Java transform catalog overview

Java transform catalog overview

Element-wise

Transform	Description
Filter	Given a predicate, filter out all elements that don't satisfy the predicate.
FlatMapElements	Applies a function that returns a collection to every element in the input and outputs all resulting elements.
Keys	Extracts the key from each element in a collection of key-value pairs.
KvSwap	Swaps the key and value of each element in a collection of key-value pairs.
MapElements	Applies a function to every element in the input and outputs the result.
ParDo	The most-general mechanism for applying a user-defined `DoFn` to every element in the input collection.
Partition	Routes each input element to a specific output collection based on some partition function.
Regex	Filters input string elements based on a regex. May also transform them based on the matching groups.
Reify	Transforms for converting between explicit and implicit form of various Beam values.
ToString	Transforms every element in an input collection to a string.
WithKeys	Produces a collection containing each element from the input collection converted to a key-value pair, with a key selected by applying a function to the input element.
WithTimestamps	Applies a function to determine a timestamp to each element in the output collection, and updates the implicit timestamp associated with each input. Note that it is only safe to adjust timestamps forwards.
Values	Extracts the value from each element in a collection of key-value pairs.

Aggregation

Transform	Description
ApproximateQuantiles	Uses an approximation algorithm to estimate the data distribution within each aggregation using a specified number of quantiles.
ApproximateUnique	Uses an approximation algorithm to estimate the number of unique elements within each aggregation.
CoGroupByKey	Similar to `GroupByKey`, but groups values associated with each key into a batch of a given size
Combine	Transforms to combine elements according to a provided `CombineFn`.
CombineWithContext	An extended version of Combine which allows accessing side-inputs and other context.
Count	Counts the number of elements within each aggregation.
Distinct	Produces a collection containing distinct elements from the input collection.
GroupByKey	Takes a keyed collection of elements and produces a collection where each element consists of a key and all values associated with that key.
GroupIntoBatches	Batches values associated with keys into `Iterable` batches of some size. Each batch contains elements associated with a specific key.
HllCount	Estimates the number of distinct elements and creates re-aggregatable sketches using the HyperLogLog++ algorithm.
Latest	Selects the latest element within each aggregation according to the implicit timestamp.
Max	Outputs the maximum element within each aggregation.
Mean	Computes the average within each aggregation.
Min	Outputs the minimum element within each aggregation.
Sample	Randomly select some number of elements from each aggregation.
Sum	Compute the sum of elements in each aggregation.
Top	Compute the largest element(s) in each aggregation.

Other

Transform	Description
Create	Creates a collection from an in-memory list.
Flatten	Given multiple input collections, produces a single output collection containing all elements from all of the input collections.
PAssert	A transform to assert the contents of a `PCollection` used as part of testing a pipeline either locally or with a runner.
View	Operations for turning a collection into view that may be used as a side-input to a `ParDo`.
Window	Logically divides up or groups the elements of a collection into finite windows according to a provided `WindowFn`.
Wait	Delays processing of a PCollection until other PCollections have finished processing.

Last updated on 2026/02/21

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