Hi
I just experienced a performance loss on inserts when redefining my
index on a table.
I have a database with the following table
table:
id1 int
id2 int
id3 int
id4 int
val1 float
....
tablespace dbspace
the data id distribution is hierarchical and even, well fitting to a
btree, there is about 20000 rows per insert (actually a jdbc COPY)
originally I had an index on all id felds
index:
btree on (id1, id2, id3, id4) tablespace indexspace
that gave me an insert performance of 230 ms
because my query does not need id2 I changed the index and removed id2
from the criteria:
index:
btree on (id1, id3, id4) tablespace indexspace
now an insert takes approx 330-430 ms
Anybody have any ideas why that is? I was expecting it to take
approximately the same amount of time or less, since there is an element
less in the criteria.
regards
thomas