Indexing sometime fails with SQLite error about UNIQUE constraint failed. #3622
Description
Sometime, during Indexing, hls returns an exception:
HieDb writer thread SQLite error:\n SQLite3 returned ErrorConstraint while attempting to perform step: UNIQUE constraint failed: defs.hieFile, defs.occ
Your environment
Using NixOS, GHC 9.6.2 (but was happening with 9.6.1 recently), neovim and HLS 1.9.1.0 built from source with minor patchs which should not be relevant (see #TODO)
The project is built with nix with a custom build system and the setup of HLS is done with custom in-house scripts.
Steps to reproduce
I have no idea.
Expected behaviour
Maybe the exception is due to a bug in the indexing mechanism, the exception should not be returned.
Actual behaviour
HieDb writer thread SQLite error:\n SQLite3 returned ErrorConstraint while attempting to perform step: UNIQUE constraint failed: defs.hieFile, defs.occ
Debug information
Note that I observed this exception and wrote #3610 (comment) because of it. In that MR, I fixed the way HLS was reacted to this exception (it was forgetting to remove the Indexing status), but not the cause of the exception.