gemini-code-assist[bot] commented on code in PR #37408:
URL: https://github.com/apache/beam/pull/37408#discussion_r2728752247
##########
sdks/typescript/src/apache_beam/pvalue.ts:
##########
@@ -163,6 +163,55 @@ export class PCollection<T> {
);
}
+ /**
+ * Returns a PCollection containing only elements that satisfy the given
+ * predicate function.
+ *
+ * This is analogous to JavaScript's `Array.filter()` method.
+ *
+ * Example usage:
+ * ```
+ * const evens = pcoll.filter(x => x % 2 === 0);
+ * const positives = pcoll.filter(x => x > 0);
+ * ```
+ *
+ * @param fn A predicate function that returns true for elements to keep,
+ * false for elements to filter out. The function receives the
+ * element and optionally a context object.
+ * @param context Optional context object to pass to the predicate function.
+ * @returns A new PCollection containing only the elements for which the
+ * predicate returned true.
+ */
+ filter<ContextT extends Object | undefined = undefined>(
+ fn:
+ | (ContextT extends undefined ? (element: T) => boolean : never)
+ | ((element: T, context: ContextT) => boolean),
+ context: ContextT = undefined!,
+ ): PCollection<T> {
+ if (extractContext(fn)) {
+ context = { ...extractContext(fn), ...context };
+ }
+ return this.apply(
+ withName(
+ "filter(" + extractName(fn) + ")",
+ parDo<T, T, ContextT>(
+ {
+ process: function (element: T, context: ContextT) {
+ // Return the element wrapped in an array if predicate is true,
+ // otherwise return an empty array to filter it out.
+ const keep =
+ context === null || context === undefined
+ ? (fn as (element: T) => boolean)(element)
+ : fn(element, context);
+ return keep ? [element] : [];
+ },
Review Comment:
For consistency with the `map` implementation and to potentially improve
performance by avoiding array allocations, consider using a generator function
for the `process` method. This would involve changing `function` to `function*`
and using `yield element` instead of returning an array.
```typescript
process: function* (element: T, context: ContextT) {
// Yield the element if the predicate is true, otherwise do
nothing to filter it out.
const keep =
context === null || context === undefined
? (fn as (element: T) => boolean)(element)
: fn(element, context);
if (keep) {
yield element;
}
},
```
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