Re: [BUGS] BUG #5412: test case produced, possible race condition.

Rusty Conover <rconover@infogears.com> writes:
> [ same stack trace for the simplified test case ]

Ah, got it finally.  There *is* a relcache flush happening during INSERT
in the 8.4 code, because of FSM extension:

(gdb) bt
#0  RegisterRelcacheInvalidation (dbId=40264, relId=848094) at inval.c:439
#1  0x000000000067a30d in CacheInvalidateRelcache (relation=0x7f39b88403f0)   at inval.c:1141
#2  0x00000000005c9c45 in fsm_extend (fsm_nblocks=<value optimized out>,    rel=<value optimized out>) at
freespace.c:589
#3  fsm_readbuf (fsm_nblocks=<value optimized out>, rel=<value optimized out>)   at freespace.c:522
#4  0x00000000005ca2e4 in fsm_set_and_search (rel=0x9d48,    addr=<value optimized out>, slot=0, newValue=220 '\334',
minValue=200 '\310') at freespace.c:608
 
#5  0x00000000005ca675 in RecordAndGetPageWithFreeSpace (rel=0x7f39b88403f0,    oldPage=<value optimized out>,
oldSpaceAvail=<valueoptimized out>,    spaceNeeded=<value optimized out>) at freespace.c:163
 
#6  0x0000000000464149 in RelationGetBufferForTuple (relation=0x7f39b88403f0,    len=<value optimized out>,
otherBuffer=0,options=<value optimized out>,    bistate=<value optimized out>) at hio.c:303
 
#7  0x0000000000462e77 in heap_insert (relation=0x7f39b88403f0, tup=0x14aa580,    cid=<value optimized out>, options=0,
bistate=0x0)at heapam.c:1890
 

This code path doesn't exist in CVS HEAD, which means (I think) that the
given test case can't fail in HEAD.  I think I got myself confused by
experimenting variously with HEAD and 8.4 in regular and
CLOBBER_CACHE_ALWAYS modes --- only one of those four combinations will
exhibit a failure with this test case.

Although the particular case apparently can't arise in HEAD, I'm going
to apply Heikki's patch there anyway, since there's clearly a risk of
related problems.
        regards, tom lane