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Fix conversion of SIMILAR TO regexes for character classes

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The code that translates SIMILAR TO pattern matching expressions to
POSIX-style regular expressions did not consider that square brackets
can be nested.  For example, in an expression like [[:alpha:]%_], the
logic replaced the placeholders '_' and '%' but it should not.

This commit fixes the conversion logic by tracking the nesting level of
square brackets marking character class areas, while considering that
in expressions like []] or [^]] the first closing square bracket is a
regular character.  Multiple tests are added to show how the conversions
should or should not apply applied while in a character class area, with
specific cases added for all the characters converted outside character
classes like an opening parenthesis '(', dollar sign '$', etc.

Author: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/16ab039d1af455652bdf4173402ddda145f2c73b.camel@cybertec.at
Backpatch-through: 13
This commit is contained in:
Michael Paquier
2025-05-28 08:58:40 +09:00
parent 3e782ca322
commit d46911e584
3 changed files with 114 additions and 6 deletions
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38
src/backend/utils/adt/regexp.c
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@ -773,8 +773,11 @@ similar_escape_internal(text *pat_text, text *esc_text)
int plen,
elen;
bool afterescape = false;
bool incharclass = false;
int nquotes = 0;
int charclass_depth = 0; /* Nesting level of character classes,
* encompassed by square brackets */
int charclass_start = 0; /* State of the character class start,
* for carets */
p = VARDATA_ANY(pat_text);
plen = VARSIZE_ANY_EXHDR(pat_text);
@ -904,7 +907,7 @@ similar_escape_internal(text *pat_text, text *esc_text)
/* fast path */
if (afterescape)
{
if (pchar == '"' && !incharclass) /* escape-double-quote? */
if (pchar == '"' && charclass_depth < 1) /* escape-double-quote? */
{
/* emit appropriate part separator, per notes above */
if (nquotes == 0)
@ -953,18 +956,41 @@ similar_escape_internal(text *pat_text, text *esc_text)
/* SQL escape character; do not send to output */
afterescape = true;
}
else if (incharclass)
else if (charclass_depth > 0)
{
if (pchar == '\\')
*r++ = '\\';
*r++ = pchar;
if (pchar == ']')
incharclass = false;
/*
* Ignore a closing bracket at the start of a character class.
* Such a bracket is taken literally rather than closing the
* class. "charclass_start" is 1 right at the beginning of a
* class and 2 after an initial caret.
*/
if (pchar == ']' && charclass_start > 2)
charclass_depth--;
else if (pchar == '[')
charclass_depth++;
/*
* If there is a caret right after the opening bracket, it negates
* the character class, but a following closing bracket should
* still be treated as a normal character. That holds only for
* the first caret, so only the values 1 and 2 mean that closing
* brackets should be taken literally.
*/
if (pchar == '^')
charclass_start++;
else
charclass_start = 3; /* definitely past the start */
}
else if (pchar == '[')
{
/* start of a character class */
*r++ = pchar;
incharclass = true;
charclass_depth++;
charclass_start = 1;
}
else if (pchar == '%')
{