On 18/12/2018 17:40, Erick Erickson wrote:
You are far better off re-indexing totally.
I would add '...if you have the original data'. Not everyone *can*
re-index, and there are various hairy ways of updating an index in
place, but they require deep-level magic.
But if you have the original source data, you should re-index.
Cheers
Charlie
Using IndexUpgraderTool has never guaranteed compatibility
across multiple major releases. I.e. if you have an index built
with 4x, using that tool will work for 5x, but then going from 5x
to 6x _even after the entire index is rewritten from 4 x format_
has never been guaranteed to work. By "guaranteed to work"
here, I mean that there can be subtle problems, regardless
of appearances
The two most succinct statements as to why this is true follow.
I will not second guess _anything_ these two people have to
say about how Lucene works ;)
From Mike McCandless:
“This really is the difference between an index and a database:
we do not store, precisely, the original documents. We store an
efficient derived/computed index from them.”
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...
The function is y = f(x) and if x is not available its not possible, so
lucene can't do it.”
As of 6x, a marker is written into each segments and the lowest
version is retained when segments are merged. 8x will refuse
to start if it detects a 6x marker so this will be enforced soon.
Best,
Erick
On Mon, Dec 17, 2018 at 12:27 PM Pushkar Raste <pushkar.ra...@gmail.com> wrote:
Hi,
I have questions about the IndexUpgrader tool.
- I want to upgrade from Solr 4 to Solr 7. Can I run upgrade the index from
4 to 5 then 5 to 6 and finally 6 to 7 using appropriate version of the
IndexUpgrader but without loading the Index in the Solr at all during the
successive upgrades.
- The note in the tool says "This tool only keeps last commit in an index".
Does this mean I have optimize the index before running the tool?
- There is another note about partially upgraded index. How can the index
be partially upgraded. One scenario I can think of is 'If I upgraded let's
say from Solr 5 to Solr 6 and then added some documents. The new documents
will be in Lucerne 6 format already, while old documents will still be Solr
5 format’ Is my understanding correct?
--
Charlie Hull
Flax - Open Source Enterprise Search
tel/fax: +44 (0)8700 118334
mobile: +44 (0)7767 825828
web: www.flax.co.uk
