I have a client website that has a Postgres backend which I consider as my remote database. I use FDWs to connect from my local database to the remote DB.
So what I have is :
Remote DB ->remote Schema -> Has a table called remote_work_packages
On my database, this would after I create an FDW server -
Local DB -> Local schema -> foreign table foreign_work_packages
Now as I said the client website connects to the Remote DB , and whenever there is an INSERT, UPDATE or DELETE into remote_work_packages, then I want some functions to be triggered on my local schema.
Please note , I do not have access to create a trigger on the Remote table.
Is there a way this can be achieved. I know since release 9.4, that it is possible to create triggers on foreign tables. But there is no way I could find out how to track activity on the remote itself. Is there a way to track staying on the local DB. Please advise.
Related
I created an RDS Postgres instance. I'm new to RDS.
db host:
demodb.xxxuxxvxxxxx.us-east-2.rds.amazonaws.com
db identifier:
demodb
Every tutorial says to connect with this URL:
jdbc:postgresql://demodb.xxxuxxvxxxxx.us-east-2.rds.amazonaws.com:5432/demodb
but every time I do I get this error-
FATAl: database "demodb" does not exist.
I am able to connect using this:
jdbc:postgresql://demodb.xxxuxxvxxxxx.us-east-2.rds.amazonaws.com:5432/postgres
Now, while I was excited to connect after I used SQL workbench to create tables and insert data into those tables, a few hours later all my tables and data were deleted/wiped/dropped. Why would this happen? and How can I prevent it from happening in the future?
FATAl: database "demodb" does not exist.
demodb is db instance identifier. It is NOT the name of your database inside of PostgreSQL.
By default RDS PostgreSQL does not create a database for you. It seems to me that you haven't created an actual database when you setup your RDS PostgreSQL.
To create a database at RDS creation there is an option called Initial database name where you should specify the name of the database you want. Otherwise, no database is created, which is a default behavior:
I'm migrating an Oracle database to Postgres 11.5 version on AWS where there are some functions that will capture logs in a table with Oracle pragma autonomous transaction since the application will rollback the database in case of exceptions.
Since the only option i could find for doing this in postgres is using dblink extension(pg_background extension is not supported in AWS), I created a dblink where source and target databases are same. I'll commit the inserts using dblink from a function that is called inside exception blocks.
How can I hide the password from the code without storing it in server side? And if the database instance password is changed how can I handle it? Because i would need to change the password for dblink everytime when it is reset.
Any ways to get/pass the instance password dynamically inside the code?
hoping for some help as I am very new to postgresql admin!
I have 2 servers added to pgadmin, server 1 is a hosted db on Heroku the other is local to the server
I want to add the Heroku db as foreign tables to the local db
can I link these 2 servers? as so far I have failed
I have the fdw extension setup locally, and I am able to use it across three local dbs ok, do I need the extension also setup on the Heroku db?
I have setup the fdw server as
host localhost --- should this be the Heroku host path? or is this ok since I have added - --server local? I get fsrvoption error if I add actual host path
dbname dbname
port 5432
and then setup user
user username
password password
any help appreciated!
mal
You don't have to set up anything on the remote server to access it via foreign data wrapper; the foreign data wrapper will access the remote database as a regular database client.
Once you hace set up postgres_fdw correctly, you can use it to access tables on the remote server just as if they were local tables. A foreign table is a bit like a view in some respects.
Maybe it helps to understand the objects involved:
The foreign data wrapper encapsulates the code to access the remote data source (PostgreSQL client).
The foreign server wraps the connect string for the remote database.
The user mapping contains the credentials for a user to access the foreign server.
The foreign table describes a table on the remote server.
You can use the command IMPORT FOREIGN SCHEMA to automatically define foreign tables for all (or part) of the tables in a schema on the remote server.
Once the foreign tables are defined correctly, you can use them in SQL statements just like local tables, but you will actually read and write data on the remote server.
After some debugging, the problem turned out to be this:
Creating the foreign server using pgAdmin caused a strange error with fsrvoption (running CREATE SERVER via the query tool worked).
Creating the foreign server with localhost rather than the correct server address unsurprisingly gave the error that the database doesn't exist.
I want to shut down one database in a db2 instance with multiple dbs.
I don't want to deactivate the db as it will reconnect when I try to connect. It should be completely shut down so I get a connection error when trying to connect to the db.
This is not a programming question so it can be viewed as off topic.
There are different techniques, each has advantages/disadvantages.
You can quiesce the database and later unquiesce it.
or you can revoke connect rights, and later grant them, but this depends on how well your role separation is done.
or you force off existing applications and then connect in exclusive mode as the instance owner (provided that your applications NEVER connect with instance-owner credentials).
One trick you could use is to temporarily recatalog the database you want to deactivate under a different name; this will prevent applications from connecting to it using the original name, regardless of the authority they use.
First, determine the database path by looking at its catalog entry:
db2 list db directory
The value of the "Local database directory" property is what you need.
Now you can recatalog the database:
db2 uncatalog db orig_db
db2 catalog db orig_db as foobar on <path>
where <path> is the local database directory determined previously.
Once you force all applications currently connected to the database in question you will be able to deactivate the database:
db2 list applications
db2 "force application (<app id 1>, <app id 2>,...)
db2 deactivate db foobar
Later on you can restore the catalog entry to its original value:
db2 uncatalog db foobar
db2 catalog db orig_db on <path>
I need to update a dababase from an other database... For this I need to search in existing database if the records exists, if not add... One of the database is locally stored in my computer, and the other one is on heroku... But I don't know how to access heroku database from my computer to create the inserts and to query if I have to insert or not...
Any idea how can I do something like this?
You can connect via any DB tool, e.g. Oracle SQL Developer with Postgres JDBC connector, to a Heroku Postgres DB. The parameters are listed in the GUI of postgres.heroku.com for your instance.