[datatable-help] data.table segfaulting, need help verifying the reason

[Chris Neff]

Narrowing it down further,

a$x

segfaults and

a[,x]

segfaults but

a[,"x", with=FALSE]

doesn't.


On Tue, Sep 10, 2013 at 1:32 PM, Chris Neff <caneff at gmail.com> wrote:

> I'm pretty sure it is some issue of a column that thinks it is bigger than
> it actually is.  I have tried, so far in vain, to make a reproducible
> example that I can share.  I have one, but can't share it.
>
> What happens is this:
>
> A data.frame is made:
>
> > d = data.frame(...)
>
> Then I call apply over every row, calling a different function that takes
> in a DT as well:
>
> l = apply(d, 1, function(x) func(x[1], x[2], DT))
>
> This returns a data.frame.  If I rbindlist this:
>
> a = rbindlist(l)
>
> I can print a just fine, and it will show me all data like normal. but if
> I try to just do
>
> a$x
>
> x is one of the columns that was a key in DT, then it segfaults.  If I ask
> for a column that was made by "func" and wasn't a column in DT, it works
> fine.  If I ask for only the first 10 rows and then ask for x:
>
> a[1:10]$x
>
> it works fine.
>
> So somewhere these key columns think they are different lengths than they
> really are, and when I try to access it I go into memory I shouldn't so I
> segfault.  How can I verify this? Is there something about the DT I can
> check to see what DT thinks these columns are?
>
>
> Also, if instead of apply when making the list, I do
>
> l = lapply(1:nrow(d), function(i) func(x[i,1],x[i,2],DT))
>
> and rbindlist that, it works fine too.
>
>
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