From 4884272644e6772a3f5ae9d87fae2236e5ac1f01 Mon Sep 17 00:00:00 2001
From: Peter Geoghegan <pg@bowt.ie>
Date: Mon, 23 Sep 2019 20:28:20 -0700
Subject: [PATCH v17 5/5] Reintroduce unique index support

---
 src/backend/access/nbtree/nbtinsert.c | 70 +++++++++++++++++++++++----
 1 file changed, 60 insertions(+), 10 deletions(-)

diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index eb9655bb78..1912fe9ee4 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -434,15 +434,36 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 			if (!ItemIdIsDead(curitemid))
 			{
 				ItemPointerData htid;
+				bool		posting;
 				bool		all_dead;
+				bool		posting_all_dead;
+				int			npost;
+
 
 				if (_bt_compare(rel, itup_key, page, offset) != 0)
 					break;		/* we're past all the equal tuples */
 
 				/* okay, we gotta fetch the heap tuple ... */
 				curitup = (IndexTuple) PageGetItem(page, curitemid);
-				Assert(!BTreeTupleIsPosting(curitup));
-				htid = curitup->t_tid;
+
+				if (!BTreeTupleIsPosting(curitup))
+				{
+					htid = curitup->t_tid;
+					posting = false;
+					posting_all_dead = true;
+				}
+				else
+				{
+					posting = true;
+					/* Initial assumption */
+					posting_all_dead = true;
+				}
+
+				npost = 0;
+doposttup:
+				if (posting)
+					htid = *BTreeTupleGetPostingN(curitup, npost);
+
 
 				/*
 				 * If we are doing a recheck, we expect to find the tuple we
@@ -453,6 +474,9 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 					ItemPointerCompare(&htid, &itup->t_tid) == 0)
 				{
 					found = true;
+					posting_all_dead = false;
+					if (posting)
+						goto nextpost;
 				}
 
 				/*
@@ -518,8 +542,7 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 					 * not part of this chain because it had a different index
 					 * entry.
 					 */
-					htid = itup->t_tid;
-					if (table_index_fetch_tuple_check(heapRel, &htid,
+					if (table_index_fetch_tuple_check(heapRel, &itup->t_tid,
 													  SnapshotSelf, NULL))
 					{
 						/* Normal case --- it's still live */
@@ -577,7 +600,7 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 													RelationGetRelationName(rel))));
 					}
 				}
-				else if (all_dead)
+				else if (all_dead && !posting)
 				{
 					/*
 					 * The conflicting tuple (or whole HOT chain) is dead to
@@ -596,6 +619,35 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 					else
 						MarkBufferDirtyHint(insertstate->buf, true);
 				}
+				else if (posting)
+				{
+nextpost:
+					if (!all_dead)
+						posting_all_dead = false;
+
+					/* Iterate over single posting list tuple */
+					npost++;
+					if (npost < BTreeTupleGetNPosting(curitup))
+						goto doposttup;
+
+					/*
+					 * Mark posting tuple dead if all hot chains whose root is
+					 * contained in posting tuple have tuples that are all
+					 * dead
+					 */
+					if (posting_all_dead)
+					{
+						ItemIdMarkDead(curitemid);
+						opaque->btpo_flags |= BTP_HAS_GARBAGE;
+
+						if (nbuf != InvalidBuffer)
+							MarkBufferDirtyHint(nbuf, true);
+						else
+							MarkBufferDirtyHint(insertstate->buf, true);
+					}
+
+					/* Move on to next index tuple */
+				}
 			}
 		}
 
@@ -770,7 +822,7 @@ _bt_findinsertloc(Relation rel,
 				insertstate->bounds_valid = false;
 			}
 
-			if (!checkingunique && PageGetFreeSpace(page) < insertstate->itemsz)
+			if (PageGetFreeSpace(page) < insertstate->itemsz)
 			{
 				_bt_dedup_one_page(rel, insertstate->buf, heapRel,
 								   insertstate->itemsz);
@@ -2615,12 +2667,10 @@ _bt_dedup_one_page(Relation rel, Buffer buffer, Relation heapRel,
 	Size		pagesaving = 0;
 
 	/*
-	 * Don't use deduplication for indexes with INCLUDEd columns and unique
-	 * indexes
+	 * Don't use deduplication for indexes with INCLUDEd columns
 	 */
 	deduplicate = (IndexRelationGetNumberOfKeyAttributes(rel) ==
-				   IndexRelationGetNumberOfAttributes(rel) &&
-				   !rel->rd_index->indisunique);
+				   IndexRelationGetNumberOfAttributes(rel));
 	if (!deduplicate)
 		return;
 
-- 
2.17.1