That doesn't give any interesting information about the usage counts of either table though; this query will be shown to them:
SELECT usagecount,count(*),isdirty FROM pg_buffercache GROUP BY isdirty,usagecount ORDER BY isdirty,usagecount;
The results don't prove anything interesting so far, they just suggest there's not very much accumulating a high usage count on a straight percentage basis:
usagecount | count | isdirty ------------+-------+--------- 0 | 10544 | f 1 | 12096 | f 2 | 2709 | f 3 | 2308 | f 4 | 3119 | f 5 | 1992 | f
usagecount | count | isdirty ------------+-------+--------- 0 | 7177 | f 1 | 7948 | f 2 | 923 | f 3 | 168 | f 4 | 51 | f 5 | 117 | f