Troubleshoot queries

Troubleshoot SQL and InfluxQL queries that return unexpected results.

• Why doesn’t my query return data?
• Optimize slow or expensive queries
• Analyze your queries
• Request help to troubleshoot queries

Why doesn’t my query return data?

If a query doesn’t return any data, it might be due to the following:

• Your data falls outside the time range (or other conditions) in the query–for example, the InfluxQL SHOW TAG VALUES command uses a default time range of 1 day.

• The query (InfluxDB server) timed out.

• The query client timed out.

• The query return type is not supported by the client library. For example, array or list types may not be supported. In this case, use array_to_string() to convert the array value to a string–for example:

  SELECT array_to_string(array_agg([1, 2, 3]), ', ')
  

If a query times out or returns an error, it might be due to the following:

• a bad request
• a server or network problem
• it queries too much data

Understand Arrow Flight responses and error messages for queries.

Optimize slow or expensive queries

If a query is slow or uses too many compute resources, limit the amount of data that it queries.

See how to optimize queries.

Analyze your queries

Use the following tools to retrieve system query information, analyze query execution, and find performance bottlenecks:

• Analyze a query plan
• Retrieve system.queries information for a query

Request help to troubleshoot queries

Some bottlenecks may result from suboptimal query execution plans and are outside your control–for example:

• Sorting (ORDER BY) data that is already sorted
• Retrieving numerous small Parquet files from the object store, instead of fewer, larger files
• Querying many overlapped Parquet files
• Performing a high number of table scans

If you’ve followed steps to optimize and troubleshoot a query, but it still doesn’t meet performance requirements, contact the InfluxData Support team for assistance.