On 29th of November 2018, Alvaro Herrera committed patch:
Add log_statement_sample_rate parameter This allows to set a lower log_min_duration_statement value without incurring excessive log traffic (which reduces performance). This can be useful to analyze workloads with lots of short queries. Author: Adrien Nayrat Discussion: https://postgr.es/m/-ee1e-db9f-fa97-@anayrat.info
Continue reading Waiting for PostgreSQL 12 – Add log_statement_sample_rate parameter