WARNING: could not open pipe (GetLastError()=5)
If you found this error when running Sphinx indexer and your system is Windows, all you have to do is search for cmd.exe and open it as administrator and try again to rotate your indexes.
If it doesn’t work you have to delete it and install it again:
searchd --delete --servicename SphinxSearch
searchd --install --config "C:/path/to/sphinx.conf" --servicename SphinxSearch