From cc39aca7d4a317a66db51a2180f7fee6e76084bd Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 13 Apr 2006 18:01:31 +0000
Subject: [PATCH] Fix similar_escape() so that SIMILAR TO works properly for
patterns involving 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.
---
src/backend/utils/adt/regexp.c | 32 +++++++++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)
diff --git a/src/backend/utils/adt/regexp.c b/src/backend/utils/adt/regexp.c
index 3db5ca9b6cf..c9d61de4180 100644
--- a/src/backend/utils/adt/regexp.c
+++ b/src/backend/utils/adt/regexp.c
@@ -8,7 +8,7 @@
*
*
* 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
* 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.")));
}
- /* 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++ = '*';
+ *r++ = '*';
+ *r++ = '*';
+ *r++ = ':';
*r++ = '^';
+ *r++ = '(';
+ *r++ = '?';
+ *r++ = ':';
while (plen > 0)
{
@@ -593,6 +618,7 @@ similar_escape(PG_FUNCTION_ARGS)
p++, plen--;
}
+ *r++ = ')';
*r++ = '$';
VARATT_SIZEP(result) = r - ((char *) result);
--
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