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From Paul Davis <paul.joseph.da...@gmail.com>
Subject Re: Inability to back up and restore properly
Date Tue, 07 Apr 2009 15:59:58 GMT
On Mon, Apr 6, 2009 at 11:04 PM, Jeff Hinrichs - DM&T
<jeffh@dundeemt.com> wrote:
> What is the proper way to backup and restore a couchdb?  I mean a real
> proper dump/load cycle.
>
> couchdb doesn't provide a way to do a proper dump/reload cycle which leaves
> us to try and write our own.  However, if you dump a document like
>
> {'_id':'foo',''_rev':'2-xyz',...}
>
> There is not a single way that I can find to load an empty database and
> recreate that same record.  If you put the
> {'_id':'foo',''_rev':'2-xyz',...}, you get
> {'_id':'foo',''_rev':'3-mno',...},  which is not the same as
> {'_id':'foo',''_rev':'2-xyz',...}.
>

You'll need to look into the bulk_docs api as it's used by
replication. Admittedly this isn't properly documented just yet but
that is exactly the endpoint that would allow for this.

Glancing at the code, it looks like to accomplish what you want it'd
be something like:

POST /db_name/_bulk_docs

{
    "new_edits": false,
    "docs": [
        {"_id": "foo", "_rev": "2-xyz", ...}
    ]
}

> In some use cases it is necessary to be able to restore data to the way it
> was at a point in time.  Sometimes for logic reasons, some times for error
> recovery and debugging and some times for legal reasons.  The seemingly only
> way possible to do that is to bring up another couchdb instance and
> replicate to it.  However, that is a bit problematic for normal long term
> storage methodologies.
>
> What is the API I should be using?   If no such api exists, is it an
> oversight or just a matter of resources?  There should be a way to load data
> into couch and have couchdb just accept it, keeping the _rev information
> that is passed.  I am not proposing to change the mode of operation, but to
> create a new one.  Even better would be to have couchdb do a /database/_dump
> that streams out documents and a post /database/_load with the posted file
> from the /database/_dump.
>
> so that you have some couchdb database foo in state 'A', you dump, then
> create database bar, and load the dump from foo and when the process is
> finished, a replication from foo state 'A' to bar results in
> {"start_time":"Tue, 07 Apr 2009 03:02:16 GMT","end_time":"Tue, 07 Apr 2009
> 03:02:16
> GMT","start_last_seq":0,"end_last_seq":100,"missing_checked":100,"missing_found":0,"docs_read":0,"docs_written":0,"doc_write_failures":0}
>
>
> Regards,
>
> Jeff Hinrichs
>

You should also check out couchdb-python's dump-load scripts and Chris
Anderson's Ruby script on the breaking changes 0.9 page for other
examples of scripts to dump/reload a database.

HTH,
Paul Davis

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