row cache hit is costlier for partiton with large rows

[nitin padalia]

Hi,

With two different families when I do a read, row cache hit is almost
15x costlier with larger rows (10000 rows per partition), in
comparison to partition with only 100 rows.

Difference in two column families is one is having 100 rows per
partition another 10000 rows per partition. Schema for two tables is:
CREATE TABLE table1_row_cache (
  user_id uuid,
  dept_id uuid,
  location_id text,
  locationmap_id uuid,
  PRIMARY KEY ((user_id, location_id), dept_id)
)

CREATE TABLE table2_row_cache (
  user_id uuid,
  dept_id uuid,
  location_id text,
  locationmap_id uuid,
  PRIMARY KEY ((user_id, dept_id), location_id)
)

Here is the tracing:

Row cache Hit with Column Family table1_row_cache, 100 rows per partition:
 Preparing statement [SharedPool-Worker-2] | 2015-01-20
14:35:47.540000 | x.x.x.x |           1023
          Row cache hit [SharedPool-Worker-5] | 2015-01-20
14:35:47.542000 | x.x.x.x |           2426

Row cache Hit with CF table2_row_cache, 10000 rows per partition:
Preparing statement [SharedPool-Worker-1] | 2015-01-20 16:02:51.696000
| x.x.x.x |            490
         Row cache hit [SharedPool-Worker-2] | 2015-01-20
16:02:51.711000 | x.x.x.x |          15146


If for both cases data is in memory why its not same? Can someone
point me what wrong here?

Nitin Padalia