cross-db queries (was Are we losing momentum?)
От | Rob Butler |
---|---|
Тема | cross-db queries (was Are we losing momentum?) |
Дата | |
Msg-id | 20030416141028.FQXP19613.out001.verizon.net@localhost обсуждение исходный текст |
Ответы |
Re: cross-db queries (was Are we losing momentum?)
Re: cross-db queries (was Are we losing momentum?) |
Список | pgsql-hackers |
Hello all, I took a look at the docs for Postgres views & rules. I also took a look at dblink. I think there is a very plausible wayto get "cross-db" queries in postgres 1) Support for 2PC added. 2) Modify dblink (if it needs modification) to operate within the current transaction created by the user (if a user transactionwas created). If no transaction exists (was created by the user) but local and remote tables / views are updatedby the SQL statement then postgres creates a transaction to operate within. That way both local and remote tables/ views are updated as a single atomic unit. (Which is what the user would expect to happen.) 3) Add a new "keyword" to Postgres. Choose any of the following:a) create remoteview ... (all necessary information aboutremote machine and query)b) create view [local | remote] .... (necessary info)c) create view remote-server.schema.table(necessary info) Postgres could then create a read only view of the remote table using dblink. A user could add additional rules to allowfor the view to be updateable just as they do now. Also, as an additional feature for postgres we could simplify creating updateable views for "simple" queries. I.E. create view [updateable] (necessary info / simple select statement). If a simple select statement is used, and updateableis specified, postgres creates all the rules to implement an updateable view. This is not necessary of course,it would just simply make the common (?) case of creating an updateable view from a simple query. The support for 2PC and modification of dblink is only necessary IF we want to be able to update tables on the remote serverAND have guarantees that the updates on both ends succeeds / fails as a unit. If we want read only access to remotetables, then one could create a view (using a custom on select rule) and use dblink right now! What do you think? Later Rob
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