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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Use SELECT ... FOR UPDATE when the transaction can identify an existing ledger row that it needs to read, validate, and change. Use a transaction-level advisory lock when the resource is logical or has no suitable row—but only if every competing writer follows the same lock-key protocol. Neither mechanism, used on just one row or key, automatically protects an invariant spanning multiple rows or tables.
The right choice depends on what the ledger must keep consistent, which rows or resources can affect that rule, and whether every writer participates in the same protocol. PostgreSQL 18’s current documentation describes the locking semantics, not a universal performance winner for ledger workloads.
What each lock protects
Row-level locks protect selected rows
A query using SELECT ... FOR UPDATE locks the rows it returns against concurrent updates, deletes, and conflicting row-lock requests until the transaction ends. This fits a ledger operation when its correctness depends on checking and changing a known account, balance, or ledger row. Ordinary reads are not blocked by row-level locks; conflicting writers and lockers are. See the PostgreSQL 18 documentation on explicit locking.
The lock must be acquired in the transaction that validates and applies the ledger change. A lock taken separately from that work does not protect the whole operation.
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Advisory locks protect an application-defined resource
An advisory lock is keyed, and the application decides what the key means—for example, a logical account or resource that does not yet have a row. PostgreSQL does not automatically associate the key with a table row or require other transactions to honor it. Every relevant writer must construct and request the same key for mutual exclusion to work. See the PostgreSQL 18 documentation on explicit locking.
For work bounded by a transaction, transaction-level advisory locks are generally easier to reason about: PostgreSQL releases them when the transaction ends, including on rollback. Session-level advisory locks remain held until explicitly unlocked or the session ends, and do not roll back with a transaction. With pooled connections, an overlooked session-level lock can outlive the operation that acquired it and affect later use of that connection. See the PostgreSQL 18 documentation on explicit locking.
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Choose by the resource and invariant
| Question | Row lock | Advisory lock |
|---|---|---|
| What is locked? | Existing table rows selected by the query. PostgreSQL 18 documentation. | An application-defined key; a matching row is optional and not enforced. PostgreSQL 18 documentation. |
| Who must participate? | Transactions that contend for the same row encounter row-lock behavior. | Every relevant writer must use the agreed key protocol. |
| How is the lock released? | At transaction end. | At transaction end for transaction-level locks; session-level locks require explicit unlock or session end. |
| Does it protect an aggregate rule? | Not by locking just one row when the rule depends on other rows or a predicate. | Only if all relevant writers honor the shared key; the key alone does not establish database-wide correctness. |
For ordinary updates to a known account or ledger row, start with a row lock on the row that is the natural unit of serialization. Choose a transaction-level advisory lock when the resource needs coordination but no suitable row represents it, and verify the protocol across all writers. The PostgreSQL explicit-locking documentation describes the mechanisms, but does not establish a universal speed or performance ranking for ledger workloads.
Handle invariants that span rows or tables
Rules such as a debit-and-credit relationship or an aggregate balance constraint may depend on more than one row. First identify every row, table, and concurrent change that can affect the rule; then choose transaction isolation and a locking protocol that covers that full set. PostgreSQL’s application-level consistency guidance explains why checks against changing data require careful transaction semantics, including the limits of relying on shifting snapshots.
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- Locking one row does not automatically protect an aggregate or predicate involving other rows.
- An advisory lock can coordinate an aggregate only when every relevant writer uses the same key. It does not independently guarantee the invariant.
- If using serializable transactions, handle transaction failures and retry the full transaction when appropriate. Validate the approach against the actual schema and workload.
Reduce contention and recover from deadlocks
- Keep the transaction bounded. Acquire the needed locks as part of the transaction that checks and applies the ledger operation, and finish promptly; locks remain held until transaction end.
- Take multiple locks in a consistent order. If concurrent transactions acquire the same set in different orders, they can deadlock.
- Retry safe, aborted transactions. PostgreSQL detects deadlocks and aborts one transaction. Where appropriate, retry the complete transaction rather than continuing from partially completed application logic. See the PostgreSQL 18 documentation on explicit locking.
Inspect active locks
Use PostgreSQL’s pg_locks view to examine active locks, including advisory locks. Correlate lock state with waiting sessions and the application’s transaction boundaries to understand which operation is holding up progress. See the pg_locks documentation.
What the documentation does—and does not—establish
The current PostgreSQL documentation surfaced for PostgreSQL 18 and checked on October 4, 2026, establishes the mechanisms’ behavior; its URLs use /current/, so confirm version-specific details against the release you deploy. It does not provide a numeric benchmark comparing these lock types for concurrent ledger workloads. Any performance conclusion needs testing against the application’s schema, data, and contention pattern.
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