Re: pgsql: Add parallel-aware hash joins.

On 2017-12-21 08:49:46 +0000, Andres Freund wrote:
> Add parallel-aware hash joins.

There's to relatively mundane failures:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=tern&dt=2017-12-21%2008%3A48%3A12
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=termite&dt=2017-12-21%2008%3A50%3A08

but also one that's a lot more interesting:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=capybara&dt=2017-12-21%2008%3A50%3A08

which shows an assert failure:

#2 0x00000000008687d1 in ExceptionalCondition (conditionName=conditionName(at)entry=0xa76a98 "!(!accessor->sts->participants[i].writing)", errorType=errorType(at)entry=0x8b2c49 "FailedAssertion", fileName=fileName(at)entry=0xa76991 "sharedtuplestore.c", lineNumber=lineNumber(at)entry=273) at assert.c:54
#3 0x000000000089883e in sts_begin_parallel_scan (accessor=0xfaf780) at sharedtuplestore.c:273
#4 0x0000000000634de4 in ExecParallelHashRepartitionRest (hashtable=0xfaec18) at nodeHash.c:1369
#5 ExecParallelHashIncreaseNumBatches (hashtable=0xfaec18) at nodeHash.c:1198
#6 0x000000000063546b in ExecParallelHashTupleAlloc (hashtable=hashtable(at)entry=0xfaec18, size=40, shared=shared(at)entry=0x7ffee26a8868) at nodeHash.c:2778
#7 0x00000000006357c8 in ExecParallelHashTableInsert (hashtable=hashtable(at)entry=0xfaec18, slot=slot(at)entry=0xfa76f8, hashvalue=<optimized out>) at nodeHash.c:1696
#8 0x0000000000635b5f in MultiExecParallelHash (node=0xf7ebc8) at nodeHash.c:288
#9 MultiExecHash (node=node(at)entry=0xf7ebc8) at nodeHash.c:112

which seems to suggest that something in the state machine logic is
borked. ExecParallelHashIncreaseNumBatches() should've ensured that
everyone has called sts_end_write()...

Greetings,

Andres Freund