Re: Table with 300 columns (ie > 255) : Row Chaining ?
- From: "Christian Antognini" <Christian.Antognini@xxxxxxxxxxxx>
- To: "Hemant K Chitale" <hkchital@xxxxxxxxxxxxxx>
- Date: Mon, 19 Oct 2009 10:02:28 +0200
Hi Hemant
> I have some interesting findings when I retrieve a single row from a
> table with >255 columns (348 columns). For the table definition in
> my test case, if I fetch the 95th column or lower, I see 1
> "consistent gets" against the table. If I fetch the 96th column or
> higher (from the *same* row), I see 2 "consistent gets" .
This is probably because the split occurs between column 95 and 96. Do a
block dump to check it... This is because the first row piece is not of
"full length". In other words, the pieces are split and stored in
"reverse order". For example, if you have a chained row that is stored
in two blocks, not only the first column is stored in a block coming
after the block containing the last row, but in addition the first piece
is smaller than the second one. Go figure why...
HTH
Chris
Troubleshooting Oracle Performance, Apress 2008
http://top.antognini.ch
--
//www.freelists.org/webpage/oracle-l
Other related posts:
