prestodb/presto · error · SemanticException

COLUMN_ALREADY_EXISTS

COLUMN_ALREADY_EXISTS

Error message

Column '%s' already exists

What it means

During ADD COLUMN processing, the connector's column handles for the target table already contain a column with the name given in the statement's ColumnDefinition. Since columns must be unique within a table, the alteration is rejected as redundant; the duplicated name is formatted into the message.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/execution/AddColumnTask.java:108

        accessControl.checkCanAddColumns(session.getRequiredTransactionId(), session.getIdentity(), session.getAccessControlContext(), tableName);

        Map<String, ColumnHandle> columnHandles = metadata.getColumnHandles(session, tableHandle.get());

        ColumnDefinition element = statement.getColumn();
        Type type;
        try {
            type = metadata.getType(parseTypeSignature(element.getType()));
        }
        catch (IllegalArgumentException | UnknownTypeException e) {
            throw new SemanticException(TYPE_MISMATCH, element, "Unknown type '%s' for column '%s'", element.getType(), element.getName());
        }
        if (type.equals(UNKNOWN)) {
            throw new SemanticException(TYPE_MISMATCH, element, "Unknown type '%s' for column '%s'", element.getType(), element.getName());
        }
        if (columnHandles.containsKey(element.getName().getValueLowerCase())) {
            if (!statement.isColumnNotExists()) {
                throw new SemanticException(COLUMN_ALREADY_EXISTS, statement, "Column '%s' already exists", element.getName());
            }
            return immediateFuture(null);
        }
        if (!element.isNullable() && !metadata.getConnectorCapabilities(session, connectorId).contains(NOT_NULL_COLUMN_CONSTRAINT)) {
            throw new SemanticException(NOT_SUPPORTED, element, "Catalog '%s' does not support NOT NULL for column '%s'", connectorId.getCatalogName(), element.getName());
        }

        Map<String, Expression> sqlProperties = mapFromProperties(element.getProperties());
        Map<String, Object> columnProperties = metadata.getColumnPropertyManager().getProperties(
                connectorId,
                tableName.getCatalogName(),
                sqlProperties,
                session,
                metadata,
                parameterExtractor(statement, parameters));

        Identifier columnIdentifier = element.getName();
        String name = metadata.normalizeIdentifier(session, tableName.getCatalogName(), columnIdentifier.getValue());

View on GitHub (pinned to 55bb57d202)

Solutions

1. Choose a different column name
2. Drop the existing column first if replacement is intended

When it happens

Trigger: Thrown at presto-main-base/src/main/java/com/facebook/presto/execution/AddColumnTask.java:108 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/07eab25d530f7c78. Report an issue: GitHub.