Massimo patch - Mailing list pgsql-hackers

Here is a description of the major patch from Massimo.  The irony of
this is that the mail message is dated January 27th, when application of
the patch would have been easier because we were not in beta testing.  I
have a copy of the patch here on my machine.

What do people want to do with this?  I have reviewed the patch, and it
looks good, but it may take work to merge in because it is against
6.2.1p7, not 6.3 beta, and it does introduce quite a bit of new code.

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Forwarded message:
> From owner-pgsql-patches@hub.org Sat Feb 14 09:31:23 1998
> From: Massimo Dal Zotto <dz@cs.unitn.it>
> Message-Id: <199802132233.XAA01003@nikita.wizard.it>
> Subject: [PATCHES] patches for 6.2.1p6
> To: pgsql-patches@postgreSQL.org (Pgsql Patches)
> Date: Tue, 27 Jan 1998 22:46:38 +0100 (MET)
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> Hi hackers,
>
> I have old patches for version 6.2.1p6 which fix some problems and add
> new features. Here is a short description of each patch file:
>
>
> assert.patch
>
>     adds a switch to turn on/off the assert checking if enabled at compile
>     time. You can now compile postgres with assert checking and disable it
>     at runtime in a production environment.
>
> async-unlisten.patch
>
>     declares Async_Unlisten() external so that it can be called by user
>     modules.
>
> exec-limit.patch
>
>     removes the #ifdef NOT_USED around ExecutorLimit(). It is used.
>
> exitpg.patch
>
>     limits recursive calls to exitpg() preventing an infinite loop
>     if an error is found inside exitpg.
>
> libpgtcl-listen.patch
>
>     Just a change from upper to lowercase of an sql command in libpgtcl,
>     totally harmless.
>
> new-locks.patch
>
>     After long studying and many debugging sessions I have finally
>     understood how the low level locks work.
>     I have completely rewritten lock.c cleaning up the code and adding
>     better assert checking. I have also added some fields to the lock
>     and xid tags for better support of user locks. This patch includes
>     also a patch submitted by Bruce Momjian which changes the handling
>     of lock priorities. It can however be disabled if an option is set
>     in pg_options, see tprintf.patch (Bruce patch works by building
>     the queue in reverse priority order, my old patch kept the queue in
>     decreasing order and traversed it from the other side).
>
> pg-flush.patch
>
>     removes an unnecessary flush in libpq reducing network traffic and
>     increasing performance.
>
> relname.patch
>
>     an utility which returns the relname corresponding to a given oid.
>     Useful for debug messages (see vacum.patch).
>
> sequence.patch
>
>     added a setval() function which enables othe owner of a sequence
>     to set its value without need to delete and recreate it.
>
> sinval.patch
>
>     fixes a problem in SI cache which causes table overflow if some
>     backend is idle for a long time while other backends keep adding
>     entries.
>     It uses the new signal handling implemented in tprintf.patch.
>     I have also increacasesed the max number of backends from 32 to 64 and
>     the table size from 1000 to 5000.
>
> spin-lock.patch
>
>     I'm not sure if this is really useful, but it seems stupid to have
>     a backend wasting cpu cycles in a busy loop while the process which
>     should release the lock is waiting for the cpu. So I added a call
>     to process_yield() if the spin lock can't obtained.
>     This has been implemented and tested only on Linux. I don't know if
>     other OS have process_yield(). If someone can check please do it.
>
> tprintf.patch
>
>     adds functions and macros which implement a conditional trace package
>     with the ability to change flags and numeric options of running
>     backends at runtime.
>     Options/flags can be specified in the command line and/or read from
>     the file pg_options in the data directory.
>     Running backends can be forced to update their options from this file
>     by sending them a SIGHUP signal (this is the convention used by most
>     unix daemons so I changed the meaning of SIGHUP).
>     Options can be debugging flags used by the trace package or any other
>     numeric    value used by the backend, for example the deadlock_timeout.
>     Having flags and options specified at runtime and changed while the
>     backends are running can greatly simplify the debugging and tuning
>     of the database. New options can be defined in utils/misc/trace.c and
>     include/utils/trace.h.  As an example of the usage of this package
>     see lock.c and proc.c which make use of new runtime options.
>
>     Old files using int flags or variables can be easily changed to
>     use the new package by substituting the old variable with a #define
>     like in the following example:
>
>       /* int my_flag = 0; */
>       #include "trace.h"
>        #define my_flag pg_options[OPT_MYFLAG]
>
>     I have done it in postgres.c and some other files and now I can turn
>     on/off any single debug flag on the fly with a simple shell script.
>     I have removed the IpcConfigTip() from ipc.c, it should better be
>     described in the postgres manual instead of being printed on stderr.
>
>     This patch provides also a new format of debugging messages which
>     are always in a single line with a timestamp and the backend pid:
>
>       #timestamp          #pid    #message
>       980127.17:52:14.173 [29271] StartTransactionCommand
>       980127.17:52:14.174 [29271] ProcessUtility:  drop table t;
>       980127.17:52:14.186 [29271] SIIncNumEntries: table is 70% full
>       980127.17:52:14.186 [29286] Async_NotifyHandler
>       980127.17:52:14.186 [29286] Waking up sleeping backend process
>       980127.19:52:14.292 [29286] Async_NotifyFrontEnd
>       980127.19:52:14.413 [29286] Async_NotifyFrontEnd done
>       980127.19:52:14.466 [29286] Async_NotifyHandler done
>
>     This improves the readability of the log and allows one to understand
>     exactly which backend is doing what and at which time. It also makes
>     easier to write simple awk or perl scripts which monitor the log to
>     detect database errors or problem, or to compute transaction times.
>
>     The patch changes also the meaning of signals used by postgres, as
>     described by the following table:
>
>             postmaster                backend
>
>     SIGHUP      kill(*,sighup)            read_pg_options
>     SIGINT        kill(*,sigint), die            die
>     SIGCHLD        reaper                -
>     SIGTTIN        ignored                -
>     SIGTTOU        ignored                -
>     SIGQUIT        die                    handle_warn
>     SIGTERM        kill(*,sigterm), kill(*,9), die    die
>     SIGCONT        dumpstatus                -
>     SIGPIPE        ignored                die
>     SIGFPE        -                    FloatExceptionHandler
>     SIGTSTP        -                    ignored (alive test)
>     SIGUSR1        kill(*,sigusr1), die        quickdie
>     SIGUSR2        kill(*,sigusr2)            Async_NotifyHandler
>                             (also SI buffer flush)
>
>     The main changes to the old implementation are SIGQUIT instead of
>     SIGHUP to handle warns, SIGHUP to reread pg_options and redirection
>     to all backends of SIGHUP, SIGINT, SIGTERM, SIGUSR1 and SIGUSR2.
>     In this way some of the signals sent to the postmaster can be sent
>     automatically to all the backends. To shut down postgres one needs
>     only to send a SIGTERM to postmaster and it will stop automatically
>     all the backends. This new signal handling mechanism is also used
>     to prevent SI cache table overflows: when a backend detects the SI
>     table full at 70% it simply sends a signal to the postmaster which
>     will wake up all idle backends and make them flush the cache.
>
> vacuum.patch
>
>     adds a debug message to vacuum that prints the name of a table or
>     index *before* vacuuming it, if the verbose keyword is set.
>     This is useful to know which table is causing troubles if a
>     vacuum all crashes. Currently table information is printed only
>     at the end of each vacuum operation and is never printed if the
>     vacuum crashes.
>
> --
> Massimo Dal Zotto


--
Bruce Momjian
maillist@candle.pha.pa.us


--
Bruce Momjian
maillist@candle.pha.pa.us