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List:       solr-user
Subject:    Re: Backup from old server and Restore to new server
From:       "Vincenzo D'Amore" <v.damore () gmail ! com>
Date:       2023-09-30 14:39:53
Message-ID: CA+8z68=esuLZKN6updXBV1fWbHK1hXrkBSWmUB1mSag6qU8aFQ () mail ! gmail ! com
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Hi Gus, given that OP said "...I copied the entire core over, conf and data
directories." I assume he has a standalone solr instance.

On Thu, Sep 28, 2023 at 6:09 PM Gus Heck <gus.heck@gmail.com> wrote:

> Scanned this thread, apologies if I missed something, but here's a few
> thoughts:
>
> To get better advice make it clear if you are running Solr in Cloud mode
> (a.k.a. self managed) or Legacy (a.k.a user managed). Some ways to know
> which quickly:
>
>    1. Is there an associated Zookeeper cluster? If yes, then you are in
>    cloud mode if not then *probably* legacy (there's a way to run zookeeper
>    embedded, but that's not the normal setup).
>    2. In the admin UI do you see the word 'Cloud' in the left navigation
>    bar? If yes, cloud, if no, legacy
>
> *Key concept: Solr is (normally) just a server providing access to an index
> of your data. It allows you to find a link, or id for a "document" but does
> not (normally) serve as a repository for your data.*
>
> This has some implications:
>
>    1. Solr is typically paired with one or more data repositories
>    (database, file system, sharepoint, etc)
>    2. Solr normally cannot reindex data all by itself. Re-indexing is the
>    process of re-reading the repository, and creating a fresh index.
>    3. Solr is just an index, and does not manage the process of reading the
>    data from sources (Exceptions like Data import handler[DIH] and
> streaming
>    expressions exist, but DIH went away in 9.x and these are exceptions not
>    the rule)
>    4. Typically *something* outside of solr sends documents to solr.
>    Re-indexing is normally the process of re-triggering something to send
> the
>    documents again.
>    5. This is unlike a database which contains both the data (the table)
>    and an index (PK/FK/index) of the data.
>    6. Versus a database, Solr's benefit is that it is an index of the
>    *words* in the text of the document rather than entire string values.
>
> Thus (exceptional cases excluded) things you do to or in solr don't
> "trigger reindexing".
>
> I have implied that sometimes solr can be the store for your data, which is
> technically true. Unfortunately, this is tricky to get right, may
> negatively impact performance, and results in long term data loss if done
> wrong, so it's rarely recommended. I hope you haven't inherited this type
> of problem!
>
> Upgrading Solr across a single minor version is often simple, but
> occasionally requires work. Always read release notes and test the result
> before going live. Upgrading across major versions is always work. Lucene
> (and therefore solr) requires that you reindex data with each major
> version. There are stopgap tools to allow an upgrade of an existing index,
> but that is a temporary measure that only works for N to N+1 and you are
> expected to re-index before N+2.
>
> - Gus
>
> --
> http://www.needhamsoftware.com (work)
> https://a.co/d/b2sZLD9 (my fantasy fiction book)
>


-- 
Vincenzo D'Amore


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