apache/druid · error · RE

Non-primitive supplied to primitive conversion

Error message

Non-primitive supplied to primitive conversion: %s (this should never happen)

What it means

Type-guard in ParquetGroupConverter.convertPrimitiveField: a logical type (e.g. LIST, MAP, or another group-based type) reached the primitive-conversion switch, meaning a non-primitive field was dispatched where only primitives are expected — 'this should never happen' per the schema, so it indicates a schema-handling bug or unexpected parquet schema.

Solutions

  1. Inspect the parquet schema for the field hitting this path; it may use an unusual logical/annotated type.
  2. Update parquet-extensions to a version supporting that schema shape.
  3. Flatten or re-write the data to use standard primitive types.
Defensive patterns

Strategy: type-guard

When it happens

Trigger: Thrown at extensions-core/parquet-extensions/src/main/java/org/apache/druid/data/input/parquet/simple/ParquetGroupConverter.java:455 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/39da0626a393d611. Report an issue: GitHub.

Appendix: source

Thrown at extensions-core/parquet-extensions/src/main/java/org/apache/druid/data/input/parquet/simple/ParquetGroupConverter.java:455

              case BINARY:
                Binary value = g.getBinary(fieldIndex, index);
                return convertBinaryToDecimal(value, precision, scale);
              default:
                throw new RE(
                    "Unknown 'DECIMAL' type supplied to primitive conversion: %s (this should never happen)",
                    pt.getPrimitiveTypeName()
                );
            }
          case UTF8:
          case ENUM:
          case JSON:
            return g.getString(fieldIndex, index);
          case LIST:
          case MAP:
          case MAP_KEY_VALUE:
          case BSON:
          default:
            throw new RE(
                "Non-primitive supplied to primitive conversion: %s (this should never happen)",
                ot.name()
            );
        }
      } else {
        // fallback to handling the raw primitive type if no logical type mapping
        switch (pt.getPrimitiveTypeName()) {
          case BOOLEAN:
            return g.getBoolean(fieldIndex, index);
          case INT32:
            return g.getInteger(fieldIndex, index);
          case INT64:
            return g.getLong(fieldIndex, index);
          case FLOAT:
            return g.getFloat(fieldIndex, index);
          case DOUBLE:
            return g.getDouble(fieldIndex, index);
          case INT96:

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