Clean up bogosities in use of random(3) and srandom(3) --- do not assume

that RAND_MAX applies to them, since it doesn't.  Instead add a
config.h parameter MAX_RANDOM_VALUE.  This is currently set at 2^31-1
but could be auto-configured if that ever proves necessary.  Also fix
some outright bugs like calling srand() where srandom() is appropriate.

doc/src/sgml/func.sgml

@@ -171,6 +171,18 @@
 	<entry>convert floating point to integer</entry>
 	<entry>integer(2.0)</entry>
        </row>
+       <row>
+	<entry>random()</entry>
+	<entry>float8</entry>
+	<entry>random value in the range 0.0 to 1.0</entry>
+	<entry>random()</entry>
+       </row>
+       <row>
+	<entry>setseed(float8)</entry>
+	<entry>int</entry>
+	<entry>set seed for subsequent random() calls</entry>
+	<entry>setseed(0.54823)</entry>
+       </row>
       </tbody>
      </tgroup>
     </table>

doc/src/sgml/ref/set.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.46 2000/07/14 15:27:14 thomas Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.47 2000/08/07 00:51:18 tgl Exp $
 Postgres documentation
 -->
 
@@ -194,9 +194,9 @@ SET TIME ZONE { '<replaceable class="PARAMETER">timezone</replaceable>' | LOCAL
 	  <listitem>
 	   <para>
 	    The value for the seed to be used by the
-	    <function>random</function> catalog function. Significant
+	    <function>random</function> function. Allowed
 	    values are floating point numbers between 0 and 1, which
-	    are then multiplied by RAND_MAX. This product will
+	    are then multiplied by 2^31-1. This product will
 	    silently overflow if a number outside the range is used.
 	   </para>
 

src/backend/optimizer/geqo/geqo_main.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: geqo_main.c,v 1.22 2000/06/28 03:31:45 tgl Exp $
+ * $Id: geqo_main.c,v 1.23 2000/08/07 00:51:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -106,9 +106,9 @@ geqo(Query *root)
 /* seed random number generator */
 /* XXX why is this done every time around? */
     if (Geqo_random_seed >= 0)
-        srandom(Geqo_random_seed);
+        srandom((unsigned int) Geqo_random_seed);
     else
-        srandom(time(NULL));
+        srandom((unsigned int) time(NULL));
 
 /* allocate genetic pool memory */
 	pool = alloc_pool(pool_size, number_of_rels);

src/backend/postmaster/postmaster.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.158 2000/07/28 02:13:26 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.159 2000/08/07 00:51:30 tgl Exp $
  *
  * NOTES
  *
@@ -1850,7 +1850,7 @@ DoBackend(Port *port)
 	 */
 	random_seed = 0;
 	gettimeofday(&now, &tz);
-	srandom(now.tv_usec);
+	srandom((unsigned int) now.tv_usec);
 
 	/* ----------------
 	 * Now, build the argv vector that will be given to PostgresMain.
@@ -2029,7 +2029,6 @@ RandomSalt(char *salt)
 static long
 PostmasterRandom(void)
 {
-
 	static bool initialized = false;
 
 	if (!initialized)

src/backend/utils/adt/float.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.67 2000/08/01 18:29:35 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.68 2000/08/07 00:51:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1315,7 +1315,7 @@ drandom(PG_FUNCTION_ARGS)
 	float8		result;
 
 	/* result 0.0-1.0 */
-	result = ((double) random()) / RAND_MAX;
+	result = ((double) random()) / ((double) MAX_RANDOM_VALUE);
 
 	PG_RETURN_FLOAT8(result);
 }
@@ -1328,7 +1328,7 @@ Datum
 setseed(PG_FUNCTION_ARGS)
 {
 	float8		seed = PG_GETARG_FLOAT8(0);
-	int			iseed = (seed * RAND_MAX);
+	int			iseed = (int) (seed * MAX_RANDOM_VALUE);
 
 	srandom((unsigned int) iseed);
 

src/backend/utils/adt/misc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.19 2000/06/05 07:28:52 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.20 2000/08/07 00:51:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,15 +45,18 @@ nonnullvalue(PG_FUNCTION_ARGS)
 
 /*
  * oidrand (oid o, int4 X)-
- *	  takes in an oid and a int4 X, and will return 'true'
- *	about 1/X of the time.
+ *	  Takes in an oid and a int4 X, and will return 'true' about 1/X of
+ *	  the time.  If X == 0, this will always return true.
  *	  Useful for doing random sampling or subsetting.
- *	if X == 0, this will always return true;
  *
  * Example use:
  *	   select * from TEMP where oidrand(TEMP.oid, 10)
  * will return about 1/10 of the tuples in TEMP
  *
+ * NOTE: the OID input is not used at all.  It is there just because of
+ * an old optimizer bug: a qual expression containing no variables was
+ * mistakenly assumed to be a constant.  Pretending to access the row's OID
+ * prevented the optimizer from treating the oidrand() result as constant.
  */
 
 static bool random_initialized = false;
@@ -61,7 +64,6 @@ static bool random_initialized = false;
 Datum
 oidrand(PG_FUNCTION_ARGS)
 {
-	/* XXX seems like we ought to be using the oid for something? */
 #ifdef NOT_USED
 	Oid			o = PG_GETARG_OID(0);
 #endif
@@ -96,7 +98,7 @@ oidsrand(PG_FUNCTION_ARGS)
 {
 	int32		X = PG_GETARG_INT32(0);
 
-	srand(X);
+	srandom((unsigned int) X);
 	random_initialized = true;
 	PG_RETURN_BOOL(true);
 }

src/include/config.h.in

@@ -8,7 +8,7 @@
  * or in config.h afterwards.  Of course, if you edit config.h, then your
  * changes will be overwritten the next time you run configure.
  *
- * $Id: config.h.in,v 1.128 2000/07/28 02:13:40 tgl Exp $
+ * $Id: config.h.in,v 1.129 2000/08/07 00:51:38 tgl Exp $
  */
 
 #ifndef CONFIG_H
@@ -484,6 +484,15 @@ extern long random(void);
 extern void srandom(unsigned int seed);
 #endif
 
+/* The random() function is expected to yield values 0 .. MAX_RANDOM_VALUE */
+/* Currently, all known implementations yield 0..2^31-1, so we just hardwire
+ * this constant.  We could do a configure test if it proves to be necessary.
+ * CAUTION: Think not to replace this with RAND_MAX.  RAND_MAX defines the
+ * maximum value of the older rand() function, which is often different from
+ * --- and considerably inferior to --- random().
+ */
+#define MAX_RANDOM_VALUE  (0x7FFFFFFF)
+
 /* Set to 1 if you have libz.a */
 #undef HAVE_LIBZ
 

src/include/optimizer/geqo_random.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: geqo_random.h,v 1.6 2000/01/26 05:58:20 momjian Exp $
+ * $Id: geqo_random.h,v 1.7 2000/08/07 00:51:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,13 +26,13 @@
 
 #include <math.h>
 
-#define GEQOMASK 2147483647
+/* geqo_rand returns a random float value between 0 and 1 inclusive */
 
-#define geqo_rand() ((double)random()/GEQOMASK)
+#define geqo_rand() (((double) random()) / ((double) MAX_RANDOM_VALUE))
 
-/* geqo_randint returns integer value
-   between lower and upper inclusive */
+/* geqo_randint returns integer value between lower and upper inclusive */
 
-#define geqo_randint(upper,lower) ( (int) floor( geqo_rand()*((upper-lower)+0.999999) )  +	lower )
+#define geqo_randint(upper,lower) \
+	( (int) floor( geqo_rand()*(((upper)-(lower))+0.999999) ) + (lower) )
 
 #endif	 /* GEQO_RANDOM_H */