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impulse_query_engine.analyze.query.channels.calculated_channel

CalculatedChannel: a labeled derived time-series channel.

CalculatedChannel​

class CalculatedChannel(TimeSeriesExpression)

A derived channel: a wrapped TimeSeriesExpression plus output identity.

Wraps an expression built from the operator DSL (e.g. rpm * 3.6) that must evaluate to a :class:SampleSeries. build() returns that series' raw (tstarts, tends, values) arrays, which :meth:QueryBuilder.solve_calculated_channels explodes into narrow silver-shaped rows plus an identity MapType column.

Arguments:

  • expr (TimeSeriesExpression): The wrapped expression; must build() to a SampleSeries.
  • identity (dict of str): Non-empty identity dict (arbitrary keys, e.g. {"channel_name": "Eng_RPM", "data_key": "TM"}), emitted per row and used to seed the deterministic :attr:channel_id.

canonical_identity​

def canonical_identity() -> str

Return a stable string encoding of the identity, used for the id hash.

Keys are sorted so the encoding (and the derived channel_id) is independent of kwarg order.

channel_id​

def channel_id() -> int

Deterministic output channel_id derived from the identity.

A CRC32 of :meth:canonical_identity masked to a positive int32, so the value is stable across runs/processes and fits both IntegerType and LongType source channel_id columns. Determinism makes writes idempotent and joins predictable; sharing this one derivation across the query-engine and reporting layers keeps their ids in lockstep.

build​

def build(cache: SeriesCache)

Evaluate the wrapped expression and return its raw (tstarts, tends, values).

Unlike a typical TimeSeriesExpression (whose build yields a SampleSeries), this returns the three parallel float64 arrays underlying that series, since the calculated-channels solve path consumes the raw samples directly.

dtype​

def dtype() -> T.DataType

Spark type of build()'s output: the raw (tstarts, tends, values) arrays.

A struct of three arrays mirroring the tuple build() returns, with element types matching the narrow calculated-channels output (tstart/tend are long, value is double).