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fix(sql): Optimize GetLatestObservations #140

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Merged
devsjc merged 1 commit into from
Mar 24, 2026
Merged

fix(sql): Optimize GetLatestObservations #140

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53 changes: 34 additions & 19 deletions internal/server/postgres/sql/queries/observations.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -82,28 +82,43 @@ WHERE
/* GetLatestObservations gets the latest observations for a given location set, source type, and
* observer. The value is returned as a 16-bit integer, with 0 representing 0%
* and 30000 representing 100% of capacity.
*
* It uses lateral joins to perform a reverse index scan for efficiency.
*/
SELECT DISTINCT ON (og.geometry_uuid, og.source_type_id, o.observer_uuid)
og.geometry_uuid,
og.source_type_id,
og.observation_timestamp_utc,
og.value_sip,
WITH target_locations AS (
SELECT UNNEST(sqlc.arg(geometry_uuids)::UUID []) AS geometry_uuid
),
target_observer AS (
SELECT observer_uuid
FROM obs.observers
WHERE observer_name = LOWER(sqlc.arg(observer_name)::TEXT)
)
SELECT
tl.geometry_uuid::UUID AS geometry_uuid, -- SQLC complains without this
sqlc.arg(source_type_id)::SMALLINT AS source_type_id,
latest_obs.observation_timestamp_utc,
latest_obs.value_sip,
sh.capacity_limit_sip,
sh.capacity_watts
FROM obs.observed_generation_values AS og
INNER JOIN loc.sources_mv AS sh USING (geometry_uuid, source_type_id)
INNER JOIN obs.observers AS o USING (observer_uuid)
WHERE
og.geometry_uuid = ANY(sqlc.arg(geometry_uuids)::UUID [])
AND og.source_type_id = $1
AND o.observer_name = LOWER(sqlc.arg(observer_name)::TEXT)
AND sh.sys_period @> og.observation_timestamp_utc
AND og.observation_timestamp_utc <= sqlc.arg(pivot_time_utc)::TIMESTAMP
ORDER BY
og.geometry_uuid ASC,
og.source_type_id ASC,
o.observer_uuid ASC,
og.observation_timestamp_utc DESC;
FROM target_locations AS tl
CROSS JOIN target_observer AS tobs
CROSS JOIN
LATERAL (
SELECT
og.observation_timestamp_utc,
og.value_sip
FROM obs.observed_generation_values AS og
WHERE og.geometry_uuid = tl.geometry_uuid
AND og.source_type_id = sqlc.arg(source_type_id)::SMALLINT
AND og.observer_uuid = tobs.observer_uuid
AND og.observation_timestamp_utc <= sqlc.arg(pivot_time_utc)::TIMESTAMP
ORDER BY og.observation_timestamp_utc DESC
LIMIT 1
) AS latest_obs
INNER JOIN loc.sources_mv AS sh
ON tl.geometry_uuid = sh.geometry_uuid
AND sh.source_type_id = sqlc.arg(source_type_id)::SMALLINT
AND sh.sys_period @> latest_obs.observation_timestamp_utc;

-- name: ListObservationsAtTimeForLocations :many
/* ListObservationsAtTimeForLocations retrieves observed generation values as percentages
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