
Analytics Toolbox for Snowflake
tiler
We currently provide procedures to create two types of tilesets: simple and aggregation tilesets, the former to visualize features individually and the latter to generate aggregated point visualizations. Visit the Overview section to learn more about tileset types.
CREATE_POINT_AGGREGATION_TILESET
Description
Generates a point aggregation tileset.
input
:VARCHAR
that can either contain a table name (e.g.database.schema.tablename
) or a full query (e.g.(SELECT * FROM database.schema.tablename)
).output_table
:VARCHAR
of the formatdatabase.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. The process will fail if the table already exists.options
:VARCHAR
containing a valid JSON with the different options. Valid options are described in the table below.
Option | Description |
---|---|
geom_column |
Default: "GEOM" . A VARCHAR that indicates the name of the geography column that will be used. The geography column must be of type GEOGRAPHY and contain only points. The capitalization (uppercase/lowercase letters) of the name must match exactly the column name; note that Snowflake by default converts names to uppercase. |
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: 15 ; 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 quadkey 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 VARCHAR 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:
|
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. |
properties |
Default: {}. A JSON object that defines the properties that will be included associated with each cell feature. Each property is defined by its name, type (Number, Boolean, String, etc.) and 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 Redshift and returns the expected type. Please note that every property different from Number will be casted to String. |
max_tile_features |
Default: 10000 . A NUMBER that sets the maximum number of features (points) a tile can contain. 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. Any value lower than 4^aggregation_resolution will be ineffective, therefore the default of 10000 only applies if aggregation_resolution is higher than 6. |
tile_feature_order |
Default: RANDOM() . A STRING defining the order in which features are added to a tile. This expects the SQL ORDER BY keyword 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. |
max_tile_size_strategy |
Default: "throw_error" . A STRING that specifies how to apply the limit defined by max_tile_features . There are four options available:
. For the drop_ strategies, features will be retained according to the tile_feature_order specified. |
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
to2^Z-1
).Y
: Y-index of the tile (0
to2^Z-1
).DATA
: contents of the tile, encoded as a GeoJSON string (a feature collection). It will contain the resulting points (location of the aggregated features) and their attributes (as defined byproperties
).
Additionally, there is a row identified with 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 inXmin, Ymin, Xmax, Ymax
format.center
: center of the geographical extents asX, Y, Z
, where theZ
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
) andtype
, it containsmin
,max
,average
,sum
andquantiles
for numeric attributes andcategories
for text attributes.
Example
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CREATE_SIMPLE_TILESET
Description
Generates a simple tileset.
input
:VARCHAR
that can either contain a table name (e.g.database.schema.tablename
) or a full query (e.g.‘SELECT * FROM db.schema.tablename’
).output_table
:VARCHAR
of the format‘database.schema.tablename’
where the resulting tileset will be stored.options
:VARCHAR
containing a valid JSON with the different options. Valid options are described in the table below.
Option | Description |
---|---|
geom_column |
Default: "GEOM" . A VARCHAR that specifies the name of the geography column that will be used. It must be of type GEOGRAPHY . The capitalization (uppercase/lowercase letters) of the name must match exactly the column name; note that Snowflake by default will use only uppercase letters for the column names, but this can be altered if column names are quoted in their definition. Do not use quotes here, just mutch the capitalization. |
zoom_min |
Default: 0 . A NUMBER 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: 10 . A NUMBER that defines the maximum zoom level at which tiles will be generated. Any zoom level over this level won’t be generated. |
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. |
properties |
Default: {}. A JSON object that defines the properties that will be included associated with each cell feature. Each property is defined by its name and type (Number, String, etc.). Please note that every property different from Number will be casted to String. Property names must correspond to column names in the input and match it’s capitalization exactly; note by default Snowflake will use only uppercase letters for the column names but this can altered if column names where quoted in their definitions. Do not use quotes here, just mutch the capitalization. The properties will appear in the GeoJSON data with the same capitalization as the column names. |
max_tile_features |
Default: 10000 . A NUMBER 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. |
max_tile_vertices |
Default: 200000 . A NUMBER 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. |
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 BY keyword 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. |
max_tile_size_strategy |
Default: "throw_error" . A STRING that specifies how to apply the limit defined by max_tile_features or max_tile_vertices . There are four options available:
. For the drop_ strategies, features will be retained according to the tile_feature_order specified. |
Example
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