Обсуждение: Escape output of pg_amcheck test

The pg_amcheck reports a skip message if the layout of the index does 
not match expectations.  That message includes the bytes that were 
expected and the ones that were found.  But the found ones are arbitrary 
bytes, which can have funny effects on the terminal when they are 
printed.  To avoid that, escape non-word characters before printing.

Hi,

> The pg_amcheck reports a skip message if the layout of the index does
> not match expectations.  That message includes the bytes that were
> expected and the ones that were found.  But the found ones are arbitrary
> bytes, which can have funny effects on the terminal when they are
> printed.  To avoid that, escape non-word characters before printing.

LGTM.

I didn't get the part about the /r modifier at first, but "man perlre" helped:

"""
r  - perform non-destructive substitution and return the new value
"""

The /a modifier requires Perl >= 5.14, which is fine [1].

[1]: https://www.postgresql.org/docs/current/install-requirements.html

-- 
Best regards,
Aleksander Alekseev

On 1/7/24 23:27, Peter Eisentraut wrote:
> The pg_amcheck reports a skip message if the layout of the index does 
> not match expectations.  That message includes the bytes that were 
> expected and the ones that were found.  But the found ones are arbitrary 
> bytes, which can have funny effects on the terminal when they are 
> printed.  To avoid that, escape non-word characters before printing.

> +            # escape non-word characters to avoid confusing the terminal
> +            $b =~ s{(\W)}{ sprintf '\x%02x', ord($1) }aegr);

The /r modifier defeats the purpose of the patch, at least for my perl 
version, perl 5, version 28, subversion 1 (v5.28.1).  With just the /aeg 
modifier, it works fine.

-- 
Mark Dilger

> On Jan 8, 2024, at 5:41 AM, Mark Dilger <hornschnorter@gmail.com> wrote:
>
> The /r modifier defeats the purpose of the patch, at least for my perl version, perl 5, version 28, subversion 1
(v5.28.1). With just the /aeg modifier, it works fine. 

Nevermind.  I might be wrong about that.  I didn't have a test case handy that would generate index corruption which
wouldresult in characters of the problematic class, and so I quickly wrote some (wrong) instrumentation to try to test
yourpatch. 

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Hi,

> [...] so I quickly wrote some (wrong) instrumentation to try to test your patch.

Yep, it confused me too at first.

Since the encoding happens right before exit() call, maybe it's worth
changing $b in-place in order to make the code slightly more readable
for most of us :)

-- 
Best regards,
Aleksander Alekseev

On 08.01.24 15:04, Aleksander Alekseev wrote:
>> [...] so I quickly wrote some (wrong) instrumentation to try to test your patch.
> 
> Yep, it confused me too at first.
> 
> Since the encoding happens right before exit() call, maybe it's worth
> changing $b in-place in order to make the code slightly more readable
> for most of us :)

My patch originally had the old-style

my $b_escaped = $b;
$b_escaped =~ s/.../;

... sprintf(..., $b_escaped);

but then I learned about the newish /r modifier and thought it was 
cooler. :)

On 08.01.24 16:06, Peter Eisentraut wrote:
> On 08.01.24 15:04, Aleksander Alekseev wrote:
>>> [...] so I quickly wrote some (wrong) instrumentation to try to test 
>>> your patch.
>>
>> Yep, it confused me too at first.
>>
>> Since the encoding happens right before exit() call, maybe it's worth
>> changing $b in-place in order to make the code slightly more readable
>> for most of us :)
> 
> My patch originally had the old-style
> 
> my $b_escaped = $b;
> $b_escaped =~ s/.../;
> 
> ... sprintf(..., $b_escaped);
> 
> but then I learned about the newish /r modifier and thought it was 
> cooler. :)

committed