Allow index AMs to return either HeapTuple or IndexTuple format during IOS.

[postgresql] / src / backend / executor / nodeIndexonlyscan.c

diff --git a/src/backend/executor/nodeIndexonlyscan.c b/src/backend/executor/nodeIndexonlyscan.c
index 66c2ad66d719e5f648b6a5a64e1b941056b7cc5d..4a7f39a7c7d096b1fe3547f7ef306cbdc5841396 100644 (file)
--- a/src/backend/executor/nodeIndexonlyscan.c
+++ b/src/backend/executor/nodeIndexonlyscan.c
@@ -149,9 +149,26 @@ IndexOnlyNext(IndexOnlyScanState *node)
                }
 
                /*
-                * Fill the scan tuple slot with data from the index.
+                * Fill the scan tuple slot with data from the index.  This might be
+                * provided in either HeapTuple or IndexTuple format.  Conceivably an
+                * index AM might fill both fields, in which case we prefer the heap
+                * format, since it's probably a bit cheaper to fill a slot from.
                 */
-               StoreIndexTuple(slot, scandesc->xs_itup, scandesc->xs_itupdesc);
+               if (scandesc->xs_hitup)
+               {
+                       /*
+                        * We don't take the trouble to verify that the provided tuple has
+                        * exactly the slot's format, but it seems worth doing a quick
+                        * check on the number of fields.
+                        */
+                       Assert(slot->tts_tupleDescriptor->natts ==
+                                  scandesc->xs_hitupdesc->natts);
+                       ExecStoreTuple(scandesc->xs_hitup, slot, InvalidBuffer, false);
+               }
+               else if (scandesc->xs_itup)
+                       StoreIndexTuple(slot, scandesc->xs_itup, scandesc->xs_itupdesc);
+               else
+                       elog(ERROR, "no data returned for index-only scan");
 
                /*
                 * If the index was lossy, we have to recheck the index quals.