PostgreSQL - Performance Tuning
To improve performance of a query using Bitmap Index Scan that suffers from slow heap access due to many random fetches, which strategy is most effective?
To improve performance of a query using Bitmap Index Scan that suffers from slow heap access due to many random fetches, which strategy is most effective?
hard📝 Application Q8 of 15
Step-by-Step Solution
Solution:
Step 1: Identify cause of slow heap access
Many random heap fetches slow down Bitmap Index Scan queries.Step 2: Use covering index
A covering index contains all needed columns, enabling Index Only Scan which avoids heap fetches.Final Answer:
Create a covering index to enable an Index Only Scan and reduce heap access -> Option AQuick Check:
Covering indexes reduce heap fetches [OK]
Quick Trick: Covering index enables Index Only Scan [OK]
Common Mistakes:
- Thinking increasing work_mem fixes heap fetch slowness
- Disabling Bitmap Index Scans reduces performance
- Switching to sequential scan ignores index benefits
Master "Performance Tuning" in PostgreSQL
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