Thank You So much. So just to avoid missing any grants synonyms and related
consequences like invalidation of package/procedure etc. Is it good to just
intact the main table but move data in and out , something as below..
1)Create a backup table as "tab1_backup" from the main table TAB1 using
CTAS approach using parallelism without creating indexes constraints etc on
the backup table.
2)Truncate the main table TAB1.
3)make the indexes UNUSABLE in the main table TAB1.
4)Alter the column in the main table TAB1 to modify the existing column
from number(15,5) to number(22,0).
5)Insert data into the main table(tab1) from the backup table(tab1_backup)
using direct path load + parallel threads. And in case of unusable indexes
this step should be pretty fast.
6)Rebuild the indexes in the main table.
Regards
Lok
On Mon, Mar 22, 2021 at 4:16 PM ahmed.fikri@xxxxxxxxxxx <
ahmed.fikri@xxxxxxxxxxx> wrote:
oracle does the same when you add the new colum, update it and remove the
old one (so doing this, the table is recreated three times).
just use direct load + parallel + constraints novalidate. This work
perfectly even for huge tables
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--- Original-Nachricht ---
*Von: *Lok P
*Betreff: *Re: Column Length modification
*Datum: *22. März 2021, 11:38
*An: *Jonathan Lewis
*Cc: *Oracle L
Just that, i think the option of creating the new object fully with the
data and rename afterwards by dropping the original object may not be a
good option if the object which we are trying to alter is in TB's and
partitioned, thinking if any other possible way to achieve the same?
On Sun, Mar 21, 2021 at 8:09 AM Lok P <loknath.73@xxxxxxxxx> wrote:
Thank you Jonathan.
Yes it's exactly the same error ORA-01440: which we are encountering. And
the column is not having any data with non zero precision. But as we are
standardizing the data elements across our applications, we want to now not
allow any junks in future and thus trying to fix the precision thing as
part of this length modification. This will make things consistent across
all our applications and easy for understanding.
Now if my understanding is correct, the way you are suggesting i..e
altering column length as (22,7) (which will not make any ORA-01440 error
happen )+ having the check constraint added to the table will technically
help us achieving the same thing (without any additional performance
overhead) as simply altering the length to number(22,0). But is it
something that will create confusion and thus we should keep it clean i.e.
column length (22,0) only without any additional constraint? And to achieve
that , is the best approach is the one suggested by Ahmed i.e. create the
object fully with the new structure(i.e. with number(22,0)) and then drop
the old one and rename the new one?
Regards
Lok
On Sun, Mar 21, 2021 at 3:30 AM Jonathan Lewis <jlewisoracle@xxxxxxxxx>
wrote:
If you're see an error then show us exactly what it is.
I assume it's
ORA-01440: column to be modified must be empty to decrease precision or
scale
You're trying to change a column from (15,5) to (22,0) which means
you're going to lose 5 decimal places - do any of the rows have data that
isn't purely integer, if not are you happy for the values to change as you
go from 5d.p. to integer?
If you need 22 digits precision, and no decimal places you could modify
your column to (27,5) and then add a check constraint that says (check colX
= trunc(colX)) as a way of ensuring that you don't have any non-integer
values. (You could update the table,set colX to trunc(colX) where colX !=
trunc(colX)before adding the constraint, or you could add the constraint
enabled but not validated, then do the update then set the constraint
validated. ** or ceiling() or round(), depending on what you think best
suits your requirements
Regards
Jonathan Lewis
On Sat, 20 Mar 2021 at 19:10, Lok P <loknath.73@xxxxxxxxx> wrote:
We are using version 11.2.0.4 of Oracle exadata. Our requirement is to
modify column length of a table from Number(15,5) to Number(22) and we are
seeing errors and its saying to make the column empty before making this
modification. So to achieve this we are thinking of doing this in multiple
steps like
1) Add new column(COL_new) with number(22,0) to the same table
2)Then update the new column with all the values of original column(say
COL1)
3)Then drop the original column(COL1) which is having length
number(15,5) 4)Then rename the new column(COL_NEW) to original i.e. COL1.
We are in the process of doing multiple such modifications to some big
partition and non partitioned table. And in this process the Update seems
to be a tedious one as it will scan the full table and may lead to row
chaining and also drop the existing column and renaming new columns will
need the application to stop pointing to this object or else they may fail.
Also stats seems to be gathered fully again on the table after this along
with if any index pointing to these columns needs to be recreated. So
multiple issues highlighted with this process by the team. Want to
understand from experts if there exists any better way of achieving this
with minimal interruption and in quick time?
Thanks
Lok
