Reduce need for palloc/pfree overhead in varstr_cmp() by using fixed-size

buffers on stack for short strings.

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index e21e59e1be8051f32527f622a6eeb1f1a997b082..1dd2901bd0ca615622154e2ee9166c2eeab36c70 100644 (file)
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.92 2002/09/04 20:31:29 momjian Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.93 2002/11/17 23:01:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -736,36 +736,47 @@ int
 varstr_cmp(char *arg1, int len1, char *arg2, int len2)
 {
        int                     result;
-       char       *a1p,
-                          *a2p;
 
        /*
         * Unfortunately, there is no strncoll(), so in the non-C locale case
         * we have to do some memory copying.  This turns out to be
         * significantly slower, so we optimize the case where LC_COLLATE is
-        * C.
+        * C.  We also try to optimize relatively-short strings by avoiding
+        * palloc/pfree overhead.
         */
+#define STACKBUFLEN            1024
+
        if (!lc_collate_is_c())
        {
-               a1p = (char *) palloc(len1 + 1);
-               a2p = (char *) palloc(len2 + 1);
+               char    a1buf[STACKBUFLEN];
+               char    a2buf[STACKBUFLEN];
+               char   *a1p,
+                          *a2p;
+
+               if (len1 >= STACKBUFLEN)
+                       a1p = (char *) palloc(len1 + 1);
+               else
+                       a1p = a1buf;
+               if (len2 >= STACKBUFLEN)
+                       a2p = (char *) palloc(len2 + 1);
+               else
+                       a2p = a2buf;
 
                memcpy(a1p, arg1, len1);
-               *(a1p + len1) = '\0';
+               a1p[len1] = '\0';
                memcpy(a2p, arg2, len2);
-               *(a2p + len2) = '\0';
+               a2p[len2] = '\0';
 
                result = strcoll(a1p, a2p);
 
-               pfree(a1p);
-               pfree(a2p);
+               if (len1 >= STACKBUFLEN)
+                       pfree(a1p);
+               if (len2 >= STACKBUFLEN)
+                       pfree(a2p);
        }
        else
        {
-               a1p = arg1;
-               a2p = arg2;
-
-               result = strncmp(a1p, a2p, Min(len1, len2));
+               result = strncmp(arg1, arg2, Min(len1, len2));
                if ((result == 0) && (len1 != len2))
                        result = (len1 < len2) ? -1 : 1;
        }