Follow-on to the plugin_metrics indexes. plugin_metrics is already retention-
bounded (core cleanup prunes > data.retention_days, default 90d) and charts top
out at 30d, so the cost wasn't growth — it was the read path shipping raw rows
to Python.
- _history_for_host: bucket + average in SQL via date_bin (epoch-aligned, ~120
buckets) instead of fetching every raw sample (a 30d range was hundreds of
thousands of rows) and downsampling in Python. Uses the new
(source_module, resource_name, recorded_at) index.
- _latest_metrics_for_host: DISTINCT ON (resource_name, metric_name) ORDER BY
recorded_at DESC — newest row per group in one index-ordered pass, replacing
the GROUP-BY-max subquery self-joined back to the whole history.
- Integration test validates both against Postgres.
Deliberately not a materialized raw→hourly rollup: these query-side changes
deliver the speed; a rollup would additionally cut storage and remains a future
option if scale demands it.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC
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