apache/druid · error · IllegalStateException

Cannot translate sqlTypeName[%s] to Druid type for field[%s]

Error message

Cannot translate sqlTypeName[%s] to Druid type for field[%s]

What it means

ArrayOfDoublesSketchSqlAggregator.toDruidAggregation validates the input column's relational type before building the native aggregator. If Calcites.getColumnTypeForRelDataType cannot map the column's SQL type name to a Druid type, it throws this ISE. It means the sketch aggregation was applied to a column with a type the Druid SQL type system cannot translate.

Source

Thrown at extensions-core/datasketches/src/main/java/org/apache/druid/query/aggregation/datasketches/tuple/sql/ArrayOfDoublesSketchSqlAggregator.java:122

          plannerContext,
          inputAccessor.getInputRowSignature(),
          columnRexNode
      );
      if (columnArg == null) {
        return null;
      }

      if (columnArg.isDirectColumnAccess() &&
          inputAccessor.getInputRowSignature()
              .getColumnType(columnArg.getDirectColumn())
              .map(type -> type.is(ValueType.COMPLEX))
              .orElse(false)) {
        fieldName = columnArg.getDirectColumn();
      } else {
        final RelDataType dataType = columnRexNode.getType();
        final ColumnType inputType = Calcites.getColumnTypeForRelDataType(dataType);
        if (inputType == null) {
          throw new ISE(
              "Cannot translate sqlTypeName[%s] to Druid type for field[%s]",
              dataType.getSqlTypeName(),
              name
          );
        }

        final DimensionSpec dimensionSpec;

        if (columnArg.isDirectColumnAccess()) {
          dimensionSpec = columnArg.getSimpleExtraction().toDimensionSpec(null, inputType);
        } else {
          String virtualColumnName = virtualColumnRegistry.getOrCreateVirtualColumnForExpression(
              columnArg,
              dataType
          );
          dimensionSpec = new DefaultDimensionSpec(virtualColumnName, null, inputType);
        }
        fieldName = dimensionSpec.getDimension();

View on GitHub (pinned to 9b90983fd2)

Solutions

Verify the input column is a plain numeric or array-of-doubles-sketch typed column; fix the query to aggregate on a supported column
Inspect the SQL type of the expression (EXPLAIN PLAN) and add an explicit CAST to a supported type (BIGINT/DOUBLE)
Ensure the datasketches extension is loaded and versions match on all nodes

Example fix

// before
SELECT APPROX_QUANTILE_DS(nested_col, 0.5) FROM t
// after
SELECT APPROX_QUANTILE_DS(CAST(nested_col AS DOUBLE), 0.5) FROM t

Defensive patterns

Strategy: validation

Validate before calling

// Validate the column type before aggregating
EXPLAIN PLAN FOR SELECT SKETCH_ESTIMATE(col) FROM t; -- confirm col's type maps to a Druid type

Try / catch

try {
  runSql(query);
} catch (ISE e) {
  if (e.getMessage().contains("Cannot translate sqlTypeName")) {
    // retry with explicit CAST on the input column
  } else throw e;
}

Prevention

Aggregate only on typed numeric or sketch columns
Use EXPLAIN PLAN to verify inferred column types
Add explicit CASTs for expressions with unclear types
Keep the datasketches extension loaded on all nodes

When it happens

Trigger: Applying SKETCH_ESTIMATE / ArrayOfDoubles sketch SQL aggregators to an expression or column whose RelDataType has a SqlTypeName with no Druid mapping (e.g. complex/unsupported types, NULL-typed expressions from bad casts).

Common situations: Aggregating over a nested/complex column that isn't typed as expected, a CAST producing an unmappable type, or extension version mismatches leaving the type registry incomplete.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/76708bd6a82d19f6. Report an issue: GitHub.