[Solved] A transaction under Read Committed isolation runs multiple queries that depend on each other's results.... How can you prevent inconsistent intermediate states without changing the isolation level? | PostgreSQL

PostgreSQL - Transactions and Concurrency

A transaction under Read Committed isolation runs multiple queries that depend on each other's results. Another transaction updates some rows and commits between these queries. How can you prevent inconsistent intermediate states without changing the isolation level?

ASet the transaction to autocommit mode.

BUse explicit row-level locks with SELECT FOR UPDATE in the first query.

CRestart the transaction after each query.

DUse advisory locks unrelated to rows.

Step-by-Step Solution

Solution:

Step 1: Identify cause of inconsistency
Other transactions committing changes between queries cause inconsistent reads.
Step 2: Apply explicit locking to prevent concurrent updates
Using SELECT FOR UPDATE locks rows so others cannot modify them until transaction ends.
Final Answer:
Use explicit row-level locks with SELECT FOR UPDATE in the first query. -> Option B
Quick Check:
Row locks prevent concurrent changes under Read Committed [OK]

Quick Trick: Lock rows early to avoid mid-transaction changes [OK]

Common Mistakes:

Restarting transactions wastes resources
Autocommit does not solve consistency
Advisory locks do not lock rows automatically

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How can you prevent inconsistent intermediate states without changing the isolation level?

Step 1: Identify cause of inconsistency

Step 2: Apply explicit locking to prevent concurrent updates

Final Answer:

Quick Check:

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