postinst is in rt3.8-db-mysql 3.8.11-1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | #!/bin/sh
set -e
# source debconf library so that the .config is executed anew
. /usr/share/debconf/confmodule
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