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arrow_transform.ts
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// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
import {Transform, TransformCallback} from 'stream';
import {
RecordBatchReader,
RecordBatch,
RecordBatchStreamReader,
DataType,
} from 'apache-arrow';
import * as protos from '../../protos/protos';
type ReadRowsResponse =
protos.google.cloud.bigquery.storage.v1.IReadRowsResponse;
type ReadSession = protos.google.cloud.bigquery.storage.v1.IReadSession;
interface TableCell {
v?: any;
}
interface TableRow {
f?: Array<TableCell>;
}
/**
* ArrowRawTransform implements a node stream Transform that reads
* ReadRowsResponse from BigQuery Storage Read API and convert
* a raw Arrow Record Batch.
*/
export class ArrowRawTransform extends Transform {
constructor() {
super({
readableObjectMode: false,
writableObjectMode: true,
});
}
_transform(
response: ReadRowsResponse,
_: BufferEncoding,
callback: TransformCallback,
): void {
if (
!(
response.arrowRecordBatch &&
response.arrowRecordBatch.serializedRecordBatch
)
) {
callback(null);
return;
}
callback(null, response.arrowRecordBatch?.serializedRecordBatch);
}
}
/**
* ArrowRecordReaderTransform implements a node stream Transform that reads
* a byte stream of raw Arrow Record Batch and convert to a stream of Arrow
* RecordBatchStreamReader.
*/
export class ArrowRecordReaderTransform extends Transform {
private session: ReadSession;
constructor(session: ReadSession) {
super({
objectMode: true,
});
this.session = session;
}
_transform(
serializedRecordBatch: Uint8Array,
_: BufferEncoding,
callback: TransformCallback,
): void {
const buf = Buffer.concat([
this.session.arrowSchema?.serializedSchema as Uint8Array,
serializedRecordBatch,
]);
const reader = RecordBatchReader.from(buf);
callback(null, reader);
}
}
/**
* ArrowRecordBatchTransform implements a node stream Transform that reads
* a RecordBatchStreamReader and convert a stream of Arrow RecordBatch.
*/
export class ArrowRecordBatchTransform extends Transform {
constructor() {
super({
objectMode: true,
});
}
_transform(
reader: RecordBatchStreamReader,
_: BufferEncoding,
callback: TransformCallback,
): void {
const batches = reader.readAll();
for (const row of batches) {
this.push(row);
}
callback(null);
}
}
/**
* ArrowRecordBatchTableRowTransform implements a node stream Transform that reads
* an Arrow RecordBatch and convert a stream of BigQuery TableRow.
*/
export class ArrowRecordBatchTableRowTransform extends Transform {
constructor() {
super({
objectMode: true,
});
}
_transform(
batch: RecordBatch,
_: BufferEncoding,
callback: TransformCallback,
): void {
const rows = new Array(batch.numRows);
for (let i = 0; i < batch.numRows; i++) {
rows[i] = {
f: new Array(batch.numCols),
};
}
for (let j = 0; j < batch.numCols; j++) {
const column = batch.selectAt([j]);
const field = column.schema.fields[0];
const columnName = field.name;
for (let i = 0; i < batch.numRows; i++) {
const fieldData = column.get(i);
const fieldValue = fieldData?.toJSON()[columnName];
rows[i].f[j] = {
v: convertArrowValue(fieldValue, field.type as DataType),
};
}
}
for (let i = 0; i < batch.numRows; i++) {
this.push(rows[i]);
}
callback(null);
}
}
function convertArrowValue(fieldValue: any, type: DataType): any {
if (fieldValue === null) {
return null;
}
if (DataType.isList(type)) {
const arr = fieldValue.toJSON();
return arr.map((v: any) => {
// Arrays/lists in BigQuery have the same datatype for every element
// so getting the first one is all we need
const elemType = type.children[0].type;
return {v: convertArrowValue(v, elemType)};
});
}
if (DataType.isStruct(type)) {
const tableRow: TableRow = {};
Object.keys(fieldValue).forEach(key => {
const elemType = type.children.find(f => f.name === key);
if (!tableRow.f) {
tableRow.f = [];
}
tableRow.f.push({
v: convertArrowValue(fieldValue[key], elemType?.type as DataType),
});
});
return tableRow;
}
if (DataType.isTimestamp(type)) {
// timestamp comes in microsecond, convert to nanoseconds
// to make it compatible with BigQuery.timestamp.
return fieldValue * 1000;
}
return fieldValue;
}