Three billion logical reads?
- From: David Aldridge <david@xxxxxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 26 Oct 2007 04:45:14 -0700 (PDT)
Part 1: If I have a table of 80 million records and I outer join that to twelve
other tables, and the tables are accessed with nested loop outer joins against
non-unique indexes having a blevel of 3, and if there is only a 50% (say)
chance of there being a matching record in those tables, then is the number of
logical reads to perform the join equal to something in the order of:
80,000,000*12*(3+.5)
?
In other words, around 3.3 billion logical reads? Or do I need more coffee
this morning?
Part 2: What would you say is a reasonable ballpark time for a logical read,
on a decently equipped server with SAN storage? Millisecond? Less?
Background: I'm stuck in version 9 with large tabes outer-joined to many
smaller tables -- no inut join swapping and hence no (reasonably efficient)
hash outer joins.
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