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Identify stale statistics in projection columns

How to check periodically whether any projection having stale statistics? 

Comments

  • Hi

     

    You can use projections table to check the same as given in below example.With has_statistics equal to false means that no. of projections has stale statistics. 

     

    vsql=> select has_statistics,count(*) from projections group by has_statistics;
    has_statistics | count
    ----------------+-------
    f | 16
    t | 8030
    (2 rows)

     

    vsql=> dbadmin=> select projection_name,has_statistics from projections where has_statistics='f';
    projection_name | has_statistics
    ----------------------------------------------------------------+----------------
    dc_requests_retried_raw_super | f
    vs_tuning_rules_raw_super | f
    client_auth_params_raw_super | f
    vs_system_tables_raw_super | f
    dc_catalog_operations_raw_super | f
    vs_projection_column_expressions_raw_super | f
    query_metrics_raw_super | f
    vs_parameters_catalog_raw_super | f
    dc_resource_acquisitions_raw_super | f
    dc_lock_requests_raw_super | f
    vs_catalog_event_add_derived_column_raw_super | f
    vs_plan_steps_raw_super | f

     

     

    You can further analyse_statistics() function to compute the statistics for found projections from above query.

     

    Thanks

    Rahul

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