PPL Lambda functions

EXISTS

Usage: exists(array, lambda) evaluates whether a Lambda predicate holds for one or more elements in the array.

Argument type: ARRAY, LAMBDA

Return type: BOOLEAN. Returns TRUE if at least one element in the array satisfies the Lambda predicate, otherwise FALSE.

Examples:

 os> source=people | eval array = json_array(1, -1, 2), result = exists(array, x -> x > 0) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| true      |
+-----------+

os> source=people | eval array = json_array(-1, -3, -2), result = exists(array, x -> x > 0) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| false     |
+-----------+    

FILTER

Usage: filter(array, lambda) filters the input array using the given Lambda function.

Argument type: ARRAY, LAMBDA

Return type: ARRAY. An ARRAY that contains all elements in the input array that satisfy the lambda predicate.

Examples:

 os> source=people | eval array = json_array(1, -1, 2), result = filter(array, x -> x > 0) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| [1, 2]    |
+-----------+

os> source=people | eval array = json_array(-1, -3, -2), result = filter(array, x -> x > 0) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| []        |
+-----------+     

TRANSFORM

Usage: transform(array, lambda) transforms elements in an array using the Lambda transform function. The second argument implies the index of the element if using binary Lambda function. This is similar to a map in functional programming.

Argument type: ARRAY, LAMBDA

Return type: ARRAY. An ARRAY that contains the result of applying the lambda transform function to each element in the input array.

Examples:

os> source=people | eval array = json_array(1, 2, 3), result = transform(array, x -> x + 1) | fields result
fetched rows / total rows = 1/1
+--------------+
| result       |
+--------------+
| [2, 3, 4]    |
+--------------+

os> source=people | eval array = json_array(1, 2, 3), result = transform(array, (x, i) -> x + i) | fields result
fetched rows / total rows = 1/1
+--------------+
| result       |
+--------------+
| [1, 3, 5]    |
+--------------+      

REDUCE

Usage: reduce(array, start, merge_lambda, finish_lambda) reduces an array to a single value by applying lambda functions. The function applies the merge_lambda to the start value and all array elements, then applies the finish_lambda to the result.

Argument type: ARRAY, ANY, LAMBDA, LAMBDA

Return type: ANY. The final result of applying the Lambda functions to the start value and the input array.

Examples:

 os> source=people | eval array = json_array(1, 2, 3), result = reduce(array, 0, (acc, x) -> acc + x) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| 6         |
+-----------+

os> source=people | eval array = json_array(1, 2, 3), result = reduce(array, 10, (acc, x) -> acc + x) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| 16        |
+-----------+

os> source=people | eval array = json_array(1, 2, 3), result = reduce(array, 0, (acc, x) -> acc + x, acc -> acc * 10) | fields result
fetched rows / total rows = 1/1
+-----------+
| result    |
+-----------+
| 60        |
+-----------+