Thread: Decrease time needed to CREATE INDEX and FOREIGN KEY on new tablecolumn which has all values NULL

> The table is huge and it takes a lot of time to add the INDEX and the FOREIGN KEY although all values are NULL.
> Considering that the new DepartmentId column is NULL for all rows at this point, is there a way to make the INDEX and
FOREIGNKEY creation run faster? 

In your script to create index add this:

set maintenance_work_mem = '1GB'
or any other figure you feel comfortable.

On 2019-Jan-22, Denisa Cirstescu wrote:

> I am trying to add a new column to a really big table and to define an INDEX and a FOREIGN KEY on that new column
usingthe following instructions:
 
> 
> ALTER TABLE Employee ADD COLUMN DepartmentId INTEGER;
> CREATE INDEX IDX_Employee_DepartmentId ON Employee(DepartmentId);
> ALTER TABLE Employee ADD CONSTRAINT FK_Employee_Department FOREIGN KEY(DepartmentId) REFERENCES
Department(DepartmentId);
> 
> The table is huge and it takes a lot of time to add the INDEX and the FOREIGN KEY although all values are NULL.
> Considering that the new DepartmentId column is NULL for all rows at this point, is there a way to make the INDEX and
FOREIGNKEY creation run faster?
 

The typical advice is to run CREATE INDEX CONCURRENTLY instead of plain
CREATE INDEX.  Also, use "ADD CONSTRAINT ... NOT VALID;" instead, and
later do another ALTER TABLE ... VALIDATE CONSTRAINT.  That decreases
the impact considerably in production scenarios.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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