From: | Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Greg Stark <stark(at)mit(dot)edu>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Autonomous Transaction (WIP) |
Date: | 2014-04-09 05:05:53 |
Message-ID: | BF2827DCCE55594C8D7A8F7FFD3AB7713DDDFC3A@SZXEML508-MBX.china.huawei.com |
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Lists: | pgsql-hackers |
On 09 April 2014 01:09, Rover Haas Wrote:
> I'm also pretty unconvinced that multiple PGPROCs is the right way to
> go. First, PGPROCs have a bunch of state in them that is assumed to
> exist once per backend. We might find pretty substantial code churn
> there if we try to go change that.
Yes you right. That is why I am not creating a separate procarray entry to
maintain autonomous transaction. Please find details in previous reply sent
today sometime back.
> Second, why do other backends
> really need to know about our ATs? As far as I can see, if other
> backends see the AT as a subtransaction of our top-level transaction up
> until it actually commits, that ought to be just fine. Maybe the
> backend needs to internally frob visibility rules, but that's not a
> matter for shared memory.
In order to get snapshot from other session, it will be required by other
session to access autonomous transaction and their sub-transactions.
During snapshot creation, autonomous transaction is considered as main
transaction and list of all running autonomous transaction and their sub-transaction
gets stored in snapshot data.
e.g. Suppose below processes are running with given transactions:
Proc-1: 100
Proc-2: 101, 102 (Auto Tx1), 103 (Auto Tx2), 104 (Sub-tx of Auto Tx2)
Proc-3: 105, 106 (Auto Tx2), 107 (Auto Tx2)
Suppose latest completed transaction is 108.
Then Snapshot data for autonomous transaction 107 will be as below:
Xmin: 100
Xmax: 109
Snapshot->xip[]: 100, 101, 102, 103, 105, 106
Snapshot->subxip[]: 104
Thanks and Regards,
Kumar Rajeev Rastogi
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