Examples

Transformations

Description

when() with only a then branch: rows that do not match keep the value they had. The nullable column is declared on the source, so the intent is explicit rather than inferred.

Documentation

Transformations are expressions over a row, evaluated column by column.

Transformations

Code

<?php

declare(strict_types=1);

use function Flow\ETL\DSL\{data_frame, from_array, int_schema, lit, ref, schema, to_output, when};

require __DIR__ . '/vendor/autoload.php';

data_frame()
    ->read(from_array(
        [
            ['id' => 1, 'value' => 1],
            ['id' => 2, 'value' => 1],
            ['id' => 3, 'value' => null],
            ['id' => 4, 'value' => 1],
            ['id' => 5, 'value' => null],
        ],
        schema(int_schema('id'), int_schema('value', nullable: true)),
    ))
    ->withEntry(
        'value',
        when(ref('value')->isNull(), then: lit(0))
    )
    ->write(to_output(truncate: false))
    ->run();

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