Re: Table with 300 columns (ie > 255) : Row Chaining ?
Date: Sun, 18 Oct 2009 16:23:36 +0800
Thanks Tanel and
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" .
I cannot yet conclude if the row is split into two pieces at the 96th column. I have tried with columns of 5 characters (3 characters filled) and 15 characters (13 characters filled), with 8KB blocks and 16KB block.
Hemant K Chitale
Tanel Poder wrote:
>If all row pieces fit into the same block (where the initial row
>piece is written) then you'll have intra-block chaining. Basically
>chained rows, where the "next row piece" pointer bytes will point
>into another row in the same block. If they don't fit, then you have
>regular row chaining, into other blocks too.
>On Thu, Oct 8, 2009 at 6:08 PM, Hemant K Chitale
>Is there a MetaLink note that explains how Oracle handles INSERTs
>into a table with more than 255 columns ?
>Is it broken into 2 row pieces ? Does Oracle write the pieces into
>separate blocks even if, say, the row length is less than 7000 bytes
>? If the row length is less than 3900 bytes ?
Hemant K ChitaleReceived on Sun Oct 18 2009 - 03:23:36 CDT