Merge pull request #2278 from wiredtiger/SERVER-21027-fix

SERVER-21027 Don't leave empty internal pages in the tree

6 files changed, 13 insertions, 29 deletions

diff --git a/src/btree/bt_split.c b/src/btree/bt_split.c
index 8f24f44eaba..5baae4aaae3 100644
--- a/src/btree/bt_split.c
+++ b/src/btree/bt_split.c
@@ -1030,17 +1030,11 @@ __split_parent(WT_SESSION_IMPL *session, WT_REF *ref,
 	result_entries = (parent_entries + new_entries) - deleted_entries;
 
 	/*
-	 * If the entire (sub)tree is empty, leave the first ref in place,
-	 * deleted.
+	 * If the entire (sub)tree is empty, give up: we can't leave an empty
+	 * internal page.
 	 */
-	if (result_entries == 0) {
-		next_ref = pindex->index[0];
-		WT_ASSERT(session, next_ref->state == WT_REF_SPLIT ||
-		    (next_ref == ref && ref->state == WT_REF_LOCKED));
-		next_ref->state = WT_REF_DELETED;
-		--deleted_entries;
-		result_entries = 1;
-	}
+	if (result_entries == 0)
+		return (0);
 
 	/*
 	 * Allocate and initialize a new page index array for the parent, then
@@ -1086,6 +1080,9 @@ __split_parent(WT_SESSION_IMPL *session, WT_REF *ref,
 			*alloc_refp++ = next_ref;
 	}
 
+	/* Check that we filled in all the entries. */
+	WT_ASSERT(session, alloc_refp - alloc_index->index == result_entries);
+
 	/*
 	 * Confirm the parent page's index hasn't moved then update it, which
 	 * makes the split visible to threads descending the tree.
diff --git a/src/btree/bt_sync.c b/src/btree/bt_sync.c
index 2851c830bcb..237d900c3d1 100644
--- a/src/btree/bt_sync.c
+++ b/src/btree/bt_sync.c
@@ -152,8 +152,6 @@ __sync_file(WT_SESSION_IMPL *session, int syncop)
 				leaf_bytes += page->memory_footprint;
 				++leaf_pages;
 			}
-			if (txn->isolation == WT_ISO_READ_COMMITTED)
-				__wt_txn_get_snapshot(session);
 			WT_ERR(__wt_reconcile(session, walk, NULL, 0));
 		}
 		break;
diff --git a/src/evict/evict_file.c b/src/evict/evict_file.c
index b1e107657bf..448de57d88e 100644
--- a/src/evict/evict_file.c
+++ b/src/evict/evict_file.c
@@ -18,11 +18,8 @@ __wt_evict_file(WT_SESSION_IMPL *session, int syncop)
 	WT_DECL_RET;
 	WT_PAGE *page;
 	WT_REF *next_ref, *ref;
-	WT_TXN *txn;
 	bool evict_reset;
 
-	txn = &session->txn;
-
 	/*
 	 * We need exclusive access to the file -- disable ordinary eviction
 	 * and drain any blocks already queued.
@@ -32,9 +29,6 @@ __wt_evict_file(WT_SESSION_IMPL *session, int syncop)
 	/* Make sure the oldest transaction ID is up-to-date. */
 	__wt_txn_update_oldest(session, true);
 
-	if (txn->isolation == WT_ISO_READ_COMMITTED)
-		__wt_txn_get_snapshot(session);
-
 	/* Walk the tree, discarding pages. */
 	next_ref = NULL;
 	WT_ERR(__wt_tree_walk(session, &next_ref, NULL,
@@ -65,10 +59,6 @@ __wt_evict_file(WT_SESSION_IMPL *session, int syncop)
 		if (syncop == WT_SYNC_CLOSE && __wt_page_is_modified(page))
 			WT_ERR(__wt_reconcile(session, ref, NULL, WT_EVICTING));
 
-		/* Update our snapshot for each new page. */
-		if (txn->isolation == WT_ISO_READ_COMMITTED)
-			__wt_txn_get_snapshot(session);
-
 		/*
 		 * We can't evict the page just returned to us (it marks our
 		 * place in the tree), so move the walk to one page ahead of
@@ -117,8 +107,5 @@ err:		/* On error, clear any left-over tree walk. */
 	if (evict_reset)
 		__wt_evict_file_exclusive_off(session);
 
-	if (txn->isolation == WT_ISO_READ_COMMITTED && session->ncursors == 0)
-		__wt_txn_release_snapshot(session);
-
 	return (ret);
 }
diff --git a/src/evict/evict_page.c b/src/evict/evict_page.c
index 7f580edad5a..4c0b2bff0bf 100644
--- a/src/evict/evict_page.c
+++ b/src/evict/evict_page.c
@@ -385,7 +385,7 @@ __evict_review(
 	 * Clean pages can't be evicted when running in memory only. This
 	 * should be uncommon - we don't add clean pages to the queue.
 	 */
-	if (F_ISSET(S2C(session), WT_CONN_IN_MEMORY) && !modified)
+	if (F_ISSET(S2C(session), WT_CONN_IN_MEMORY) && !modified && !closing)
 		return (EBUSY);
 
 	/*
diff --git a/src/include/txn.i b/src/include/txn.i
index 92ea96c9be9..e49e3d1257b 100644
--- a/src/include/txn.i
+++ b/src/include/txn.i
@@ -192,10 +192,11 @@ __wt_txn_visible(WT_SESSION_IMPL *session, uint64_t id)
 		return (true);
 
 	/*
-	 * A visibility check that is not read-uncommitted must have an
-	 * active snapshot.
+	 * If we don't have a transactional snapshot, only make stable updates
+	 * visible.
 	 */
-	WT_ASSERT(session, F_ISSET(txn, WT_TXN_HAS_SNAPSHOT));
+	if (!F_ISSET(txn, WT_TXN_HAS_SNAPSHOT))
+		return (__wt_txn_visible_all(session, id));
 
 	/* Transactions see their own changes. */
 	if (id == txn->id)
diff --git a/src/reconcile/rec_write.c b/src/reconcile/rec_write.c
index c1e07215ad8..46c5a38796f 100644
--- a/src/reconcile/rec_write.c
+++ b/src/reconcile/rec_write.c
@@ -819,6 +819,7 @@ __rec_write_init(WT_SESSION_IMPL *session,
 	r->flags = flags;
 
 	/* Track if the page can be marked clean. */
+	r->max_txn = WT_TXN_NONE;
 	r->leave_dirty = false;
 
 	/* Raw compression. */