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In PostgreSQL, what is the primary function of a Bitmap Index Scan during query execution?

easy📝 Conceptual Q1 of 15
PostgreSQL - Performance Tuning
In PostgreSQL, what is the primary function of a Bitmap Index Scan during query execution?
ATo create a bitmap of matching row locations from an index before accessing the heap
BTo directly retrieve rows from the table without using an index
CTo perform a sequential scan on the entire table
DTo update index entries during data modification
Step-by-Step Solution
Solution:
  1. Step 1: Understand Bitmap Index Scan

    A Bitmap Index Scan builds a bitmap of tuple locations that satisfy the index condition.
  2. Step 2: Purpose

    This bitmap is then used to efficiently fetch rows from the heap in a subsequent Bitmap Heap Scan.
  3. Final Answer:

    To create a bitmap of matching row locations from an index before accessing the heap -> Option A
  4. Quick Check:

    Bitmap Index Scan does not fetch rows directly [OK]
Quick Trick: Bitmap Index Scan builds bitmap of row pointers [OK]
Common Mistakes:
  • Confusing Bitmap Index Scan with sequential scan
  • Thinking it fetches rows directly
  • Assuming it updates indexes

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