Initial description of dataviews mapconfig extension

docs/MapConfig-Dataviews-extension.md

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+# 1. Purpose
+
+This specification describes an extension for
+[MapConfig 1.4.0](https://github.com/CartoDB/Windshaft/blob/master/doc/MapConfig-1.4.0.md) version.
+
+
+# 2. Changes over specification
+
+This extension depends on Analyses extension. It extends MapConfig with a new attribute: `dataviews`.
+
+It makes possible to get tabular data from analysis nodes: lists, aggregated lists, aggregations, and histograms.
+
+## 2.1. Dataview types
+
+### List
+
+A list is a simple result set per row where is possible to retrieve several columns from the original layer query.
+
+Definition
+```
+{
+    // REQUIRED
+    // string, `type` the list type
+    “type”: “list”,
+    // REQUIRED
+    // object, `options` dataview params
+    “options”: {
+        // REQUIRED
+        // array, `columns` to select for the list
+        “columns”: [“name”, “description”]
+    }
+}
+```
+
+Expected output
+```
+{
+  "type": "list",
+  "rows": [
+    {
+      "{columnName1}": "val1",
+      "{columnName2}": 100
+    },
+    {
+      "{columnName1}": "val2",
+      "{columnName2}": 200
+    }
+  ]
+}
+```
+
+### Aggregation
+
+An aggregation is very similar to a list but results are aggregated by a column and a given aggregation function.
+
+Definition
+```
+{
+    // REQUIRED
+    // string, `type` the aggregation type
+    “type”: “aggregation”,
+    // REQUIRED
+    // object, `options` dataview params
+    “options”: {
+        // REQUIRED
+        // string, `column` column name to aggregate by
+        “column”: “country”,
+        // REQUIRED
+        // string, `aggregation` operation to perform
+        “aggregation”: “count”
+        // OPTIONAL
+        // string, `aggregationColumn` column value to aggregate
+        // This param is required when `aggregation` is different than "count"
+        “aggregationColumn”: “population”
+    }
+}
+```
+
+Expected output
+```
+{
+  "type": "aggregation",
+  "categories": [
+    {
+      "category": "foo",
+      "value": 100
+    },
+    {
+      "category": "bar",
+      "value": 200
+    }
+  ]
+}
+```
+
+### Histograms
+
+Histograms represent the data distribution for a column.
+
+Definition
+```
+{
+    // REQUIRED
+    // string, `type` the histogram type
+    “type”: “histogram”,
+    // REQUIRED
+    // object, `options` dataview params
+    “options”: {
+        // REQUIRED
+        // string, `column` column name to aggregate by
+        “column”: “name”,
+        // OPTIONAL
+        // number, `bins` how many buckets the histogram should use
+        “bins”: 10
+    }
+}
+```
+
+Expected output
+```
+{
+  "type": "histogram",
+  "bins": [{"bin": 0, "start": 2, "end": 2, "min": 2, "max": 2, "freq": 1}, null, null, {"bin": 3, "min": 40, "max": 44, "freq": 2}, null],
+  "width": 10
+}
+```
+
+### Formula
+
+Formulas given a final value representing the whole dataset.
+
+Definition
+```
+{
+    // REQUIRED
+    // string, `type` the formula type
+    “type”: “formula”,
+    // REQUIRED
+    // object, `options` dataview params
+    “options”: {
+        // REQUIRED
+        // string, `column` column name to aggregate by
+        “column”: “name”,
+        // REQUIRED
+        // string, `aggregation` operation to perform
+        “operation”: “count”
+    }
+}
+```
+
+Operation must be: “min”, “max”, “count”, “avg”, or “sum”.
+
+Result
+```
+{
+  "type": "formula",
+  "operation": "count",
+  "result": 1000,
+  "nulls": 0
+}
+```
+
+
+## 2.2 Dataviews attribute
+
+The new dataviews attribute must be a dictionary of dataviews.
+
+An analysis node id can be referenced from dataviews to consume its output query.
+
+
+The layer consuming the output must reference it with the following option:
+
+```
+{
+    // REQUIRED
+    // object, `source` as in the future we might want to have other source options
+    "source": {
+        // REQUIRED
+        // string, `id` the analysis node identifier
+        "id": "HEAD"
+    }
+}
+```
+
+## 2.3. Complete example
+
+```
+{
+    "version": "1.4.0",
+    "layers": [
+        {
+            "type": "cartodb",
+            "options": {
+                "source": {
+                    "id": "HEAD"
+                },
+                "cartocss": "...",
+                "cartocss_version": "2.3.0"
+            }
+        }
+    ],
+    "dataviews" {
+        "basic_histogram": {
+            "source": {
+                "id": "HEAD"
+            },
+            "type": "histogram",
+            "options": {
+                "column": "pop_max"
+            }
+        }
+    },
+    "analyses": [
+        {
+            "id": "HEAD",
+            "type": "source",
+            "params": {
+                "query": "select * from your_table"
+            }
+        }
+    ]
+}
+```
+
+## 3. Filters
+
+Camshaft's analyses expose a filtering capability and `aggregation` and `histogram` dataviews get them for free with
+ this extension. Filters are available with the very dataview id, so if you have a "basic_histogram" histogram dataview
+ you can filter with a range filter with "basic_histogram" name.
+
+
+## 3.1 Filter types
+
+### Category
+
+Allows to remove results that are not contained within a set of elements.
+Initially this filter can be applied to a `numeric` or `text` columns.
+
+Params
+
+```
+{
+    “accept”: [“Spain”, “Germany”]
+    “reject”: [“Japan”]
+}
+```
+
+### Range filter
+
+Allows to remove results that don’t satisfy numeric min and max values.
+Filter is applied to a numeric column.
+
+Params
+
+```
+{
+    “min”: 0,
+    “max”: 1000
+}
+```
+
+## 3.2. How to apply filters
+
+Filters must be applied at map instantiation time.
+
+With :mapconfig as a valid MapConfig and with :filters (a valid JSON) as:
+
+### Anonymous map
+
+`GET /api/v1/map?config=:mapconfig&filters=:filters`
+
+`POST /api/v1/map?filters=:filters`
+with `BODY=:mapconfig`
+
+If in the future we need to support a bigger filters param and it doesn’t fit in the query string,
+ we might solve it by accepting:
+
+`POST /api/v1/map`
+with `BODY={“config”: :mapconfig, “filters”: :filters}`
+
+### Named map
+
+Assume :params (a valid JSON) as named maps params, like in: `{“color”: “red”}`
+
+`GET /api/v1/named/:name/jsonp?config=:params&filters=:filters&callback=cb`
+
+`POST /api/v1/named/:name?filters=:filters`
+with `BODY=:params`
+
+If, again, in the future we need to support a bigger filters param that doesn’t fit in the query string,
+ we might solve it by accepting:
+
+`POST /api/v1/named/:name`
+with `BODY={“config”: :params, “filters”: :filters}`
+
+
+## 3.3 Bounding box special filter
+
+A bounding box filter allows to remove results that don’t satisfy a geospatial range.
+
+The bounding box special filter is available per dataview and there is no need to create a bounding box definition as
+it’s always possible to apply a bbox filter per dataview.
+
+A dataview can get its result filtered by bounding box by sending a bbox param in the query string,
+param must be in the form `west,south,east,north`.
+
+So applying a bbox filter to a dataview looks like:
+GET /api/v1/map/:layergroupid/dataview/:dataview_name?bbox=-90,-45,90,45
+
+# History
+
+## 1.0.0-alpha
+
+ - WIP document