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Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

UDF Constraints

Within the constraints listed in this topic, you can use UDFs anywhere you use the Amazon Redshift built-in scalar functions. For more information, see SQL Functions Reference.

Amazon Redshift UDFs have the following constraints:

  • UDFs cannot access the network or read or write to the file system.

  • The total size of user-installed libraries cannot exceed 100 MB.

  • The number of UDFs that can run concurrently per cluster is limited to one-fourth of the total concurrency level for the cluster. For example, if the cluster is configured with a concurrency of 15, a maximum of three UDFs can run concurrently. After the limit is reached, UDFs are queued for execution within workload management queues. For more information, see Implementing Workload Management.