Silver Layer Schema

The Silver layer stores measurement data in a normalized, tag-based model. Time-series samples live in channels; metadata is split across tag tables (EAV key-value pairs) and metric tables (pre-computed statistics).

The five tables and columns on this page describe the typical default-solver shape — what Impulse's default solvers (DeltaSolver, KeyValueStoreSolver) expect when no SolverConfig overrides are applied. The framework hard-requires only a small subset of this shape:

• container_id on every silver table (engine join key);
• (container_id, channel_id) on the channel-side tables and channels;
• key, value columns on the tag tables (EAV layout);
• one of the two channels formats below (RLE with tstart/tend or raw with timestamp).

Any other column on container_metrics and channel_metrics is optional and only consulted when referenced by your config (e.g. via measurement_dimensions or metric_filters). For physical layouts that diverge further, see Adapting to existing data layouts.

Entity-relationship diagram

---

container_metrics

One row per measurement container with timestamps, duration, and channel count.

Column	Type	Nullable	Description
container_id	long	No	Unique container identifier.
start_dt	timestamp	Yes	Container start datetime.
stop_dt	timestamp	Yes	Container stop datetime.
duration_ms	int	Yes	Total duration in milliseconds.
num_channels	int	Yes	Number of channels in the container.

Additional columns commonly populated

container_metrics typically carries additional metadata columns that get surfaced into the gold-layer measurement_dimension table when listed in the report's measurement_dimensions config. The framework recognises the following names through the MeasurementDimensions enum — populate any subset that fits your data; none are required by the engine.

Column	Type	Description
uut_id	long	Unit-under-test identifier.
vehicle_key	string	Vehicle identifier.
project_id	long	Project identifier.
file_name	string	Source measurement file name.
source_file_path	string	Full path to the source file.
start_ts	long	Measurement start timestamp (epoch).
stop_ts	long	Measurement stop timestamp (epoch).
environment	string	Recording environment (e.g. PUMA, datalogger).

Two timestamp conventions

start_dt/stop_dt (datetime, listed in the table at the top of this section) and start_ts/stop_ts (epoch long, listed here) are different columns, not naming variants. Real-world container_metrics tables typically carry both: start_dt/stop_dt for human-readable display, start_ts/stop_ts for the gold measurement_dimension because the corresponding MeasurementDimensions enum values map to the epoch-typed columns. Populate whichever your queries and measurement_dimensions config need.

---

container_tags

Key-value metadata tags for measurement containers. Strict EAV layout — TSAL queries select recordings by tag key (e.g. query.havingTag(vehicle_key="Seat_Leon") looks up value where key = 'vehicle_key').

Column	Type	Nullable	Description
container_id	long	No	Unique container identifier.
key	string	Yes	Tag key (e.g. "vehicle_key", "project_id").
value	string	Yes	Tag value.

---

channel_metrics

Pre-computed statistics per channel. The percentile columns (pz1, pz10, pz90, pz99) and nan_ratio enable container/channel pre-filtering before scanning the much larger channels table.

Column	Type	Nullable	Description
container_id	long	No	Parent container identifier.
channel_id	int	No	Channel identifier.
value_type	string	Yes	Data type of channel values.
sample_count	int	Yes	Number of samples.
nan_ratio	float	Yes	Ratio of NaN values.
begin_s	float	Yes	Channel start time (seconds).
end_s	float	Yes	Channel end time (seconds).
duration_ms	int	Yes	Channel duration in milliseconds.
original_sample_count	int	Yes	Sample count before processing.
original_sr	float	Yes	Original sample rate.
min	float	Yes	Minimum value.
max	float	Yes	Maximum value.
mean	float	Yes	Mean value.
std	float	Yes	Standard deviation.
pz1	float	Yes	1st percentile.
pz10	float	Yes	10th percentile.
pz90	float	Yes	90th percentile.
pz99	float	Yes	99th percentile.

---

channel_tags

Key-value metadata tags per channel. Strict EAV layout — TSAL channel selectors look up signals by tag key (e.g. query.channel(channel_name="Engine_RPM") looks up value where key = 'channel_name').

Column	Type	Nullable	Description
container_id	long	No	Parent container identifier.
channel_id	int	No	Channel identifier within the container.
key	string	Yes	Tag key (e.g. "channel_name", "brand", "model").
value	string	Yes	Tag value.

---

channels

The actual time-series data. Two format variants are supported.

RLE format (default)

Pre-encoded with run-length encoding. Each row represents one sample interval [tstart, tend) with a constant value. Used when data_type is omitted or set to RLE in the report config.

Column	Type	Nullable	Description
container_id	long	No	Parent container identifier.
channel_id	int	No	Channel identifier.
tstart	long	No	Sample start timestamp (microseconds).
tend	long	No	Sample end timestamp (microseconds).
value	double	Yes	Sample value.

Raw format

Raw timestamp-based data without RLE encoding — one row per sample. Used when data_type: RAW is set in the report config; the engine derives tend from subsequent timestamps and transforms the data into RLE before query execution.

Column	Type	Nullable	Description
container_id	long	No	Parent container identifier.
channel_id	int	No	Channel identifier.
timestamp	long	No	Sample timestamp (microseconds).
value	double	Yes	Sample value.

Optional is_plausible column

An optional is_plausible: boolean column may be present on channels in either format. It is only consulted when the solver is constructed with drop_implausible_data=True — in that mode, samples with is_plausible = False are filtered before RLE encoding. If the flag is False (the default), the column is ignored and may be omitted.

---

channel_mapping (optional)

Alias-resolution table used by KeyValueStoreSolver when selectors are created via QueryBuilder.channel_with_alias(). Each row maps a logical channel name to one or more physical channels keyed by project_id / data_key, with an optional priority tie-breaker.

Column	Type	Nullable	Description
project_id	int	No	Project identifier the mapping belongs to.
concept_id	int	No	Concept identifier (foreign key to the concept table).
element_id	int	No	Element identifier (foreign key to the concept-elements table).
project_name	string	Yes	Human-readable project name.
element_name	string	Yes	Human-readable element name.
channel_name	string	No	Logical channel name to match against channel_with_alias selectors.
data_key	string	No	Physical lookup key joined to channel_metrics.
priority	int	Yes	Tie-breaker when multiple physical channels match a logical name.

Configured via source.channel_mapping_table (see Configuration). Joins to channel_metrics on (project_id, data_key, channel_name).