dhis2-users team mailing list archive

[Bob Jolliffe <bobjolliffe@xxxxxxxxx>]

If database B is restored off a backup of database A then it will
probably work with some caveats.  Clearly they are not exactly the
same because you've got extra data in A which you are trying to push
into B.  So it depends really on what else might have changed in A.

If you have made any changes to orgunits, datelements or periods then
that will cause at best a database integrity violation when you try to
import that way.  At worst cause a very horrible mess.

Even though the process is fragile, there is a related use case where
one might need to do such a thing or something similar.  If a country
system is hosted somewhere in the cloud (because they have poor or
expensive local bandwidth) then there is a real problem to solve about
getting data backups from the server back into the country.

In particular we'd like to be able to pull not all the datavalues but
only those which have been changed ie. do an incremental backup of the
datavalues table.  The same could apply to events.

One possible approach might be to first do a metadata backup and
restore.  And then pull the changed datavalues - though you would have
to do this through the api with uids or codes as the metadata backup
and restore would have ignored the database identifiers.

Yet another approach would be to take a reduced postgres backup
excluding the datavalues table, restore that and then try and pull in
the delta of datavalues table something like you describe.

Its a tough problem.  Jason, what do you suggest?  Downloading the
full postgres backup (with ephemeral tables like analytics excluded)
can be a serious challenge for many countries to do with regularity
and reliability.  So how best to go about incremental backup and
restore of data?

On 20 April 2015 at 15:36, Muyepa A. <muyepaa@xxxxxxxxx> wrote:
> I had thought of  data import/export functionality, however this will
> require two instances of tomcat to be running. (or one instance with one
> database at a time, however there will be an associated down time).
> Since upgrading to 2.18, when exported, the resultant download zip file says
> invalid for all formats (xml, json, excel) and is only 2kb in size
> regardless of the hierarchy I choose.
>
> Since one database is copy of the other, i thought I could easily update
> from the other as described.
>
> On Mon, Apr 20, 2015 at 3:48 PM, Jason Pickering
> <jason.p.pickering@xxxxxxxxx> wrote:
>>
>> It may work, but in general, it will not because the internal IDs of
>> different DHIS2 databases are not the same. So, it might work, but it
>> requires both databases to be in essentially the same state. Better to use
>> the data import/export functionality if you can.
>>
>> Regards,
>> Jason
>>
>>
>> On Mon, Apr 20, 2015 at 3:28 PM Muyepa A. <muyepaa@xxxxxxxxx> wrote:
>>>
>>> Can I safely update DHIS2 database A with data from DHIS database B both
>>> on the same PostgreSQL server by cross query. B is backup of A
>>>
>>> From database B, I can retrieve and save the data that is required using:
>>>
>>> psql B -c "\copy (select * from datavalue where  periodid='xxxx') TO
>>> STDOUT" > /tmp/data.tsv;
>>>
>>>
>>> And to restore:
>>> psql A -c "\copy datavaue (x, y, z, ...) FROM /tmp/data.tsv"
>>>
>>>
>>> Is this recommended, and what else should be cross  transferred.
>>>
>>>
>>>
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