Postgresql - Identify duplicate rows

SELECT (mytablename.*)::text, count(*)

FROM mytablename

GROUP BY mytablename.*

HAVING count(*) > 1

Postgresql - Copy data from one table to another

 INSERT INTO mytablenamenew SELECT * FROM mytablenameold;

Postgresql - Delete N number of rows

DELETE FROM mytablename

WHERE id IN (SELECT id FROM mytablename ORDER BY 1 LIMIT 30000)

Postgresql - Random number generation

update foo set bar = floor(random() * 9 + 1); 

SELECT random(),floor(random() * 9 + 1) LIMIT 10;

select floor(7000000000 + random() * 8999);  

PostgreSQL - How to find and kill a hanging query?

First, check all the processes that are running:

SELECT * FROM pg_stat_activity;

So you can identify the PID of the hanging query you want to terminate, run this:

Option #1 (graceful):

SELECT pg_cancel_backend(PID);

Option #2 (forceful):

SELECT pg_terminate_backend(PID);

SELECT 

    pg_terminate_backend(pid) 

FROM 

    pg_stat_activity 

WHERE 

    -- don't kill my own connection!

    pid <> pg_backend_pid()

    AND state = 'idle'

How do I get the list of primary key(s) of a table from Postgres via pgadmin?

SELECT c.column_name, c.data_type

FROM information_schema.table_constraints tc 

JOIN information_schema.constraint_column_usage AS ccu USING (constraint_schema, constraint_name) 

JOIN information_schema.columns AS c ON c.table_schema = tc.constraint_schema

AND tc.table_name = c.table_name AND ccu.column_name = c.column_name

WHERE constraint_type = 'PRIMARY KEY' and tc.table_name = 'mytablename';

SQL Error : Multiple ResultSets were returned by the query

Upon using the custom query in the source object, the mapping fails with the following error:

The select query for read operation failed because of the following error: [org.postgresql.util.PSQLException: Multiple ResultSets were returned by the query​

However, the same query works as expected in PostGresDB.​

If the custom query has more than two query statements, one which is commented and separated by a semicolon, then multiple ResultSets were returned by the query. 

This is expected behavior as the JDBC driver verifies both the statement and returns a null value for the blank query which is a commented line.

Solution:

To resolve the issue, either remove the commented lines from the query or keep the commented lines at the top of the query, so it can be disregarded while running the original query