Search Postgresql Archives

Re: Dropping column from big table

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 7/10/24 13:13, sud wrote:
Hi All,
It's postgres database version 15.4. We have a table which is daily and is approx. ~2TB in size having a total ~90 partitions. We have a requirement to drop columns and add new columns to this table.

I Want to understand, If this can be done online? what is the fastest way to drop/add columns from such a big table and what will be the consequence of this in regards to vacuum, post this activity? Or if any other issues we may face post this?

Regards
Sud

https://www.postgresql.org/docs/current/sql-altertable.html

"The DROP COLUMN form does not physically remove the column, but simply makes it invisible to SQL operations. Subsequent insert and update operations in the table will store a null value for the column. Thus, dropping a column is quick but it will not immediately reduce the on-disk size of your table, as the space occupied by the dropped column is not reclaimed. The space will be reclaimed over time as existing rows are updated.

To force immediate reclamation of space occupied by a dropped column, you can execute one of the forms of ALTER TABLE that performs a rewrite of the whole table. This results in reconstructing each row with the dropped column replaced by a null value.
"

--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx






[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]

  Powered by Linux