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Overview
Comment:Change the way that the random() SQL function prevents the maximum negative integer so that it is testable. (CVS 6436)
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SHA1: 995f2b9b1031fadc85e179701536b9dd4153654b
User & Date: drh 2009-04-02 14:05:22.000
Context
2009-04-02
16:59
Disable the query flattening optimization when the subquery is a compound query with an ORDER BY clause. Ticket #3773 shows why that combination does not work. (CVS 6437) (check-in: 23f90d5073 user: drh tags: trunk)
14:05
Change the way that the random() SQL function prevents the maximum negative integer so that it is testable. (CVS 6436) (check-in: 995f2b9b10 user: drh tags: trunk)
13:36
Use ALWAYS and NEVER macros on unchangeable conditions within func.c. (CVS 6435) (check-in: eb65e64e7e user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/func.c.
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** This file contains the C functions that implement various SQL
** functions of SQLite.  
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.229 2009/04/02 13:36:37 drh Exp $
*/
#include "sqliteInt.h"
#include <stdlib.h>
#include <assert.h>
#include "vdbeInt.h"

/*








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** This file contains the C functions that implement various SQL
** functions of SQLite.  
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.230 2009/04/02 14:05:22 drh Exp $
*/
#include "sqliteInt.h"
#include <stdlib.h>
#include <assert.h>
#include "vdbeInt.h"

/*
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  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **NotUsed2
){
  sqlite_int64 r;
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  sqlite3_randomness(sizeof(r), &r);

  if( (r<<1)==0 ) r = 0;  /* Prevent 0x8000.... as the result so that we */
                          /* can always do abs() of the result */








  sqlite3_result_int64(context, r);
}

/*
** Implementation of randomblob(N).  Return a random blob
** that is N bytes long.
*/








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  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **NotUsed2
){
  sqlite_int64 r;
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  sqlite3_randomness(sizeof(r), &r);
  if( r<0 ){
    /* We need to prevent a random number of 0x8000000000000000 
    ** (or -9223372036854775808) since when you do abs() of that
    ** number of you get the same value back again.  To do this
    ** in a way that is testable, mask the sign bit off of negative
    ** values, resulting in a positive value.  Then take the 
    ** 2s complement of that positive value.  The end result can
    ** therefore be no less than -9223372036854775807.
    */
    r = -(r ^ (((sqlite3_int64)1)<<63));
  }
  sqlite3_result_int64(context, r);
}

/*
** Implementation of randomblob(N).  Return a random blob
** that is N bytes long.
*/
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