OBS_MetadataValidation

New function to check the metadata in order to search for errors like
for example if we have the metadata for a median aggregation and the
normalization is by are it'll fail.

src/pg/sql/41_observatory_augmentation.sql

@@ -1076,3 +1076,46 @@ BEGIN
   RETURN result;
 END;
 $$ LANGUAGE plpgsql STABLE;
+
+-- MetadataValidation checks the metadata parameters and the geometry type
+-- of the data in order to find possible wrong cases
+CREATE OR REPLACE FUNCTION cdb_observatory.obs_metadatavalidation(
+  geometry_extent geometry(Geometry, 4326),
+  geometry_type text,
+  params JSON,
+  target_geoms INTEGER DEFAULT NULL
+)
+RETURNS TABLE(valid boolean, errors text[]) AS $$
+DECLARE
+  meta json;
+  errors text[];
+BEGIN
+  errors := (ARRAY[])::TEXT[];
+  IF geometry_type IN ('ST_Polygon', 'ST_MultiPolygon') THEN
+      FOR meta IN EXECUTE 'SELECT json_array_elements(cdb_observatory.OBS_GetMeta($1, $2, 1, 1, $3))' USING geometry_extent, params, target_geoms
+      LOOP
+          IF (meta->>'normalization' = 'denominated' AND meta->>'denom_id' is NULL) THEN
+              errors := array_append(errors, 'Normalizated measure should have a numerator and a denominator. Please review the provided options.');
+          END IF;
+          IF (meta->>'numer_aggregate' IS NULL) THEN
+              errors := array_append(errors, 'For polygon geometries, aggregation is mandatory. Please review the provided options');
+          END IF;
+          IF (meta->>'numer_aggregate' IN ('median', 'average') AND meta->>'denom_id' IS NULL) THEN
+              errors := array_append(errors, 'Median or average aggregation for polygons requires a denominator to provide weights. Please review the provided options');
+          END IF;
+          IF (meta->>'numer_aggregate' IN ('median', 'average') AND meta->>'normalization' NOT LIKE 'pre%') THEN
+              errors := array_append(errors, format('Median or average aggregation only supports prenormalized normalization, %s passed. Please review the provided options', meta->>'normalization'));
+          END IF;
+      END LOOP;
+
+      IF CARDINALITY(errors) > 0 THEN
+          RETURN QUERY EXECUTE 'SELECT FALSE, $1' USING errors;
+      ELSE
+          RETURN QUERY SELECT TRUE, ARRAY[]::TEXT[];
+      END IF;
+  ELSE
+    RETURN QUERY SELECT TRUE, ARRAY[]::TEXT[];
+  END IF;
+  RETURN;
+END;
+$$ LANGUAGE plpgsql STABLE;

src/pg/test/expected/41_observatory_augmentation_test.out

@@ -304,3 +304,12 @@ tract_sample|tract_max_error|tract_avg_error|tract_min_error
 no_bg_point_error
 t
 (1 row)
+valid|errors
+t|{}
+(1 row)
+valid|errors
+f|{"Median or average aggregation only supports prenormalized normalization, denominated passed. Please review the provided options"}
+(1 row)
+valid|errors
+f|{"Normalizated measure should have a numerator and a denominator. Please review the provided options."}
+(1 row)

src/pg/test/sql/41_observatory_augmentation_test.sql

@@ -973,3 +973,9 @@ WITH _geoms AS (
 FROM geoms, results
 WHERE cartodb_id = id
 ;
+
+-- OBS_MetadataValidation
+
+SELECT * FROM cdb_observatory.OBS_MetadataValidation(NULL, 'ST_Polygon', '[{"numer_id": "us.census.acs.B01003001","denom_id": null,"normalization": "prenormalized","geom_id": null,"numer_timespan": "2010 - 2014"}]'::json, 500);
+SELECT * FROM cdb_observatory.OBS_MetadataValidation(NULL, 'ST_Polygon', '[{"numer_id": "us.census.acs.B25058001","denom_id": null,"normalization": "denominated","geom_id": null,"numer_timespan": "2010 - 2014"}]'::json, 500);
+SELECT * FROM cdb_observatory.OBS_MetadataValidation(NULL, 'ST_Polygon', '[{"numer_id": "us.census.acs.B15003001","denom_id": null,"normalization": "denominated","geom_id": null,"numer_timespan": "2010 - 2014"}]'::json, 500);