8.8. Data Management

GeoMesa provides many ways to optimize your data storage. You can add additional indices to speed up certain queries, disable indices to speed up ingestion, pre-split tables for optimal data distribution and migrate data between tables or environments.

8.8.1. Accumulo Attribute Indices

See Attribute Index for an overview of attribute indices. The Accumulo data store extends the normal attribute indices with an additional ‘join’ format that stores less data.

8.8.1.1. Join Indices

Join indices store a reduced subset of data in the index - just the feature ID, the default date and the default geometry. To answer most queries, a join against the record index is required to retrieve the full simple features - hence the name join index. Joining against the record table is slow when returning many results, and should generally be avoided except for small queries.

GeoMesa will avoid joining against the record table if it is possible to answer a query with only the data in the join index. In general, this means that the query is only returning the properties for the default date, default geometry and the attribute being queried. In addition, any CQL filters must only operate on those three attributes as well.

To enable a join index, the keyword join may be used in place of true when specifying an attribute index in the SimpleFeatureType.

8.8.1.2. Full Indices

Full indices store the full simple feature. This takes up the most space on disk, but allows for any query to be answered without joining against the record table. This is the only option for non-Accumulo data stores. To use a full index, the keyword full or true may be used when specifying an attribute index in the SimpleFeatureType.

8.8.2. Accumulo Logical Timestamps

By default, GeoMesa index tables are created using Accumulo’s logical time. This ensures that updates to a given simple feature will be ordered correctly, however it obscures the actual insert time for the underlying data row. For advanced use cases, standard system time can be used instead of logical time. To disble logical time, add the following user data hint to the simple feature type before calling createSchema:

// append the hints to the end of the string, separated by a semi-colon
String spec = "name:String,dtg:Date,*geom:Point:srid=4326;geomesa.logical.time='false'";
SimpleFeatureType sft = SimpleFeatureTypes.createType("mySft", spec);

Warning

If table sharing is enabled, then the index tables may have already been created with logical time enabled. If this is the case, then disabling it will have no effect. To ensure the tables are created correctly, you may wish to disable table sharing by adding the user data string geomesa.table.sharing='false'

8.8.3. Table Sharing

By default, multiple SimpleFeatureTypes in a single catalog table will share the same physical Accumulo index tables. This will reduce the total number of Accumulo tables created. However, it may complicate administrator tasks, such as by making it impossible to set different tablet split sizes for different feature types. In addition, deleting a schema will generally be slower, as it requires deleting each data row, instead of just dropping the entire table.

Table sharing can be disabled by setting the user data geomesa.table.sharing to false:

// disable table sharing for this feature type
sft.getUserData().put("geomesa.table.sharing", "false");

See Setting Schema Options for more details on how to set user data values.

8.8.4. Upgrading Existing Indices

GeoMesa often makes updates to indexing formats to improve query and write performance. However, the index format for a given schema is fixed when it is first created. Updating GeoMesa versions will provide bug fixes and new features, but will not update existing data to new index formats.

The exact version of an index used for each schema can be read from the SimpleFeatureType user data, or by simple examining the name of the index tables created by GeoMesa. See below for a description of current index versions.

Using the GeoMesa command line tools, you can add or update an index to a newer version using add-index. For example, you could add the XZ3 index to replace the Z3 index for a feature type with non-point geometries. The command will populate the new index using a distributed job. For large data sets, you can choose to only populate features matching a CQL filter (e.g. the last month), or choose to not populate any data. The update is seamless, and clients can continue to query and ingest while it runs.

See add-index for more details on the command line tools.

8.8.5. Accumulo Index Versions

See Index Versioning for an explanation of index versions. The following versions are available in Accumulo:

Index Version GeoMesa Version Notes
1 1.1.0 Initial implementation
2 1.2.1

Support for non-point geometries

Support for shards

3 1.2.5

Removed support for non-point geometries in favor of xz

Removed redundant feature ID in row value to reduce size on disk

Support for per-attribute visibility

4 1.3.1 Support for table sharing
5 2.0.0 Uses fixed Z-curve implementation
Index Version GeoMesa Version Notes
1 1.2.2 Initial implementation
2 1.2.5

Removed support for non-point geometries in favor of xz

Removed redundant feature ID in row value to reduce size on disk

Support for per-attribute visibility

3 1.3.1 Optimized deletes
4 2.0.0 Uses fixed Z-curve implementation
Index Version GeoMesa Version Notes
1 1.2.5 Initial implementation
Index Version GeoMesa Version Notes
1 1.2.5 Initial implementation
Index Version GeoMesa Version Notes
1 1.0.0 Initial implementation
2 1.1.0 Added secondary date index
3 1.2.5

Removed redundant feature ID in row value to reduce size on disk

Support for per-attribute visibility

4 1.3.1 Added secondary Z index
5 1.3.2 Support for shards
6 2.0.0-m.1 Internal row layout change
7 2.0.0 Uses fixed Z-curve implementation
Index Version GeoMesa Version Notes
1 1.0.0 Initial implementation
2 1.2.5

Removed redundant feature ID in row value to reduce size on disk

Support for per-attribute visibility

3 2.0.0 Standardized index identifier to ‘id’

Note that GeoMesa versions prior to 1.2.2 included a geohash index. That index has been replaced with the Z indices and is no longer supported.