How to replace source list in old postgres:9 image before effectively run apt-get update

I would like to install java in final dockerfile stage from postgres:9, and I have to change following outdated addresses:

RUN sed -i s/deb.debian.org/archive.debian.org/g /etc/apt/sources.list
RUN sed -i s/apt.postgresql.org/apt-archive.postgresql.org/g /etc/apt/sources.list
RUN sed -i s/security.debian.org/archive.debian.org/g /etc/apt/sources.list
RUN sed -i s/stretch-updates/stretch/g /etc/apt/sources.list
RUN sed -i s/stretch-updates/stretch/g /etc/apt/sources.list

but after command RUN apt-get update && apt-get install -y openjdk-8-jre-headless && apt-get clean update command inside docker is still looking for http://apt.postgresql.org/ ... ex. `Err:6 http://apt.postgresql.org/pub/repos/apt stretch-pgdg/main amd64 Packages 2.414 404 Not Found [IP: 87.238.57.227 80]` where can I find the http://apt.postgresql.org/pub/repos/apt resource to effectively replace?