according to, this answer https://discuss.elastic.co/t/optimize-logstash-configuration/239574/3 I realized I have to compare
lastest row date and
last run date.
but the problem is I don't know that.
I can find last run date from my $HOME path.
there is a date. like this.
--- 2020-07-02 09:00:00 blahblah
I think I have to compare this my pg latest row's date column.
how can I get this as a variable in input plugin?