prestodb/presto · error · PrestoException

ALREADY_EXISTS

ALREADY_EXISTS

Error message

Partition already exists for table '%s.%s': %s

What it means

While adding a partition inside a semi-transactional session, an existing pending action for the same partition conflicts: e.g. a DROP followed by an ADD issued by a different user, or otherwise incompatible sequential actions, so a TRANSACTION_CONFLICT PrestoException is thrown to prevent two users mutating the same partition in one transaction.

Source

Thrown at presto-hive-metastore/src/main/java/com/facebook/presto/hive/metastore/SemiTransactionalHiveMetastore.java:894

            partitionActionsOfTable.put(
                    partition.getValues(),
                    new Action<>(ActionType.ADD, new PartitionAndMore(partition, currentLocation, Optional.empty(), statistics, statistics), context));
            return;
        }
        switch (oldPartitionAction.getType()) {
            case DROP: {
                if (!oldPartitionAction.getContext().getIdentity().getUser().equals(session.getUser())) {
                    throw new PrestoException(TRANSACTION_CONFLICT, "Operation on the same partition with different user in the same transaction is not supported");
                }
                partitionActionsOfTable.put(
                        partition.getValues(),
                        new Action<>(ActionType.ALTER, new PartitionAndMore(partition, currentLocation, Optional.empty(), statistics, statistics), context));
                break;
            }
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new PrestoException(ALREADY_EXISTS, format("Partition already exists for table '%s.%s': %s", databaseName, tableName, partition.getValues()));
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void dropPartition(
            ConnectorSession session,
            String databaseName,
            String tableName,
            String tablePath,
            List<String> partitionValues)
    {
        setShared();
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        Action<PartitionAndMore> oldPartitionAction = partitionActionsOfTable.get(partitionValues);
        if (oldPartitionAction == null) {
            HdfsContext context = new HdfsContext(session, databaseName, tableName, tablePath, false);
            partitionActionsOfTable.put(partitionValues, new Action<>(ActionType.DROP, null, context));

View on GitHub (pinned to 55bb57d202)

Solutions

1. Ensure a single transaction does not interleave partition drop/add across different users
2. Split conflicting operations into separate transactions
3. Coordinate concurrent jobs so they do not target the same partition simultaneously

When it happens

Trigger: Thrown at presto-hive-metastore/src/main/java/com/facebook/presto/hive/metastore/SemiTransactionalHiveMetastore.java:894 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/3e7487bb767fe33e. Report an issue: GitHub.