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From John Sichi <>
Subject Re: HCatalog feature wish list
Date Fri, 29 Apr 2011 18:23:35 GMT
Regarding column-level properties in the metastore, I think Ashish was working on this; not
sure how far along that is.


On Apr 29, 2011, at 11:03 AM, Devaraj Das wrote:

> Hi Bill,
> Responses inline.
> Devaraj.
> On 4/29/11 9:39 AM, "Bill Graham" <> wrote:
> hi,
> We're starting to look into HCatalog to see if it can help us organize
> and catalog our data/schemas owned by various groups across our
> organization. As a result I have a few questions about some
> functionality that I don't think exists yet, but I could be mistaken
> (it's been a while since I last worked with Hive).
> If these aren't currently supported, would there be interest in
> including these features in the roadmap? If so we might be able to
> contribute resources to help implement some of them.
> - Custom table and field metadata
> Is it possible to annotate a table or columns with custom key/value
> metadata (i.e. table POCs, descriptions, column data formats, etc)?
> This Howl wiki ( had a one-liner about
> custom table metadata, but that's the only reference I've been able to
> find about this.
> Devaraj: Yes, tables can be annotated, with properties that look like key/value pairs.
> - Support for non-RDMS metadata storage
> We have groups that currently store a custom schema definition file in
> HDFS along side of their actual data. Would it be possible to direct
> HCatalog to consult this file instead of the DB for the schema info
> for this class of tables?
> Devaraj: HCatalog will soon have a tool that can import data schema to the metadata store.
At Yahoo!, the plan is to use this tool to migrate all old data. All new data should be directly
registered in HCatalog by the data producers. Would this suffice? 
> - Web UI
> Are there any know web UIs (or plans for one) to expose and even
> modify HCatalog data? We'd like to build a web UI that would help with
> data discovery. IIRC, facebook had something similar at one point.
> Devaraj: At Yahoo!, there is some internal effort going on in this direction.
> - Support for columnar DBs (i.e., HBase)
> I know this doesn't exist currently, but is this something being
> considered or requested? HCatalog is focused on fixed-width schemas,
> so this would be tricky to represent, but it seems worth exploring.
> There seems to be an emerging need to effectively manage and
> understand the schemas of such schema-less data stores. :)
> Devaraj: HCatalog will support HBase schemas at some point. Again, this is something
that Yahoo! has started looking at internally.
> thanks,
> Bill

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