PG config improvements

- load `pg_stat_statement`, `auto_explain` modules
- void autovacuum in the "tx ID wraparound prevention" mode

Author: NikolayS

configs/postgres/postgresql.conf

@@ -14,6 +14,12 @@
 #logging_collector
 #log_directory
 
+# Load pg_stat_statements and auto_explain for query analysis
+shared_preload_libraries = 'pg_stat_statements, auto_explain'
+
+# Avoid running autovacuum in the "transaction ID wraparound prevention" mode
+autovacuum_freeze_max_age = 1000000000
+
 listen_addresses = '*'
 
 log_destination = 'stderr'
@@ -24,7 +30,9 @@ log_connections = on
 ## If you want to have more clones use a lower value.
 shared_buffers = '1GB'
 
-# detect idle clones
+# To be able to detect idle clones, we need to log all queries.
+# We are going to do so with duration.
+# TODO: switch to "auto_explain.log_min_duration = 0" instead (set log_min_duration_statement = -1)
 log_min_duration_statement = 0
 log_statement = 'none'
 log_timezone = 'Etc/UTC'