[MarkLogic Dev General] Querying across 2 or more MarkLogic databases

Michael Blakeley mike at blakeley.com
Sun Mar 11 16:44:41 PDT 2012


I presume that's flexible replication? That should be fine as long as the document URIs do not conflict. If they do, you will have documents from one database overwriting others. You could address that with a custom flex-rep apply module, which would be pretty easy to write.

-- Mike

On 11 Mar 2012, at 21:51 , Betty Harvey wrote:

> Thanks Mike and Geert:
> 
> Unfortunately the previous contractor architecture had multiple databases
> and these are in production and can't be modified without major overhaul
> the system.
> 
> Currently we have another MarkLogic instance where we have combined all
> the databases into a single repository for querying and reporting
> purposes. This isn't a long term solution because there is a lot of manual
> extraction and copying going on.
> 
> In the next few months hopefully we can replicate the database production
> database.
> 
> Another question about replication -- is it possible to replicate the
> multiple databases into a single repository.  In the temporary reporting
> environment we have set up we have all 3 databases in a single repository
> in separate directories.
> 
> If the replication into a single repository is possible that is a better
> solution.  We won't have to modify any of the standard reports that have
> been developed.
> 
> As always -- thanks for the advice!
> 
> Betty
> 
>> I agree with Geert. While cross-database queries are possible, it's often
>> better to use collections or directories rather than separate databases.
>> For example, text search results are generally ranked by score. Scores are
>> calculated per-database. So merging text search results between multiple
>> databases may produce odd rankings.
>> 
>> -- Mike
>> 
>> On 11 Mar 2012, at 20:15 , Geert Josten wrote:
>> 
>>> Hi Betty,
>>> 
>>> Yes, you can use xdmp:invoke, or xdmp:eval for that purpose, but you'll
>>> have to combine results yourself in memory, so that comes with a
>>> penalty.
>>> Might be worth considering replication/syncing between databases..
>>> 
>>> Kind regards,
>>> Geert
>>> 
>>>> -----Oorspronkelijk bericht-----
>>>> Van: general-bounces at developer.marklogic.com [mailto:general-
>>>> bounces at developer.marklogic.com] Namens Danny Sinang
>>>> Verzonden: zondag 11 maart 2012 20:55
>>>> Aan: MarkLogic Developer Discussion
>>>> Onderwerp: Re: [MarkLogic Dev General] Querying across 2 or more
>>> MarkLogic
>>>> databases
>>>> 
>>>> I think you can do so using xdmp:invoke with an Options clause
>>>> specifying a different database. Assign the results of that query to a
>>>> variable and use it in other queries on other db's.
>>>> 
>>>> Sent from my iPhone
>>>> 
>>>> On Mar 11, 2012, at 3:21 PM, "Betty Harvey" <harvey at eccnet.com> wrote:
>>>> 
>>>>> Is it possible to query across databases in MarkLogic?  I need to
>>> query
>>>>> across multiple databases to get a single view of data.
>>>>> 
>>>>> I haven't been able to find if this is possible.
>>>>> 
>>>>> TIA!
>>>>> 
>>>>> Betty
>>>>> 
>>>>> 
>>>>> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
>>>>> Betty Harvey                         | Phone:  410-787-9200  FAX: 9830
>>>>> Electronic Commerce Connection, Inc. |
>>>>> harvey at eccnet.com                    | Washington,DC XML Users Grp
>>>>> URL:  http://www.eccnet.com          | http://www.eccnet.com/xmlug
>>>>> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\\/\/
>>>>> Member of XML Guild (www.xmlguild.org)
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> 
> 
> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
> Betty Harvey                         | Phone:  410-787-9200  FAX: 9830
> Electronic Commerce Connection, Inc. |
> harvey at eccnet.com                    | Washington,DC XML Users Grp
> URL:  http://www.eccnet.com          | http://www.eccnet.com/xmlug
> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\\/\/
> Member of XML Guild (www.xmlguild.org)
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