prestodb/presto · error · PrestoException

ICEBERG_INCOMPATIBLE_COLUMN_TYPE

ICEBERG_INCOMPATIBLE_COLUMN_TYPE

Error message

Failed to set column type: 

What it means

Wraps any RuntimeException from the Iceberg schema-update commit when a column's type is changed (ALTER TABLE ... ALTER COLUMN TYPE). The underlying Iceberg updateColumn rejected the type change, typically because the new type is not a promotable primitive type for the existing column.

Source

Thrown at presto-iceberg/src/main/java/com/facebook/presto/iceberg/IcebergAbstractMetadata.java:2878

    private boolean viewExists(ConnectorSession session, ConnectorTableMetadata viewMetadata)
    {
        return getViewMetadata(session, viewMetadata.getTable()).isPresent();
    }

    @Override
    public void setColumnType(ConnectorSession session, ConnectorTableHandle tableHandle, ColumnHandle columnHandle, com.facebook.presto.common.type.Type type)
    {
        IcebergTableHandle table = (IcebergTableHandle) tableHandle;
        IcebergColumnHandle column = (IcebergColumnHandle) columnHandle;

        Table icebergTable = getIcebergTable(session, table.getSchemaTableName());
        try {
            icebergTable.updateSchema()
                    .updateColumn(column.getName(), toIcebergType(type).asPrimitiveType())
                    .commit();
        }
        catch (RuntimeException e) {
            throw new PrestoException(ICEBERG_INCOMPATIBLE_COLUMN_TYPE, "Failed to set column type: " + firstNonNull(e.getMessage(), e), e);
        }
    }

    protected void openCreateTableTransaction(SchemaTableName tableName, Transaction transaction)
    {
        transactionContext.registerTransaction(tableName, transaction);
    }

    /**
     * Check and ensure that the specified statement can only run in a transaction with autocommit context set to true.
     * */
    protected void shouldRunInAutoCommitTransaction(String statement)
    {
        if (!transactionContext.isAutoCommitContext()) {
            throw new PrestoException(ICEBERG_TRANSACTION_CONFLICT_ERROR, statement + " cannot be called within a transaction (use autocommit mode) in Iceberg connector.");
        }
    }
}

View on GitHub (pinned to 55bb57d202)

Solutions

1. Only use Iceberg-supported type promotions (e.g. int->long, float->double, decimal precision widening)
2. Read the wrapped cause (the last exception in the chain) for the exact schema-update failure reason
3. Add a new column, backfill with UPDATE, and drop the old column instead of an in-place type change
4. Retry if the failure was a concurrent-commit conflict (ConcurrentModificationException from Iceberg)

Example fix

// before
ALTER TABLE t ALTER COLUMN c SET DATA TYPE VARCHAR; -- int -> varchar not promotable
// after
ALTER TABLE t ADD COLUMN c_str VARCHAR;
UPDATE t SET c_str = CAST(c AS VARCHAR);
ALTER TABLE t DROP COLUMN c;

// only attempt Iceberg-promotable widenings
Set<String> promotable = Set.of("integer->bigint","float->double","decimal->decimal(precision,wider scale)");
if (!isPromotable(currentType, newType)) throw new IllegalArgumentException("Unsupported Iceberg type change: " + currentType + " -> " + newType);

try { ALTER ... } catch (PrestoException e) { if ("ICEBERG_INCOMPATIBLE_COLUMN_TYPE".equals(e.getErrorCode().getName())) { /* inspect e.getCause() for the schema-commit failure; fall back to add/backfill/drop */ } else throw e; }

When it happens

Trigger: Calling IcebergAbstractMetadata.setColumnType (ALTER TABLE ... SET COLUMN TYPE) where icebergTable.updateSchema().updateColumn(...).commit() throws, e.g. widening int to varchar, changing a nested field type, or conflicting concurrent schema updates.

Common situations: Attempting unsupported type promotions (int->varchar, timestamp<->timestamptz, decimal precision narrowing), altering columns inside nested structs/maps, or concurrent schema evolution conflicts.

Related errors

• ICEBERG_MISSING_COLUMN
• NOT_SUPPORTED
• NOT_SUPPORTED
• Not a Hive table:
• Not an Iceberg table: ${getSchemaTableName()}

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/85de932e618d09a1. Report an issue: GitHub.