On 2015/09/02 16:40, Amit Langote wrote:
On 2015-09-02 PM 04:07, Albe Laurenz wrote:
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.
Sorry, I failed to see why that would be the case. Could you elaborate?
I think Laurenz would assume that the updates 1. and 2. in the above
transactions are performed *in a non-inherited manner*. If that's
right, T1 and T2 could deadlock, but I think we assume here to run
transactions over shards *in an inherited manner*.
Best regards,
Etsuro Fujita
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