Consider a table orders with an index on status. If a query filters on multiple statuses and the EXPLAIN plan shows a Bitmap Index Scan, what does this imply about the query's filtering?
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PostgreSQL - Performance Tuning
Consider a table orders with an index on status. If a query filters on multiple statuses and the EXPLAIN plan shows a Bitmap Index Scan, what does this imply about the query's filtering?
AThe Bitmap Index Scan is combining multiple index entries to efficiently locate matching rows
BThe query is performing a full table scan ignoring the index
CThe index is not used because the filter is on multiple values
DThe query is updating rows matching the statuses
Step-by-Step Solution
Solution:
Step 1: Understand Bitmap Index Scan with multiple filters
Bitmap Index Scan can combine multiple index entries (e.g., multiple statuses) into a bitmap.
Step 2: Implication
This allows efficient filtering of rows matching any of the specified statuses.
Final Answer:
The Bitmap Index Scan is combining multiple index entries to efficiently locate matching rows -> Option A
Quick Check:
Bitmap Index Scan implies index usage, not full scan [OK]
Quick Trick:Bitmap Index Scan combines multiple index entries [OK]
Common Mistakes:
Assuming full table scan despite Bitmap Index Scan
Believing index is unused with multiple filters
Confusing filtering with updating
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