[Solved] A Bitmap Index Scan is used but the query returns no rows. What is a possible explanation? — Ans: The bitmap was empty, so no heap fetch occurred | PostgreSQL

PostgreSQL - Performance Tuning

A Bitmap Index Scan is used but the query returns no rows. What is a possible explanation?

AThe index was corrupted and returned wrong results

BThe bitmap was empty, so no heap fetch occurred

CThe query syntax was invalid

DThe table was locked by another transaction

Step-by-Step Solution

Solution:

Step 1: Understand empty bitmap effect
If no rows match, bitmap is empty and no heap fetch happens, so query returns zero rows.
Step 2: Exclude other causes
Corrupted index or invalid syntax would cause errors, not empty results; locks do not affect result count.
Final Answer:
The bitmap was empty, so no heap fetch occurred -> Option B
Quick Check:
Empty bitmap means zero rows returned [OK]

Quick Trick: Empty bitmap means no rows fetched [OK]

Common Mistakes:

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A Bitmap Index Scan is used but the query returns no rows. What is a possible explanation?