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Posted to github@beam.apache.org by "junaiddshaukat (via GitHub)" <gi...@apache.org> on 2026/01/24 06:11:50 UTC
[PR] Add filter() method to PCollection in TypeScript SDK [beam]
junaiddshaukat opened a new pull request, #37408:
URL: https://github.com/apache/beam/pull/37408
### Description:
Adds a `filter()` method to the `PCollection` class in the TypeScript SDK, addressing a TODO from README-dev.md.
Fixes #37407
## Changes
- Added `filter()` method to `PCollection` class in `pvalue.ts`
- Added 5 test cases for the filter functionality in `primitives_test.ts`
## Usage Examples
// Basic filtering
const evens = pcoll.filter(x => x % 2 === 0);
// Filter with context
const filtered = pcoll.filter((x, threshold) => x > threshold, 5);
// Filter strings
const aWords = words.filter(s => s.startsWith('a'));
## Implementation Details
- Follows the same pattern as existing `map()` and `flatMap()` methods
- Uses `parDo` internally with a process function that returns `[element]` or `[]`
- Supports optional context parameter for side inputs, counters, etc.
- Added proper TypeScript constraint (`ContextT extends Object | undefined`) to match `parDo` signature
## Tests Added
| Test Case | Description |
|-----------|-------------|
| `runs a filter` | Basic even number filtering |
| `runs a filter with predicate returning false for all` | Empty result case |
| `runs a filter with predicate returning true for all` | All elements pass |
| `runs a filter with context` | Context parameter support |
| `runs a filter on strings` | Non-numeric type support |
## Checklist
- [x] Tests added and passing (297 tests total)
- [x] Follows existing code patterns (`map`, `flatMap`)
- [x] Documentation added (JSDoc comments with examples)
- [X] Mention the appropriate issue in your description
------------------------
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "junaiddshaukat (via GitHub)" <gi...@apache.org>.
junaiddshaukat commented on PR #37408:
URL: https://github.com/apache/beam/pull/37408#issuecomment-3793932962
Hi @damccorm
This PR adds a `filter()` method to `PCollection`, addressing the TODO in README-dev.md. It follows the same pattern as `map()` and `flatMap()` with 5 test cases covering various scenarios.
Fixes #37407
Would appreciate your review when you have time. Thanks!
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "gemini-code-assist[bot] (via GitHub)" <gi...@apache.org>.
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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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "damccorm (via GitHub)" <gi...@apache.org>.
damccorm commented on PR #37408:
URL: https://github.com/apache/beam/pull/37408#issuecomment-3801061036
/gemini review
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "gemini-code-assist[bot] (via GitHub)" <gi...@apache.org>.
gemini-code-assist[bot] commented on PR #37408:
URL: https://github.com/apache/beam/pull/37408#issuecomment-3793920206
## Summary of Changes
Hello @junaiddshaukat, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request enhances the TypeScript SDK by introducing a `filter()` method to the `PCollection` class. This addition provides a familiar and powerful way to selectively process data within a pipeline, allowing users to easily retain only the elements that meet specific criteria. The implementation is robust, leveraging existing primitives and supporting flexible predicate functions, including those that require additional context.
### Highlights
* **New `filter()` method for PCollection**: A `filter()` method has been added to the `PCollection` class in the TypeScript SDK, allowing users to filter elements based on a provided predicate function. This addresses a TODO item from `README-dev.md` and mirrors the functionality of JavaScript's `Array.filter()`.
* **Internal Implementation using `parDo`**: The `filter()` method is implemented internally using the existing `parDo` primitive. It leverages a process function that returns the element wrapped in an array if the predicate is true, or an empty array if false, effectively filtering the `PCollection`.
* **Context Parameter Support**: The new `filter()` method supports an optional context parameter, allowing the predicate function to access side inputs, counters, or other contextual data, aligning with the `parDo` signature.
* **Comprehensive Test Coverage**: Five new test cases have been added to `primitives_test.ts` to validate the `filter()` functionality. These tests cover basic filtering, cases where all or no elements pass, filtering with context, and filtering on string types.
* **Documentation and Code Patterns**: The `filter()` method includes JSDoc comments with usage examples. Its implementation follows the established patterns of existing `map()` and `flatMap()` methods within the SDK.
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #37408:
URL: https://github.com/apache/beam/pull/37408#issuecomment-3793985724
Assigning reviewers:
R: @damccorm added as fallback since no labels match configuration
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "damccorm (via GitHub)" <gi...@apache.org>.
damccorm commented on code in PR #37408:
URL: https://github.com/apache/beam/pull/37408#discussion_r2728758403
##########
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:
Not a great suggestion
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Re: [PR] Add filter() method to PCollection in TypeScript SDK [beam]
Posted by "damccorm (via GitHub)" <gi...@apache.org>.
damccorm merged PR #37408:
URL: https://github.com/apache/beam/pull/37408
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