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From Steven Jacobs <sjaco...@ucr.edu>
Subject Re: Metadata changes
Date Mon, 14 Dec 2015 19:12:53 GMT
Here are the conclusions that Ildar and I have drawn from looking at the
secondary indexes:

First of all it seems that datasets are local to node groups, but
dataverses can span node groups, which seems a little odd to me.

There are three Metadata secondary indexes:  GROUPNAME_ON_DATASET_INDEX,
DATATYPENAME_ON_DATASET_INDEX, DATATYPENAME_ON_DATATYPE_INDEX

The first is used in only one case:
When dropping a node group, check if there are any datasets using this node
group. If so, don't allow the drop
BUT, this index has a field called "dataverse" which is not used at all.

The second is used when dropping a datatype. If there is a dataset using
this datatype, don't allow the drop.
Similarly, this index has a "dataverse" which is never used.

The third index is used to go in two cases, using two different ideas of
"keys"
It seems like this should actually be two different indexes.

This is my understanding so far. It would be good to discuss what the
"correct" version should be.
Steven




On Mon, Dec 14, 2015 at 10:12 AM, Steven Jacobs <sjaco002@ucr.edu> wrote:

> Hi all,
> I'm implementing a change so that datasets can use datatypes from
> alternate data verses (previously the type and set had to be from the same
> dataverse). Unfortunately this means another change for Dataset Metadata
> (which will now store the dataverse for its type).
>
> As such, I had a couple of questions:
>
> 1) Should this change be thrown into the release branch, as it is another
> Metadata change?
>
> 2) In implementing this change, I've been looking at the Metadata
> secondary indexes. I had a discussion with Ildar, and it seems the thread
> on Metadata secondary indexes being "hacked" has been lost. Is this also
> something that should get into the release? Is there anyone currently
> looking at it?
>
> Steven
>

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