| From: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
|---|---|
| To: | "'Amit Langote *EXTERN*'" <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, 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 07:07:56 |
| Message-ID: | A737B7A37273E048B164557ADEF4A58B50F9F235@ntex2010i.host.magwien.gv.at |
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| Lists: | pgsql-hackers |
Amit Langote wrote:
> On 2015-09-02 PM 03:25, Amit Kapila wrote:
>> 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?
That would only hold for a single query, right?
If 1. and 2. in the above example come from different queries within one
transaction, you cannot guarantee that shards are processed in the same order.
So T1 and T2 could deadlock.
Yours,
Laurenz Albe
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