Subject: Re: Grants not working on partitions

From: Adrian Klaver <[email-masked]>
Date: Sat, 28 Sep 2024 08:16:06 -0700

On 9/28/24 04:02, Lok P wrote:
> Hi,
> While we are creating any new tables, we used to give SELECT privilege 
> on the newly created tables using the below command. But we are seeing 
> now , in case of partitioned tables even if we had given the privileges 
> in the same fashion, the user is not able to query specific partitions 
> but only the table. Commands like "select * from 
> schema1.<partition_name> " are erroring out with the "insufficient 
> privilege" error , even if the partition belongs to the same table.
> 
> Grant SELECT ON <table_name> to <user_name>;
> 
> Grant was seen as a one time command which needed while creating the 
> table and then subsequent partition creation for that table was handled 
> by the pg_partman extension. But that extension is not creating or 
> copying any grants on the table to the users. We were expecting , once 
> the base table is given a grant , all the inherited partitions will be 
> automatically applied to those grants. but it seems it's not working 
> that way. So is there any other way to handle this situation?

The docs are there for a reason:

https://github.com/pgpartman/pg_partman/blob/master/doc/pg_partman.md#child-table-property-inheritance

"Privileges & ownership are NOT inherited by default. If enabled by 
pg_partman, note that this inheritance is only at child table creation 
and isn't automatically retroactive when changed (see 
reapply_privileges()). Unless you need direct access to the child 
tables, this should not be needed. You can set the inherit_privileges 
option if this is needed (see config table information below)."

And:

"reapply_privileges(
     p_parent_table text
)
RETURNS void

     This function is used to reapply ownership & grants on all child 
tables based on what the parent table has set.
     Privileges that the parent table has will be granted to all child 
tables and privileges that the parent does not have will be revoked 
(with CASCADE).
     Privileges that are checked for are SELECT, INSERT, UPDATE, DELETE, 
TRUNCATE, REFERENCES, & TRIGGER.
     Be aware that for large partition sets, this can be a very long 
running operation and is why it was made into a separate function to run 
independently. Only privileges that are different between the parent & 
child are applied, but it still has to do system catalog lookups and 
comparisons for every single child partition and all individual 
privileges on each.
     p_parent_table - parent table of the partition set. Must be schema 
qualified and match a parent table name already configured in pg_partman.
"

> 
> In other databases(say like Oracle) we use to create standard 
> "roles"(Read_role, Write_role etc..) and then provide grants to the user 
> through those roles. And the objects were given direct grants to those 
> roles. Similarly here in postgres we were granting "read" or "write" 
> privileges on objects to the roles and letting the users login to the 
> database using those roles and thus getting all the read/write 
> privileges assigned to those roles. Are we doing anything wrong?
> 
> Regards
> Lok

-- 
Adrian Klaver
[email-masked]

---

From: Lok P <[email-masked]>
Date: Sat, 28 Sep 2024 21:26:05 +0530

> qualified and match a parent table name already configured in pg_partman.
Thank you. I was not aware about this function which copies the grants from
parent to child ,so we can give a call to this function at the end of the
pg_partman job call which is happening through the cron job. But I see ,
the only issue is that this function only has one parameter
"p_parent_table" but nothing for "child_table" and that means it will try
to apply grants on all the childs/partitions which have been created till
today and may already be having the privileges already added in them.

And we have just ~60 partitions in most of the table so hope that will not
take longer but considering we create/purge one partition daily for each
partition table using the pg_partman, every time we give it a call, it will
try to apply/copy the grants on all the partitions(along with the current
day live partition), will it cause the existing running queries on the live
partitions to hard parse? or say will it cause any locking effect when it
will try to apply grant on the current/live partitions , which must be
inserted/updated/deleted data into or being queries by the users?

---

From: Adrian Klaver <[email-masked]>
Date: Sat, 28 Sep 2024 09:58:34 -0700

On 9/28/24 08:56, Lok P wrote:
> 
> 
> On Sat, Sep 28, 2024 at 8:46 PM Adrian Klaver <[email-masked] 
> <mailto:[email-masked]>> wrote:
> 
>     https://github.com/pgpartman/pg_partman/blob/master/doc/pg_partman.md#child-table-property-inheritance <https://github.com/pgpartman/pg_partman/blob/master/doc/pg_partman.md#child-table-property-inheritance>
> 
> Thank you. I was not aware about this function which copies the grants 
> from parent to child ,so we can give a call to this function at the end 
> of the pg_partman job call which is happening through the cron job. But 
> I see , the only issue is that this function only has one parameter 
> "p_parent_table" but nothing for "child_table" and that means it will 
> try to apply grants on all the childs/partitions which have been created 
> till today and may already be having the privileges already added in them.
> 
> And we have just ~60 partitions in most of the table so hope that will 
> not take longer but considering we create/purge one partition daily for 
> each partition table using the pg_partman, every time we give it a call, 
> it will try to apply/copy the grants on all the partitions(along with 
> the current day live partition), will it cause the existing running 
> queries on the live partitions to hard parse? or say will it cause any 
> locking effect when it will try to apply grant on the current/live 
> partitions , which must be inserted/updated/deleted data into or being 
> queries by the users?
> 

1) You seem to have missed the first part of the answer:

"Privileges & ownership are NOT inherited by default. If enabled by 
pg_partman, note that this inheritance is only at child table creation 
and isn't automatically retroactive when changed (see 
reapply_privileges()). Unless you need direct access to the child 
tables, this should not be needed. **You can set the 
inherit_privileges** option if this is needed (see config table 
information below)."

Read ** ...** part.

2) This is open source the code is available for you to see what is 
actually going on:

https://github.com/pgpartman/pg_partman/blob/master/sql/functions/reapply_privileges.sql

which in turn uses:

https://github.com/pgpartman/pg_partman/blob/master/sql/functions/apply_privileges.sql

3) This is something that is easily tested on you end.