Re: Speedup twophase transactions

On Tue, Mar 22, 2016 at 1:53 AM, Jesper Pedersen
<jesper(dot)pedersen(at)redhat(dot)com> wrote:
> On 03/18/2016 12:50 PM, Stas Kelvich wrote:
>>>
>>> On 11 Mar 2016, at 19:41, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>
>>> wrote:
>>>
>>
>> Thanks for review, Jesper.
>>
>>> Some comments:
>>>
>>> * The patch needs a rebase against the latest TwoPhaseFileHeader change
>>
>>
>> Done.
>>
>>> * Rework the check.sh script into a TAP test case (src/test/recovery), as
>>> suggested by Alvaro and Michael down thread
>>
>>
>> Done. Originally I thought about reducing number of tests (11 right now),
>> but now, after some debugging, I’m more convinced that it is better to
>> include them all, as they are really testing different code paths.
>>
>>> * Add documentation for RecoverPreparedFromXLOG
>>
>>
>> Done.
>
>
> Thanks, Stas.
>
> I have gone over this version, and tested with --enable-tap-tests + make
> check in src/test/recovery, which passes.
>
> Simon, do you want to move this entry to "Ready for Committer" and take the
> 2REVIEWER section as part of that, or leave it in "Needs Review" and update
> the thread ?

Looking at this patch....

+++ b/src/test/recovery/t/006_twophase.pl
@@ -0,0 +1,226 @@
+# Checks for recovery_min_apply_delay
+use strict;
This description is wrong, this file has been copied from 005.

+my $node_master = get_new_node("Candie");
+my $node_slave = get_new_node('Django');
Please let's use a node names that are more descriptive.

+# Switch to synchronous replication
+$node_master->append_conf('postgresql.conf', qq(
+synchronous_standby_names = '*'
+));
+$node_master->restart;
Reloading would be fine.

+ /* During replay that lock isn't really necessary, but let's take
it anyway */
+ LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
+ for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
+ {
+ gxact = TwoPhaseState->prepXacts[i];
+ proc = &ProcGlobal->allProcs[gxact->pgprocno];
+ pgxact = &ProcGlobal->allPgXact[gxact->pgprocno];
+
+ if (TransactionIdEquals(xid, pgxact->xid))
+ {
+ gxact->locking_backend = MyBackendId;
+ MyLockedGxact = gxact;
+ break;
+ }
+ }
+ LWLockRelease(TwoPhaseStateLock);
Not taking ProcArrayLock here?

The comment at the top of XlogReadTwoPhaseData is incorrect.

RecoverPreparedFromXLOG and RecoverPreparedFromFiles have a lot of
code in common, having this duplication is not good, and you could
simplify your patch.
--
Michael