PostgreSQL - Transactions and Concurrency
You want a transaction under Read Committed isolation to execute multiple queries without seeing changes committed by other transactions between them. Which method achieves this?
You want a transaction under Read Committed isolation to execute multiple queries without seeing changes committed by other transactions between them. Which method achieves this?
hard📝 Application Q8 of 15
Step-by-Step Solution
Solution:
Step 1: Understand Read Committed limitations
Read Committed allows different queries to see different snapshots, so changes committed between queries are visible.Step 2: Prevent changes between queries
Explicit locking (e.g., SELECT ... FOR SHARE or FOR UPDATE) can lock rows to prevent concurrent commits affecting them.Step 3: Evaluate other options
Read Uncommitted is not supported in PostgreSQL; separate transactions or disabling autocommit do not solve the problem.Final Answer:
Use explicit locking (e.g., SELECT ... FOR SHARE) to prevent concurrent modifications -> Option DQuick Check:
Explicit locks prevent concurrent changes [OK]
Quick Trick: Use explicit locks to prevent mid-transaction changes [OK]
Common Mistakes:
- Assuming Read Uncommitted exists in PostgreSQL
- Thinking separate transactions isolate queries
- Believing disabling autocommit affects isolation
Master "Transactions and Concurrency" in PostgreSQL
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