In multi-insert, don't go into infinite loop on a huge tuple and fillfactor.

If a tuple is larger than page size minus space reserved for fillfactor,
heap_multi_insert would never find a page that it fits in and repeatedly ask
for a new page from RelationGetBufferForTuple. If a tuple is too large to
fit on any page, taking fillfactor into account, RelationGetBufferForTuple
will always expand the relation. In a normal insert, heap_insert will accept
that and put the tuple on the new page. heap_multi_insert, however, does a
fillfactor check of its own, and doesn't accept the newly-extended page
RelationGetBufferForTuple returns, even though there is no other choice to
make the tuple fit.

Fix that by making the logic in heap_multi_insert more like the heap_insert
logic. The first tuple is always put on the page RelationGetBufferForTuple
gives us, and the fillfactor check is only applied to the subsequent tuples.

Report from David Gould, although I didn't use his patch.

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 74c41fac3e96d6ac9e8f5b2a702f619346c85a0a..e114d3dc45b1c111b9982443bec94115df69446e 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2185,8 +2185,12 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
                /* NO EREPORT(ERROR) from here till changes are logged */
                START_CRIT_SECTION();
 
-               /* Put as many tuples as fit on this page */
-               for (nthispage = 0; ndone + nthispage < ntuples; nthispage++)
+               /*
+                * RelationGetBufferForTuple has ensured that the first tuple fits.
+                * Put that on the page, and then as many other tuples as fit.
+                */
+               RelationPutHeapTuple(relation, buffer, heaptuples[ndone]);
+               for (nthispage = 1; ndone + nthispage < ntuples; nthispage++)
                {
                        HeapTuple       heaptup = heaptuples[ndone + nthispage];