Re: [HACKERS] WIP aPatch: Pgbench Serialization and deadlock errors

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>
Cc: Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>, thomas(dot)munro(at)gmail(dot)com, m(dot)polyakova(at)postgrespro(dot)ru, alvherre(at)2ndquadrant(dot)com, pgsql-hackers(at)postgresql(dot)org, teodor(at)sigaev(dot)ru
Subject: Re: [HACKERS] WIP aPatch: Pgbench Serialization and deadlock errors
Date: 2022-03-12 14:54:54
Message-ID: alpine.DEB.2.22.394.2203121550300.3679190@pseudo
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Hello Yugo-san,

About Pgbench error handling v16:

This patch set needs a minor rebase because of 506035b0. Otherwise, patch
compiles, global and local "make check" are ok. Doc generation is ok.

This patch is in good shape, the code and comments are clear.
Some minor remarks below, including typos and a few small suggestions.

## About v16-1

This refactoring patch adds a struct for managing pgbench variables, instead of
mixing fields into the client state (CState) struct.

Patch compiles, global and local "make check" are both ok.

Although this patch is not necessary to add the feature, I'm fine with it as
improves pgbench source code readability.

## About v16-2

This last patch adds handling of serialization and deadlock errors to pgbench
transactions. This feature is desirable because it enlarge performance testing
options, and makes pgbench behave more like a database client application.

Possible future extension enabled by this patch include handling deconnections
errors by trying to reconnect, for instance.

The documentation is clear and well written, at least for my non-native speaker
eyes and ears.

English: "he will be aborted" -> "it will be aborted".

I'm fine with renaming --report-latencies to --report-per-command as the later
is clearer about what the options does.

I'm still not sure I like the "failure detailed" option, ISTM that the report
could be always detailed. That would remove some complexity and I do not think
that people executing a bench with error handling would mind having the details.
No big deal.

printVerboseErrorMessages: I'd make the buffer static and initialized only once
so that there is no significant malloc/free cycle involved when calling the function.

advanceConnectionState: I'd really prefer not to add new variables (res, status)
in the loop scope, and only declare them when actually needed in the state branches,
so as to avoid any unwanted interaction between states.

typo: "fullowing" -> "following"

Pipeline cleaning: the advance function is already soooo long, I'd put that in a
separate function and call it.

I think that the report should not remove data when they are 0, otherwise it makes
it harder to script around it (in failures_detailed on line 6284).

The test cover the different cases. I tried to suggest a simpler approach
in a previous round, but it seems not so simple to do so. They could be
simplified later, if possible.


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