Re: crash in DROP INDEX CONCURRENTLY

On Wed, Nov 07, 2012 at 12:54:57PM -0300, Alvaro Herrera wrote:
> I just observed that if I run src/test/regress' "make
> installcheck-parallel" and concurrently src/test/isolation's "make
> installcheck", I very reproducibly get a segfault (in an assert-enabled
> build).  Apparently the problem is that somebody is trying to transfer
> predicate locks to a relation, but the index' relcache entry is pfreed.

Yes, the location of TransferPredicateLocksToHeapRelation is bad...

> I think the fix is just to move the heap_open calls some lines upwards, as in
> the attached patch.

> diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
> index 756f6d9..d2d91c1 100644
> --- a/src/backend/catalog/index.c
> +++ b/src/backend/catalog/index.c
> @@ -1475,6 +1475,8 @@ index_drop(Oid indexId, bool concurrent)
>  		 * conflicts with existing predicate locks, so now is the time to move
>  		 * them to the heap relation.
>  		 */
> +		userHeapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
> +		userIndexRelation = index_open(indexId, ShareUpdateExclusiveLock);
>  		TransferPredicateLocksToHeapRelation(userIndexRelation);
>
>  		/*
> @@ -1484,9 +1486,6 @@ index_drop(Oid indexId, bool concurrent)
>  		 */
>  		indexRelation = heap_open(IndexRelationId, RowExclusiveLock);
>
> -		userHeapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
> -		userIndexRelation = index_open(indexId, ShareUpdateExclusiveLock);
> -
>  		tuple = SearchSysCacheCopy1(INDEXRELID,
>  									ObjectIdGetDatum(indexId));
>  		if (!HeapTupleIsValid(tuple))

Looks like the right thing to me.

Greetings,

Andres