apache/beam · error

Attempted to encode null for non-nullable field \

Error message

Attempted to encode null for non-nullable field \"${this.schema.fields[i].name}\".

What it means

During encode, the row value supplied for the named field was null or undefined while the schema declares that field non-nullable, and the null-bitmask machinery refuses to encode it. The faulty inputs are the element being encoded and the specific field named in the message.

Solutions

1. Mark the field nullable in the schema (Field with nullable=true) if null is a legitimate value.
2. Fix the upstream DoFn so it never emits null/undefined for the named non-nullable field.
3. If null means 'absent', restructure the row to omit the field or use a sentinel value consistent with the schema.

When it happens

Trigger: Thrown at sdks/typescript/src/apache_beam/coders/row_coder.ts:411 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/6b74d3322c1f1689. Report an issue: GitHub.

Appendix: source

Thrown at sdks/typescript/src/apache_beam/coders/row_coder.ts:411

          }
          running |= (attr === null || attr === undefined ? 1 : 0) << i % 8;
        });
        nullFields.push(running);
      }
    }

    writer.bytes(new Uint8Array(nullFields));

    // An encoding for each non-null field, concatenated together.
    let positions = this.encodingPositionsAreTrivial
      ? this.encodingPositions
      : this.encodingPositionsArgsSorted;

    positions.forEach((i) => {
      let attr = attrs[i];
      if (attr === null || attr === undefined) {
        if (!this.fieldNullable[i]) {
          throw new Error(
            `Attempted to encode null for non-nullable field \"${this.schema.fields[i].name}\".`,
          );
        }
      } else {
        this.components[i].encode(attr, writer, Context.needsDelimiters);
      }
    });
  }

  decode(reader: Reader, context: Context): any {
    let nFields = reader.int32();

    // Addressing Null values
    let nulls: any[],
      hasNulls = false,
      nullMaskBytes = reader.int32(),
      nullMask = reader.buf.slice(reader.pos, reader.pos + nullMaskBytes);

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