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Prevent to_number() from losing data when template doesn't match exactly.

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Non-data template patterns would consume characters whether or not those
characters were what the pattern expected, for example
	SELECT TO_NUMBER('1234', '9,999');
produced 134 because the '2' got eaten by the comma pattern.  This seems
undesirable, not least because it doesn't happen in Oracle.  For the ','
and 'G' template patterns, we can fix this by consuming characters only
if they match what the pattern would output.  For non-data patterns such
as 'L' and 'TH', it seems impractical to tighten things up to the point of
consuming only exact matches to what the pattern would output; but we can
improve matters quite a lot by redefining the behavior as "consume only
characters that aren't digits, signs, decimal point, or comma".

Also, fix it so that the behavior is to consume the number of *characters*
the pattern would output, not the number of *bytes*.  The old coding would
do surprising things with non-ASCII currency symbols, for example.  (It
would be good to apply that rule for literal text as well, but this commit
only fixes it for non-data patterns.)

Oliver Ford, reviewed by Thomas Munro and Nathan Wagner, and whacked around
a bit more by me

Discussion: https://postgr.es/m/CAGMVOdvpbMqPf9XWNzOwBpzJfErkydr_fEGhmuDGa015z97mwg@mail.gmail.com
This commit is contained in:
Tom Lane
2017-11-17 12:04:06 -05:00
parent be92769e4e
commit e87d4965bd
4 changed files with 197 additions and 32 deletions
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28
doc/src/sgml/func.sgml
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@ -5850,7 +5850,10 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
data based on the given value. Any text that is not a template pattern is
simply copied verbatim. Similarly, in an input template string (for the
other functions), template patterns identify the values to be supplied by
the input data string.
the input data string. If there are characters in the template string
that are not template patterns, the corresponding characters in the input
data string are simply skipped over (whether or not they are equal to the
template string characters).
</para>
<para>
@ -6176,13 +6179,15 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
Ordinary text is allowed in <function>to_char</function>
templates and will be output literally. You can put a substring
in double quotes to force it to be interpreted as literal text
even if it contains pattern key words. For example, in
even if it contains template patterns. For example, in
<literal>'"Hello Year "YYYY'</literal>, the <literal>YYYY</literal>
will be replaced by the year data, but the single <literal>Y</literal> in <literal>Year</literal>
will not be. In <function>to_date</function>, <function>to_number</function>,
and <function>to_timestamp</function>, double-quoted strings skip the number of
input characters contained in the string, e.g. <literal>"XX"</literal>
skips two input characters.
will not be.
In <function>to_date</function>, <function>to_number</function>,
and <function>to_timestamp</function>, literal text and double-quoted
strings result in skipping the number of characters contained in the
string; for example <literal>"XX"</literal> skips two input characters
(whether or not they are <literal>XX</literal>).
</para>
</listitem>
@ -6483,6 +6488,17 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
</para>
</listitem>
<listitem>
<para>
In <function>to_number</function>, if non-data template patterns such
as <literal>L</literal> or <literal>TH</literal> are used, the
corresponding number of input characters are skipped, whether or not
they match the template pattern, unless they are data characters
(that is, digits, sign, decimal point, or comma). For
example, <literal>TH</literal> would skip two non-data characters.
</para>
</listitem>
<listitem>
<para>
<literal>V</literal> with <function>to_char</function>