Pulse Documentation

name: op-synth-constant
description: Emit a constant value on every row; useful for unit testing, sentinel columns, and placeholder fields.
kind: operator
category: SYNTH
operator: constant
type: reference
applies_to: inspect, predict, manifest
examples_tags: [synth, data-quality]

Synth distributions emit per-row values; no Response.Components.

Use when

Puts the same value on every row, for a placeholder field or a fixed flag in a test fixture.

Questions it answers:

• How do I fill a column with the same country code?
• How do I add a fixed version field to test data?

Use something else:

• monotonic_from when each row needs a distinct ID.
• weighted_categorical when the value should vary over a few labels.
• bernoulli when a flag should be set on only some rows.

Params

• value — any, required. Per-row payload. Interpreted by the declared field type at write time.

value is checked and normalised to the field’s row shape once, at spec parse — never at write time.

Inputs

field type: — any .pulse field type. Categorical takes a string, set_* a list of option names, numeric/date a number or bool (decimal128 also a string).

Output

Same value returned on every row. RNG state untouched.

Gotchas

• Missing value param → SERVICE_VALIDATION (“requires param value”).
• A value the field cannot hold (text on a number field) → SERVICE_VALIDATION at spec parse.
• Consumes NO RNG — like monotonic_from, adding / removing a constant field preserves byte-equality of every other field’s stream.
• A constant categorical still emits a one-entry dictionary block (one byte per row at categorical_u8); for a packed-bool equivalent use bernoulli with p=0 / p=1.

See

• pulse_examples_search tags=[synth]
• Skills: synthetic-data, op-synth-monotonic-from, op-synth-bernoulli