Re: Horizontal scalability/sharding

On 2015-09-02 PM 03:25, Amit Kapila wrote:
> On Wed, Sep 2, 2015 at 11:35 AM, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
>>
>> The UPDATE/DELETE pushdown, which I've proposed, would ensure the sane
>> behaviour for inherited UPDATEs/DELETEs, as existing non-pushed-down
>> UPDATE/DELETE does, because inheritance_planner guarantees that all
>> backends lock inheritance children in the same order to avoid needless
>> deadlocks.
>>
>>
> Will it be able to do it for row level locks, row level locking occurs
> during updation of a row, so will it be possible to ensure the order of
> locks on rows?
> 
> Will it handle deadlocks across different table partitions. Consider
> a case as below:
> 
> T1
> 1. Updates row R1 of T1 on shard S1
> 2. Updates row R2 of T2 on shard S2
> 
> T2
> 1. Updates row R2 of T2 on shard S2
> 2. Updates row R1 of T1 on shard S1
> 

As long as shards are processed in the same order in different
transactions, ISTM, this issue should not arise? I can imagine it becoming
a concern if parallel shard processing enters the scene. Am I missing
something?

Thanks,
Amit