tree 21610bb4f279ebf5a06433a32466e2d11033857a
parent 1bfe14d0356764597b1b23adb45dd2a1f299538e
author Luca Milanesio <luca.milanesio@gmail.com> 1666825608 +0100
committer Luca Milanesio <luca.milanesio@gmail.com> 1667557779 +0000

Allow indexing of change numbers imported from other servers

When importing repositories form other Gerrit servers, you may
have change numbers that are conflicting with other existing
changes created locally.

The conflict is not an issue from a project's perspective
because they are still unique within the same repository.
However, the Change.Id is used as primary key in Lucene
and therefore the imported changes would not be able to
be indexed.

By creating a virtual Change.Id for imported changes, the
Lucene indexing works as expected and the changes are
discoverable.

The Gerrit's ServerIds of the changes imported from other servers
are encoded in the three MSB (Most Significant Bit) of the
Change number, allowing up to 64 Gerrit servers with different
ServerIds to be imported, each one having up to 250M changes.

The above constraints are good enough for an initial solution
in Gerrit v3.7 that doesn't require any migration or reindex.

The encoding of the Gerrit imported ServerIds is done using a
dictionary that take the id as key and its position in the list as
the encoded value. That is a simple solution that gives complete
control and understanding of which change comes from where
to the Gerrit admin and allows a smoother migration to a
more general solution on master and the forthcoming v3.8.

The normal upgrade to v3.8 typically requires an on-line
reindex of the 'changes' index which will also automatically
regenerate the index entries with the virtual-id, making this
change fully forward-compatible.

Release-Notes: allow indexing of imported changes
Forward-Compatible: checked
Change-Id: I7b9acabb69d20ca071629257cacbd5a893e6f4a0