Aggregation: Extract the query to get the grid data

lib/cartodb/models/aggregation/aggregation-query.js

@@ -300,7 +300,7 @@ const havingClause = ctx => {
 // We limit the the minimum resolution to avoid division by zero problems. The limit used is
 // the pixel size of zoom level 30 (i.e. 1/2*(30+8) of the full earth web-mercator extent), which is about 0.15 mm.
 //
-// NOTE: We'd rather use !pixel_height!, but in Mapnik this value is extent / 256 for raster
+// NOTE: We'd rather use !scale_denominator!, but in Mapnik this value is extent / 256 for raster
 // and extent / tile_extent {4096 default} for MVT, so since aggregations are always based
 // on 256 we can't have the same query in both cases
 // As this scale change doesn't happen in !scale_denominator! we use that instead
@@ -309,6 +309,26 @@ const gridResolution = ctx => {
     return `${256/ctx.res} * GREATEST(!scale_denominator! * 0.00028, ${minimumResolution})::double precision`;
 };
 
+// SQL query to extra the boundaries of the area to be aggregated and the grid resolution
+const gridInfoQuery = ctx => {
+    return `
+    SELECT
+        res,
+        CEIL (ST_XMIN(cdb_full_bbox) / res) * res AS cdb_xmin,
+        FLOOR(ST_XMAX(cdb_full_bbox) / res) * res AS cdb_xmax,
+        CEIL (ST_YMIN(cdb_full_bbox) / res) * res AS cdb_ymin,
+        FLOOR(ST_YMAX(cdb_full_bbox) / res) * res AS cdb_ymax
+    FROM
+    (
+        SELECT
+            ${gridResolution(ctx)} AS res,
+            !bbox! cdb_full_bbox
+        OFFSET 0
+    ) _cdb_input_resources
+`;
+};
+
+
 // Function to generate the resulting point for a cell from the aggregated
 const aggregatedPoint = (ctx, aggregated) => {
     const placement = ctx.placement || DEFAULT_PLACEMENT;
@@ -387,19 +407,7 @@ SELECT * FROM
                 ((cdb_ymax - cdb_ymin) /  res)::int as cdb_limit_y
             FROM
             (
-                SELECT
-                    res,
-                    CEIL (ST_XMIN(cdb_full_bbox) / res) * res AS cdb_xmin,
-                    FLOOR(ST_XMAX(cdb_full_bbox) / res) * res AS cdb_xmax,
-                    CEIL (ST_YMIN(cdb_full_bbox) / res) * res AS cdb_ymin,
-                    FLOOR(ST_YMAX(cdb_full_bbox) / res) * res AS cdb_ymax
-                FROM
-                (
-                    SELECT
-                        ${gridResolution(ctx)} AS res,
-                        !bbox! cdb_full_bbox
-                    OFFSET 0
-                ) _cdb_input_resources
+                ${gridInfoQuery(ctx)}
             ) _cdb_grid_bbox_margins OFFSET 0
         ) __cdb_src_params
         WHERE the_geom_webmercator && cdb_point_bbox OFFSET 0