Re: [HACKERS] logical decoding of two-phase transactions

From: Nikhil Sontakke <nikhils(at)2ndquadrant(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Nikhil Sontakke <nikhils(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Sokolov Yura <y(dot)sokolov(at)postgrespro(dot)ru>, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] logical decoding of two-phase transactions
Date: 2018-07-26 14:54:00
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>> I think we even can just do something like a global
>> TransactionId check_if_transaction_is_alive = InvalidTransactionId;
>> and just set it up during decoding. And then just check it whenever it's
>> not set tot InvalidTransactionId.
> Ok. I will work on something along these lines and re-submit the set of patches.
PFA, latest patchset, which completely removes the earlier
LogicalLock/LogicalUnLock implementation using groupDecode stuff and
uses the newly suggested approach of checking the currently decoded
XID for abort in systable_* API functions. Much simpler to code and
easier to test as well.

Out of the patchset, the specific patch which focuses on the above
systable_* API based XID checking implementation is part of
0003-Gracefully-handle-concurrent-aborts-of-uncommitted-t.patch. So,
it might help to take a look at this patch first for any additional
feedback on this approach.

There's an additional test case in
0005-Additional-test-case-to-demonstrate-decoding-rollbac.patch which
uses a sleep in the "change" plugin API to allow a concurrent rollback
on the 2PC being currently decoded. Andres generally doesn't like this
approach :-), but there are no timing/interlocking issues now, and the
sleep just helps us do a concurrent rollback, so it might be ok now,
all things considered. Anyways, it's an additional patch for now.

Comments, feedback appreciated.

Nikhil Sontakke
PostgreSQL Development, 24x7 Support, Training & Services

Attachment Content-Type Size
0001-Cleaning-up-of-flags-in-ReorderBufferTXN-structure.patch application/octet-stream 7.9 KB
0002-Support-decoding-of-two-phase-transactions-at-PREPAR.patch application/octet-stream 40.2 KB
0003-Gracefully-handle-concurrent-aborts-of-uncommitted-t.patch application/octet-stream 9.0 KB
0004-Teach-test_decoding-plugin-to-work-with-2PC.patch application/octet-stream 25.3 KB
0005-Additional-test-case-to-demonstrate-decoding-rollbac.patch application/octet-stream 8.7 KB

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