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Dictionary

info

This page is aligned to Apache Arrow JS v21.x (apache-arrow).

A Dictionary DataType that describes dictionary-encoded values (index + dictionary lookup table).

Usage​

import {Dictionary, Utf8, Int32} from 'apache-arrow';

const type = new Dictionary(new Utf8(), new Int32());
console.log(type.isOrdered, type.id);
import {Dictionary, Utf8, Int32} from 'apache-arrow';

const type = new Dictionary(new Utf8(), new Int32());
console.log(type.toString());

Members​

  • id: bigint | number | null — Dictionary type identifier used in message metadata.
  • indices: TKey — Integer index key type (Int8, Int16, Int32, Uint8, Uint16, Uint32).
  • dictionary: T — Logical value type of the dictionary payload.
  • isOrdered: boolean — Whether dictionary index values are order-preserving.
  • children: Field[] — Nested field descriptors (inherited from DataType).
  • valueType: T — Alias for dictionary.
  • ArrayType: T['ArrayType'] — Value array constructor for dictionary index type.
  • typeId: Type.Dictionary — Data type enum value for this type.

Constructor​

constructor(dictionary: T, indices: TKey, id?: bigint | number | null, isOrdered?: boolean | null)​

Construct a dictionary type with explicit dictionary values and index type.

Methods​

  • toString(): string — Returns canonical "Dictionary<...>" representation.