Re: UPDATE of partition key

On 15 February 2017 at 20:26, David Fetter <david(at)fetter(dot)org> wrote:
> When an UPDATE can't happen, there are often ways to hint at
> what went wrong and how to correct it. Violating a uniqueness
> constraint would be one example.
>
> When an UPDATE can't happen and the depth of the subtree is a
> plausible candidate for what prevents it, there might be a way to say
> so.
>
> Let's imagine a table called log with partitions on "stamp" log_YYYY
> and subpartitions, also on "stamp", log_YYYYMM. If you do something
> like
>
> UPDATE log_2017 SET "stamp"='2016-11-08 23:03:00' WHERE ...
>
> it's possible to know that it might have worked had the UPDATE taken
> place on log rather than on log_2017.
>
> Does that make sense, and if so, is it super invasive to HINT that?

Yeah, I think it should be possible to find the root partition with
the help of pg_partitioned_table, and then run ExecFindPartition()
again using the root. Will check. I am not sure right now how involved
that would turn out to be, but I think that logic would not change the
existing code, so in that sense it is not invasive.

--
Thanks,
-Amit Khandekar
EnterpriseDB Corporation
The Postgres Database Company