Check whether a NOT NULL check constraint has been validated

On 11/30/25 16:59, Stuart Campbell wrote:

Hello,

I have several NOT NULL check constraints in my schema that were
originally added as NOT VALID. I would like to determine whether they
have all since been validated, or not.

I thought maybe pg_constraint.convalidated might help, but it seems like
the version of Postgres I'm using (16) doesn't store not null
constraints in that table. And even in later versions, maybe it doesn't
hold the information I need.

Is there another way to discover this?

1) Select count(*) from <table> where <col> IS NULL;

2) From here

https://www.postgresql.org/docs/current/sql-altertable.html#SQL-ALTERTABLE-NOTES

ALTER TABLE <table> VALIDATE CONSTRAINT <constraint_name>;

As described:

". Once the constraint is in place, no new violations can be inserted,
and the existing problems can be corrected at leisure until VALIDATE
CONSTRAINT finally succeeds."

This communication and any attachments may contain confidential
information and are intended to be viewed only by the intended
recipients. If you have received this message in error, please notify
the sender immediately by replying to the original message and then
delete all copies of the email from your systems.

--
Adrian Klaver
adrian.klaver@aklaver.com

On 11/30/25 19:07, Adrian Klaver wrote:

On 11/30/25 16:59, Stuart Campbell wrote:

Hello,

I have several NOT NULL check constraints in my schema that were
originally added as NOT VALID. I would like to determine whether they
have all since been validated, or not.

I thought maybe pg_constraint.convalidated might help, but it seems
like the version of Postgres I'm using (16) doesn't store not null
constraints in that table. And even in later versions, maybe it
doesn't hold the information I need.

Is there another way to discover this?

1) Select count(*) from <table> where <col> IS NULL;

2) From here

https://www.postgresql.org/docs/current/sql-altertable.html#SQL-
ALTERTABLE-NOTES

ALTER TABLE <table> VALIDATE CONSTRAINT <constraint_name>;

As described:

". Once the constraint is in place, no new violations can be inserted,
and the existing problems can be corrected at leisure until VALIDATE
CONSTRAINT finally succeeds."

Realized I was looking at current docs and I should be looking at your
version

From the 16 version of the docs:

"This form adds a new constraint to a table using the same constraint
syntax as CREATE TABLE, plus the option NOT VALID, which is currently
only allowed for foreign key and CHECK constraints."

Now I am not sure what you did.

Are you saying you used a CHECK constraint to check for NULL values?

If so then pg_constraint.convalidated would work.

If not are you sure you are on Postgres 16?

This communication and any attachments may contain confidential
information and are intended to be viewed only by the intended
recipients. If you have received this message in error, please notify
the sender immediately by replying to the original message and then
delete all copies of the email from your systems.

--
Adrian Klaver
adrian.klaver@aklaver.com

Hi Adrian,

Now I am not sure what you did.

Are you saying you used a CHECK constraint to check for NULL values?

That's right. Something like:

ALTER TABLE foo ADD CONSTRAINT bar_not_null CHECK (bar IS NOT NULL) NOT
VALID

If so then pg_constraint.convalidated would work.

You're right. I didn't immediately find what I was looking for, and when I
looked at the docs for pg_constraints, I guess I confused myself with this
comment:

Not-null constraints are represented in the pg_attribute

<https://www.postgresql.org/docs/16/catalog-pg-attribute.html&gt; catalog, not
here.

Thanks for the assistance.

--
This communication and any attachments may contain confidential information
and are intended to be viewed only by the intended recipients. If you have
received this message in error, please notify the sender immediately by
replying to the original message and then delete all copies of the email
from your systems.