Make hot rank not crash on future (#3517)

* make hot rank zero for future

* parallel safe

migrations/2023-07-06-151124_hot-rank-future/down.sql

@@ -0,0 +1,11 @@
+CREATE OR REPLACE FUNCTION hot_rank(score numeric, published timestamp without time zone)
+    RETURNS integer
+    AS $$
+BEGIN
+    -- hours_diff:=EXTRACT(EPOCH FROM (timezone('utc',now()) - published))/3600
+    RETURN floor(10000 * log(greatest(1, score + 3)) / power(((EXTRACT(EPOCH FROM(timezone('utc', now()) - published)) / 3600) + 2), 1.8))::integer;
+END;
+$$
+LANGUAGE plpgsql
+IMMUTABLE;
+

migrations/2023-07-06-151124_hot-rank-future/up.sql

@@ -0,0 +1,16 @@
+CREATE OR REPLACE FUNCTION hot_rank(score numeric, published timestamp without time zone)
+    RETURNS integer
+    AS $$
+DECLARE
+    hours_diff numeric := EXTRACT(EPOCH FROM (timezone('utc', now()) - published)) / 3600;
+BEGIN
+    IF (hours_diff > 0) THEN
+        RETURN floor(10000 * log(greatest(1, score + 3)) / power((hours_diff + 2), 1.8))::integer;
+    ELSE
+        RETURN 0;
+    END IF;
+END;
+$$
+LANGUAGE plpgsql
+IMMUTABLE PARALLEL SAFE;
+