The % Selects Scanning alert notifies you when its configured condition is met on MySQL and MariaDB instances so you can investigate and respond.
Mini DBA describes this alert as: % of select statements that are using table scans. Found by using the metrics: select_scans / com_select. The active alert only evaluates when there is enough SELECT volume and measurable server workload, so idle or near-idle servers do not alert on tiny samples. The lower the better, look to write queries and tune indexes so index seeks are used instead of table scans. Mini DBA evaluates this alert once a minute so changes are detected quickly. Because duration is used, Mini DBA can avoid treating a single short spike as a full incident when the condition clears quickly.
This alert helps reveal query and workload pressure. It points you toward expensive statements, plan changes, inefficient access patterns, or bursts of work that need investigation before they affect service levels.
Enable it on any monitored MySQL and MariaDB instance where this condition would require an administrator to investigate or communicate with the application team. Tune noisy development systems after you have a short baseline.
Threshold meaning: %. Major threshold: 90 %. Minor threshold: 70 %. Comparison direction: over. Duration is used, so prefer requiring the condition to persist before paging people for transient spikes. For an over-threshold alert, decreasing a threshold makes that severity fire sooner; increasing it tolerates more load or pressure. Set the minor threshold as an early-warning level and the major threshold at the highest acceptable value for the service.
Use the query, wait, and performance views to find the statement or subsystem behind the pressure. Compare against the recent baseline, update statistics, tune indexes, adjust application batching, and move maintenance work away from peak periods where possible.
If the alert creates repeated noise, review whether it is enabled on the correct instances, whether maintenance windows are configured, and whether the minor and major routes match the real business impact. Keep enough history to prove the new setting before changing it broadly.