sql

lib/sql/scripts-available/CDB_ZoomFromScale.sql

@@ -0,0 +1,36 @@
+-- Maximum supported zoom level
+CREATE OR REPLACE FUNCTION @extschema@._CDB_MaxSupportedZoom()
+RETURNS int
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE
+AS $$
+  -- The maximum zoom level has to be limited for various reasons,
+  -- e.g. zoom levels greater than 31 would require tile coordinates
+  -- that would not fit in an INTEGER (which is signed, 32 bits long).
+  -- We'll choose 20 as a limit which is safe also when the JavaScript shift
+  -- operator (<<) is used for computing powers of two.
+  SELECT 29;
+$$;
+
+CREATE OR REPLACE FUNCTION @extschema@.CDB_ZoomFromScale(scaleDenominator numeric)
+RETURNS int
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE
+AS $$
+  SELECT
+    CASE
+      WHEN scaleDenominator > 600000000 THEN
+        -- Scale is smaller than zoom level 0
+        NULL
+      WHEN scaleDenominator = 0 THEN
+        -- Actual zoom level would be infinite
+        @extschema@._CDB_MaxSupportedZoom()
+      ELSE
+        CAST (
+          LEAST(
+            ROUND(LOG(2, 559082264.028/scaleDenominator)),
+            @extschema@._CDB_MaxSupportedZoom()
+          )
+        AS INTEGER)
+    END;
+$$;