Function readParquetStream

Read a Parquet file into a stream of Arrow RecordBatches.

This returns a ReadableStream containing RecordBatches in WebAssembly memory. To transfer the Arrow table to JavaScript memory you have two options:

• (Easier): Call RecordBatch.intoIPCStream to construct a buffer that can be parsed with Arrow JS's tableFromIPC function. (The table will have a single internal record batch).
• (More performant but bleeding edge): Call RecordBatch.intoFFI to construct a data representation that can be parsed zero-copy from WebAssembly with arrow-js-ffi using parseRecordBatch.

Example with IPC stream:

import { tableFromIPC } from "apache-arrow";
import initWasm, {readParquetStream} from "parquet-wasm";

// Instantiate the WebAssembly context
await initWasm();

const stream = await wasm.readParquetStream(url);

const batches = [];
for await (const wasmRecordBatch of stream) {
  const arrowTable = tableFromIPC(wasmRecordBatch.intoIPCStream());
  batches.push(...arrowTable.batches);
}
const table = new arrow.Table(batches);
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Example with arrow-js-ffi:

import { parseRecordBatch } from "arrow-js-ffi";
import initWasm, {readParquetStream, wasmMemory} from "parquet-wasm";

// Instantiate the WebAssembly context
await initWasm();
const WASM_MEMORY = wasmMemory();

const stream = await wasm.readParquetStream(url);

const batches = [];
for await (const wasmRecordBatch of stream) {
  const ffiRecordBatch = wasmRecordBatch.intoFFI();
  const recordBatch = parseRecordBatch(
    WASM_MEMORY.buffer,
    ffiRecordBatch.arrayAddr(),
    ffiRecordBatch.schemaAddr(),
    true
  );
  batches.push(recordBatch);
}
const table = new arrow.Table(batches);
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