From: Ran Benita <ran@unusedvar.com>
To: pgsql-bugs@lists.postgresql.org
Subject: Broken PQtrace CopyData display
Date: Fri, 29 Aug 2025 22:45:18 +0300
Message-ID: <a3383211-4539-459b-9d51-95c736ef08e0@app.fastmail.com> (raw)
I used PQtrace to trace a logical decoding session, and was confused to see
lines like this:
2025-08-29 22:09:57.633980 F 38 CopyData 'r\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\xffffff8e\x07\xffffff85x\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\xffffffe0\xffffff84\xffffff89R\xffffffd7\xffffffb8\x00'
The data doesn't make sense and has the wrong length. A quick look shows that
the \xffffff85 parts are a signedness issue (on my compiler char is signed).
I instead expect to see output like this:
2025-08-29 22:39:17.041261 F 38 CopyData 'r\x00\x00\x00\x00\x8e\x07\x89\xf8\x00\x00\x00\x00\x8e\x07\x89\xf8\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\xe0\x84\xf21Dh\x00'
The diff below fixes this particular problem, though they say bugs are like
mushrooms, if you find one then there are probably others nearby, so a more
comprehensive fix may be warranted.
diff --git i/src/interfaces/libpq/fe-trace.c w/src/interfaces/libpq/fe-trace.cindex a45f0d85587..f487c111fc7 100644--- i/src/interfaces/libpq/fe-trace.c+++ w/src/interfaces/libpq/fe-trace.c@@ -212,7 +212,7 @@ pqTraceOutputNchar(FILE *pfdebug, int len, const char *data, int *cursor, bool s
else
{
fwrite(v + next, 1, i - next, pfdebug);
- fprintf(pfdebug, "\\x%02x", v[i]);+ fprintf(pfdebug, "\\x%02x", (unsigned char) v[i]);
next = i + 1;
}
}
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To: pgsql-bugs@postgresql.org
Cc: ran@unusedvar.com, pgsql-bugs@lists.postgresql.org
Subject: Re: Broken PQtrace CopyData display
In-Reply-To: <a3383211-4539-459b-9d51-95c736ef08e0@app.fastmail.com>
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