Re: asynchronous and vectorized execution

Hello,

At Tue, 12 Jul 2016 11:42:55 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in
<20160712.114255.156540680.horiguchi.kyotaro@lab.ntt.co.jp>
> >   3% slower for local 1*seqscan (2-parallel)
> >  14% slower for append-4*seqscan (no-prallel)
> >  19% faster for append-4*foreignscan (all scans on one connection)
> >  78% faster for append-4*foreignscan (scans have dedicate connection)
> > 
> > ExecProcNode might be able to be optimized a bit.
> > ExecAppend seems to need some fix.

After some refactoring, degradation for a simple seqscan is
reduced to 1.4% and that of "Append(SeqScan())" is reduced to
1.7%. The gains are the same to the previous measurement. Scale
has been changed from previous measurement in some test cases.

t0- (SeqScan()) (2 parallel)
pl- (Append(4 * SeqScan()))
pf0 (Append(4 * ForeignScan())) all ForeignScans are on the same connection.
pf1 (Append(4 * ForeignScan())) all ForeignScans have their own connections.
                            
patched-O2    time(ms)  stddev(ms)  gain from unpatched (%)       t0      4121.27      1.1      -1.44       pl
1757.41     0.94     -1.73       pf0     6458.99    192.4      20.26       pf1     1747.4      24.81     78.39
              
 
unpatched-O2                                           t0      4062.6       1.95           pl      1727.45      9.41
      pf0     8100.47     24.51          pf1     8086.52     33.53   
 

> > Addition to the aboves, I will try reentrant ExecAsyncWaitForNode
> > or something.

After some consideration, I found that ExecAsyncWaitForNode
cannot be reentrant because it means that the control goes into
async-unaware nodes while having not-ready nodes, that is
inconsistent state. To inhibit such reentering, I allocated node
identifiers in depth-first order so that ascendant-descendant
relationship can be checked (nested-set model) in simple way and
call ExecAsyncConfigureWait only for the descendant nodes of the
parameter planstate.

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center