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From Keith Turner <ke...@deenlo.com>
Subject Re: Column Scan / table metadata
Date Wed, 18 Sep 2013 19:37:46 GMT
On Wed, Sep 18, 2013 at 3:25 PM, Josh Elser <josh.elser@gmail.com> wrote:

> On Wed, Sep 18, 2013 at 3:15 PM, Keith Turner <keith@deenlo.com> wrote:
>
> > On Wed, Sep 18, 2013 at 2:42 PM, Devin Pinkston <
> devinfpinkston@gmail.com
> > >wrote:
> >
> > > I have been looking through the Accumulo source to try and find the
> best
> > > way to derive the column structure/metadata of a table.  If I have a
> > table
> > >
> >
> > Metadata in RFile contains some info about column families, but not
> column
> > qualifiers.   For the default locality group rfile keeps track of up to
> > 1000 column families.  If you run "accumulo rfile-info" you can see this
> > info.
> >
>
> Isn't that metadata only updated on compaction, Keith?
>

Yes, you would only see data flushed to disk.  Also RFiles on disk may
contain data thats deleted in another RFile.  So you could see columns in
the rfile metadata that would never show up in a scan.


>
>
> >
> >
> > > "sample", and I want to find all the column families/qualifiers, is
> > there a
> > > built-in facility in Accumulo to get a list of columns in that table?
>  Or
> > > would my best option be to scan() the entire table, and only put unique
> > > column families/qualifiers into a list and return to the user?
> > >
> > > I am imagining the user has no idea of what their columns are like in
> > this
> > > table, that is why I ask.
> > >
> > > Thanks!
> > >
> >
>

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