This specification describes an extension for MapConfig 1.7.0 version.
This extension introduces a new layer options for aggregated data tile generation.
The layer options attribute is extended with a new optional aggregation
attribute.
The value of this attribute can be false
to explicitly disable aggregation for the layer.
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{
aggregation: {
// OPTIONAL
// string, defines the placement of aggregated geometries. Can be one of:
// * "point-sample", the default places geometries at a sample point (one of the aggregated geometries)
// * "point-grid" places geometries at the center of the aggregation grid cells
// * "centroid" places geometriea at the average position of the aggregated points
// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#placement for more details
placement: "point-sample",
// OPTIONAL
// object, defines the columns of the aggregated datasets. Each property corresponds to a columns name and
// should contain an object with two properties: "aggregate_function" (one of "sum", "max", "min", "avg", "mode" or "count"),
// and "aggregated_column" (the name of a column of the original layer query or "*")
// A column defined as `"_cdb_feature_count": {"aggregate_function": "count", aggregated_column: "*"}`
// is always generated in addition to the defined columns.
// The column names `cartodb_id`, `the_geom`, `the_geom_webmercator` and `_cdb_feature_count` cannot be used
// for aggregated columns, as they correspond to columns always present in the result.
// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#columns for more details
columns: {
"aggregated_column_1": {
"aggregate_function": "sum",
"aggregated_column": "original_column_1"
}
},
// OPTIONAL
// Number, defines the cell-size of the spatial aggregation grid as a pixel resolution power of two (1/4, 1/2,... 2, 4, 16)
// to scale from 256x256 pixels; the default is 1 corresponding to 256x256 cells per tile.
// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#resolution for more details
resolution: 1,
// OPTIONAL
// Number, the minimum number of (estimated) rows in the dataset (query results) for aggregation to be applied.
// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#threshold for more details
threshold: 500000
}
}