From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Daniel Verite <daniel(at)manitou-mail(dot)org> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Ronan Dunklau <ronan(dot)dunklau(at)dalibo(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg_dump / copy bugs with "big lines" ? |
Date: | 2016-11-29 17:15:20 |
Message-ID: | 20161129171520.6s6xnr47vgaejykl@alvherre.pgsql |
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Daniel Verite wrote:
> If we consider what would happen with the latest patch on a platform
> with sizeof(int)=8 and a \copy invocation like this:
>
> \copy (select big,big,big,big,big,big,big,big,...... FROM
> (select lpad('', 1024*1024*200) as big) s) TO /dev/null
>
> if we put enough copies of "big" in the select-list to grow over 2GB,
> and then over 4GB.
Oh, right, I was forgetting that.
> On a platform with sizeof(int)=4 this should normally fail over 2GB with
> "Cannot enlarge string buffer containing $X bytes by $Y more bytes"
>
> I don't have an ILP64 environment myself to test, but I suspect
> it would malfunction instead of cleanly erroring out on such
> platforms.
I suspect nobody has such platforms, as they are mostly defunct. But I
see an easy way to fix it, which is to use sizeof(int32).
> Also, without this limit, we can "COPY FROM/TO file" really huge rows, 4GB
> and beyond, like I tried successfully during the tests mentioned upthread
> (again with len as int64 on x86_64).
> So such COPYs would succeed or fail depending on whether they deal with
> a file or a network connection.
> Do we want this difference in behavior?
Such a patch would be for master only.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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