We currently provide procedures to create the following kind of tilesets:
Spatial index tiles (aggregates spatial indexes into tiles at specific resolutions)
Geometry-based tiles of two types:
simple tilesets to visualize features individually
aggregation tilesets to generate aggregated point visualizations
CREATE_VECTOR_TILESET
CREATE_VECTOR_TILESET(input, output, options)
Description
Generates a simple tileset.
input: STRING that can either contain a table name (e.g. database.schema.tablename) or a full query (e.g.(SELECT * FROM database.schema.tablename)).
output: STRING of the format database.schema.tablename where the resulting tileset will be stored. The database and schema must exist and the caller needs to have permissions to create a new table in it.
options: STRING containing a valid JSON with the different options. Valid options are described in the table below.
warning
If a query is passed in input, it might be evaluated multiple times to generate the tileset. Thus, non-deterministic functions, such as [ROW_NUMBER] should be avoided. If such a function is needed, the query should be saved into a table first and then passed as input, to avoid inconsistent results.
Option
Description
if_exists
Default: "fail". A STRING that indicates if the process will fail if the table already exists, if set to "fail". Or any existing table will be replaced, if set to "replace".
geom_column
Default: "geom". A STRING that indicates the name of the geography column that will be used. The geography column must be a WKB with type BINARY. If your input table contains geographies in WKT format, they can be converted to WKB by using ST_ASWKB(ST_GEOMFROMWKT(<geom_column>)) AS <geom_column> in your input query.
zoom_min
Default: 0. A INTEGER that defines the minimum zoom level at which tiles will be generated. Any zoom level under this level won't be generated.
zoom_max
Default: 12. A INTEGER that defines the maximum zoom level at which tiles will be generated. Any zoom level over this level won't be generated.
max_tile_vertices
Default: 200000. A INTEGER that sets the maximum number of vertices a tile can contain. This limit only applies when the input geometries are lines or polygons. When this maximum is reached, the procedure will drop features according to the chosen max_tile_size_strategy. You can configure in which order the features are kept by setting the tile_feature_order property.
max_tile_features
Default: 10000. A INTEGER that sets the maximum number of features a tile can contain. This limit only applies when the input geometries are points. When this limit is reached, the procedure will stop adding features into the tile. You can configure in which order the features are kept by setting the tile_feature_order property.
tile_feature_order
Default: RANDOM() for points, ST_AREA() DESC for polygons, ST_LENGTH() DESC for lines. A STRING defining the order in which properties are added to a tile. This expects the SQL ORDER BYkeyword definition, such as "aggregated_total DESC". The "ORDER BY" part must not be included. You can use any source column even if it is not included in the tileset as a property.
include_geoids
Default: false. Generates an additional geoids column that contains the geoid value from each row in the input data that intersects with the tile. This option is required to use the resulting tileset as a boundary.
metadata
Default: {}. A JSON object to specify the associated metadata of the tileset. Use this to set the name, description and legend to be included in the TileJSON. Other fields will be included in the object extra_metadata.
properties
Default: "". A STRING that defines the properties that will be included associated with each cell feature. Each property is defined by using SQL syntax and can make use of the columns present in the input table. Note that every property different from Number will be casted to String.
input: STRING that can either contain a table name (e.g. database.schema.tablename) or a full query (e.g.(SELECT * FROM database.schema.tablename)).
output: STRING of the format database.schema.tablename where the resulting tileset will be stored. The database and schema must exist and the caller needs to have permissions to create a new table in it.
options: STRING containing a valid JSON with the different options. Valid options are described in the table below.
warning
If a query is passed in input, it might be evaluated multiple times to generate the tileset. Thus, non-deterministic functions, such as [ROW_NUMBER] should be avoided. If such a function is needed, the query should be saved into a table first and then passed as input, to avoid inconsistent results.
Option
Description
if_exists
Default: "fail". A STRING that indicates if the process will fail if the table already exists, if set to "fail". Or any existing table will be replaced, if set to "replace".
geom_column
Default: "geom". A STRING that indicates the name of the geography column that will be used. The geography column must be a WKB with type BINARY. If your input table contains geographies in WKT format, they can be converted to WKB by using ST_ASWKB(ST_GEOMFROMWKT(<geom_column>)) AS <geom_column> in your input query.
zoom_min
Default: 0. An INTEGER that defines the minimum zoom level at which tiles will be generated. Any zoom level under this level won't be generated.
zoom_max
Default: 12; maximum: 20. An INTEGER that defines the maximum zoom level at which tiles will be generated. Any zoom level over this level won't be generated.
aggregation_resolution
Default: 6. An INTEGER that specifies the resolution of the spatial aggregation.
Aggregation for zoom z is based on quadgrid cells at z + resolution level. For example, with resolution 6, the z0 tile will be divided into cells that match the z6 tiles, or the cells contained in the z10 tile will be the boundaries of the z16 tiles within them. In other words, each tile is subdivided into 4^resolution cells, which is the maximum number of resulting features (aggregated) that the tiles will contain.
Note that adding more granularity necessarily means heavier tiles which take longer to be transmitted and processed in the final client, and you are more likely to hit the internal memory limits.
aggregation_placement
Default: "cell-centroid". A STRING that defines what type of geometry will be used to represent the cells generated in the aggregation, which will be the features of the resulting tileset. There are currently four options:
"cell-centroid": Each feature will be defined as the centroid of the cell, that is, all points that are aggregated together into the cell will be represented in the tile by a single point positioned at the centroid of the cell.
"features-any": The aggregation cell will be represented by any random point from the source data contained within it. That is, if 10 points fall inside a cell, the procedure will randomly choose the location of one of them to represent the aggregation cell.
"features-centroid": The feature will be defined as the centroid (point) of the collection of points within the cell.
metadata
Default: {}. A JSON object to specify the associated metadata of the tileset. Use this to set the name, description and legend to be included in the TileJSON. Other fields will be included in the object extra_metadata.
properties
Default: "". A STRING that defines the properties that will be included associated with each cell feature. Each property is defined by using SQL syntax and should include a formula to be applied to the values of the points that fall under the cell. This formula can be any SQL formula that uses an aggregate function supported by Databricks. Note that every property different from Number will be casted to String.
FEATURES PER TILE LIMITS
The value of aggregation_resolution sets an upper bound to how many features can be present in a tile. For a value of n, a maximum of 4^n (4 raised to n) features can be present in a tile. For example, for an aggregation resolution of 8, the maximum number of features (points) will be 65536 per tile. This value can be too high and produce tiles that are too large when either the aggregation resolution is high or many properties are included. In that case, to improve the performance of the map visualizations, the max_tile_features should be used to limit the size of the tiles to about 1MB.
Result
The generated tileset consists of a table with the following columns, where each row represents a tile:
Z: zoom level of the tile.
X: X-index of the tile (0 to 2^Z-1).
Y: Y-index of the tile (0 to 2^Z-1).
DATA: contents of the tile, encoded as a MVT gzipped binary. It will contain the resulting points (location of the aggregated features) and their attributes (as defined by properties).
Additionally, there is a row identified by Z=-1 which contains metadata about the tileset in the DATA column in JSON format. It contains the following properties:
bounds: geographical extents of the source as a string in Xmin, Ymin, Xmax, Ymax format.
center: center of the geographical extents as X, Y, Z, where the Z represents the zoom level where a single tile spans the whole extents size.
zmin: minimum zoom level in the tileset.
zmax: maximum zoom level in the tileset.
tilestats: stats about the feature's properties. In addition to its name (attribute) and type, it contains min, max, average, sum and quantiles for numeric attributes and categories for text attributes.
Example
import com.carto.analytics.toolbox.ATExecuteATExecute.sql(""" |CALL_CARTO carto_un.carto.CREATE_POINT_AGG_TILESET( | | '(SELECT * FROM database.schema.cities_table)', | 'database.schema.cities_tileset', | '{ | "if_exists": "replace", | "geom_column": "geom", | "zoom_min": 0, | "zoom_max": 12, | "aggregation_resolution": 6, | "aggregation_placement": "cell-centroid", | "properties": "COUNT(*) AS num_cities, SUM(POPULATION) AS population_sum, CASE WHEN COUNT(*) <= 1 THEN ANY_VALUE(city_name) ELSE NULL END AS city_name",
| "metadata": { | "name": "Population", | "description": "Population in the cities" | } | }' | ); | """.stripMargin, spark)
In the example above, for all features we would get a property "num_cities" with the number of points that fall in it and "population_sum" with the sum of the population in those cities. In addition to this, when there is only one point that belongs to this property (and only in that case) we will also get the column values from the source data in "city_name".
CREATE_H3_AGG_TILESET
CREATE_H3_AGG_TILESET(input, output, options)
Description
Creates a tileset that uses a H3 spatial index, aggregating data from an input table that uses that same spatial index.
Aggregated data is computed for all levels between resolution_min and resolution_max. For each resolution level, all tiles for the area covered by the source table are added, with data aggregated at level resolution + aggregation resolution.
input: STRING that can either contain a table name (e.g. database.schema.tablename) or a full query (e.g.(SELECT * FROM database.schema.tablename)).
output: STRING of the format database.schema.tablename where the resulting tileset will be stored. The database and schema must exist and the caller needs to have permissions to create a new table in it.
options: STRING containing a valid JSON with the different options. Valid options are described in the table below.
warning
If a query is passed in input, it might be evaluated multiple times to generate the tileset. Thus, non-deterministic functions, such as [ROW_NUMBER] should be avoided. If such a function is needed, the query should be saved into a table first and then passed as input, to avoid inconsistent results.
Option
Description
if_exists
Default: "fail". A STRING that indicates if the process will fail if the table already exists, if set to "fail". Or any existing table will be replaced, if set to "replace".
resolution_min
Default: 0. A INTEGER that defines the minimum resolution level for tiles. Any resolution level under this level won't be generated.
resolution_max
Default: 6. A INTEGER that defines the maximum resolution level for tiles. Any resolution level over this level won't be generated.
h3_column
Default: h3. A STRING that indicates the name of the H3 spatial index column that will be used.
h3_resolution
A INTEGER defining the resolution of the tiles in the input table.
aggregation_resolution
Default: 4. A INTEGER defining the resolution to use when aggregating data at each resolution level. For a given h3_resolution, data is aggregated at resolution_level + aggregation resolution.
metadata
Default: {}. A JSON object to specify the associated metadata of the tileset. Use this to set the name, description and legend to be included in the TileJSON. Other fields will be included in the object extra_metadata.
properties
Default: "". A STRING that defines the properties that will be included associated with each cell feature. Each property is defined by using SQL syntax and should include a formula to be applied to the values of the points that fall under the cell. This formula can be any SQL formula that uses an aggregate function supported by Databricks. Note that every property different from Number will be casted to String.
Creates a tileset that uses a quadbin spatial index, aggregating data from an input table that uses that same spatial index.
Aggregated data is computed for all levels between resolution_min and resolution_max. For each resolution level, all tiles for the area covered by the source table are added, with data aggregated at level resolution + aggregation resolution.
input: STRING that can either contain a table name (e.g. database.schema.tablename) or a full query (e.g.(SELECT * FROM database.schema.tablename)).
output: STRING of the format database.schema.tablename where the resulting tileset will be stored. The database and schema must exist and the caller needs to have permissions to create a new table in it.
options: STRING containing a valid JSON with the different options. Valid options are described in the table below.
warning
If a query is passed in input, it might be evaluated multiple times to generate the tileset. Thus, non-deterministic functions, such as [ROW_NUMBER] should be avoided. If such a function is needed, the query should be saved into a table first and then passed as input, to avoid inconsistent results.
Option
Description
if_exists
Default: "fail". A STRING that indicates if the process will fail if the table already exists, if set to "fail". Or any existing table will be replaced, if set to "replace".
resolution_min
Default: 0. A INTEGER that defines the minimum resolution level for tiles. Any resolution level under this level won't be generated.
resolution_max
Default: 12. A INTEGER that defines the maximum resolution level for tiles. Any resolution level over this level won't be generated.
quadbin_column
Default: quadbin. A STRING that indicates the name of the quadbin spatial index column that will be used.
quadbin_resolution
A INTEGER defining the resolution of the tiles in the input table.
aggregation_resolution
Default: 6. A INTEGER defining the resolution to use when aggregating data at each resolution level. For a given quadbin_resolution, data is aggregated at resolution_level + aggregation resolution.
metadata
Default: {}. A JSON object to specify the associated metadata of the tileset. Use this to set the name, description and legend to be included in the TileJSON. Other fields will be included in the object extra_metadata.
properties
Default: "". A STRING that defines the properties that will be included associated with each cell feature. Each property is defined by using SQL syntax and should include a formula to be applied to the values of the points that fall under the cell. This formula can be any SQL formula that uses an aggregate function supported by Databricks. Note that every property different from Number will be casted to String.
