apache/iceberg · error · UnsupportedOperationException

readDoubles is not supported

Error message

readDoubles is not supported

What it means

readDoubles(total, vec, rowId) is the batch double read on VectorizedValuesReader; its default body throws UnsupportedOperationException. Concrete readers override it to bulk-decode doubles into an Arrow Float8Vector. When nextVals() reaches the default implementation, the active reader class does not implement bulk double decoding.

Source

Thrown at arrow/src/main/java/org/apache/iceberg/arrow/vectorized/parquet/VectorizedValuesReader.java:100

  /** Read `total` integers into `vec` starting at `vec[rowId]` */
  default void readIntegers(int total, FieldVector vec, int rowId) {
    throw new UnsupportedOperationException("readIntegers is not supported");
  }

  /** Read `total` longs into `vec` starting at `vec[rowId]` */
  default void readLongs(int total, FieldVector vec, int rowId) {
    throw new UnsupportedOperationException("readLongs is not supported");
  }

  /** Read `total` floats into `vec` starting at `vec[rowId]` */
  default void readFloats(int total, FieldVector vec, int rowId) {
    throw new UnsupportedOperationException("readFloats is not supported");
  }

  /** Read `total` doubles into `vec` starting at `vec[rowId]` */
  default void readDoubles(int total, FieldVector vec, int rowId) {
    throw new UnsupportedOperationException("readDoubles is not supported");
  }

  /**
   * Initialize the reader from a page. See {@link ValuesReader#initFromPage(int,
   * ByteBufferInputStream)}.
   */
  void initFromPage(int valueCount, ByteBufferInputStream in) throws IOException;
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

  1. Disable vectorized reads (read.arrow.enabled=false) so doubles go through the standard reader.
  2. Upgrade Iceberg to a release with vectorized double batch support.
  3. Override readDoubles() in the concrete reader to fill vec[rowId..rowId+total).

Example fix

// before
// default readDoubles throws
// after
@Override
public void readDoubles(int total, FieldVector vec, int rowId) {
  for (int i = 0; i < total; i++) ((Float8Vector) vec).setSafe(rowId + i, readDouble());
}
Defensive patterns

Strategy: try-catch

Validate before calling

// check double support before enabling vectorization
if (schema.columns().stream().anyMatch(c -> c.type().equals(Types.DoubleType.get())) && !doublesBatchSupported) {
  props.put("read.arrow.enabled", "false");
}

Try / catch

try {
  vectorizedScan();
} catch (UnsupportedOperationException e) {
  rowScan();
}

Prevention

When it happens

Trigger: nextVals(total) attempts to bulk-fill a double Arrow vector for a Parquet DOUBLE column while the selected reader subclass has no readDoubles() override.

Common situations: Vectorized scans of double columns on Iceberg versions whose reader only implements numeric batch paths for integers/longs; pages with encodings lacking a dedicated batch reader; custom reader implementations.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/97cecd99cbbbf2d4. Report an issue: GitHub.