PostgreSQL error 40003 indicates the result of a SQL statement is unknown, typically due to network interruptions or connection failures during transaction execution. Recover by rolling back the failed transaction and retrying with proper error handling.
PostgreSQL error 40003 ("Statement completion unknown") is a transaction rollback error that occurs when the database cannot determine whether a SQL statement completed successfully or failed. This error belongs to the Class 40 category of errors, which indicate various transaction rollback scenarios. Unlike syntax errors or constraint violations where the database knows exactly what went wrong, this error represents genuine uncertainty—the network connection was lost, a timeout occurred, or the transaction was interrupted mid-execution, leaving the outcome unknown. The database conservatively rolls back the entire transaction to ensure data integrity, since it cannot guarantee that a partially-executed statement left the database in a consistent state.
When you receive error 40003, the transaction is already in a failed state. Execute a ROLLBACK command to exit the failed transaction and reset your session:
ROLLBACK;This clears the transaction state and allows you to begin a new transaction.
Look at the PostgreSQL server logs to understand what happened on the database side. The server may have additional error details:
# On Linux/macOS
tail -f /var/log/postgresql/postgresql-<version>-main.log
# Or query the current session activity
SELECT * FROM pg_stat_activity WHERE pid = pg_backend_pid();Server logs will show if the connection was terminated, if a timeout occurred, or if there were resource constraints.
Test that your application can reliably connect to the PostgreSQL server and that network latency is acceptable:
# Test basic connectivity
psql -h <hostname> -U <user> -d <database> -c "SELECT 1"
# Check network latency
ping <hostname>
# Use pg_isready for connection health check
pg_isready -h <hostname> -p 5432 -U <user>If latency is high or connections are failing, address network issues (DNS, firewall, ISP problems) before retrying.
If your legitimate queries are taking a long time and timing out, increase the timeout settings:
-- Set statement timeout for the current session (in milliseconds)
SET statement_timeout TO '30s';
-- Set idle transaction timeout
SET idle_in_transaction_session_timeout TO '5min';
-- For connection poolers, configure server-side settings in postgresql.conf
statement_timeout = 30000 # 30 seconds
idle_in_transaction_session_timeout = 300000 # 5 minutesFor connection poolers like PgBouncer, also check their timeout settings separately.
Since error 40003 means the outcome is unknown, your application should safely retry the entire transaction using idempotent operations:
// Pseudo-code for retry logic
async function executeWithRetry(query: string, maxRetries = 3) {
for (let attempt = 1; attempt <= maxRetries; attempt++) {
try {
const result = await db.query(query);
return result;
} catch (error) {
if (error.code === '40003' && attempt < maxRetries) {
// Exponential backoff: 100ms, 200ms, 400ms
const delay = Math.pow(2, attempt - 1) * 100;
await new Promise(r => setTimeout(r, delay));
continue;
}
throw error; // Give up after max retries or non-40003 error
}
}
}Make sure your operations are idempotent (safe to execute multiple times) before implementing retries.
If you need to continue a transaction despite partial failures, use savepoints to isolate risky operations:
BEGIN;
INSERT INTO accounts (name) VALUES ('Alice');
SAVEPOINT sp1;
-- This statement might fail
INSERT INTO transactions (account_id, amount) VALUES (1, 100);
-- If the previous statement fails, rollback only to sp1
ROLLBACK TO sp1;
-- Continue with different logic
INSERT INTO errors_log (message) VALUES ('Transaction failed for account 1');
COMMIT;This prevents error 40003 from rolling back your entire transaction if you can handle partial failures gracefully.
If using a connection pooler like PgBouncer or pgPool, verify settings match your workload:
; PgBouncer configuration (pgbouncer.ini)
server_lifetime = 3600
server_idle_timeout = 600
client_idle_timeout = 600
server_connect_timeout = 15
server_login_retry = 15Bad pool settings can cause connections to drop mid-transaction. Also check that your application is properly releasing connections after queries complete.
Error 40003 is distinct from other transaction errors: it's not about constraint violations (40002), deadlocks (40P01), or serialization failures (40001). It's about genuine uncertainty. In distributed systems or when using replication, you may encounter this when the primary server fails over to a replica—the transaction outcome on the failed primary is unknown.
Some applications attempt to work around this by querying for side effects (e.g., "SELECT * FROM accounts WHERE id = ?") to determine if an UPDATE actually completed. This works for idempotent operations but is error-prone and should be a last resort after proper retry logic.
For connection poolers, be aware that 40003 might appear when the pooler drops a backend connection due to timeout. The pooler may not clearly indicate this in error messages, so you need to distinguish between true 40003 errors from PostgreSQL versus connection resets from the pooler.
PostgreSQL 14+ introduced improved idle transaction handling. If you're on an older version, consider upgrading for better timeout behavior.
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