On Thu, Nov 5, 2020 at 6:33 PM Hou, Zhijie <houzj.f...@cn.fujitsu.com> wrote:
>
> Hi
>
> >
> > my $bytes = $ARGV[0];
> > for(my $i = 0; $i < $bytes; $i+=8){
> > print "longdata";
> > }
> > print "\n";
> > --------
> >
> > postgres=# copy longdata from program 'perl /tmp/longdata.pl 100000000'
> > with (parallel 2);
> >
> > This gets stuck forever (or at least I didn't have the patience to wait
> > it finish). Both worker processes are consuming 100% of CPU.
>
> I had a look over this problem.
>
> the ParallelCopyDataBlock has size limit:
> uint8 skip_bytes;
> char data[DATA_BLOCK_SIZE]; /* data read from file */
>
> It seems the input line is so long that the leader process run out of the
> Shared memory among parallel copy workers.
> And the leader process keep waiting free block.
>
> For the worker process, it wait util line_state becomes LINE_LEADER_POPULATED,
> But leader process won't set the line_state unless it read the whole line.
>
> So it stuck forever.
> May be we should reconsider about this situation.
>
> The stack is as follows:
>
> Leader stack:
> #3 0x000000000075f7a1 in WaitLatch (latch=<optimized out>,
> wakeEvents=wakeEvents@entry=41, timeout=timeout@entry=1,
> wait_event_info=wait_event_info@entry=150994945) at latch.c:411
> #4 0x00000000005a9245 in WaitGetFreeCopyBlock
> (pcshared_info=pcshared_info@entry=0x7f26d2ed3580) at copyparallel.c:1546
> #5 0x00000000005a98ce in SetRawBufForLoad (cstate=cstate@entry=0x2978a88,
> line_size=67108864, copy_buf_len=copy_buf_len@entry=65536,
> raw_buf_ptr=raw_buf_ptr@entry=65536,
> copy_raw_buf=copy_raw_buf@entry=0x7fff4cdc0e18) at copyparallel.c:1572
> #6 0x00000000005a1963 in CopyReadLineText (cstate=cstate@entry=0x2978a88) at
> copy.c:4058
> #7 0x00000000005a4e76 in CopyReadLine (cstate=cstate@entry=0x2978a88) at
> copy.c:3863
>
> Worker stack:
> #0 GetLinePosition (cstate=cstate@entry=0x29e1f28) at copyparallel.c:1474
> #1 0x00000000005a8aa4 in CacheLineInfo (cstate=cstate@entry=0x29e1f28,
> buff_count=buff_count@entry=0) at copyparallel.c:711
> #2 0x00000000005a8e46 in GetWorkerLine (cstate=cstate@entry=0x29e1f28) at
> copyparallel.c:885
> #3 0x00000000005a4f2e in NextCopyFromRawFields
> (cstate=cstate@entry=0x29e1f28, fields=fields@entry=0x7fff4cdc0b48,
> nfields=nfields@entry=0x7fff4cdc0b44) at copy.c:3615
> #4 0x00000000005a50af in NextCopyFrom (cstate=cstate@entry=0x29e1f28,
> econtext=econtext@entry=0x2a358d8, values=0x2a42068, nulls=0x2a42070) at
> copy.c:3696
> #5 0x00000000005a5b90 in CopyFrom (cstate=cstate@entry=0x29e1f28) at
> copy.c:2985
>
Thanks for providing your thoughts. I have analyzed this issue and I'm
working on the fix for this, I will be posting a patch for this
shortly.
Regards,
Vignesh
EnterpriseDB: http://www.enterprisedb.com
