We have a very wide table (will call it A)
which I'm looking at splitting into 3 tables each with the same PK and each partitioned in the same way
called AVP1, AVP2, AVP3
I then create a view over the 3 tables joining them with an outer join
create view ANEW
as
select ...
from AVP1, AVP2, AVP3
where AVP1.Col1 *= AVP2.Col1
and AVP1.Col2 *= AVP2.Col2
and AVP1.Col1 *= AVP3.Col1
and AVP1.Col2 *= AVP3.Col2
with some data in AVP1 and AVP2 but AVP3 is empty.
Selecting 987 rows out of the view
select <only cols from AVP1> from ANEW where Col1 = "ABCDEF"
I get odd statistics....
Table: AVP1 (VP1) scan count 1, logical reads: (regular=64 apf=0 total=64), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: AVP2 (VP2) scan count 987, logical reads: (regular=36 apf=0 total=36), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: AVP3 (VP3) scan count 987, logical reads: (regular=1974 apf=0 total=1974), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
I get large amounts of IO on an empty table whereas the table which actually has some data only shows 36 page reads.
All tables are partitioned using the same criteria - yet I'm getting 2 pages per row read from an empty table.
Can't make out why ?
