Fix pr_cmp() and have pr_lt() and pr_gt() use it rather than the othe…

…r way round

README.txt

@@ -162,22 +162,22 @@ The operators <=, <, =, <>, >= and > are read as usual, @> is read
 *contains*, <@ is read *is contained by*, && is read *overlaps*, and | is
 "union" and "&" is "intersect".
 
-  prefix=# select a, b, 
-     a <= b as "<=", a < b as "<", a = b as "=", a <> b as "<>", a >= b as ">=", a > b as ">",
-     a @> b as "@>", a <@ b as "<@", a && b as "&&" 
+  prefix=# select a, b,
+    a <= b as "<=", a < b as "<", a = b as "=", a <> b as "<>", a >= b as ">=", a > b as ">",
+    a @> b as "@>", a <@ b as "<@", a && b as "&&"
   from  (select a::prefix_range, b::prefix_range
-           from (values('123', '123'), 
-                       ('123', '124'), 
-                       ('123', '123[4-5]'), 
-                       ('123[4-5]', '123[2-7]'), 
+           from (values('123', '123'),
+                       ('123', '124'),
+                       ('123', '123[4-5]'),
+                       ('123[4-5]', '123[2-7]'),
                        ('123', '[2-3]')) as t(a, b)
         ) as x;
       a     |    b     | <= | < | = | <> | >= | > | @> | <@ | && 
   ----------+----------+----+---+---+----+----+---+----+----+----
    123      | 123      | t  | f | t | f  | t  | f | t  | t  | t
    123      | 124      | t  | t | f | t  | f  | f | f  | f  | f
    123      | 123[4-5] | t  | t | f | t  | f  | f | t  | f  | t
-   123[4-5] | 123[2-7] | f  | f | f | t  | f  | f | f  | t  | t
+   123[4-5] | 123[2-7] | f  | f | f | t  | t  | t | f  | t  | t
    123      | [2-3]    | t  | t | f | t  | f  | f | f  | f  | f
   (5 rows)
 

prefix.c

@@ -9,7 +9,7 @@
  * writting of this opclass, on the PostgreSQL internals, GiST inner
  * working and prefix search analyses.
  *
- * $Id: prefix.c,v 1.50 2009/06/05 21:05:23 dim Exp $
+ * $Id: prefix.c,v 1.51 2009/06/14 23:13:46 dim Exp $
  */
 
 #include <stdio.h>
@@ -447,112 +447,76 @@ bool pr_eq(prefix_range *a, prefix_range *b) {
  *
  * Baring bug, the constraint is to have non-overlapping data.
  */
-static inline
+
+/*static inline
 bool pr_lt(prefix_range *a, prefix_range *b, bool eqval) {
+*/
+
+static inline
+int pr_cmp(prefix_range *a, prefix_range *b) {
   int cmp = 0;
   int alen = strlen(a->prefix);
   int blen = strlen(b->prefix);
   int mlen = alen; /* minimum length */
   char *p  = a->prefix;
   char *q  = b->prefix;
 
+  /*
+   * First case, common prefix length
+   */
   if( alen == blen ) {
     cmp = memcmp(p, q, alen);
 
-    if( cmp < 0 ) 
-      return true;
+    /* Uncommon prefix, easy to compare */
+    if( cmp != 0 ) 
+      return cmp;
 
-    else if( cmp == 0 ) {
-      if( a->first == 0 ) {
-	if( b->first == 0 )
-	  return eqval;
-	return true;
-      }
-      else	
-	return (eqval ? a->first <= b->first : a->first < b->first);
-    }
+    /* Common prefix, check for (sub)ranges */
     else
-      return false;
+      return (a->first == b->first) ? (a->last - b->last) : (a->first - b->first);
   }
+
+  /* For memcmp() safety, we need the minimum length */
   if( mlen > blen )
     mlen = blen;
 
+  /*
+   * Don't forget we may have [x-y] prefix style, that's empty prefix, only range.
+   */
   if( alen == 0 && a->first != 0 ) {
-    return (eqval ? (a->first <= q[0]) : (a->first < q[0]));
+    /* return (eqval ? (a->first <= q[0]) : (a->first < q[0])); */
+    return a->first - q[0];
   }
   else if( blen == 0 && b->first != 0 ) {
-    return (eqval ? (p[0] <= b->first) : (p[0] < b->first));
+    /* return (eqval ? (p[0] <= b->first) : (p[0] < b->first)); */
+    return p[0] - b->first;
   }
-  else {
-    /*
-     * When memcmp() on the shorter of p and q returns 0, that means they
-     * share a common prefix: avoid to say that '93' < '9377' and '9377' <
-     * '93'.
-     */
-    cmp = memcmp(p, q, mlen);
 
-    if( cmp == 0 )
-      return (eqval ? alen <= blen : alen < blen);
+  /*
+   * General case
+   *
+   * When memcmp() on the shorter of p and q returns 0, that means they
+   * share a common prefix: avoid to say that '93' < '9377' and '9377' <
+   * '93'.
+   */
+  cmp = memcmp(p, q, mlen);
+
+  if( cmp == 0 )
+    return (a->first == b->first) ? (a->last - b->last) : (a->first - b->first);
 
-    return (eqval ? cmp <= 0 : cmp < 0);
-  }
+  return cmp;
 }
 
 static inline
-bool pr_gt(prefix_range *a, prefix_range *b, bool eqval) {
-  int cmp = 0;
-  int alen = strlen(a->prefix);
-  int blen = strlen(b->prefix);
-  int mlen = alen;
-  char *p  = a->prefix;
-  char *q  = b->prefix;
-
-  if( alen == blen ) {
-    cmp = memcmp(p, q, alen);
-
-    if( cmp > 0 )
-      return true;
-
-    else if( cmp == 0 ) {
-      if( a->last == 0 ) {
-	if( b->last == 0 )
-	  return eqval;
-	return false;
-      }
-      else	
-	return (eqval ? a->last >= b->last : a->last > b->last);
-    }
-    else
-      return false;
-  }
-  if( mlen > blen )
-    mlen = blen;
-
-  if( alen == 0 && a->last != 0 ) {
-    return (eqval ? (a->last >= q[0]) : (a->last > q[0]));
-  }
-  else if( blen == 0 && b->first != 0 ) {
-    return (eqval ? (p[0] >= b->last) : (p[0] > b->last));
-  }
-  else {
-    cmp = memcmp(p, q, mlen);
-
-    if( cmp == 0 )
-      return (eqval ? alen >= blen : alen > blen);
-
-    return (eqval ? cmp >= 0 : cmp > 0);
-  }
+bool pr_lt(prefix_range *a, prefix_range *b, bool eqval) {
+  int cmp = pr_cmp(a, b);
+  return eqval ? cmp <= 0 : cmp < 0;
 }
 
 static inline
-int pr_cmp(prefix_range *a, prefix_range *b) {
-  if( pr_eq(a, b) )
-    return 0;
-
-  if( pr_lt(a, b, false) )
-    return -1;
-
-  return 1;
+bool pr_gt(prefix_range *a, prefix_range *b, bool eqval) {
+  int cmp = pr_cmp(a, b);
+  return eqval ? cmp >= 0 : cmp > 0;
 }
 
 static inline

queries.sql

@@ -0,0 +1,29 @@
+select a, b,
+   a <= b as "<=", a < b as "<", a = b as "=", a <> b as "<>", a >= b as ">=", a > b as ">",
+   a @> b as "@>", a <@ b as "<@", a && b as "&&"
+from  (select a::prefix_range, b::prefix_range
+         from (values('123', '123'),
+                     ('123', '124'),
+                     ('123', '123[4-5]'),
+                     ('123[4-5]', '123[2-7]'),
+                     ('123', '[2-3]')) as t(a, b)
+      ) as x;
+
+select a, b, c, a <= b as "a <= b", b <= c as "b <= c", a <= c as "a <= c"
+from  (select a::prefix_range, b::prefix_range, c::prefix_range
+         from (values('123', '123', '123'),
+                     ('123', '124', '125'),
+                     ('123', '123[4-5]', '123[4-6]'),
+                     ('123[4-5]', '123[2-7]', '123[1-8]'),
+                     ('123', '[2-3]', '4')) as t(a, b, c)
+      ) as x;
+
+select a, b, a | b as union, a & b as intersect
+  from  (select a::prefix_range, b::prefix_range
+           from (values('123', '123'),
+                       ('123', '124'),
+                       ('123', '123[4-5]'),
+                       ('123[4-5]', '123[2-7]'),
+                       ('123', '[2-3]')) as t(a, b)
+        ) as x;
+