Re: Declarative partitioning - Mailing list pgsql-hackers

On 2015-08-19 PM 09:23, Simon Riggs wrote:
> On 18 August 2015 at 11:30, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
> wrote:
> 
>>
>> There is no need to define tuple routing triggers. CopyFrom() and
>> ExecInsert() determine target partition just before performing
>> heap_insert() and ExecInsertIndexTuples(). IOW, any BR triggers and
>> constraints (on parent) are executed for tuple before being routed to a
>> partition. If no partition can be found, it's an error.
>>
>> Because row-level AFTER triggers need to save ItemPointers in trigger
>> event data and defining triggers on partitions (which is where tuples
>> really go) is not allowed, I could not find a straightforward way to
>> implement them. So, perhaps we should allow (only) row-level AFTER
>> triggers on partitions or think of modifying trigger.c to know about this
>> twist explicitly.
>>
> 
> I think tables will eventually need FK support; its not sustainable as a
> long term restriction, though perhaps its something we can do in a later
> patch.
> 

Sure. Solving the row-level AFTER trigger problem should hopefully open up
the possibility of partitioned-table-as-FK-rel implementation.

> You haven't specified what would happen if an UPDATE would change a row's
> partition. I'm happy to add this to the list of restrictions by saying that
> the partition key cannot be updated.
> 

UPDATEs that change a row's partition would cause error. I haven't
implemented that yet but will that way in the next patch.

By the last sentence, do you mean only UPDATEs to the partition key that
cause rows to jump partitions or simply any UPDATEs to the partition key?

> We'll need regression tests that cover each restriction and docs that
> match. This is not something we should leave until last. People read the
> docs to understand the feature, helping them to reach consensus. So it is
> for you to provide the docs before, not wait until later. I will begin a
> code review once you tell me docs and tests are present. We all want the
> feature, so its all about the details now.
> 

Sorry, should have added tests and docs already. I will add them in the
next version of the patch. Thanks for willing to review.

Thanks,
Amit