PostgresqlInvalidIndex

PostgresqlInvalidIndex #

The table {{ $labels.relname }} has an invalid index: {{ $labels.indexrelname }}. You should execute DROP INDEX {{ $labels.indexrelname }};

Alert Rule
alert: PostgresqlInvalidIndex
annotations:
  description: |-
    The table {{ $labels.relname }} has an invalid index: {{ $labels.indexrelname }}. You should execute `DROP INDEX {{ $labels.indexrelname }};`
      VALUE = {{ $value }}
      LABELS = {{ $labels }}    
  runbook: https://srerun.github.io/prometheus-alerts/runbooks/postgres-exporter/postgresqlinvalidindex/
  summary: Postgresql invalid index (instance {{ $labels.instance }})
expr: pg_general_index_info_pg_relation_size{indexrelname=~".*ccnew.*"}
for: 6h
labels:
  severity: warning

Meaning #

The PostgresqlInvalidIndex alert is triggered when Prometheus detects an invalid index in a PostgreSQL database. This alert is raised when the pg_general_index_info_pg_relation_size metric, which monitors the size of indexes in the database, reports an index with a name matching the pattern .*ccnew.*. This indicates that there is an invalid index present in the database, which can lead to performance issues and errors.

Impact #

The presence of an invalid index can have several negative impacts on the database performance and reliability:

  • Query performance degradation: Invalid indexes can cause queries to take longer to execute, leading to slower response times and decreased overall system performance.
  • Error propagation: Invalid indexes can cause errors to propagate through the system, leading to data inconsistencies and potential data loss.
  • Maintenance complexity: Invalid indexes can make database maintenance tasks, such as backups and upgrades, more difficult and prone to errors.

Diagnosis #

To diagnose the issue, follow these steps:

  1. Identify the affected database instance: Check the instance label in the alert notification to determine which database instance is affected.
  2. Identify the affected table and index: Check the relname and indexrelname labels in the alert notification to determine which table and index are affected.
  3. Verify the index validity: Run the following command to verify the index validity: psql -d <database_name> -c "SELECT * FROM pg_index WHERE indexrelname = '<index_name>'" (replace <database_name> and <index_name> with the actual values).
  4. Check the index size: Run the following command to check the index size: psql -d <database_name> -c "SELECT pg_relation_size('<index_name>')" (replace <database_name> and <index_name> with the actual values).

Mitigation #

To mitigate the issue, follow these steps:

  1. Drop the invalid index: Run the following command to drop the invalid index: psql -d <database_name> -c "DROP INDEX <index_name>" (replace <database_name> and <index_name> with the actual values).
  2. Re-create the index (optional): If the index is essential for query performance, re-create the index after dropping it. Make sure to create the index with the correct parameters and options.
  3. Verify database consistency: Run database consistency checks to ensure that the database is in a consistent state.
  4. Monitor database performance: Closely monitor database performance and query execution times to ensure that the issue is fully resolved.

Remember to follow your organization’s change management procedures and database maintenance best practices when performing these mitigation steps.

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