Em sex., 29 de dez. de 2023 às 10:33, Tomas Vondra < tomas.von...@enterprisedb.com> escreveu:
> > > On 12/29/23 12:53, Ranier Vilela wrote: > > Em qui., 28 de dez. de 2023 às 22:16, Tomas Vondra > > <tomas.von...@enterprisedb.com <mailto:tomas.von...@enterprisedb.com>> > > escreveu: > > > > > > > > On 12/27/23 12:37, Ranier Vilela wrote: > > > Em ter., 26 de dez. de 2023 às 19:07, Tomas Vondra > > > <tomas.von...@enterprisedb.com > > <mailto:tomas.von...@enterprisedb.com> > > <mailto:tomas.von...@enterprisedb.com > > <mailto:tomas.von...@enterprisedb.com>>> > > > escreveu: > > > > > > > > > > > > On 12/26/23 19:10, Ranier Vilela wrote: > > > > Hi, > > > > > > > > The commit b437571 > > > <http://b437571714707bc6466abde1a0af5e69aaade09c > > <http://b437571714707bc6466abde1a0af5e69aaade09c> > > > <http://b437571714707bc6466abde1a0af5e69aaade09c > > <http://b437571714707bc6466abde1a0af5e69aaade09c>>> I > > > > think has an oversight. > > > > When allocate memory and initialize private spool in > function: > > > > _brin_leader_participate_as_worker > > > > > > > > The behavior is the bs_spool (heap and index fields) > > > > are left empty. > > > > > > > > The code affected is: > > > > buildstate->bs_spool = (BrinSpool *) > > palloc0(sizeof(BrinSpool)); > > > > - buildstate->bs_spool->heap = buildstate->bs_spool->heap; > > > > - buildstate->bs_spool->index = buildstate->bs_spool->index; > > > > + buildstate->bs_spool->heap = heap; > > > > + buildstate->bs_spool->index = index; > > > > > > > > Is the fix correct? > > > > > > > > > > Thanks for noticing this. > > > > > > You're welcome. > > > > > > > > > Yes, I believe this is a bug - the assignments > > > are certainly wrong, it leaves the fields set to NULL. > > > > > > I wonder how come this didn't fail during testing. Surely, if > > the leader > > > participates as a worker, the tuplesort_begin_index_brin shall > > be called > > > with heap/index being NULL, leading to some failure during the > > sort. But > > > maybe this means we don't actually need the heap/index fields, > > it's just > > > a copy of TuplesortIndexArg, but BRIN does not need that > > because we sort > > > the tuples by blkno, and we don't need the descriptors for > that. > > > > > > Unfortunately I can't test on Windows, since I can't build with > > meson on > > > Windows. > > > > > > > > > In any case, the _brin_parallel_scan_and_build does not > > actually need > > > the separate heap/index arguments, those are already in the > spool. > > > > > > Yeah, for sure. > > > > > > > > > I'll try to figure out if we want to simplify the tuplesort or > > remove > > > the arguments from _brin_parallel_scan_and_build. > > > > > > > Here is a patch simplifying the BRIN parallel create code a little > bit. > > As I suspected, we don't need the heap/index in the spool at all, > and we > > don't need to pass it to tuplesort_begin_index_brin either - we only > > need blkno, and we have that in the datum1 field. This also means we > > don't need TuplesortIndexBrinArg. > > > > With Windows 10, msvc 2022, compile end pass ninja test. > > > > But, if you allow me, I would like to try another approach to > > simplification. > > Instead of increasing the arguments in the call, wouldn't it be better > > to decrease them > > and this way all arguments will be passed in the registers instead of on > > a stack? > > > > If this was beneficial, we'd be passing everything through structs and > not as explicit arguments. But we don't. If you're arguing it's > beneficial in this case, it'd be good to see it demonstrated. > Please see the https://www.agner.org/optimize/optimizing_cpp.pdf Excerpt: "Use 64-bit mode Parameter transfer is more efficient in 64-bit mode than in 32-bit mode, and more efficient in 64-bit Linux than in 64-bit Windows. In 64-bit Linux, the first six integer parameters and the first eight floating point parameters are transferred in registers, totaling up to fourteen register parameters. In 64-bit Windows, the first four parameters are transferred in registers, regardless of whether they are integers or floating point numbers." With function: _brin_parallel_scan_and_build(buildstate, buildstate->bs_spool, brinshared, sharedsort, heapRel, indexRel, sortmem, false); We have: Linux -> six first parameters in registers and two parameters in stack Windows -> four parameters in registers and four parameters in stack > > bs_spool may well contain this data and will probably be useful in the > > future. > > > > I made a v1 version, based on your patch, for your consideration. > > > > I did actually consider doing it this way yesterday, but I don't like > this approach. I don't believe it's faster (and even if it was, the > difference is going to be negligible), and parameters hidden in some > struct increase the cognitive load. I like explicit arguments. > Personally I prefer data in structs, of course, always thinking about size and alignment, to optimize loading. Best regards, Ranier Vilela
