On Fri, May 05, 2023 at 02:13:28PM +0000, gkokola...@pm.me wrote: > Good point. I thought about it before submitting the patch. I > concluded that given the complexity and operations involved in > LZ4Stream_read_internal() and the rest of t he pg_dump/pg_restore > code, the memset() call will be negligible. However from the > readability point of view, the function is a bit cleaner with the > memset(). > > I will not object to any suggestion though, as this is a very > trivial point. Please find attached a v2 of the patch following the > suggested approach.
Hmm. I was looking at this patch, and what you are trying to do sounds rather right to keep a parallel with the gzip and zstd code paths. Looking at the code of gzread.c, gzgets() enforces a null-termination on the string read. Still, isn't that something we'd better enforce in read_none() as well? compress_io.h lists this as a requirement of the callback, and Zstd_gets() does so already. read_none() does not enforce that, unfortunately. + /* No work needs to be done for a zero-sized output buffer */ + if (size <= 0) + return 0; Indeed. This should be OK. - ret = LZ4Stream_read_internal(state, ptr, size, true); + Assert(size > 1); The addition of this assertion is a bit surprising, and this is inconsistent with Zstd_gets where a length of 1 is authorized. We should be more consistent across all the callbacks, IMO, not less, so as we apply the same API contract across all the compression methods. While testing this patch, I have triggered an error pointing out that the decompression path of LZ4 is broken for table data. I can reproduce that with a dump of the regression database, as of: make installcheck pg_dump --format=d --file=dump_lz4 --compress=lz4 regression createdb regress_lz4 pg_restore --format=d -d regress_lz4 dump_lz4 pg_restore: error: COPY failed for table "clstr_tst": ERROR: extra data after last expected column CONTEXT: COPY clstr_tst, line 15: "32 6 seis xyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzyxyzzy..." pg_restore: warning: errors ignored on restore: 1 This does not show up with gzip or zstd, and the patch does not influence the result. In short it shows up with and without the patch, on HEAD. That does not look really stable :/ -- Michael
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