On 2018-Feb-02, Robert Haas wrote: > Support parallel btree index builds.
While looking at a complaint related to progress report of parallel index builds[1], I noticed this comment + /* + * Execute this worker's part of the sort. + * + * Unlike leader and serial cases, we cannot avoid calling + * tuplesort_performsort() for spool2 if it ends up containing no dead + * tuples (this is disallowed for workers by tuplesort). + */ + tuplesort_performsort(btspool->sortstate); + if (btspool2) + tuplesort_performsort(btspool2->sortstate); I've been trying to understand why this says "Unlike leader and serial cases, ...". I understand the "serial" part -- it refers to _bt_leafbuild. So I'm to understand that that one works differently; see below. But why does it say "the leader case"? As far as I can see, the leader executes exactly the same code, so what is the comment talking about? Now, if you do look at _bt_leafbuild(), it can be seen that nothing is done differently there either; we're not actually skipping any calls to tuplesort_performsort(). Any differentiation between serial/leader/ worker cases seems to be done inside that routine. So the comment is not very useful there either. I am wondering if these comments are leftovers from early development versions of this patch. Maybe we could remove them -- or rewrite them to indicate not that we avoid calling tuplesort_performsort(), but instead to say that that function behaves differently. [1] https://postgr.es/m/caeze2wgm-nnze3ronwjytvris8xsvhzzvbcgj34h06cdnua...@mail.gmail.com -- Álvaro Herrera 39°49'30"S 73°17'W "Puedes vivir sólo una vez, pero si lo haces bien, una vez es suficiente"
