I use select pg_prewarm('table1','read','main') to load data of table1 into
the memory.
when I use select count(1) from table1 group by aa to query data.
I find the speed of query is not fast, I wonder whether it query data from
memory.
And it is slower than Oracle, both of Oracle and Postgresql has same table and
count of data.
when pg_prewarm use 'read' mode, the data is put into the OS cache, how to
examine the table which is pg_prewarmed into the OS cache .
I know pg_buffercache ,but it just examine the table in the shared buffer of
Postgresql, not the table in the OS cache.
