| From: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Bruce Momjian <bruce(at)momjian(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>, Mason S <masonlists(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Horizontal scalability/sharding |
| Date: | 2015-09-02 06:40:40 |
| Message-ID: | 55E699E8.6080106@lab.ntt.co.jp |
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| Lists: | pgsql-hackers |
On 2015-09-02 PM 03:25, Amit Kapila wrote:
> On Wed, Sep 2, 2015 at 11:35 AM, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)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
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