I´m asking because there were different date formats I can
imagine:
...
With this format it´s very efficient to query a date range
because only one table scan is needed.
...
...
...
When querying for [07-10-2015 til 09-10-2015] we need
multiple table scans and building an additional index would
be less efficient. (But now we can efficiently ask for
queries on a special day, e.g. 7th day. Although I believe
this type of query is very rare.)
> From:
cne1x@xxxxxxxx
> To:
geomesa-users@xxxxxxxxxxxxxxxx
> Date: Fri, 9 Oct 2015 07:23:57 -0400
> Subject: Re: [geomesa-users] Attribute Indexing
>
> Marcel,
>
> Roughly in order that you asked...
>
> 1. Yes, it is always possible to get the raw
key-value pairs out of
> Accumulo. The easiest way is via the Accumulo shell:
>
>
>
http://accumulo.apache.org/1.6/accumulo_user_manual.html#_accumulo_shell
>
> Login, and then scan the "_attr_idx" table with a
command somewhat
> similar to this:
>
> scan -t geomesa_attr_idx
>
> 2. There is nothing particularly novel about the way
GeoMesa stores
> secondary attribute indexes in the "_attr_idx" table.
This is a
> straight lexicographically-encoded-value storage.
>
> 3. There are two parts to using secondary indexes
effectively:
> encoding and querying. The best references are to the
GeoMesa source
> where these occur:
>
> encoding:
>
https://github.com/locationtech/geomesa/blob/master/geomesa-accumulo/geomesa-accumulo-datastore/src/main/scala/org/locationtech/geomesa/accumulo/data/tables/AttributeTable.scala
>
> querying:
>
https://github.com/locationtech/geomesa/blob/master/geomesa-accumulo/geomesa-accumulo-datastore/src/main/scala/org/locationtech/geomesa/accumulo/index/AttributeIdxStrategy.scala
>
> Enjoy!
>
> Sincerely,
> -- Chris
>
>
> On Fri, 2015-10-09 at 11:27 +0200, Marcel wrote:
> > Hello,
> >
> > is there a possibility to get the complete "raw"
key-value pair of a
> > table as it is saved (a sample would be enough)?
I want to look in the
> > "_attr_idx" table and understand how the index
is built, e.g. when
> > indexing additional attributes like another
Date, an Integer or a
> > String. Is it this a special or a common
strategy (adapted for Accumulo)
> > for indexing? What fields available in the
Accumulo table dsign did you
> > use (RowId, ColumnFamily, etc.)?
> >
> > Thanks,
> > Marcel Jacob.
> >
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