Re: Behaviour adding a column with and without a default (prior toPG11) - Mailing list pgsql-general

From Joe Horsnell
Subject Re: Behaviour adding a column with and without a default (prior toPG11)
Date
Msg-id 6D7DB32C-A4BC-4FB1-9AB8-F2E035D14A59@bambooloans.com
Whole thread Raw
In response to Re: Behaviour adding a column with and without a default (prior to PG11)  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Thanks for the quick response Tom.

Cheers,

Joe.

On 30/09/2019, 22:19, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:

    Joe Horsnell <Joe@bambooloans.com> writes:
    > The documentation (https://www.postgresql.org/docs/10/ddl-alter.html) clearly states that adding a column with a
defaultrequires updating all the rows in the table, to store the new column value (this is prior to PG11, obviously).
 

    > Obviously the desired effect of adding the column default without rewriting all the rows in the table can be
achievedby adding the nullable column first with no default, then changing the default, but out of curiosity; was there
aspecific technical reason for the behaviour described above, or was it a conscious design choice?
 

    We read the SQL spec as requiring this behavior.

    regards, tom lane



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