Thread: Parser emits mysterious error message for very long tokens
Hello, this is a problem on an extreme situation. When parser encounters very long tokens, it returns an error message which should be mysterious for users. > $ perl -e "print \"select '\" . \"x\"x(512*1024*1024) . \"'\"" | psql postgres > ERROR: invalid memory alloc request size 1073741824 Since parser repeats repalloc doubling in size starting from 1024 bytes, it practically fails for tokens longer than 512MiB. Most tokens doesn't touch the limit but text literal may do. If we don't assume this as a problem, the following discussion would be useless. ======== 1. Supplying context meessage or something would be needed anyway. > ERROR: invalid memory alloc request size 1073741824 > DETAIL: maybe encoutered too long token in parsing query 2. Edit the documentaion, or modify the behavior? http://www.postgresql.org/docs/devel/static/datatype-character.html > In any case, the longest possible character string that can be> stored is about 1 GB. Maximum possible text length would be about 1GB but it is farshorter when parsing text literal. I thought it is better to avoid 512MiB limit than addingdiscription about it to documentation. It could easily be doneusingMaxAllocSize (I don't like this but enlargeStringInfoalready does this..), or start from (1024 - 1) and repallocwith((last_size + 1) * 2 - 1) would do assuming MaxAllocSize is 2^n(this looks unwantedly complex), or simply startsfrom 1023works enough. On the other hand, any of these fixes caused "out of memory" ofreceive buffer on my environment. So I think such fix mightbeuseless. Thoughts? Sugestions? or is this totally useless? regards, -- Kyotaro Horiguchi NTT Open Source Software Center
Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> writes:
> Hello, this is a problem on an extreme situation.
> When parser encounters very long tokens, it returns an error
> message which should be mysterious for users.
>> $ perl -e "print \"select '\" . \"x\"x(512*1024*1024) . \"'\"" | psql postgres
>> ERROR: invalid memory alloc request size 1073741824
I can't get terribly excited about that, because there is not that
much daylight between there and where the query fails because the
entire input string exceeds 1GB. Moreover, anyone who tries working
with literals in this size range will soon learn not to ;-). So
it seems quite an artificial example to me ...
regards, tom lane
Hello, thank you for the opinion. At Fri, 11 Sep 2015 09:31:30 -0400, Tom Lane <tgl@sss.pgh.pa.us> wrote in <884.1441978290@sss.pgh.pa.us> > Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> writes: > > Hello, this is a problem on an extreme situation. > > When parser encounters very long tokens, it returns an error > > message which should be mysterious for users. > > >> $ perl -e "print \"select '\" . \"x\"x(512*1024*1024) . \"'\"" | psql postgres > >> ERROR: invalid memory alloc request size 1073741824 > > I can't get terribly excited about that, because there is not that > much daylight between there and where the query fails because the > entire input string exceeds 1GB. Moreover, anyone who tries working > with literals in this size range will soon learn not to ;-). So > it seems quite an artificial example to me ... > > regards, tom lane Yes, so 'an extreme situation'. I wanted to know what to think about this kind of situation. Thanks for the comment, I'm confident that fixing it and the similars in clean way should be too-much for the necessity. regards, -- Kyotaro Horiguchi NTT Open Source Software Center