update postgresql parameters for db investigations

ops/services/postgres_db/main.tf

@@ -66,3 +66,40 @@ resource "azurerm_postgresql_flexible_server_configuration" "pgms_wait_sampling_
   server_id = azurerm_postgresql_flexible_server.db.id
   value     = "ALL"
 }
+
+# resource "azurerm_postgresql_flexible_server_configuration" "extensions" {
+#   name      = "azure.extensions"
+#   server_id = azurerm_postgresql_flexible_server.db.id
+#   value     = "PG_STAT_STATEMENTS"
+# }
+
+# AzureDiagnostics
+# | where ResourceProvider =="MICROSOFT.DBFORPOSTGRESQL" 
+# | where Category == "PostgreSQLLogs"
+# | where Message contains "duration:"
+
+resource "azurerm_postgresql_flexible_server_configuration" "log_min_duration_statement" {
+  name      = "log_min_duration_statement"
+  server_id = azurerm_postgresql_flexible_server.db.id
+  value     = 0
+}
+
+# This is useful for finding queries that have the most impact on our system. It's disabled by default for performance reasons.
+
+# Top 10 I/O intensive queries:
+# select userid::regrole, dbid, query
+# from pg_stat_statements
+# order by (blk_read_time+blk_write_time)/calls desc
+# limit 10;
+
+# Top 10 time comsuming queries:
+# select userid::regrole, dbid, query
+# from pg_stat_statements
+# order by mean_time desc
+# limit 10;
+
+resource "azurerm_postgresql_flexible_server_configuration" "pg_stat_statements" {
+  name      = "pg_stat_statements.track"
+  server_id = azurerm_postgresql_flexible_server.db.id
+  value     = "top"
+}