Function readSchema

Read an Arrow schema from a Parquet file in memory.

This returns an Arrow schema in WebAssembly memory. To transfer the Arrow schema to JavaScript memory you have two options:

• (Easier): Call Schema.intoIPCStream to construct a buffer that can be parsed with Arrow JS's tableFromIPC function. This results in an Arrow JS Table with zero rows but a valid schema.
• (More performant but bleeding edge): Call Schema.intoFFI to construct a data representation that can be parsed zero-copy from WebAssembly with arrow-js-ffi using parseSchema.

Example with IPC Stream:

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

// Instantiate the WebAssembly context
await initWasm();

const resp = await fetch("https://example.com/file.parquet");
const parquetUint8Array = new Uint8Array(await resp.arrayBuffer());
const arrowWasmSchema = readSchema(parquetUint8Array);
const arrowTable = tableFromIPC(arrowWasmSchema.intoIPCStream());
const arrowSchema = arrowTable.schema;
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Example with arrow-js-ffi:

import { parseSchema } from "arrow-js-ffi";
import initWasm, {readSchema, wasmMemory} from "parquet-wasm";

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

const resp = await fetch("https://example.com/file.parquet");
const parquetUint8Array = new Uint8Array(await resp.arrayBuffer());
const arrowWasmSchema = readSchema(parquetUint8Array);
const ffiSchema = arrowWasmSchema.intoFFI();
const arrowTable = parseSchema(WASM_MEMORY.buffer, ffiSchema.addr());
const arrowSchema = arrowTable.schema;
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