How to fix currval is not yet defined in this session in PostgreSQL

Always initialize the sequence with nextval() before attempting to retrieve its current value with currval():

SELECT nextval('my_sequence');
SELECT currval('my_sequence');

The nextval() call initializes the sequence in the current session, allowing currval() to return the generated value.

For most use cases, the RETURNING clause is more reliable and avoids this error entirely:

INSERT INTO my_table (column1, column2)
VALUES ('value1', 'value2')
RETURNING id;

This directly returns the generated ID without requiring a separate currval() call, and it works in all sessions and transactions.

If you want the last sequence value from the current session without specifying a sequence name, use lastval():

SELECT nextval('my_sequence');
SELECT lastval();

lastval() returns the most recent nextval() result in the current session regardless of which sequence was used. It does not require the sequence name and works across multiple sequences.

If you are using transactions, make sure both nextval() and currval() calls are in the same transaction block:

BEGIN;
  SELECT nextval('my_sequence');
  SELECT currval('my_sequence');
COMMIT;

Keeping them in the same transaction ensures the sequence state persists throughout the operation. Avoid committing between nextval() and currval() calls.

If you are using an ORM or application framework, update your code to:

- Use RETURNING clauses for INSERT statements (Prisma, SQLAlchemy, TypeORM all support this)
- Call nextval() explicitly before currval() if you must use currval()
- Use lastval() if the sequence name is unknown at query time
- Ensure sequence calls are in the same database session

Example with Prisma:

const user = await prisma.user.create({
  data: { email: '[email protected]' },
  select: { id: true }
});
// id is directly available, no need for currval()

Verify that you are not opening a new database connection or session after calling nextval(). Each PostgreSQL session maintains its own sequence state, so if you:

1. Connect to database (Session A)
2. Call nextval()
3. Close connection
4. Open new connection (Session B)
5. Call currval()

You will get this error because Session B has no currval() state. Always use the same connection/session for related sequence operations.