pg_stat_statement not collecting information about queries inside functions.

Hello all

pg_stat_statements does not seem to collect metrics for queries inside functions, in my understanding this should be possible.
Is there a documentation about restrictions or has someone a clue why this is not working for me?

Values of parameters that may influence the behaviour:

shared_preload_libraries = 'pgaudit,pg_stat_statements'
pg_stat_statements.track = 'all'
pg_stat_statements.max = 20000
track_functions = 'all'

the function header:
CREATE OR REPLACE FUNCTION core.sf_generic_daily_merge_landing_to_target(
p_sys_daily_load_run_key bigint)
RETURNS integer
LANGUAGE 'plpgsql'
COST 100
VOLATILE PARALLEL UNSAFE
AS $BODY$
Declare

Best Regards
Rolf


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