I am migrating Oracle database to Postgres Aurora. There is one Oracle PL/SQL block which checks if the database is in read write open mode. Below is the query like:
Select open_mode into v_open_mode from v$database;
if v_open_mode = 'READ WRITE' then
-- perform some steps.
I want to know if we have any equivalent query in Postgres. Or even if I can know the postgres node is WRITE mode.
I am also open to get anything which is native to Aurora which show if the node is reader or writer.
I am not sure what the Oracle thing does, but I assume the closest thing would be to check if Postgres is in recovery mode using pg_is_in_recovery()
So something like:
if not pg_is_in_recovery() then
-- do some steps
end if;
That is from "stock" Postgres, I don't know if Amazon Aurora does anything different or provides other functions.
Related
I am trying to use IBM APP Connect Enterprise to connect to a Postgresql Datasource and execute Database complex queries (Complex SELECT, INSERT, UPDATE Statements)
All I can find is the loopback node which is using limited (select, insert and update) statements.
Is there any option that I can include an esql having a PASSTHRU function as the one used with ODBC (Oracle datasources)?
You could use App Connect for the interactions with Postgresql: https://www.ibm.com/docs/en/app-connect/containers_cd?topic=examples-connecting-app-connect-postgresql
You should be able to call your App Connecto flow using a Callable Flow (via the Switch Server): https://www.ibm.com/docs/en/app-connect/12.0?topic=pecf-preparing-environment-split-processing-between-app-connect-enterprise-app-connect-cloud
You should be able to add a postgresql database as an ODBC database through the UnixODBC layer (i.e. add an entry to the odbcinst.ini file), it's not directly supported though, so if you find an issue you'd need to reproduce with a supported database.
I haven't tried it myself yet, I should hopefully have time in the not too distant future.
Searching the internet for "unixodbc postgres odbcinst.ini" gave some good results, which is where I'd start.
There is a postgres 9 with database AAA that is used by my application. I use pgadmin 4 to manage it manually.
I would like to check what queries are executed by this application on database AAA in real time.
I did a research about monitoring options in pgadmin in vain.
Is is possible to do that by using just pgadmin4? Or is it necessary to use another tool (if yes - what is he name of this tool)?
When I point pgAdmin4 at a 9.6 server, I see a dashboard by default which shows every session (done by querying pg_stat_activity). You can then drill down in a session to see the query. If a query last for less time than the monitoring interval, then you might not see it if the sample is taken at the wrong time.
If that isn't acceptable, then you should probably use a logging solution (like log_statemnt='all') or maybe the pg_stat_statements extension, rather than sample-based monitoring. pg_stat_statements doesn't integrate with the dashboard in pgAdmin4, but you can select from the view from an SQL window just like you can run any other SQL. I don't believe pgAdmin4 offers a built-in way to monitor the database server's log files, the way pgAdmin3 did.
I know the basic syntax of queries but otherwise I'm a beginner with SQL.
I have an SQL file (.sql) and I downloaded a couple programs (pgadmin and sql workbench).
I have no idea how to get from where I am now to actually writing queries and finding information. How do I set up so I can actually import my SQL file and start writing queries?
pgAdmin is the default GUI for PostgreSQL.
SQL Workbench is a free, DBMS-independent, cross-platform SQL query tool.
Either way, you need to connect to a database to actually run queries. The DBMS can either run on your local machine or you can connect to a remote server - where you need access privileges of course.
I am beginner to PostgreSQL.
I want to connect to another database from the query editor of Postgres - like the USE command of MySQL or MS SQL Server.
I found \c databasename by searching the Internet, but its runs only on psql. When I try it from the PostgreSQL query editor I get a syntax error.
I have to change the database by pgscripting. Does anyone know how to do it?
When you get a connection to PostgreSQL it is always to a particular database. To access a different database, you must get a new connection.
Using \c in psql closes the old connection and acquires a new one, using the specified database and/or credentials. You get a whole new back-end process and everything.
You must specify the database to use on connect; if you want to use psql for your script, you can use "\c name_database"
user_name=# CREATE DATABASE testdatabase;
user_name=# \c testdatabase
At this point you might see the following output
You are now connected to database "testdatabase" as user "user_name".
testdatabase=#
Notice how the prompt changes. Cheers, have just been hustling looking for this too, too little information on postgreSQL compared to MySQL and the rest in my view.
In pgAdmin you can also use
SET search_path TO your_db_name;
The basic problem while migrating from MySQL I faced was, I thought of the term database to be same in PostgreSQL also, but it is not. So if we are going to switch the database from our application or pgAdmin, the result would not be as expected.
As in my case, we have separate schemas (Considering PostgreSQL terminology here.) for each customer and separate admin schema. So in application, I have to switch between schemas.
For this, we can use the SET search_path command. This does switch the current schema to the specified schema name for the current session.
example:
SET search_path = different_schema_name;
This changes the current_schema to the specified schema for the session. To change it permanently, we have to make changes in postgresql.conf file.
Use this commad when first connect to psql
=# psql <databaseName> <usernamePostgresql>
set search_path = 'schema name here'
while connecting to the postgres, you have to opt for default database to connect. If you have nothing, you can use 'postgres' as default.
You can use dbeaver to connect to postgres. UI is good
PgAdmin 4, GUI Tool: Switching between databases
In the PgAdmin Browser on the left hand side, right click on the database you are willing to switch to.
Select a QueryTool from the drop down menu (or any other option that you need, I will stick with the QueryTool for now).
You will see the QueryTool in the PgAdmin window, and on top you will see the active database and the role name.
Now you can write queries against the chosen database.
You can open multiple QueryTools for multiple database, and work with them as you do with your graphical text editor.
In order to be sure that you are querying the proper database, issue the following query:
SELECT session_user, current_database();
Currently, I have an application that uses Firebird in embedded mode to connect to a relatively simple database stored as a file on my hard drive. I want to switch to using PostgreSQL to do the same thing (Yes, I know it's overkill). I know that PostgreSQL cannot operate in embedded mode and that is fine - I can leave the server process running and that's OK with me.
I'm trying to figure out a connection string that will achieve this, but have been unsuccessful. I've tried variations on the following:
jdbc:postgresql:C:\myDB.fdb
jdbc:postgresql://C:\myDB.fdb
jdbc:postgresql://localhost:[port]/C:\myDB.fdb
but nothing seems to work. PostgreSQL's directions don't include an example for this case. Is this even possible?
You can trick it. If you are running PostGRESQL on a UNIXlike system, then you should be able to create a RAMDISK and use that for the database storage. Here's a pretty good step by step guide for RAMdisks on Linux.
In general though, I would suggest using SQLITE for an SQL db in RAM type of application.
Postgres databases are not a single file. There will be one file for each table and each index in the data directory, inside a directory for the database. All files will be named with the object ID (OID) of db / table / index.
The JDBC urls point to the database name, not any specific file:
jdbc:postgresql:foodb (localhost is implied)
If by "disk that behaves like memory", you mean that the db only exists for the lifetime of your program, there's no reason why you can't create a db at program start and drop it at program exit. Note that this is just DDL to create the DB, not creating the data dir via the init-db program. You could connect to the default 'postgres' db, create your db then connect to it.
Firebird 2.1 onwards supports global temporary tables, which only exist for the duration of the database connection.
Syntax goes something like CREATE GLOBAL TEMPORARY TABLE ... ON COMMIT PRESERVE ROWS