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



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