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Code review for regexp_matches/regexp_split patch. Refactor to avoid assuming

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that cached compiled patterns will still be there when the function is next
called.  Clean up looping logic, thereby fixing bug identified by Pavel
Stehule.  Share setup code between the two functions, add some comments, and
avoid risky mixing of int and size_t variables.  Clean up the documentation a
tad, and accept all the flag characters mentioned in table 9-19 rather than
just a subset.
This commit is contained in:
Tom Lane
2007-08-11 03:56:24 +00:00
parent d0e5c0c0ee
commit 1b70619311
4 changed files with 399 additions and 334 deletions
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65
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.383 2007/07/18 03:12:42 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.384 2007/08/11 03:56:24 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -1499,7 +1499,7 @@
<entry><literal><function>regexp_matches</function>(<parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type>])</literal></entry>
<entry><type>setof text[]</type></entry>
<entry>
Return all capture groups resulting from matching POSIX regular
Return all captured substrings resulting from matching a POSIX regular
expression against the <parameter>string</parameter>. See
<xref linkend="functions-posix-regexp"> for more information.
</entry>
@ -1511,7 +1511,7 @@
<entry><literal><function>regexp_replace</function>(<parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type>])</literal></entry>
<entry><type>text</type></entry>
<entry>
Replace substring matching POSIX regular expression. See
Replace substring(s) matching a POSIX regular expression. See
<xref linkend="functions-posix-regexp"> for more information.
</entry>
<entry><literal>regexp_replace('Thomas', '.[mN]a.', 'M')</literal></entry>
@ -1522,7 +1522,7 @@
<entry><literal><function>regexp_split_to_array</function>(<parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type> ])</literal></entry>
<entry><type>text[]</type></entry>
<entry>
Split <parameter>string</parameter> using POSIX regular expression as
Split <parameter>string</parameter> using a POSIX regular expression as
the delimiter. See <xref linkend="functions-posix-regexp"> for more
information.
</entry>
@ -1534,7 +1534,7 @@
<entry><literal><function>regexp_split_to_table</function>(<parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> [, <parameter>flags</parameter> <type>text</type>])</literal></entry>
<entry><type>setof text</type></entry>
<entry>
Split <parameter>string</parameter> using POSIX regular expression as
Split <parameter>string</parameter> using a POSIX regular expression as
the delimiter. See <xref linkend="functions-posix-regexp"> for more
information.
</entry>
@ -2856,11 +2856,9 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
<acronym>SQL</acronym> <function>LIKE</function> operator, the
more recent <function>SIMILAR TO</function> operator (added in
SQL:1999), and <acronym>POSIX</acronym>-style regular
expressions.
Additionally, a pattern matching function,
<function>substring</function>, is available, using either
<function>SIMILAR TO</function>-style or POSIX-style regular
expressions.
expressions. Aside from the basic <quote>does this string match
this pattern?</> operators, functions are available to extract
or replace matching substrings and to split a string at the matches.
</para>
<tip>
@ -3186,15 +3184,20 @@ substring('foobar' from '#"o_b#"%' for '#') <lineannotation>NULL</lineannotat
end of the string.
</para>
<para>
Some examples:
<para>
Some examples:
<programlisting>
'abc' ~ 'abc' <lineannotation>true</lineannotation>
'abc' ~ '^a' <lineannotation>true</lineannotation>
'abc' ~ '(b|d)' <lineannotation>true</lineannotation>
'abc' ~ '^(b|c)' <lineannotation>false</lineannotation>
</programlisting>
</para>
</para>
<para>
The <acronym>POSIX</acronym> pattern language is described in much
greater detail below.
</para>
<para>
The <function>substring</> function with two parameters,
@ -3246,9 +3249,7 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
function's behavior. Flag <literal>i</> specifies case-insensitive
matching, while flag <literal>g</> specifies replacement of each matching
substring rather than only the first one. Other supported flags are
<literal>m</>, <literal>n</>, <literal>p</>, <literal>w</> and
<literal>x</>, whose meanings correspond to those shown in
<xref linkend="posix-embedded-options-table">.
described in <xref linkend="posix-embedded-options-table">.
</para>
<para>
@ -3264,23 +3265,25 @@ regexp_replace('foobarbaz', 'b(..)', E'X\\1Y', 'g')
</para>
<para>
The <function>regexp_matches</> function returns all of the capture
groups resulting from matching a POSIX regular expression pattern.
The <function>regexp_matches</> function returns all of the captured
substrings resulting from matching a POSIX regular expression pattern.
It has the syntax
<function>regexp_matches</function>(<replaceable>string</>, <replaceable>pattern</>
<optional>, <replaceable>flags</> </optional>).
If there is no match to the <replaceable>pattern</>, the function returns no rows.
If there is a match, the function returns the contents of all of the capture groups
in a text array, or if there were no capture groups in the pattern, it returns the
contents of the entire match as a single-element text array.
If there is no match to the <replaceable>pattern</>, the function returns
no rows. If there is a match, the function returns a text array whose
<replaceable>n</>'th element is the substring matching the
<replaceable>n</>'th parenthesized subexpression of the pattern
(not counting <quote>non-capturing</> parentheses; see below for
details). If the pattern does not contain any parenthesized
subexpressions, then the result is a single-element text array containing
the substring matching the whole pattern.
The <replaceable>flags</> parameter is an optional text
string containing zero or more single-letter flags that change the
function's behavior. Flag <literal>i</> specifies case-insensitive
matching, while flag <literal>g</> causes the return of each matching
substring rather than only the first one. Other supported
flags are <literal>m</>, <literal>n</>, <literal>p</>, <literal>w</> and
<literal>x</>, whose meanings are described in
<xref linkend="posix-embedded-options-table">.
function's behavior. Flag <literal>g</> causes the function to find
each match in the string, not only the first one, and return a row for
each such match. Other supported
flags are described in <xref linkend="posix-embedded-options-table">.
</para>
<para>
@ -3319,16 +3322,14 @@ SELECT regexp_matches('foobarbequebaz', 'barbeque');
returns the text from the end of the last match to the end of the string.
The <replaceable>flags</> parameter is an optional text string containing
zero or more single-letter flags that change the function's behavior.
<function>regexp_split_to_table</function> supports the flags <literal>i</>,
<literal>m</>, <literal>n</>, <literal>p</>, <literal>w</> and
<literal>x</>, whose meanings are described in
<function>regexp_split_to_table</function> supports the flags described in
<xref linkend="posix-embedded-options-table">.
</para>
<para>
The <function>regexp_split_to_array</> function behaves the same as
<function>regexp_split_to_table</>, except that <function>regexp_split_to_array</>
returns its results as a <type>text[]</>. It has the syntax
returns its result as an array of <type>text</>. It has the syntax
<function>regexp_split_to_array</function>(<replaceable>string</>, <replaceable>pattern</>
<optional>, <replaceable>flags</> </optional>).
The parameters are the same as for <function>regexp_split_to_table</>.