Hello,
I am
using postgres version 7.4, and I read this in the
documentation:
"The aggregate
functions sum and count always require a sequential scan if applied to the
entire table."
My understanding of
this statement is that if I use count() without a WHERE clause, then
essentially, it is applied to the entire table and hence requires a seq
scan.
But it should not
require a seq scan if I have a condition.
For example: I
have a table vm_message with an index on column msgid.
Will the following
do a sequential scan or an index?
select count(*) from
vm_message where msgid = 3;
I used explain, and
it said it would do a sequential scan. Why is that?
In fact explain
select * from vm_message where msgid = 3 also did a sequential
scan.
What am I doing
wrong here? I want it to use my index.
Thanks,
Kashmira
