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Re: [geomesa-users] Schema of st_idx table 
Vaibhav,

For what it's worth, the "st_idx" table is about to be deprecated in
favor of a new Z3 structure.  We will shortly have documentation up
describing how the new structure works.  (The short version is that it's
a concatenation of the most-significant bits of T and a Z-order
combination of X, Y, and the low-order bits of T.)

In the "st_idx" table, the value is typically a Kryo-encoded version of
the entire Feature, which allows us to do fine-grained filtering within
the Accumulo iterators beyond the spatio-temporal constraints.

Secondary indexes, those not involving (X, Y, T), are created by
concatenating the feature-type name with the attribute name and the
value within the "attr_idx" table.  The value in this table will be
either a Kryo-encoded version of the Feature or the record ID (depending
on the index type requested in the SimpleFeature specification, "full"
or "join", respectively.)  This way, if we know that an attribute's
value has high selectivity (high cardinality), we can seek directly to
the part of the "attr_idx" table where those records reside.  This
structure also enables range queries and right-hand wildcards on
attribute values.

I hope this helps.  If you have any additional questions, please just
let us know.

Thanks!

Sincerely,
  -- Chris


On Thu, 2015-09-10 at 17:45 +0530, vaibhav.thapliyal wrote:
> Hello everyone,
> 
> I am trying to use geomesa for querying geo-spatial data. While doing 
> so, I came across the st_idx table which is used to index 
> spatio-temporal data. On reading the research paper I found out the way 
> indexing is being done, and how data is mapped on Row, colf and 
> col-qualifier, using geo-hashed value of the lat-lon ie how the key is 
> being generated. What I am failing to understand is what is contained 
> inside the Value field of Accumulo.
> 
> Also if someone could explain how is non-spatial temporal data (for eg 
> Customer Name)is stored/indexed in geomesa, it would be very helpful.
> 
> Thanks
> Vaibhav
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