Format Values From Two Array Elements Using :

Format Values from Two Array Elements using : as a separator

Query

flowchart LR; %%{init: {"flowchart": {"defaultRenderer": "elk"}} }%% repo{{Events}} 1[\Add Field/] result{{Result Set}} repo --> 1 1 --> result
flowchart LR; %%{init: {"flowchart": {"defaultRenderer": "elk"}} }%% repo{{Events}} 1[\Add Field/] result{{Result Set}} repo --> 1 1 --> result
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objectArray:eval("in[]", asArray="out[]", function={out := format("%s:%s", field=[in.key, in.value])})

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 (use dot notation), arrays of arrays (use bracket notation), and other arrays of structured data is: "in" (the input array) followed by: 

.subselection

or 

[number]

or any combination of the above. For example: 

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

Use in.key for accessing fields in arrays of objects, and in[0][1] for arrays of arrays.

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].

In this example, the objectArray:eval() function is used to format the array entries in[].key and in[].value separating the concatenated values with a : in the output field out[]. The output must be a single field in this example as format() is only capable of creating a single value.

Example incoming data might look like this:

JSON
in[0].key = x
in[0].value = y
in[1].key = a
in[1].value = b

Step-by-Step

  1. Starting with the source repository events.

  2. flowchart LR; %%{init: {"flowchart": {"defaultRenderer": "elk"}} }%% repo{{Events}} 1[\Add Field/] result{{Result Set}} repo --> 1 1 --> result style 1 fill:#ff0000,stroke-width:4px,stroke:#000;
    flowchart LR; %%{init: {"flowchart": {"defaultRenderer": "elk"}} }%% repo{{Events}} 1[\Add Field/] result{{Result Set}} repo --> 1 1 --> result style 1 fill:#ff0000,stroke-width:4px,stroke:#000;
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    objectArray:eval("in[]", asArray="out[]", function={out := format("%s:%s", field=[in.key, in.value])})

    Iterates (executes a loop) 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[].

    Notice that a var parameter can be used to give a different name to the input array variable inside the function argument. This is particularly useful whenever the input array name is very long. Example:

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    objectArray:eval("someVeryLongName[]", asArray="out[]",
var=x, function={out := format("%s:%s", field=[x.key,
x.value])})

  3. Event Result set.

Summary and Results

The query is used to format arrays of objects.

Sample output from the incoming example data: 

out[0] = x:y
out[1] = a:b