Thread: Re: [HACKERS] Patch to warn about oid/xid wraparound

> Bruce Momjian writes:
>
> > Here is an new patch that updates the percentage display when it is run,
> > rather than just displaying 75%.  I had to do the computation using
> > floats to prevent overflow.


Sorry, I should have been doing this on patches list.

> You could use ldiv().

It is overflow that I am worried about:  curr/max * 100
I don't see how ldiv helps here.

>
> Also, UINT_MAX (for transaction id) and OID_MAX (for Oid) might be
> preferred over ~0.

Done.  Patch attached.

>
> Btw., there is a typo here:
>
> >     GetCurrentTransactionId() - (float)(~(TransactionId)0) * 100);

Thanks.  Fixed.  I hadn't gotten to testing the transaction code yet,
just the oid test.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
Index: src/backend/commands/vacuum.c
===================================================================
RCS file: /home/projects/pgsql/cvsroot/pgsql/src/backend/commands/vacuum.c,v
retrieving revision 1.195
diff -c -r1.195 vacuum.c
*** src/backend/commands/vacuum.c    2001/05/25 15:45:32    1.195
--- src/backend/commands/vacuum.c    2001/06/13 21:01:37
***************
*** 17,22 ****
--- 17,23 ----
  #include <fcntl.h>
  #include <unistd.h>
  #include <time.h>
+ #include <limits.h>
  #include <sys/time.h>
  #include <sys/types.h>
  #include <sys/file.h>
***************
*** 159,166 ****
  static bool enough_space(VacPage vacpage, Size len);
  static void init_rusage(VacRUsage *ru0);
  static char *show_rusage(VacRUsage *ru0);

-
  /*
   * Primary entry point for VACUUM and ANALYZE commands.
   */
--- 160,167 ----
  static bool enough_space(VacPage vacpage, Size len);
  static void init_rusage(VacRUsage *ru0);
  static char *show_rusage(VacRUsage *ru0);
+ static void check_limits(void);

  /*
   * Primary entry point for VACUUM and ANALYZE commands.
   */
***************
*** 236,241 ****
--- 237,243 ----

      /* clean up */
      vacuum_shutdown();
+     check_limits();
  }

  /*
***************
*** 2645,2648 ****
--- 2647,2674 ----
               (int) (ru1.tv.tv_usec - ru0->tv.tv_usec) / 10000);

      return result;
+ }
+
+ /*
+  *    check if we are near OID or XID wraparound
+  */
+ static void check_limits(void)
+ {
+     Oid nextOid;
+
+     /* If we are 75% to the limit, warn the user */
+     if (GetCurrentTransactionId() > UINT_MAX - UINT_MAX / 4)
+         elog(NOTICE,"You are %.0f%% toward the limit for transaction ids.\n"
+             "\t Dumping your databases, running initdb, and reloading will reset\n"
+             "\t the transaction id counter.",
+             GetCurrentTransactionId() / (float)UINT_MAX * 100);
+
+     /* If we are 75% to the limit, warn the user */
+     GetNewObjectId(&nextOid);
+     if (nextOid > OID_MAX - OID_MAX / 4)
+         elog(NOTICE,"You are %.0f%% toward the limit for object ids.\n"
+             "\t If you are not using object ids as primary keys, dumping your\n"
+             "\t databases, running initdb, and reloading will reset\n"
+             "\t the oid counter.",
+             (float)nextOid / OID_MAX * 100);
  }