casting. For most standard date/time formats, simply casting the
source string to the required data type works, and is much easier.
Similarly, <function>to_number</> is unnecessary for standard numeric
representations.
</para>
</tip>
<para>
In a <function>to_char</> output template string, there are certain
patterns that are recognized and replaced with appropriately-formatted
@ -6038,7 +6049,7 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
</row>
<row>
<entry><literal>Q</literal></entry>
<entry>quarter (ignored by <function>to_date</> and <function>to_timestamp</>)</entry>
<entry>quarter</entry>
</row>
<row>
<entry><literal>RM</literal></entry>
@ -6156,20 +6167,6 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
</para>
</listitem>
<listitem>
<para>
<function>to_timestamp</function> and <function>to_date</function>
exist to handle input formats that cannot be converted by
simple casting. These functions interpret input liberally,
with minimal error checking. While they produce valid output,
the conversion can yield unexpected results. For example,
input to these functions is not restricted by normal ranges,
thus <literal>to_date('20096040','YYYYMMDD')</literal> returns
<literal>2014-01-17</literal> rather than causing an error.
Casting does not have this behavior.
</para>
</listitem>
<listitem>
<para>
Ordinary text is allowed in <function>to_char</function>
@ -6195,7 +6192,8 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
If the year format specification is less than four digits, e.g.
In <function>to_timestamp</function> and <function>to_date</function>,
if the year format specification is less than four digits, e.g.
<literal>YYY</>, and the supplied year is less than four digits,
the year will be adjusted to be nearest to the year 2020, e.g.
<literal>95</> becomes 1995.
@ -6204,8 +6202,9 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
The <literal>YYYY</literal> conversion from string to <type>timestamp</type> or
<type>date</type> has a restriction when processing years with more than 4 digits. You must
In <function>to_timestamp</function> and <function>to_date</function>,
the <literal>YYYY</literal> conversion has a restriction when
processing years with more than 4 digits. You must
use some non-digit character or template after <literal>YYYY</literal>,
otherwise the year is always interpreted as 4 digits. For example
(with the year 20000):
@ -6219,12 +6218,12 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
In conversions from string to <type>timestamp</type> or
<type>date</type>, the <literal>CC</literal> (century) field is ignored
In <function>to_timestamp</function> and <function>to_date</function>,
the <literal>CC</literal> (century) field is accepted but ignored
if there is a <literal>YYY</literal>, <literal>YYYY</literal> or
<literal>Y,YYY</literal> field. If <literal>CC</literal> is used with
<literal>YY</literal> or <literal>Y</literal> then the year is computed
as the year in the specified century. If the century is
<literal>YY</literal> or <literal>Y</literal> then the result is
computed as that year in the specified century. If the century is
specified but the year is not, the first year of the century
is assumed.
</para>
@ -6232,9 +6231,19 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
An ISO 8601 week-numbering date (as distinct from a Gregorian date)
can be specified to <function>to_timestamp</function> and
<function>to_date</function> in one of two ways:
In <function>to_timestamp</function> and <function>to_date</function>,
weekday names or numbers (<literal>DAY</literal>, <literal>D</literal>,
and related field types) are accepted but are ignored for purposes of
computing the result. The same is true for quarter
(<literal>Q</literal>) fields.
</para>
</listitem>
<listitem>
<para>
In <function>to_timestamp</function> and <function>to_date</function>,
an ISO 8601 week-numbering date (as distinct from a Gregorian date)
can be specified in one of two ways:
<itemizedlist>
<listitem>
<para>
@ -6276,23 +6285,24 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
In a conversion from string to <type>timestamp</type>, millisecond
In <function>to_timestamp</function>, millisecond
(<literal>MS</literal>) or microsecond (<literal>US</literal>)
values are used as the
fields are used as the
seconds digits after the decimal point. For example
<literal>to_timestamp('12:3', 'SS:MS')</literal> is not 3 milliseconds,
but 300, because the conversion counts it as 12 + 0.3 seconds.
This means for the format <literal>SS:MS</literal>, the input values
<literal>12:3</literal>, <literal>12:30</literal>, and <literal>12:300</literal> specify the
same number of milliseconds. To get three milliseconds, one must use
<literal>12:003</literal>, which the conversion counts as
<literal>to_timestamp('12.3', 'SS.MS')</literal> is not 3 milliseconds,
but 300, because the conversion treats it as 12 + 0.3 seconds.
So, for the format <literal>SS.MS</literal>, the input values
<literal>12.3</literal>, <literal>12.30</literal>,
and <literal>12.300</literal> specify the
same number of milliseconds. To get three milliseconds, one must write
<literal>12.003</literal>, which the conversion treats as
12 + 0.003 = 12.003 seconds.
</para>
<para>
Here is a more
complex example:
<literal>to_timestamp('15:12:02.020.001230', 'HH:MI:SS.MS.US')</literal>
<literal>to_timestamp('15:12:02.020.001230', 'HH24:MI:SS.MS.US')</literal>
is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds +
1230 microseconds = 2.021230 seconds.
</para>
@ -6310,9 +6320,10 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<listitem>
<para>
<function>to_char(interval)</function> formats <literal>HH</> and
<literal>HH12</> as shown on a 12-hour clock, i.e. zero hours
and 36 hours output as <literal>12</>, while <literal>HH24</>
outputs the full hour value, which can exceed 23 for intervals.
<literal>HH12</> as shown on a 12-hour clock, for example zero hours
and 36 hours both output as <literal>12</>, while <literal>HH24</>
outputs the full hour value, which can exceed 23 in
an <type>interval</> value.
</para>
</listitem>