Improve similar_escape() in two different ways:

tglsfdc · tglsfdc · commit 05d249717d65 · 2009-10-10T03:50:15.000Z
* 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
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.488 2009/10/09 21:02:55 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.489 2009/10/10 03:50:15 tgl Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -3154,6 +3154,31 @@ cast(-44 as bit(12))           <lineannotation>111111010100</lineannotation>
       or more times.
      </para>
     </listitem>
+    <listitem>
+     <para>
+      <literal>?</literal> denotes repetition of the previous item zero
+      or one time.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      <literal>{</><replaceable>m</><literal>}</literal> denotes repetition
+      of the previous item exactly <replaceable>m</> times.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      <literal>{</><replaceable>m</><literal>,}</literal> denotes repetition
+      of the previous item <replaceable>m</> or more times.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      <literal>{</><replaceable>m</><literal>,</><replaceable>n</><literal>}</>
+      denotes repetition of the previous item at least <replaceable>m</> and
+      not more than <replaceable>n</> times.
+     </para>
+    </listitem>
     <listitem>
      <para>
       Parentheses <literal>()</literal> can be used to group items into
@@ -3168,9 +3193,8 @@ cast(-44 as bit(12))           <lineannotation>111111010100</lineannotation>
     </listitem>
    </itemizedlist>
 
-    Notice that bounded repetition operators (<literal>?</> and
-    <literal>{...}</>) are not provided, though they exist in POSIX.
-    Also, the period (<literal>.</>) is not a metacharacter.
+    Notice that the period (<literal>.</>) is not a metacharacter
+    for <function>SIMILAR TO</>.
    </para>
 
    <para>
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.82 2009/06/11 14:49:04 momjian Exp $`
	`11`	`+ * $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.83 2009/10/10 03:50:15 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`* Alistair Crooks added the code for the regex caching`
`14`	`14`	`* agc - cached the regular expressions used - there's a good chance`
`@@ -639,7 +639,7 @@ textregexreplace(PG_FUNCTION_ARGS)`
`639`	`639`
`640`	`640`	`/*`
`641`	`641`	`* similar_escape()`
`642`		`- * Convert a SQL99 regexp pattern to POSIX style, so it can be used by`
	`642`	`+ * Convert a SQL:2008 regexp pattern to POSIX style, so it can be used by`
`643`	`643`	`* our regexp engine.`
`644`	`644`	`*/`
`645`	`645`	`Datum`
`@@ -740,8 +740,8 @@ similar_escape(PG_FUNCTION_ARGS)`
`740`	`740`	`}`
`741`	`741`	`else if (pchar == '_')`
`742`	`742`	`*r++ = '.';`
`743`		`- else if (pchar == '\\' \|\| pchar == '.' \|\| pchar == '?' \|\|`
`744`		`- pchar == '{')`
	`743`	`+ else if (pchar == '\\' \|\| pchar == '.' \|\|`
	`744`	`+ pchar == '^' \|\| pchar == '$')`
`745`	`745`	`{`
`746`	`746`	`*r++ = '\\';`
`747`	`747`	`*r++ = pchar;`