To install qt4-mac-postgresql83-plugin, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install qt4-mac-postgresql83-plugin
To see what files were installed by qt4-mac-postgresql83-plugin, run:
port contents qt4-mac-postgresql83-plugin
To later upgrade qt4-mac-postgresql83-plugin, run:
sudo port selfupdate && sudo port upgrade qt4-mac-postgresql83-plugin
Reporting an issue on MacPorts Trac
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Though anyone may search Trac for tickets, you must have a GitHub account in order to login to Trac to create tickets.