First version of DO precheck

client/sql/35_precheck_functions.sql

@@ -0,0 +1,39 @@
+CREATE OR REPLACE FUNCTION cdb_dataservices_client._OBS_PreCheck(
+    source_query text,
+    parameters jsonb
+) RETURNS boolean AS $$
+DECLARE
+    username text;
+    orgname text;
+    errors text[];
+    geoms record;
+BEGIN
+    errors := (ARRAY[])::TEXT[];
+    FOR geoms IN
+    EXECUTE FORMAT('SELECT ST_GeometryType(the_geom) as geom_type,
+                    bool_and(st_isvalid(the_geom)) as valid,
+                    avg(st_npoints(the_geom)) as avg_vertex
+                    FROM (%s) as _source GROUP BY ST_GeometryType(the_geom)', source_query)
+    LOOP
+        IF geoms.geom_type NOT IN ('ST_Polygon', 'ST_MultiPolygon', 'ST_Point') THEN
+            errors := array_append(errors, format($data$'Geometry type %s not supported'$data$, geoms.geom_type));
+        END IF;
+
+        IF geoms.valid IS FALSE THEN
+            errors := array_append(errors, 'There are invalid geometries in the input data, please review them');
+        END IF;
+
+        -- 1000 vertex for a geometry is a limit we have in the obs_getdata function. You can check here
+        -- https://github.com/CartoDB/observatory-extension/blob/1.6.0/src/pg/sql/41_observatory_augmentation.sql#L813
+        IF geoms.avg_vertex > 1000 THEN
+            errors := array_append(errors, 'The average number of geometries vertex is greater than 1000, please try to simplify them');
+        END IF;
+    END LOOP;
+
+    IF CARDINALITY(errors) > 0 THEN
+        RAISE EXCEPTION '%', format('%s', errors);
+    END IF;
+
+    RETURN TRUE;
+END;
+$$ LANGUAGE 'plpgsql';

client/sql/95_grant_execute_manual.sql

@@ -1,2 +1,3 @@
 GRANT EXECUTE ON FUNCTION cdb_dataservices_client._DST_PrepareTableOBS_GetMeasure(output_table_name text, params json) TO publicuser;
 GRANT EXECUTE ON FUNCTION cdb_dataservices_client._DST_PopulateTableOBS_GetMeasure(table_name text, output_table_name text, params json) TO publicuser;
+GRANT EXECUTE ON FUNCTION cdb_dataservices_client._OBS_PreCheck(source_query text, params JSONB) TO publicuser;