Link to home
Start Free TrialLog in
Avatar of Putoch
PutochFlag for Afghanistan

asked on

Alter Table Problem - over 125 million rows in table and query takes to long.

Hi,
I have a table with 125million rows in it on the live db
i replicate ths db to a mysql db daily
For reporting reaons, i want to pull in the data from this table into my SQL SERVER db.
i only pull in the previous days entries to the SQL SERVER.

however to do this i want to add a colunm called DW_TIMESTAMP

So i would use this syntax
ALTER TABLE MYTABLENAME
ADD COLUMN dw_timestamp TIMESTAMP
DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

however because there are soo many rows this is taking forever, in fact it stopped the Mysql server because i believe it timmed out.

Can anyone suggest how i can speed up this process.

I was thinking if i could add a where clause but i don't believe that would work.

Kind Regards,
Putoch
Avatar of Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3]
Flag of Luxembourg image

please clarify: is this MS SQL Server, or MySQL?
which version / sp ?

this "alter table" should not take "forever", unless it's blocked all the time by other processes issuing schema locks on the table ...
Maybe if you add the column, allowing nulls first.

Then assign the default value as a separate transaction.

If this is a always live DB, then you may just have to wait it out. You should only need to do it once.

Avatar of Putoch

ASKER

Its a MYSQL db (version 5.1.44 )

i was able to alter any other table i needed to with out any trouble, it seems to only be this table.
i will try to do it seperatly now and see how this works.

Something strange though happened with the other tables.
i set up the timestamp to Default current_timestamp on update.
however when i updated all those other tables the timestamp defaulted to 0000-00-00.

Why would this happen do you know?
Is there something i'm missing on my syntax.
the timestamp is set up as NOT NULL.

ALTER TABLE MYTABLENAME
ADD COLUMN dw_timestamp TIMESTAMP
DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

Thanks a million,
putoch
ASKER CERTIFIED SOLUTION
Avatar of colin_o_brien
colin_o_brien
Flag of Ireland image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial