V17.3 very slow to open Tools > Preferences

>> so the index does not appear to be saved between sessions.

Correct, the index isn't persisted between sessions. We're looking at a way to make that possible.

It seems the code which indexes the preferences got restructured (at least), if not enhanced for 17.3.  The Java class for this (for which you can grab jstack full thread dumps when opening Tools > Preferences) does not exist in 17.2 even though it was last updated more than one month before 17.2 got released.  Possibly 17.3 does a better job of indexing keywords deeper down in the Preferences UI for the various extension pages.

As Jeff indicates, it seems very desirable to get this index cached in each release's user settings, perhaps in the system_cache.

Often my local network drives aren't available when I have a VPN started.

If you take multiple thread dumps with jstack while the index preferences task is running, one line you will always see in the "RaptorTaskThread01-IndexPreferencesTask" dump is...

at sun.awt.shell.Win32ShellFolder2.listFiles(Win32ShellFolder2.java:680)

usually after a...

at sun.awt.shell.Win32ShellFolderManager2.isFileSystemRoot(Win32ShellFolderManager2.java:456)

No idea what that does, or how long it takes, when local drives are hidden, so that could well be the the culprit.  But I doubt the processing is different just due to being on VPN.  The indexer is just looking for strings in Preferences UI.

Are you seeing the same 17.3 is much slower here than 17.2 as me on Windows 10 64 bit

Oh, definitely yes. Once SQL Developer's startup processing finishes after a few seconds, opening the preferences in 17.2 is almost instantaneous. The 9 second delay on 17.3 is reproducible, but the difference I see between VPN and non-VPN on 17.3 is minimal, maybe an additional 5 or 6 seconds.

Basically, in 17.3, the indexer's strategy is to instantiate panels present under the Preferences UI's tree (without actually displaying anything), then search for strings to index in the labels (of titles, combo boxes, input fields, etc).  So if you decide you wish to switch from English to Spanish by putting

AddVMOption  -Duser.language=es

in your sqldeveloper.conf file, the indexer will automatically index on the Spanish in the translated labels the Preferences UI will then display.  The problem is that some of those panels have as a component a URLFileChooser panel, which needs to check the file system.  This may not be a full or completely accurate depiction, but you get the point. 

We're looking at a fix now, thanks for the great info and your local perf #'s based on the different scenarios.