Re: how does oracle manage hash maps?
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 13 Feb 2004 09:38:40 -0000
> Traditional hashing uses an array for the hash,
> then a linked list for the collisions.
I believe this is exactly what Oracle does when
building the hash table (build table) for a hash
join. Bear in mind that all the columns from the
hashed data set (select columns and join columns)
are copied into the hash table, so any references
to the cache buffer are a distraction.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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----- Original Message -----
From: "Ryan" <ryan.gaffuri@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Friday, February 13, 2004 4:12 AM
Subject: how does oracle manage hash maps?
When Oracle performs a hash-join it first creates a hashmap. This hash map
is placed in the PGA. Now, Oracle uses linked lists to manage the buffer
cache. Traditional hashing uses an array for the hash, then a linked list
for the collisions. How does Oracle manage this?
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