You cannot upgrade more than one major version, you must re-index from scratch.
There’s a long discussion of why, but basically it’s summed up by this quote
from Robert Muir:
“I think the key issue here is Lucene is an index not a database. Because it is
a lossy index and does not retain all of the user's data, its not possible to
safely migrate some things automagically. In the norms case IndexWriter needs
to re-analyze the text ("re-index") and compute stats to get back the value, so
it can be re-encoded. The function is y = f(x) and if x is not available its
not possible, so lucene can't do it.”
This has always been true, before 8x it would just fail silently as you have
found. Solr/Lucene starts up but don’t work quite as expected. As of Lucene
8x, Lucene (and therefore Solr) will not even open an index that has _ever_
been touched by Lucene 6x, no matter what intervening steps have been taken. Or
in general, Lucene/Solr X will not open indexes touched by X-2, starting
with 8x rather than behave unexpectedly.
Best,
Erick
> On Jun 5, 2019, at 8:27 AM, Riccardo Tasso <riccardo.ta...@gmail.com> wrote:
>
> Hello everybody,
> I have a (very big) lucene 4 index with documents using IntField. On that
> field, which should be stored and sortable, I should search and execute
> range queries.
>
> I've tried to upgrade it from 4 to 7 with IndexUpgrader but I observed that
> IntFields aren't searchable anymore.
>
> Which is the most efficient way to convert IntFields to IntPoints, which
> are stored and sortable?
>
> Thanks,
> Riccardo
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