Re: replication - Mailing list pgsql-general
From | Michael Fork |
---|---|
Subject | Re: replication |
Date | |
Msg-id | Pine.BSI.4.21.0009211618550.22952-100000@glass.toledolink.com Whole thread Raw |
In response to | Re: replication ("Adam Lang" <aalang@rutgersinsurance.com>) |
List | pgsql-general |
You can continue to use the same Access app, just link the tables through ODBC to the postgres sever (save you from reinventing the wheel) Michael Fork - CCNA - MCP - A+ Network Support - Toledo Internet Access - Toledo Ohio On Thu, 21 Sep 2000, Adam Lang wrote: > That is not the situation though. The reason I want to have to databases is > to have one at the site that actual production is going to be worked on, and > then a replicated database at a remote location where the webserver is. > > As for the interface, they use Access forms, which I'll just write a new VB > app using ODBC to replace. > > Adam Lang > Systems Engineer > Rutgers Casualty Insurance Company > ----- Original Message ----- > From: "Len Morgan" <len-morgan@crcom.net> > To: "Adam Lang" <aalang@rutgersinsurance.com> > Sent: Thursday, September 21, 2000 2:52 PM > Subject: Re: [GENERAL] replication > > > > There is another approach that I have used: Convert all of the tables in > the > > current Access system to Postgres tables and then use ODBC links in the > > current program instead of internal tables. This way you only have one > > database, no need to replicate and it's much more "live". If you give the > > tables in Postgres the same names they have in access, you won't have to > > change any of the forms/queries/reports, etc. > > > > Just my 2 cent's worth. > > > > Len Morgan > > > > > > -----Original Message----- > > From: Adam Lang <aalang@rutgersinsurance.com> > > Cc: pgsql-general@postgresql.org <pgsql-general@postgresql.org> > > Date: Thursday, September 21, 2000 1:43 PM > > Subject: Re: [GENERAL] replication > > > > > > >Well, this is the situation. A client has a database application > currently > > >running on Access (which multiple people share over a network). They > want > > >to make data accessible via the internet. So, what I was thinking was > keep > > >the production database at their location, convert it to postgresql, and > > >make a replacement application for them to do their work. Then, host > their > > >webserver remotely and have another database there. The main location has > a > > >DSL connection. I figured then that once a day, three times a day > > >(whatever) the main database synchs up the remote one. (The remote > database > > >will only be used by PHP to extract data, no modifications). > > > > > >The point of this is that no matter what the main location will always be > > >able to get their work done while still being able to host their website > > >offsite. > > > > > >If there was only a single database at either end, the whole setup is > > >susceptible to a telecomm link going down and cutting something off. > > > > > >Adam Lang > > >Systems Engineer > > >Rutgers Casualty Insurance Company > > >----- Original Message ----- > > >From: "Rob Hutton" <rhutton@istmanagement.com> > > >To: "Adam Lang" <aalang@rutgersinsurance.com>; "Stephan Szabo" > > ><sszabo@megazone23.bigpanda.com>; "Daryl Chance" <dchance@valuedata.net> > > >Cc: <pgsql-general@postgresql.org> > > >Sent: Thursday, September 21, 2000 3:19 PM > > >Subject: RE: [GENERAL] replication > > > > > > > > >> I asked a similar question earlier in the week and got no response. > If > > >> there is transaction logging, then it is fairly easy to implement > > syncing, > > >> even real time, the only question is to play back the log every x > amount > > >of > > >> time on the remote db. The tricky part is two fold. > > >> > > >> First, you have to maintain a table of all of the remote DBs that are > > >> syncing and the last two send and receive timestamps, and whether the > > last > > >> was successful. If not, then at the next sync time, you have to replay > > >the > > >> logs again back to the previous time that was successful. Then you > have > > >to > > >> have a process that cleans up all of the transactions that are previous > > to > > >> the most recent successful sync. > > >> > > >> The second part is collision resolution. That is, what happens when > an > > >> edit is made to a DB at both ends in between the sync period. Most of > > the > > >> time the later timestamp wins, but what happens if that effects > business > > >> rules, range limitations, etc. For instance, if b must be between a > and > > >c, > > >> and b and c are lowered on one end, and on the other b is raised above > > the > > >> new setting for c, how is this resolved. You end up writing a rules > > >engine > > >> for this stuff... > > >> > > >> Rob > > >> > > >> > -----Original Message----- > > >> > From: pgsql-general-owner@hub.org > > [mailto:pgsql-general-owner@hub.org]On > > >> > Behalf Of Adam Lang > > >> > Sent: Thursday, September 21, 2000 12:42 PM > > >> > To: Stephan Szabo; Daryl Chance > > >> > Cc: pgsql-general@postgresql.org > > >> > Subject: Re: [GENERAL] replication > > >> > > > >> > > > >> > Well, if I end up needing to do something with it, I'll get back > > >> > to the list > > >> > on ideas/solutions I encountered and see about potential pitfalls. > > >> > > > >> > Adam Lang > > >> > Systems Engineer > > >> > Rutgers Casualty Insurance Company > > >> > ----- Original Message ----- > > >> > From: "Stephan Szabo" <sszabo@megazone23.bigpanda.com> > > >> > To: "Daryl Chance" <dchance@valuedata.net> > > >> > Cc: <pgsql-general@postgresql.org> > > >> > Sent: Thursday, September 21, 2000 12:59 PM > > >> > Subject: Re: [GENERAL] replication > > >> > > > >> > > > >> > > On Thu, 21 Sep 2000, Daryl Chance wrote: > > >> > > > > >> > > > Could this possibly be done using triggers? I'm new to > > >> > > > postgres, but I know on a project I was doing using oracle > > >> > > > the dba could setup triggers to run on the OnInsert() (not > > >> > > > sure what it's actually called in oracle...). Do maybe > > >> > > > on the "OnInsert" of table foo you could do: > > >> > > > > > >> > > > Insert into foo@remotesite1 .... > > >> > > > > > >> > > > Is this possible in postgres? I'm looking at using postgres > > >> > > > for the next version of my SW and if replication isn't in, > > >> > > > I'm gonna need something like this :). > > >> > > > > >> > > You could probably write a C trigger that would propogate > > >> > > changes, except that there are still problems. What do you > > >> > > do when you roll back the transaction? Currently, there > > >> > > aren't triggers for transaction start and end. Triggers that > > >> > > do stuff outside the database right now are a bad idea unless > > >> > > you have some other mechanism to determine whether something > > >> > > was really supposed to be done. It could be done, but isn't > > >> > > trivial. > > >> > > > >> > > > > > > > >
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