On Thu, Jun 27, 2013 at 12:02 AM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > Amit Langote escribió: > >> The segfault in question happens at line 1141: >> >> off = att_align_pointer(off, thisatt->attalign, -1, tp + off); >> >> char *tp; /* ptr to tuple data */ >> long off; /* offset in tuple data */ >> >> Disassembling seems to suggest (tp + off) is the faulting address. >> Apparently, the segfault happens when 5th text column is being >> extracted from a tuple (char(n), char(n), int4, char(n), text, ...). >> Since, tp is fixed for the whole duration of loop and only off is >> subject to change over iterations, it may have happened due to wrong >> offset in this iteration. >> >> Has anything of this kind been encountered/reported before? > > Yes, I vaguely recall I have seen this in cases where tuples contain > corrupt data. I think you just need the length word of the fourth datum > to be wrong. >
I want to find exactly that. Is there any way to get that value? AFAIU, a tuple would not contain all of the data of individual attributes; some might be TOAST'd, but is the total length (including TOAST'd part) added to offset (in 'tp + offset') to point to the next attribute in the tuple? Looking at the attlen == -1 value in tupDescriptor of the ResultTupleSlot, VARSIZE_ANY() is used to calculate the length and added to offset, but I find no way to calculate that while I am dubugging. -- Amit Langote -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
