Which Redshift System Table Records Query Optimizer Performance Alerts?

DEA-C01 By islever Editorial Last updated

Maintain and monitor data pipelines.

Short answer

B Use STL_ALERT_EVENT_LOG in Amazon Redshift to capture query optimizer alerts that flag conditions likely to cause performance issues.

Question

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?
  1. STL_USAGE_CONTROL
  2. STL_ALERT_EVENT_LOG Correct Answer
  3. STL_QUERY_METRICS
  4. STL_PLAN_INFO

Key Takeaways

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.

Common mistake: 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.

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

These links open the official vendor documentation in a new tab.

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.

More DEA-C01 FAQ →

Community Votes

B
100%

100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. Felix_G 👍 5
    B STL_ALERT_EVENT_LOG records any alerts/notifications related to queries or user-defined performance thresholds. This would capture optimizer alerts about potential performance issues. STL_PLAN_INFO provides detailed info on execution plans. The optimizer statistics and warnings provide insight into problematic query plans. STL_USAGE_CONTROL limits user activity but does not log anomalies. STL_QUERY_METRICS has execution stats but no plan diagnostics. By enabling alerts and checking STL_ALERT_EVENT_LOG and STL_PLAN_INFO, the data engineer can best detect and troubleshoot queries flagged by the optimizer as problematic before they impair performance. This meets the requirement to catch potential long running queries.
  2. GiorgioGss 👍 5 Answered B
    https://docs.aws.amazon.com/redshift/latest/dg/r_STL_ALERT_EVENT_LOG.html
  3. pypelyncar 👍 1 Answered B
    this table records alerts that are generated by the Amazon Redshift system when it detects certain conditions that might indicate performance issues. These alerts are triggered by the query optimizer when it detects suboptimal query plans or other issues that could affect performance.
  4. rralucard_ 👍 1 Answered B
    https://docs.aws.amazon.com/redshift/latest/dg/cm_chap_system-tables.html STL_ALERT_EVENT_LOG table view to meet this requirement. This system table in Amazon Redshift is designed to record anomalies when a query optimizer identifies conditions that might indicate performance issues
  5. HagarTheHorrible 👍 1 Answered B
    Control table is related to usage control metrics and doesn't focus on performance issues or anomalies related to query optimization. It's more about usage limits and controls.

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