select_random_ranges.lua: use param "range_size" as cnt limit of fetch table

Author: rockeet

src/lua/select_random_ranges.lua

@@ -48,7 +48,8 @@ function thread_init()
       stmt = con:prepare(string.format([[
          SELECT sum(length(c))
             FROM sbtest1
-            WHERE %s]], ranges))
+            WHERE %s limit %d]], ranges,
+            sysbench.cmdline.options.range_size))
    end
 
    params = {}