Update faq's.

acad203c · Bruce Momjian · bff5dce9 · acad203c · bff5dce9 · acad203c
Commit acad203c authored Jun 02, 2000 by Bruce Momjian
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doc/FAQ_NT doc/FAQ_NT +0 -0

doc/README.BSDI doc/README.BSDI +0 -31

doc/TODO.detail/replication doc/TODO.detail/replication +101 -4

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--- a/doc/README.NT
+++ b/doc/README.NT
--- a/doc/README.BSDI
+++ b/doc/README.BSDI
-This outlines how to increase the number of shared memory buffers
-supported by BSD/OS.  By default, only 4MB of shared memory is supported
-by BSDI.
-
-Bruce Momjian (pgman@candle.pha.pa.us)
-
---------------------------------------------------------------------------
-
-First, increase SHMMAXPGS by 1024 for every additional 4MB of shared
-memory:
-
-/sys/sys/shm.h:69:#define       SHMMAXPGS       1024    /* max hardware pages...
-
-The default setting of 1024 is for a maximum of 4MB of shared memory.
-
-Second, use bpatch to find the sysptsize value for the current kernel. 
-This is computed dynamically at bootup.
-
-	$ bpatch -r sysptsize
-	0x9 = 9
-
-Next, change SYSPTSIZE to a hard-coded value.  Use the bpatch value,
-plus add 1 for every additional 4MB of shared memory you desire.
-
-/sys/i386/i386/i386_param.c:28:#define  SYSPTSIZE 0        /* dynamically...
-
-sysptsize can not be changed by sysctl on the fly.
-
-This should clearly be easier to do on BSDI.  I will add a BSDI FAQ for
-PostgreSQL to cover this.  One downside is that shared memory is not
-pageable.  It is locked in RAM.
--- a/doc/TODO.detail/replication
+++ b/doc/TODO.detail/replication
@@ -43,7 +43,7 @@ From owner-pgsql-hackers@hub.org Fri Dec 24 10:01:18 1999
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@@ -905,3 +905,100 @@ Sys Admin

 ************

+From owner-pgsql-hackers@hub.org Thu Dec 30 08:01:09 1999
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+From: Duane Currie <dcurrie@sandman.acadiau.ca>
+Message-Id: <199912301030.GAA18698@sandman.acadiau.ca>
+Subject: Re: [HACKERS] database replication
+In-Reply-To: <OFD38C9424.B391F434-ON85256851.0054F41A@black-oak.COM> from "DWalker@black-oak.com" at "Dec 24, 99 10:27:59 am"
+To: DWalker@black-oak.com
+Date: Thu, 30 Dec 1999 10:30:58 +0000 (AST)
+Cc: pgsql-hackers@postgresql.org
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+Status: OR
+
+Hi Guys,
+
+Now for one of my REALLY rare posts.
+Having done a little bit of distributed data systems, I figured I'd
+pitch in a couple cents worth.
+
+> 2) The replication system will need to add at least one field to each 
+>    table in each database that needs to be re plicated. &nbsp;This 
+>    field will be a date/time stamp which identifies the &quot; last 
+>    update&quot; of the record. &nbsp;This field will be called PGR_TIME 
+>    for la ck of a better name. &nbsp;Because this field will be used 
+>    from within programs and triggers it can be longer so as to not 
+>    mistake it for a user field.
+
+I just started reading this thread, but I figured I'd throw in a couple
+suggestions for distributed data control  (a few idioms I've had to
+deal with b4):
+	- Never use time (not reliable from system to system).  Use
+	  a version number of some sort that can stay consistent across
+	  all replicas
+
+	  This way, if a system's time is or goes out of wack, it doesn't
+	  cause your database to disintegrate, and it's easier to track
+	  conflicts (see below.  If using time, the algorithm gets
+	  nightmarish)
+
+	- On an insert, set to version 1
+
+	- On an update, version++
+
+	- On a delete, mark deleted, and add a delete stub somewhere for the
+	  replicator process to deal with in sync'ing the databases.
+
+	- If two records have the same version but different data, there's
+	  a conflict.  A few choices:
+	  	1.  Pick one as the correct one (yuck!! invisible data loss)
+		2.  Store both copies, pick one as current, and alert 
+		    database owner of the conflict, so they can deal with
+		    it "manually."
+		3.  If possible, some conflicts can be merged.  If a disjoint
+		    set of fields were changed in each instance, these changes
+		    may both be applied and the record merged.  (Problem:
+		    takes a lot more space.  Requires a version number for
+		    every field, or persistent storage of some old records.
+		    However, this might help the "which fields changed" issue
+		    you were talking about in #6)
+
+	- A unique id across all systems should exist (or something that
+	  effectively simulates a unique id.  Maybe a composition of the
+	  originating oid (from the insert) and the originating database
+	  (oid of the database's record?) might do it.  Store this as
+	  an extra field in every record.  
+	  
+	  (Two extra fieldss so far: 'unique id' and 'version')
+
+I do like your approach:  triggers and a separate process. (Maintainable!! :)
+
+Anyway, just figured I'd throw in a few suggestions,
+Duane
+
+************
+