Which Redshift System Table Records Query Optimizer Performance Alerts?
A data engineering team is using an Amazon Redshift data warehouse for operational reporting. The team wants to prevent performance issues that might result from long- running queries. A data engineer must choose a system table in Amazon Redshift to record anomalies when a query optimizer identifies conditions that might indicate performance issues. Which table views should the data engineer use to meet this requirement?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
The exam tests whether you can match Redshift system-table purposes to a monitoring requirement, and the trap is choosing a table that exposes query metrics or plan details instead of optimizer alert events.
Amazon Redshift's STL_ALERT_EVENT_LOG stores query optimizer alerts that signal conditions likely to cause performance problems. This page confirms why STL_ALERT_EVENT_LOG, not STL_QUERY_METRICS or STL_PLAN_INFO, is the correct system table for recording those anomalies.
A frequent mistake is selecting STL_QUERY_METRICS because it sounds performance-related, but it returns query metric rows rather than the optimizer-generated alert events requested.
Community Discussion (5 comments)
Comments & Corrections
No comments yet — spotted an error or have a note? Share it below.
Expert Analysis
Why the Answer Is Correct
STL_ALERT_EVENT_LOG is the Redshift system table specifically built to record alerts emitted by the query optimizer when it detects conditions that may degrade query performance, such as missing statistics or suboptimal plans. The requirement asks for a table that records anomalies when the optimizer identifies potential performance issues, which is exactly this table's role. As Felix_G noted, it "records any alerts/notifications related to queries or user-defined performance thresholds". pypelyncar similarly described alerts generated when Redshift detects conditions that might indicate performance issues. Therefore B satisfies the wording directly.Why the Other Options Are Wrong
STL_USAGE_CONTROL tracks usage-control limits and related events, not query optimizer performance warnings; as HagarTheHorrible explained, it is about "usage limits and controls." STL_QUERY_METRICS exposes per-query metric values such as rows processed and bytes transferred, but it does not log optimizer-detected anomalies. STL_PLAN_INFO provides execution-plan details for queries, so it can help diagnose a plan but is not the alert-event table that records the optimizer's performance warnings. None of these tables replaces STL_ALERT_EVENT_LOG for the stated requirement.Community Comment Notes
Several learners converged on STL_ALERT_EVENT_LOG, with GiorgioGss and rralucard_ pointing to the AWS documentation page for the table. Felix_G highlighted its role in capturing query-related alerts, while HagarTheHorrible contrasted it with STL_USAGE_CONTROL as a limits/control table. The community consensus aligns with the independent analysis, but the deciding factor remains the question's wording about optimizer-identified performance conditions.Official Reference
Exam Strategy
When a Redshift question asks for optimizer warnings or performance anomalies, eliminate tables whose names point to metrics, plan details, or usage control before selecting the alert/event log. Read the exact noun in the stem—alert, event, or anomaly—because it usually maps directly to STL_ALERT_EVENT_LOG.
Frequently Asked Questions
Why is STL_QUERY_METRICS not the right table for optimizer alerts?
STL_QUERY_METRICS returns per-query metric values such as rows and bytes, but it does not record optimizer-generated alert events; those are in STL_ALERT_EVENT_LOG.
Does STL_PLAN_INFO show optimizer warnings?
No, STL_PLAN_INFO provides execution-plan details, not the alert/event records that document optimizer-detected performance conditions.
Related Analysis
Practice All DEA-C01 Questions
Access 100 questions with complete answers and detailed explanations.
View Full DEA-C01 Practice Test →