Probably related: 99505 X_81=[10]:bat[:str] := algebra.projection(r1_73=[10]:bat[:oid],X_80=[10]:bat[:str]); 1185329 X_101=[10]:bat[:str] := algebra.projection(r1_73=[10]:bat[:oid],X_100=[10]:bat[:str]); These operations cannot possibly take this much time on 10 rows. But X_80 and X_100 are probably views on string bats with large heaps. On 16 March 2017 at 15:20, Roberto Cornacchia wrote:

Update (on the same 1-tuple view):

// SLOW bn = COLcopy(l, l->ttype, TRUE, TRANSIENT);

// SLOW bn = COLnew(0, l->ttype, BATcount(l), TRANSIENT); BATappend(bn,l,FALSE);

// FAST bn = COLnew(0, l->ttype, BATcount(l), TRANSIENT); BATloop(l, p, q) { bunfastapp(bn, BUNtail(li, p)); }

// FAST bn = COLnew(0, l->ttype, BATcount(l), TRANSIENT); BATloop(l, p, q) { BUNappend(bn, BUNtail(li, p), FALSE); }

It gets slow also when using BATappend. It seems again related to trying to be smart with a bulk copy of the heap.

On 16 March 2017 at 13:03, Sjoerd Mullender wrote:

...

On 16/03/17 12:23, Roberto Cornacchia wrote:

...

I'm seeing a strange behaviour with COLcopy(). (Dec2016, optimized, non-devel compilation)

In short, it seems to take almost half second to copy a 1-tuple string (view) bat.

Inspected with gdb, I see that the copy falls in "(3) we can copy the heaps (memcopy, or even VM page sharing)", with the following values:

cnt = 1 bunstocopy = BUN_NONE isVIEW(b) = TRUE VIEWtparent(b) = 0 b->T.heap.size = 1024 b->T.vheap.size = 1094320128

The actual tail and heap copy then takes place:

heapcopy(bn, "tail", &bthp, &b->theap) heapcopy(bn, "theap", &thp, b->tvheap)

Does this mean that a heap of almost 1GB has been copied for a 1-tuple view?

Looks like it. ;-)

A little higheer in the code is a comment "reduced slice view". That seems to be to not copy the whole heap when only a small (less than half) part of the "tail" heap is actually needed. A similar check should probably be made for the tvheap.

...

Roberto

_______________________________________________ users-list mailing list users-list@monetdb.org https://www.monetdb.org/mailman/listinfo/users-list

-- Sjoerd Mullender

_______________________________________________ users-list mailing list users-list@monetdb.org https://www.monetdb.org/mailman/listinfo/users-list