How to diagnose and fix the 39000 external_routine_invocation_exception error code in Postgres.

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The 39000 error code in PostgreSQL, known as external_routine_invocation_exception, indicates that there is an exception related to the invocation of an external routine. This error can occur in various situations, such as when an external function is called with incorrect parameters or when there is an issue with the external environment that the function depends on. To diagnose and fix this error, consider the following steps:

  1. Review the Function Call: Check the function call for any incorrect parameters or syntax errors. Ensure that the number and type of arguments passed to the function match its definition.
  2. Check the External Environment: If the function relies on an external service or system, verify that it is accessible and functioning correctly. Issues like network connectivity problems, service outages, or authentication failures can trigger this error.
  3. Examine Function Definitions and Return Types: Ensure that the function definition in PostgreSQL matches the actual implementation of the external routine. The return type specified in PostgreSQL should match the expected return type of the external function.
  4. Look for NULL Values: If the function is not designed to handle NULL values and one is passed as an argument, it may result in a 39000 error. Modify the function to handle NULL values appropriately or ensure that NULLs are not passed as arguments.
  5. Consult PostgreSQL Logs: Review the PostgreSQL server logs for more detailed information about the error. The logs may provide insights into what went wrong during the external routine invocation.

Here are some examples and sample code to illustrate potential scenarios:

  • Scenario 1: Incorrect number of function arguments.
  -- Suppose the external function expects two arguments but only one is provided
  SELECT my_external_function('argument1');

To fix this, provide the correct number of arguments as expected by the function:

  SELECT my_external_function('argument1', 'argument2');
  • Scenario 2: Handling NULL values improperly.
  -- Suppose 'my_external_function' does not handle NULL input well
  SELECT my_external_function(NULL);

Modify the function to handle NULL values correctly, or ensure that the input is not NULL:

  SELECT my_external_function(COALESCE(input_value, 'default_value'));
  • Scenario 3: External service is not reachable.
  -- External function relies on an external service
  SELECT my_external_service_function('parameter');

In this case, verify that the external service is running and reachable from the PostgreSQL server.

Remember, when diagnosing and fixing the 39000 error code, it’s important to carefully inspect all error messages and logs, check the external routine’s configuration and dependencies, and ensure that the function is being called correctly. If the issue persists after checking these areas, consulting the official PostgreSQL Error Codes documentation or seeking assistance from the PostgreSQL community may provide further guidance.

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