perf(grafana): add user_id filter to direct cml_data queries - #60
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The four queries in cml-realtime.json that hit cml_data directly
(RSL/TSL × auto/raw) filtered only by cml_id. The PostgreSQL planner
therefore scanned data for all users matching that CML id, taking
12-16 s for a 2-day window on a hypertable with ~1 B rows.
Adding AND user_id = '${__user.login}' supplies user_id as a literal
constant (Grafana substitutes the variable before sending SQL to
PostgreSQL), enabling the composite index on (user_id, cml_id, time DESC)
to restrict the scan to only the authenticated user's data. Measured
speedup: ~1.4 s vs ~16 s (~11×) for a 2-day window.
Note: Row-Level Security cannot be used here because TimescaleDB
rejects ENABLE ROW LEVEL SECURITY when compression is active on the
hypertable. The composite index with an explicit user_id predicate
achieves the equivalent performance benefit.
The ${__user.login} Grafana variable matches the PostgreSQL role name
because Grafana and PostgreSQL user provisioning are kept in sync via
users.yml / generate_config.py.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #60 +/- ##
==========================================
+ Coverage 86.10% 87.59% +1.48%
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Files 39 35 -4
Lines 3418 3038 -380
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- Hits 2943 2661 -282
+ Misses 475 377 -98
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The four queries in cml-realtime.json that hit cml_data directly (RSL/TSL × auto/raw) filtered only by cml_id. The PostgreSQL planner therefore scanned data for all users matching that CML id, taking 12-16 s for a 2-day window on a hypertable with ~1 B rows.
Adding AND user_id = '${__user.login}' supplies user_id as a literal constant (Grafana substitutes the variable before sending SQL to PostgreSQL), enabling the composite index on (user_id, cml_id, time DESC) to restrict the scan to only the authenticated user's data. Measured speedup: ~1.4 s vs ~16 s (~11×) for a 2-day window.
Note: Row-Level Security cannot be used here because TimescaleDB rejects ENABLE ROW LEVEL SECURITY when compression is active on the hypertable. The composite index with an explicit user_id predicate achieves the equivalent performance benefit.
The ${__user.login} Grafana variable matches the PostgreSQL role name because Grafana and PostgreSQL user provisioning are kept in sync via users.yml / generate_config.py.