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Merge pull request #242 from CartoDB/240-overviews-pixels

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Adjust overview points to pixel centers
This commit is contained in:
Javier Goizueta
2016-04-25 17:30:25 +02:00
parent 18267477da 3c12cf629f
commit f7cce21eb7
1 changed files with 25 additions and 3 deletions
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28
scripts-available/CDB_Overviews.sql
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@@ -651,7 +651,13 @@ AS $$
overview_rel TEXT;
reduction FLOAT8;
base_name TEXT;
pixel_m FLOAT8;
grid_m FLOAT8;
offset_m FLOAT8;
offset_x TEXT;
offset_y TEXT;
cell_x TEXT;
cell_y TEXT;
aggr_attributes TEXT;
attributes TEXT;
columns TEXT;
@@ -677,8 +683,10 @@ AS $$
SELECT * FROM _cdb_split_table_name(reloid) INTO schema_name, table_name;
-- compute grid cell size using the overview_z dimension...
SELECT CDB_XYZ_Resolution(overview_z)*grid_px INTO grid_m;
-- pixel_m: size of a pixel in webmercator units (meters)
SELECT CDB_XYZ_Resolution(overview_z) INTO pixel_m;
-- grid size in meters
grid_m = grid_px * pixel_m;
attributes := _CDB_Aggregable_Attributes_Expression(reloid);
aggr_attributes := _CDB_Aggregated_Attributes_Expression(reloid);
@@ -689,7 +697,21 @@ AS $$
aggr_attributes := aggr_attributes || ', ';
END IF;
point_geom = Format('ST_SetSRID(ST_MakePoint(gx*%1$s + %2$s, gy*%1$s + %2$s), 3857)', grid_m, grid_m/2);
-- Center of each cell:
cell_x := Format('gx*%1$s + %2$s', grid_m, grid_m/2);
cell_y := Format('gy*%1$s + %2$s', grid_m, grid_m/2);
-- Displacement to the nearest pixel center:
IF MOD(grid_px::numeric, 1.0::numeric) = 0 THEN
offset_m := pixel_m/2 - MOD((grid_m/2)::numeric, pixel_m::numeric)::float8;
offset_x := Format('%s', offset_m);
offset_y := Format('%s', offset_m);
ELSE
offset_x := Format('%2$s/2 - MOD((%1$s)::numeric, (%2$s)::numeric)::float8', cell_x, pixel_m);
offset_y := Format('%2$s/2 - MOD((%1$s)::numeric, (%2$s)::numeric)::float8', cell_y, pixel_m);
END IF;
point_geom := Format('ST_SetSRID(ST_MakePoint(%1$s + %3$s, %2$s + %4$s), 3857)', cell_x, cell_y, offset_x, offset_y);
-- compute the resulting columns in the same order as in the base table
WITH cols AS (