Concatenate Values From Nested Array Elements

Concatenate deeply nested objects and arrays using objectArray:eval() function with concat()

Query

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objectArray:eval("in[]", asArray="out[]", function={out := concat(["in.a", "in.b.c", "in.others[1].d"])})

Introduction

The objectArray:eval()function is a structured array query function that follows normal array syntax. The array syntax is similar to the one used by JSON, where [ and ] are used for indexing and . for selecting members in objects. For more information, see Array Syntax. The objectArray:eval() function operates on arrays of objects using a function that supports a special pattern to access sub-selections of array entries.

The special pattern that allows the function to operate on arrays of objects, and arrays of arrays, and other arrays of structured data is: "in" (the input array) followed by:

.subselection

[number]

or any combination of the above. For example:

in.key,
in.others[0].foo
in[0][1]

Semantically, given the input array in, an array index i, and an access in.subselection this will be translated to the field name in[i].subselection. Similarly, in[2] is translated to in[i][2].

The objectArray:eval() function can be combined with other array functions (or itself), in order to support processing nested arrays. When used with nested arrays, multiple values can be accessed and processed.

In this example, the objectArray:eval() function is used with the concat() function to concatenate deeply nested arrays of objects values in the array in[] and return the concatenated values in the output field out[].

Example incoming data might look like this:

JSON

in[0].a: 1
in[0].b.c: 2
in[0].others[0].d: 3
in[0].others[1].d: 4

Step-by-Step

Starting with the source repository events.
flowchart LR; %%{init: {"flowchart": {"defaultRenderer": "elk"}} }%% repo{{Events}} 0[\Add Field/] result{{Result Set}} repo --> 0 0 --> result style 0 fill:#ff0000,stroke-width:4px,stroke:#000;
logscale
```
objectArray:eval("in[]", asArray="out[]", function={out := concat(["in.a", "in.b.c", "in.others[1].d"])})
```
Iterates over the array from start to end (or to the first empty index in the array), applies the given function, and returns the concatenated results in a new output array name field out[].
Event Result set.