Re: HOT chain validation in verify_heapam()

Hi Hackers,

On Sun, Jan 22, 2023 at 8:48 PM Himanshu Upadhyaya <
upadhyaya(dot)himanshu(at)gmail(dot)com> wrote:

>
> The test if (pred_in_progress || TransactionIdDidCommit(curr_xmin))
>> seems wrong to me. Shouldn't it be &&? Has this code been tested at
>> all? It doesn't seem to have a test case. Some of these other errors
>> don't, either. Maybe there's some that we can't easily test in an
>> automated way, but we should test what we can. I guess maybe casual
>> testing wouldn't reveal the problem here because of the recheck, but
>> it's worrying to find logic that doesn't look right with no
>> corresponding comments or test cases.
>>
>> This is totally my Mistake, apologies for that. I will fix this in my
> next patch. Regarding the missing test cases, I need one in-progress
> transaction for these test cases to be included in 004_verify_heapam.pl
> but I don't find a clear way to have an in-progress transaction(as per the
> design of 004_verify_heapam.pl ) that I can use in the test cases. I will
> be doing more research on a solution to add these missing test cases.
>
>>
>> I am trying to add test cases related to in-progress transactions in
004_verify_heapam.pl but I am not able to find a proper way to achieve
this.
We have a logic where we manually corrupt each tuple.
Please refer to the code just after the below comment in
004_verify_heapam.pl

"# Corrupt the tuples, one type of corruption per tuple. Some types of
# corruption cause verify_heapam to skip to the next tuple without
# performing any remaining checks, so we can't exercise the system properly
if
# we focus all our corruption on a single tuple."

Before this we stop the node by "$node->stop;" and then only we progress to
manual corruption. This will abort all running/in-progress transactions.
So, if we create an in-progress transaction and comment "$node->stop;"
then somehow all the code that we have for manual corruption does not work.

I think it is required to stop the server and then only proceed for manual
corruption?
If this is the case then please suggest if there is a way to get an
in-progress transaction
that we can use for manual corruption.
--
Regards,
Himanshu Upadhyaya
EnterpriseDB: http://www.enterprisedb.com