PostgreSQL Objective Questions & Answers for Professionals Set-3
1. In PostgreSQL, what is the purpose of the "pg_rewind" utility?
Explanation: The "pg_rewind" utility in PostgreSQL is used to rewind a replica to a previous state in a replication setup.
2. Which PostgreSQL extension provides support for handling hll (HyperLogLog) data types, useful for approximate distinct value counting?
Explanation: The "pg_hll" extension in PostgreSQL provides support for handling hll (HyperLogLog) data types, useful for approximate distinct value counting.
3. Which PostgreSQL function is used to return the current transaction's unique identifier (XID)?
Explanation: The "txid_current()" function in PostgreSQL is used to return the current transaction's unique identifier (XID).
4. Which PostgreSQL extension allows you to create custom operators for use in SQL queries?
Explanation: The "CREATE OPERATOR" statement in PostgreSQL allows you to create custom operators that can be used in SQL queries.
5. Which parameter in PostgreSQL controls the maximum number of simultaneously allowed background worker processes?
Explanation: The "max_worker_processes" parameter in PostgreSQL controls the maximum number of simultaneously allowed background worker processes.
6. Which PostgreSQL extension provides support for data encryption at rest, transparently encrypting data stored on disk?
Explanation: The "pg_crypto" extension in PostgreSQL provides support for data encryption at rest, allowing transparent encryption of data stored on disk.
7. What is the purpose of the "pg_bouncer" utility in PostgreSQL?
Explanation: The "pg_bouncer" utility in PostgreSQL is used for connection pooling, helping to manage and reuse database connections efficiently.
8. What is the role of the "pg_snapshot" directory in PostgreSQL?
Explanation: The "pg_snapshot" directory in PostgreSQL is used to manage snapshot files, which are used for point-in-time recovery and other purposes.
9. In PostgreSQL, which function is used to return the current user's name?
Explanation: The "current_user()" function in PostgreSQL is used to return the name of the currently logged-in user.
10. In PostgreSQL, which parameter controls the maximum size of the shared memory segment used by the database system?
Explanation: The "max_shm_size" parameter in PostgreSQL controls the maximum size of the shared memory segment used by the database system.
11. What is the purpose of the "pg_depend" system catalog table in PostgreSQL?
Explanation: The "pg_depend" system catalog table in PostgreSQL is used to store information about database object dependencies.
12. Which parameter in PostgreSQL controls the maximum number of simultaneously allowed replication connections?
Explanation: The "max_replication_connections" parameter in PostgreSQL controls the maximum number of simultaneously allowed replication connections.
13. What is the purpose of the "pg_collation" system catalog table in PostgreSQL?
Explanation: The "pg_collation" system catalog table in PostgreSQL is used to store information about table collations, which define the ordering and comparison rules for character data.
14. Which PostgreSQL extension provides support for handling binary large objects (BLOBs)?
Explanation: The "pg_largeobj" extension in PostgreSQL provides support for handling binary large objects (BLOBs), allowing efficient storage and retrieval of large binary data.
15. In PostgreSQL, which statement is used to create a foreign key constraint?
Explanation: The "ADD CONSTRAINT FOREIGN KEY" statement in PostgreSQL is used to create a foreign key constraint on a table.
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