65 lines
2.8 KiB
Markdown
65 lines
2.8 KiB
Markdown
## MapConfig Aggregation Extension
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### 1. Purpose
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This specification describes an extension for
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[MapConfig 1.7.0](https://github.com/CartoDB/Windshaft/blob/master/doc/MapConfig-1.7.0.md) version.
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### 2. Changes over specification
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This extension introduces a new layer options for aggregated data tile generation.
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#### 2.1 Aggregation options
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The layer options attribute is extended with a new optional `aggregation` attribute.
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The value of this attribute can be `false` to explicitly disable aggregation for the layer.
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```javascript
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{
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aggregation: {
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// OPTIONAL
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// string, defines the placement of aggregated geometries. Can be one of:
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// * "point-sample", the default places geometries at a sample point (one of the aggregated geometries)
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// * "point-grid" places geometries at the center of the aggregation grid cells
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// * "centroid" places geometriea at the average position of the aggregated points
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// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#placement for more details
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placement: "point-sample",
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// OPTIONAL
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// object, defines the columns of the aggregated datasets. Each property corresponds to a columns name and
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// should contain an object with two properties: "aggregate_function" (one of "sum", "max", "min", "avg", "mode" or "count"),
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// and "aggregated_column" (the name of a column of the original layer query or "*")
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// A column defined as `"_cdb_feature_count": {"aggregate_function": "count", aggregated_column: "*"}`
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// is always generated in addition to the defined columns.
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// The column names `cartodb_id`, `the_geom`, `the_geom_webmercator` and `_cdb_feature_count` cannot be used
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// for aggregated columns, as they correspond to columns always present in the result.
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// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#columns for more details
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columns: {
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"aggregated_column_1": {
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"aggregate_function": "sum",
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"aggregated_column": "original_column_1"
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}
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},
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// OPTIONAL
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// Number, defines the cell-size of the spatial aggregation grid as a pixel resolution power of two (1/4, 1/2,... 2, 4, 16)
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// to scale from 256x256 pixels; the default is 1 corresponding to 256x256 cells per tile.
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// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#resolution for more details
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resolution: 1,
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// OPTIONAL
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// Number, the minimum number of (estimated) rows in the dataset (query results) for aggregation to be applied.
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// See https://github.com/CartoDB/Windshaft-cartodb/blob/master/docs/aggregation.md#threshold for more details
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threshold: 500000
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}
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}
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```
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### History
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#### 1.0.0
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- Initial version
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