ENH break histogram function into more convenient chunks

etc/org-sql/viz_setup.sql

@@ -4,36 +4,62 @@ as $$
   select ts::time at time zone 'US/Eastern';
 $$ language SQL;
 
-CREATE OR REPLACE FUNCTION histogram(tname text, cname text, width int)
-RETURNS TABLE(bin_number int, bin_interval text, count bigint)
+create or replace function get_bin_num(x numeric, width int)
+returns int
+as $$
+  -- select (floor(x/width)*width)::int;
+  select floor(x/width)::int;
+$$ language SQL;
+
+CREATE OR REPLACE FUNCTION bin_ranges(tname text, cname text, width int)
+RETURNS TABLE(bin_number int, bin_interval text)
 AS $func$
 BEGIN
 RETURN QUERY EXECUTE format('
   with recursive
     no_bins_t as (
-      select min(floor(a.%1$s/%2$s)*%2$s)::int as bin_number from %3$s a
+      select min(get_bin_num(%1$s,%2$s)) as bin_number from %3$s a
 
       union all
 
       select bin_number + 1 as bin_number from no_bins_t
       where
-        bin_number < (select max(floor(a.%1$s/%2$s)) + 1 from %3$s a)
+        bin_number < (select max(get_bin_num(%1$s,%2$s)) + 1 from %3$s a)
     )
 
   select
     bin_number,
-    concat(bin_number*%2$s, ''-'', bin_number*%2$s + %2$s - 1) as bin_interval,
-    case when count is null then 0 else count end as count
+    concat(bin_number*%2$s, ''-'', bin_number*%2$s + %2$s - 1) as bin_interval
     from no_bins_t
-    left join
-      (select
-        floor(a.%1$s/%2$s)*%2$s as ab_floor,
+    order by no_bins_t.bin_number;',
+  cname,
+  width,
+  tname
+  );
+END
+$func$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION histogram(tname text, cname text, width int)
+RETURNS TABLE(bin_number int, bin_interval text, count bigint)
+AS $func$
+BEGIN
+RETURN QUERY EXECUTE format('
+  with binned as (
+      select
+        get_bin_num(%1$s,%2$s) as ab_floor,
         count(*) as count
       from %3$s a
       group by ab_floor
-      order by ab_floor) as binned
-    on no_bins_t.bin_number*%2$s=binned.ab_floor
-    order by no_bins_t.bin_number;',
+      order by ab_floor
+  )
+
+  select
+    bin_number,
+    bin_interval,
+    case when b.count is null then 0 else b.count end as count
+    from bin_ranges(''%3$s'',''%1$s'',%2$s) r
+    left join binned b on r.bin_number=b.ab_floor
+    order by r.bin_number;',
   cname,
   width,
   tname