[Solved] After deleting many rows from a PostgreSQL table, why is it necessary to run VACUUM? — Ans: To mark the space occupied by deleted rows as reusable for future inserts or... | PostgreSQL

PostgreSQL - Transactions and Concurrency

After deleting many rows from a PostgreSQL table, why is it necessary to run VACUUM?

ATo immediately remove the deleted rows from the disk permanently.

BTo mark the space occupied by deleted rows as reusable for future inserts or updates.

CTo rebuild all indexes on the table automatically.

DTo compress the table data to reduce disk usage.

Step-by-Step Solution

Solution:

Step 1: Understand what happens after DELETE
Deleted rows remain as dead tuples until VACUUM marks their space reusable.
Step 2: Analyze options
VACUUM does not immediately remove rows from disk (B), rebuild indexes (C), or compress data (D).
Final Answer:
To mark the space occupied by deleted rows as reusable for future inserts or updates. -> Option B
Quick Check:
VACUUM frees space logically, not physically removing rows instantly [OK]

Quick Trick: VACUUM frees space for reuse after deletes [OK]

Common Mistakes:

Master "Transactions and Concurrency" in PostgreSQL

9 interactive learning modes - each teaches the same concept differently

After deleting many rows from a PostgreSQL table, why is it necessary to run VACUUM?