Is Identify Tables With Missing Statistics Query Resutl redshift_audot_health_check Meaningful?

Question

I executing the diagnostic queries for Redshift. The query below is the  one for *Identifying tables with missing statistics*.  The page discussing these queries, and this query specifically, is located at this link[ here](https://docs.aws.amazon.com/redshift/latest/dg/diagnostic-queries-for-query-tuning.html#identify-tables-with-missing-statistics).

```
-- https://docs.aws.amazon.com/redshift/latest/dg/diagnostic-queries-for-query-tuning.html#identify-tables-with-missing-statistics
select substring(trim(plannode),1,100) as plannode, count(*)
from stl_explain
where plannode like '%missing statistics%'
group by plannode
order by 2 desc;
```

This is the result set. I obfuscated the eight-digit portion to be the string of `9` characters from the original value 
```
plannode,count
----- Tables missing statistics: redshift_auto_health_check_99999999 -----,10223
```

Per the documentation, I ran the `ANALYZE` command on the table `redshift_auto_health_check_99999999'. The error response was:
[42P01] ERROR: relation "redshift_auto_health_check_9999999" does not exist

In the parameter group for my Redshift cluster, the `auto_analyze` parameter is set to `true`.

**Question:** Is there any recommended action to improve operations of my cluster given the `----- Tables missing statistics: redshift_auto_health_check_99999999 -----,10223` that this table is not found?

This seems like a situation where there's nothing further important with regard to tuning and to just move forward.

**EDIT:** Looking further at the results from the diagnostic queries. I think the missing statistics for the list table is a trivial concern.

Answer

Hello,

That table `redshift_auto_health_check_99999999` is an internal table used by internal Redshift monitoring tool to periodically monitor the health of the cluster.

You can disregard this table from the output of the query. In your particular case, since it returned only this table, it means the statistic of recent queried tables is up to date.

There are other factors that may affect the query performance, such as uneven data distribution, unsorted rows, cluster node configuration, WLM configuration, etc. This [doc](https://docs.aws.amazon.com/redshift/latest/dg/diagnostic-queries-for-query-tuning.html) addresses most of this factors. Additionally, you can also refer to this [article](https://repost.aws/knowledge-center/redshift-cluster-degrade ) with some recommended actions to troubleshoot cluster or query performance.

You are also welcome to open a support case with AWS using the following [link](https://console.aws.amazon.com/support/home#/case/create) so that a Support Engineer will be able to investigate details of your cluster workload to provide a more accurate recommendation.

Is Identify Tables With Missing Statistics Query Resutl redshift_audot_health_check Meaningful?

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