postgres.git / summary / log / commit / refs

commit    06fa6670fb6bf430739cb1f69d28429a0e24851f
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Mon Dec 05 20:54:28 2016 +0000

    Ensure gatherstate->nextreader is properly initialized.
    
    The previously code worked OK as long as a Gather node was never
    rescanned, or if it was rescanned, as long as it got at least as
    many workers on rescan as it had originally.  But if the number
    of workers ever decreased on a rescan, then it could crash.
    
    Andreas Seltenreich


 src/backend/executor/nodeGather.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index 438d1b24fc2..7342aadfbb4 100644
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -172,6 +172,7 @@ ExecGather(GatherState *node)
 			if (pcxt->nworkers_launched > 0)
 			{
 				node->nreaders = 0;
+				node->nextreader = 0;
 				node->reader =
 					palloc(pcxt->nworkers_launched * sizeof(TupleQueueReader *));
 
@@ -334,6 +335,7 @@ gather_readnext(GatherState *gatherstate)
 		CHECK_FOR_INTERRUPTS();
 
 		/* Attempt to read a tuple, but don't block if none is available. */
+		Assert(gatherstate->nextreader < gatherstate->nreaders);
 		reader = gatherstate->reader[gatherstate->nextreader];
 		tup = TupleQueueReaderNext(reader, true, &readerdone);
 


[parent: efeb3135061d]