The PostgreSQL source code for released versions
   can be obtained from the download section of our website:
   https://www.postgresql.org/ftp/source/.
   Download the
   postgresql-
   or version.tar.gzpostgresql-
   file you're interested in, then unpack it:
version.tar.bz2
tar xf postgresql-version.tar.bz2
   This will create a directory
   postgresql- under
   the current directory with the PostgreSQL sources.
   Change into that directory for the rest of the installation procedure.
  version
Alternatively, you can use the Git version control system; see Section I.1 for more information.