Improve similar_escape() in two different ways:

* Stop escaping ? and {.  As of SQL:2008, SIMILAR TO is defined to have
POSIX-compatible interpretation of ? as well as {m,n} and related constructs,
so we should allow these things through to our regex engine.

* Escape ^ and $.  It appears that our regex engine will treat ^^ at the
beginning of the string the same as ^, and similarly for $$ at the end of
the string, which meant that SIMILAR TO was effectively ignoring ^ at the
start of the pattern and $ at the end.  Since these are not supposed to be
metacharacters, this is a bug.

The second part of this is arguably a back-patchable bug fix, but I'm
hesitant to do that because it might break applications that are expecting
something like "col SIMILAR TO '^foo$'" to work like a POSIX pattern.
Seems safer to only change it at a major version boundary.

Per discussion of an example from Doug Gorley.

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index da558668c8ac34505f4a15ac4169731120e16c9e..211a450ce305fa21a9502b3bf9326e07884b9492 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   Functions and Operators
@@ -3154,6 +3154,31 @@ cast(-44 as bit(12))           111111010100
       or more times.
      
     
+    
+     
+      ? denotes repetition of the previous item zero
+      or one time.
+     
+    
+    
+     
+      {m} denotes repetition
+      of the previous item exactly m times.
+     
+    
+    
+     
+      {m,} denotes repetition
+      of the previous item m or more times.
+     
+    
+    
+     
+      {m,n}
+      denotes repetition of the previous item at least m and
+      not more than n times.
+     
+    
     
      
       Parentheses () can be used to group items into
@@ -3168,9 +3193,8 @@ cast(-44 as bit(12))           111111010100
     
    
 
-    Notice that bounded repetition operators (? and
-    {...}) are not provided, though they exist in POSIX.
-    Also, the period (.) is not a metacharacter.
+    Notice that the period (.) is not a metacharacter
+    for SIMILAR TO.
    
 
    

diff --git a/src/backend/utils/adt/regexp.c b/src/backend/utils/adt/regexp.c
index e4e3c7766582c9f6c556671fdc2a634c4bd42429..118d42d2a0acf7befaf7249391cabb4081c16346 100644 (file)
--- 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 1.82 2009/06/11 14:49:04 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.83 2009/10/10 03:50:15 tgl Exp $
  *
  *     Alistair Crooks added the code for the regex caching
  *     agc - cached the regular expressions used - there's a good chance
@@ -639,7 +639,7 @@ textregexreplace(PG_FUNCTION_ARGS)
 
 /*
  * similar_escape()
- * Convert a SQL99 regexp pattern to POSIX style, so it can be used by
+ * Convert a SQL:2008 regexp pattern to POSIX style, so it can be used by
  * our regexp engine.
  */
 Datum
@@ -740,8 +740,8 @@ similar_escape(PG_FUNCTION_ARGS)
        }
        else if (pchar == '_')
            *r++ = '.';
-       else if (pchar == '\\' || pchar == '.' || pchar == '?' ||
-                pchar == '{')
+       else if (pchar == '\\' || pchar == '.' ||
+                pchar == '^' || pchar == '$')
        {
            *r++ = '\\';
            *r++ = pchar;