Document the PostgreSQL schema contract in doc.go

internal/sinks/postgres/doc.go

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+// Package postgres documents weatherfeeder's PostgreSQL sink contract for
+// downstream SQL consumers.
+//
+// This package wires weatherfeeder canonical events into normalized relational
+// tables. Downstream consumers can reconstruct the same canonical JSON objects
+// that were written by joining parent/child tables as described below.
+//
+// Canonical input schemas:
+//   - weather.observation.v1 -> model.WeatherObservation
+//   - weather.forecast.v1    -> model.WeatherForecastRun
+//   - weather.alert.v1       -> model.WeatherAlertRun
+//
+// Parent/child relationships:
+//   - observations.event_id -> observation_cloud_layers.event_id
+//   - observations.event_id -> observation_present_weather.event_id
+//   - forecasts.event_id    -> forecast_periods.run_event_id
+//   - alert_runs.event_id   -> alerts.run_event_id
+//   - alerts.(run_event_id, alert_index) -> alert_references.(run_event_id, alert_index)
+//
+// Dedupe and retention behavior:
+//   - Parent primary keys (event_id): observations, forecasts, alert_runs.
+//   - Child primary keys use positional indexes to preserve payload order.
+//   - Prune columns:
+//   - observations.observed_at
+//   - observation_cloud_layers.observed_at
+//   - observation_present_weather.observed_at
+//   - forecasts.issued_at
+//   - forecast_periods.issued_at
+//   - alert_runs.as_of
+//   - alerts.as_of
+//   - alert_references.as_of
+//
+// Envelope field mapping (shared parent columns)
+//
+// These columns exist on observations, forecasts, and alert_runs:
+//   - event_id TEXT -> event.id
+//   - event_kind TEXT -> event.kind
+//   - event_source TEXT -> event.source
+//   - event_schema TEXT -> event.schema
+//   - event_emitted_at TIMESTAMPTZ -> event.emitted_at
+//   - event_effective_at TIMESTAMPTZ NULL -> event.effective_at
+//
+// Table contract
+//
+//  1. observations (PK: event_id)
+//
+//     - event_id TEXT -> event.id
+//     - event_kind TEXT -> event.kind
+//     - event_source TEXT -> event.source
+//     - event_schema TEXT -> event.schema
+//     - event_emitted_at TIMESTAMPTZ -> event.emitted_at
+//     - event_effective_at TIMESTAMPTZ NULL -> event.effective_at
+//     - station_id TEXT NULL -> payload.stationId
+//     - station_name TEXT NULL -> payload.stationName
+//     - observed_at TIMESTAMPTZ -> payload.timestamp
+//     - condition_code INTEGER -> payload.conditionCode
+//     - condition_text TEXT NULL -> payload.conditionText
+//     - is_day BOOLEAN NULL -> payload.isDay
+//     - provider_raw_description TEXT NULL -> payload.providerRawDescription
+//     - text_description TEXT NULL -> payload.textDescription
+//     - icon_url TEXT NULL -> payload.iconUrl
+//     - temperature_c DOUBLE PRECISION NULL -> payload.temperatureC
+//     - dewpoint_c DOUBLE PRECISION NULL -> payload.dewpointC
+//     - wind_direction_degrees DOUBLE PRECISION NULL -> payload.windDirectionDegrees
+//     - wind_speed_kmh DOUBLE PRECISION NULL -> payload.windSpeedKmh
+//     - wind_gust_kmh DOUBLE PRECISION NULL -> payload.windGustKmh
+//     - barometric_pressure_pa DOUBLE PRECISION NULL -> payload.barometricPressurePa
+//     - sea_level_pressure_pa DOUBLE PRECISION NULL -> payload.seaLevelPressurePa
+//     - visibility_meters DOUBLE PRECISION NULL -> payload.visibilityMeters
+//     - relative_humidity_percent DOUBLE PRECISION NULL -> payload.relativeHumidityPercent
+//     - apparent_temperature_c DOUBLE PRECISION NULL -> payload.apparentTemperatureC
+//     - elevation_meters DOUBLE PRECISION NULL -> payload.elevationMeters
+//     - raw_message TEXT NULL -> payload.rawMessage
+//
+//  2. observation_cloud_layers (PK: event_id, layer_index)
+//
+//     - event_id TEXT -> observations.event_id / payload.cloudLayers[i]
+//     - layer_index INTEGER -> i (array position in payload.cloudLayers)
+//     - observed_at TIMESTAMPTZ -> payload.timestamp
+//     - base_meters DOUBLE PRECISION NULL -> payload.cloudLayers[i].baseMeters
+//     - amount TEXT NULL -> payload.cloudLayers[i].amount
+//
+//  3. observation_present_weather (PK: event_id, weather_index)
+//
+//     - event_id TEXT -> observations.event_id / payload.presentWeather[i]
+//     - weather_index INTEGER -> i (array position in payload.presentWeather)
+//     - observed_at TIMESTAMPTZ -> payload.timestamp
+//     - raw_text TEXT NULL -> JSON-encoded payload.presentWeather[i].raw
+//
+// Note: raw_text stores compact JSON text. Consumers that need the original
+// object should parse raw_text as JSON.
+//
+//  4. forecasts (PK: event_id)
+//
+//     - event_id TEXT -> event.id
+//     - event_kind TEXT -> event.kind
+//     - event_source TEXT -> event.source
+//     - event_schema TEXT -> event.schema
+//     - event_emitted_at TIMESTAMPTZ -> event.emitted_at
+//     - event_effective_at TIMESTAMPTZ NULL -> event.effective_at
+//     - location_id TEXT NULL -> payload.locationId
+//     - location_name TEXT NULL -> payload.locationName
+//     - issued_at TIMESTAMPTZ -> payload.issuedAt
+//     - updated_at TIMESTAMPTZ NULL -> payload.updatedAt
+//     - product TEXT -> payload.product
+//     - latitude DOUBLE PRECISION NULL -> payload.latitude
+//     - longitude DOUBLE PRECISION NULL -> payload.longitude
+//     - elevation_meters DOUBLE PRECISION NULL -> payload.elevationMeters
+//     - period_count INTEGER -> len(payload.periods)
+//
+//  5. forecast_periods (PK: run_event_id, period_index)
+//
+//     - run_event_id TEXT -> forecasts.event_id / payload.periods[i]
+//     - period_index INTEGER -> i (array position in payload.periods)
+//     - issued_at TIMESTAMPTZ -> payload.issuedAt (copied from parent)
+//     - start_time TIMESTAMPTZ -> payload.periods[i].startTime
+//     - end_time TIMESTAMPTZ -> payload.periods[i].endTime
+//     - name TEXT NULL -> payload.periods[i].name
+//     - is_day BOOLEAN NULL -> payload.periods[i].isDay
+//     - condition_code INTEGER -> payload.periods[i].conditionCode
+//     - condition_text TEXT NULL -> payload.periods[i].conditionText
+//     - provider_raw_description TEXT NULL -> payload.periods[i].providerRawDescription
+//     - text_description TEXT NULL -> payload.periods[i].textDescription
+//     - detailed_text TEXT NULL -> payload.periods[i].detailedText
+//     - icon_url TEXT NULL -> payload.periods[i].iconUrl
+//     - temperature_c DOUBLE PRECISION NULL -> payload.periods[i].temperatureC
+//     - temperature_c_min DOUBLE PRECISION NULL -> payload.periods[i].temperatureCMin
+//     - temperature_c_max DOUBLE PRECISION NULL -> payload.periods[i].temperatureCMax
+//     - dewpoint_c DOUBLE PRECISION NULL -> payload.periods[i].dewpointC
+//     - relative_humidity_percent DOUBLE PRECISION NULL -> payload.periods[i].relativeHumidityPercent
+//     - wind_direction_degrees DOUBLE PRECISION NULL -> payload.periods[i].windDirectionDegrees
+//     - wind_speed_kmh DOUBLE PRECISION NULL -> payload.periods[i].windSpeedKmh
+//     - wind_gust_kmh DOUBLE PRECISION NULL -> payload.periods[i].windGustKmh
+//     - barometric_pressure_pa DOUBLE PRECISION NULL -> payload.periods[i].barometricPressurePa
+//     - visibility_meters DOUBLE PRECISION NULL -> payload.periods[i].visibilityMeters
+//     - apparent_temperature_c DOUBLE PRECISION NULL -> payload.periods[i].apparentTemperatureC
+//     - cloud_cover_percent DOUBLE PRECISION NULL -> payload.periods[i].cloudCoverPercent
+//     - probability_of_precipitation_percent DOUBLE PRECISION NULL -> payload.periods[i].probabilityOfPrecipitationPercent
+//     - precipitation_amount_mm DOUBLE PRECISION NULL -> payload.periods[i].precipitationAmountMm
+//     - snowfall_depth_mm DOUBLE PRECISION NULL -> payload.periods[i].snowfallDepthMm
+//     - uv_index DOUBLE PRECISION NULL -> payload.periods[i].uvIndex
+//
+//  6. alert_runs (PK: event_id)
+//
+//     - event_id TEXT -> event.id
+//     - event_kind TEXT -> event.kind
+//     - event_source TEXT -> event.source
+//     - event_schema TEXT -> event.schema
+//     - event_emitted_at TIMESTAMPTZ -> event.emitted_at
+//     - event_effective_at TIMESTAMPTZ NULL -> event.effective_at
+//     - location_id TEXT NULL -> payload.locationId
+//     - location_name TEXT NULL -> payload.locationName
+//     - as_of TIMESTAMPTZ -> payload.asOf
+//     - latitude DOUBLE PRECISION NULL -> payload.latitude
+//     - longitude DOUBLE PRECISION NULL -> payload.longitude
+//     - alert_count INTEGER -> len(payload.alerts)
+//
+//  7. alerts (PK: run_event_id, alert_index)
+//
+//     - run_event_id TEXT -> alert_runs.event_id / payload.alerts[i]
+//     - alert_index INTEGER -> i (array position in payload.alerts)
+//     - as_of TIMESTAMPTZ -> payload.asOf (copied from parent)
+//     - alert_id TEXT -> payload.alerts[i].id
+//     - event TEXT NULL -> payload.alerts[i].event
+//     - headline TEXT NULL -> payload.alerts[i].headline
+//     - severity TEXT NULL -> payload.alerts[i].severity
+//     - urgency TEXT NULL -> payload.alerts[i].urgency
+//     - certainty TEXT NULL -> payload.alerts[i].certainty
+//     - status TEXT NULL -> payload.alerts[i].status
+//     - message_type TEXT NULL -> payload.alerts[i].messageType
+//     - category TEXT NULL -> payload.alerts[i].category
+//     - response TEXT NULL -> payload.alerts[i].response
+//     - description TEXT NULL -> payload.alerts[i].description
+//     - instruction TEXT NULL -> payload.alerts[i].instruction
+//     - sent TIMESTAMPTZ NULL -> payload.alerts[i].sent
+//     - effective TIMESTAMPTZ NULL -> payload.alerts[i].effective
+//     - onset TIMESTAMPTZ NULL -> payload.alerts[i].onset
+//     - expires TIMESTAMPTZ NULL -> payload.alerts[i].expires
+//     - area_description TEXT NULL -> payload.alerts[i].areaDescription
+//     - sender_name TEXT NULL -> payload.alerts[i].senderName
+//     - reference_count INTEGER -> len(payload.alerts[i].references)
+//
+//  8. alert_references (PK: run_event_id, alert_index, reference_index)
+//
+//     - run_event_id TEXT -> alert_runs.event_id / payload.alerts[i].references[j]
+//     - alert_index INTEGER -> i (array position in payload.alerts)
+//     - reference_index INTEGER -> j (array position in payload.alerts[i].references)
+//     - as_of TIMESTAMPTZ -> payload.asOf (copied from parent)
+//     - id TEXT NULL -> payload.alerts[i].references[j].id
+//     - identifier TEXT NULL -> payload.alerts[i].references[j].identifier
+//     - sender TEXT NULL -> payload.alerts[i].references[j].sender
+//     - sent TIMESTAMPTZ NULL -> payload.alerts[i].references[j].sent
+//
+// Reconstructing canonical JSON payloads
+//
+//   - WeatherObservation:
+//     read one row from observations, then join child rows by event_id ordered by
+//     layer_index / weather_index to rebuild cloudLayers and presentWeather arrays.
+//
+//   - WeatherForecastRun:
+//     read one row from forecasts, then join forecast_periods by run_event_id
+//     ordered by period_index to rebuild periods.
+//
+//   - WeatherAlertRun:
+//     read one row from alert_runs, join alerts by run_event_id ordered by
+//     alert_index, then join alert_references by (run_event_id, alert_index)
+//     ordered by reference_index to rebuild references per alert.
+package postgres