Knowing about lots of Oracle's patents with Håkan Jakobsson in the authors'
list, I think it was his invention.
--
Best regards,
Sayan Malakshinov
Oracle performance tuning expert
Oracle Database Developer Choice Award winner
Oracle ACE Associate
http://orasql.org
вс, 6 дек. 2020 г., 15:38 Michael D O'Shea/Woodward Informatics Ltd <
woodwardinformatics@xxxxxxxxxxxxxxxx>:
and (possibly) side effects of the *Hakan factor*.
From where does this name come? I did a quick online search, expecting the
top hit to be Wikipedia and something to do with bitmap indexes and Bloom
filters, but no, the top hits are Oracle „names“, including Jonathan
https://jonathanlewis.wordpress.com/2013/05/10/hakan-factor/ explaining
what it is and side effects *etc*.
Furthermore the search hit just a bit down the page is „Everything about
Hakan Factor, yes EVERYTHING“,
http://secondhalforacle.blogspot.com/2013/10/everything-about-hakan-factor.html
except
it seems the origin of the name Hakan.
Can anyone throw any light onto the source of this name?
Mike
Am 06/12/2020 um 10:26 schrieb Jonathan Lewis <jlewisoracle@xxxxxxxxx>:
Not made any easier by the fact that it varies with version of Oracle
(though after 11.2.?.? it may have become consistent across versions -
there are too many to check.
And ctas, insert /*+append */, insert, alter table move can introduce
variations, and then there's the possibility of Exadata specials, and
(possibly) side effects of the Hakan factor. You just don't know what
you've missed until someone else gets a result that says that you 've
missed SOMETHING.
You've reminded me, by the way, of a note that I wrote some time ago that
included a demonstration of the differences that might appear.
https://jonathanlewis.wordpress.com/2017/05/19/255-columns-2/
There's a parameter in 11.2.0.4 that's relevant:
name: _rowlen_for_chaining_threshold
default value: 1000
description: maximum rowlen above which rows may be chained across blocks
Regards
Jonathan Lewis
On Sun, 6 Dec 2020 at 08:49, Lothar Flatz <l.flatz@xxxxxxxxxx> wrote:
Hi,
I was studying block dumps for several weeks to find out what is going
on. In my test it was like that:
On an insert /*+ APPEND */ the db was filling a block bottom to top(low
block address) and fit as much as possible in one block.
On conventional insert it was filling the block top to bottom and was
using a new block after a number of row pieces. There seems to be a
threshold of some kind.
Alter table move is insert /*+ APPEND */, thus it can be used to
consolidate the result of a conventional insert.
Regards
Lothar
*Sent:* Wednesday, December 02, 2020 2:44 PM
*To:* Oracle L
*Subject:* Re: Table with ~255+ columns
And while we're on the topic of row chaining because of excessive (> 255)
columns, I have seen a table get BIGGER because of a rebuild because when
you do the move Oracle tries to keep all the row pieces of a single row in
the same block as they are re-created, but this can mean a block gets full
prematurely because (e.g.) two rows that were sharing their fragments
across a couple of blocks with another couple of rows both end up "filling"
a block and denying the available space to any other row because no other
row will fit completely in the available free space in their blocks. LIke:
I can fit 5 rows in 4 blocks if I put 1 anda quarter rows per block, but
I'm not going to spread a row over 4 blocks on a new insert, I'll put it in
its own block.
Regards
Jonathan Lewis
