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Fix similar_escape() so that SIMILAR TO works properly for patterns involving

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alternatives ("|" symbol).  The original coding allowed the added ^ and $
constraints to be absorbed into the first and last alternatives, producing
a pattern that would match more than it should.  Per report from Eric Noriega.

I also changed the pattern to add an ARE director ("***:"), ensuring that
SIMILAR TO patterns do not change behavior if regex_flavor is changed.  This
is necessary to make the non-capturing parentheses work, and seems like a
good idea on general principles.

Back-patched as far as 7.4.  7.3 also has the bug, but a fix seems impractical
because that version's regex engine doesn't have non-capturing parens.
This commit is contained in:
Tom Lane 2006-04-13 18:01:31 +00:00
parent dcdf738abb
commit cc39aca7d4
1 changed files with 29 additions and 3 deletions
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32
src/backend/utils/adt/regexp.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.62 2006/03/05 15:58:43 momjian Exp $ * $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.63 2006/04/13 18:01:31 tgl Exp $
* *
* Alistair Crooks added the code for the regex caching * Alistair Crooks added the code for the regex caching
* agc - cached the regular expressions used - there's a good chance * agc - cached the regular expressions used - there's a good chance
@ -549,11 +549,36 @@ similar_escape(PG_FUNCTION_ARGS)
errhint("Escape string must be empty or one character."))); errhint("Escape string must be empty or one character.")));
} }
/* We need room for ^, $, and up to 2 output bytes per input byte */ /*----------
result = (text *) palloc(VARHDRSZ + 2 + 2 * plen); * We surround the transformed input string with
* ***:^(?: ... )$
* which is bizarre enough to require some explanation. "***:" is a
* director prefix to force the regex to be treated as an ARE regardless
* of the current regex_flavor setting. We need "^" and "$" to force
* the pattern to match the entire input string as per SQL99 spec. The
* "(?:" and ")" are a non-capturing set of parens; we have to have
* parens in case the string contains "|", else the "^" and "$" will
* be bound into the first and last alternatives which is not what we
* want, and the parens must be non capturing because we don't want them
* to count when selecting output for SUBSTRING.
*----------
*/
/*
* We need room for the prefix/postfix plus as many as 2 output bytes per
* input byte
*/
result = (text *) palloc(VARHDRSZ + 10 + 2 * plen);
r = VARDATA(result); r = VARDATA(result);
*r++ = '*';
*r++ = '*';
*r++ = '*';
*r++ = ':';
*r++ = '^'; *r++ = '^';
*r++ = '(';
*r++ = '?';
*r++ = ':';
while (plen > 0) while (plen > 0)
{ {
@ -593,6 +618,7 @@ similar_escape(PG_FUNCTION_ARGS)
p++, plen--; p++, plen--;
} }
*r++ = ')';
*r++ = '$'; *r++ = '$';
VARATT_SIZEP(result) = r - ((char *) result); VARATT_SIZEP(result) = r - ((char *) result);