Fix full table scans in reminder storage overview queries#92
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Aaronontheweb merged 1 commit intoMar 9, 2026
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…wAsync GetNextRemindersAsync had two performance bugs introduced during the provider package split (0ce1026): 1. Called GetRemindersOverviewAsync and discarded the result, loading all rows and deserializing all payloads for nothing. 2. Opened a second connection to load ALL rows (including completed) into memory, just to compute COUNT and MIN(WhenUtc) of remaining reminders. GetRemindersOverviewAsync itself had the same issue — loading all rows to compute two scalar values. Replace GetOverviewSql (SELECT * FROM table) with: - GetOverviewAggregateSql: SELECT COUNT(*), MIN(when_utc) - GetNextReminderTimeSql: SELECT when_utc ... OFFSET @Skip LIMIT 1 This eliminates all full table scans and payload deserialization from the overview/summary code paths across all three SQL providers (SqlServer, PostgreSQL, SQLite). Also adds XML doc comments to IReminderStorage.GetRemindersOverviewAsync clarifying it is for diagnostics/testing/monitoring only and must not be called from the scheduling hot path.
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This was referenced Mar 13, 2026
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Summary
GetNextRemindersAsyncandGetRemindersOverviewAsyncacross all three SQL providers (SqlServer, PostgreSQL, SQLite)GetOverviewSql(which returned all columns for all rows) with two efficient aggregate queries:GetOverviewAggregateSql:SELECT COUNT(*), MIN(when_utc) WHERE is_completed = 0GetNextReminderTimeSql:SELECT when_utc ... ORDER BY when_utc OFFSET @Skip LIMIT 1GetRemindersOverviewAsynccall insideGetNextRemindersAsync(result was discarded)IReminderStorage.GetRemindersOverviewAsyncclarifying it is for diagnostics/testing/monitoring only and must not be called from the scheduling hot pathContext
GetNextRemindersAsynchad two performance bugs introduced during the provider package split (0ce1026):GetRemindersOverviewAsyncand stored result in an unused variable — loading all rows and deserializing all payloads for nothing.COUNTandMIN(WhenUtc)of remaining reminders.GetRemindersOverviewAsyncitself had the same issue — loading every row to compute two scalar values.Structural safeguard
GetOverviewSqlhas been removed from theISqlDialectinterface entirely. The only overview-related queries now return aggregate scalars, making it structurally impossible to accidentally reintroduce a full table scan through the overview path.Test plan