Spill pages, take 3

libraries/liblmdb/mdb.c

@@ -585,6 +585,7 @@ typedef struct MDB_page {
 #define	P_DIRTY		 0x10		/**< dirty page */
 #define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
 #define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
+#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
 /** @} */
 	uint16_t	mp_flags;		/**< @ref mdb_page */
 #define mp_lower	mp_pb.pb.pb_lower
@@ -824,6 +825,10 @@ struct MDB_txn {
 	/** The list of pages that became unused during this transaction.
 	 */
 	MDB_IDL		mt_free_pgs;
+	/** The list of dirty pages we temporarily wrote to disk
+	 *	because the dirty list was full.
+	 */
+	MDB_IDL		mt_spill_pgs;
 	union {
 		MDB_ID2L	dirty_list;	/**< for write txns: modified pages */
 		MDB_reader	*reader;	/**< this thread's reader table slot or NULL */
@@ -857,6 +862,7 @@ struct MDB_txn {
 #define MDB_TXN_RDONLY		0x01		/**< read-only transaction */
 #define MDB_TXN_ERROR		0x02		/**< an error has occurred */
 #define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
+#define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
 /** @} */
 	unsigned int	mt_flags;		/**< @ref mdb_txn */
 	/** dirty_list maxsize - # of allocated pages allowed, including in parent txns */
@@ -1306,7 +1312,7 @@ mdb_dpage_free(MDB_env *env, MDB_page *dp)
 	}
 }
 
-/* Return all dirty pages to dpage list */
+/**	Return all dirty pages to dpage list */
 static void
 mdb_dlist_free(MDB_txn *txn)
 {
@@ -1320,6 +1326,148 @@ mdb_dlist_free(MDB_txn *txn)
 	dl[0].mid = 0;
 }
 
+static int mdb_page_flush(MDB_txn *txn);
+
+/**	Spill pages from the dirty list back to disk.
+ * This is intended to prevent running into #MDB_TXN_FULL situations,
+ * but note that they may still occur in a few cases:
+ *	1) pages in #MDB_DUPSORT sub-DBs are never spilled, so if there
+ *	 are too many of these dirtied in one txn, the txn may still get
+ *	 too full.
+ *	2) child txns may run out of space if their parents dirtied a
+ *	 lot of pages and never spilled them. TODO: we probably should do
+ *	 a preemptive spill during #mdb_txn_begin() of a child txn, if
+ *	 the parent's dirty_room is below a given threshold.
+ *	3) our estimate of the txn size could be too small. At the
+ *	 moment this seems unlikely.
+ *
+ * Otherwise, if not using nested txns, it is expected that apps will
+ * not run into #MDB_TXN_FULL any more. The pages are flushed to disk
+ * the same way as for a txn commit, e.g. their P_DIRTY flag is cleared.
+ * If the txn never references them again, they can be left alone.
+ * If the txn only reads them, they can be used without any fuss.
+ * If the txn writes them again, they can be dirtied immediately without
+ * going thru all of the work of #mdb_page_touch(). Such references are
+ * handled by #mdb_page_unspill().
+ *
+ * Also note, we never spill DB root pages, nor pages of active cursors,
+ * because we'll need these back again soon anyway. And in nested txns,
+ * we can't spill a page in a child txn if it was already spilled in a
+ * parent txn. That would alter the parent txns' data even though
+ * the child hasn't committed yet, and we'd have no way to undo it if
+ * the child aborted.
+ *
+ * @param[in] m0 cursor A cursor handle identifying the transaction and
+ *	database for which we are checking space.
+ * @param[in] key For a put operation, the key being stored.
+ * @param[in] data For a put operation, the data being stored.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
+{
+	MDB_txn *txn = m0->mc_txn;
+	MDB_page *dp;
+	MDB_ID2L dl = txn->mt_u.dirty_list;
+	unsigned int i, j;
+	int rc;
+
+	if (m0->mc_flags & C_SUB)
+		return MDB_SUCCESS;
+
+	/* Estimate how much space this op will take */
+	i = m0->mc_db->md_depth;
+	/* Named DBs also dirty the main DB */
+	if (m0->mc_dbi > MAIN_DBI)
+		i += txn->mt_dbs[MAIN_DBI].md_depth;
+	/* For puts, roughly factor in the key+data size */
+	if (key)
+		i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize;
+	i += i;	/* double it for good measure */
+
+	if (txn->mt_dirty_room > i)
+		return MDB_SUCCESS;
+
+	if (!txn->mt_spill_pgs) {
+		txn->mt_spill_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX);
+		if (!txn->mt_spill_pgs)
+			return ENOMEM;
+	}
+
+	/* Mark all the dirty root pages we want to preserve */
+	for (i=0; i<txn->mt_numdbs; i++) {
+		if (txn->mt_dbflags[i] & DB_DIRTY) {
+			j = mdb_mid2l_search(dl, txn->mt_dbs[i].md_root);
+			if (j <= dl[0].mid) {
+				dp = dl[j].mptr;
+				dp->mp_flags |= P_KEEP;
+			}
+		}
+	}
+	/* Mark all the pages of active cursors we want to preserve */
+	for (i=0; i<txn->mt_numdbs; i++) {
+		MDB_cursor *mc = txn->mt_cursors[i];
+		/* See if m0 is tracked or not */
+		if (i == m0->mc_dbi && !(m0->mc_flags & C_UNTRACK)) {
+				/* nope. tack it on in front */
+				m0->mc_next = mc;
+				mc = m0;
+		}
+		for (; mc; mc=mc->mc_next) {
+			if (mc->mc_flags & C_INITIALIZED) {
+				for (j=0; j<mc->mc_snum; j++) {
+					if (mc->mc_pg[j]->mp_flags & P_DIRTY)
+						mc->mc_pg[j]->mp_flags |= P_KEEP;
+				}
+				if (txn->mt_dbs[i].md_flags & MDB_DUPSORT) {
+					MDB_cursor *mx = &mc->mc_xcursor->mx_cursor;
+					if (mx->mc_flags & C_INITIALIZED) {
+						for (j=0; j<mx->mc_snum; j++) {
+							if ((mx->mc_pg[j]->mp_flags & (P_SUBP|P_DIRTY))
+									== P_DIRTY)
+								mx->mc_pg[j]->mp_flags |= P_KEEP;
+						}
+					}
+				}
+			}
+		}
+	}
+
+	/* Save the page IDs of all the pages we're flushing */
+	for (i=1; i<=dl[0].mid; i++) {
+		dp = dl[i].mptr;
+		if (dp->mp_flags & P_KEEP)
+			continue;
+		/* Can't spill twice, make sure it's not already in a parent's
+		 * spill list.
+		 */
+		if (txn->mt_parent) {
+			MDB_txn *tx2;
+			for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) {
+				if (tx2->mt_spill_pgs) {
+					j = mdb_midl_search(tx2->mt_spill_pgs, dl[i].mid);
+					if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == dl[i].mid) {
+						dp->mp_flags |= P_KEEP;
+						break;
+					}
+				}
+			}
+			if (tx2)
+				continue;
+		}
+		if ((rc = mdb_midl_append(&txn->mt_spill_pgs, dl[i].mid)))
+			return rc;
+	}
+	mdb_midl_sort(txn->mt_spill_pgs);
+
+	rc = mdb_page_flush(txn);
+	if (rc == 0) {
+		txn->mt_dirty_room = MDB_IDL_UM_MAX - dl[0].mid;
+		txn->mt_flags |= MDB_TXN_SPILLS;
+	}
+	return rc;
+}
+
 /** Find oldest txnid still referenced. Expects txn->mt_txnid > 0. */
 static txnid_t
 mdb_find_oldest(MDB_txn *txn)
@@ -1533,6 +1681,61 @@ mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize)
 	}
 }
 
+/** Pull a page off the txn's spill list, if present.
+ * If a page being referenced was spilled to disk in this txn, bring
+ * it back and make it dirty/writable again.
+ * @param[in] tx0 the transaction handle.
+ * @param[in] mp the page being referenced.
+ * @param[out] ret the writable page, if any. ret is unchanged if
+ * mp wasn't spilled.
+ */
+static int
+mdb_page_unspill(MDB_txn *tx0, MDB_page *mp, MDB_page **ret)
+{
+	MDB_env *env = tx0->mt_env;
+	MDB_txn *txn;
+	unsigned x;
+	pgno_t pgno = mp->mp_pgno;
+
+	for (txn = tx0; txn; txn=txn->mt_parent) {
+		if (!txn->mt_spill_pgs)
+			continue;
+		x = mdb_midl_search(txn->mt_spill_pgs, pgno);
+		if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pgno) {
+			MDB_page *np;
+			int num;
+			if (IS_OVERFLOW(mp))
+				num = mp->mp_pages;
+			else
+				num = 1;
+			if (env->me_flags & MDB_WRITEMAP) {
+				np = mp;
+			} else {
+				np = mdb_page_malloc(txn, num);
+				if (!np)
+					return ENOMEM;
+				if (num > 1)
+					memcpy(np, mp, num * env->me_psize);
+				else
+					mdb_page_copy(np, mp, env->me_psize);
+			}
+			if (txn == tx0) {
+				/* If in current txn, this page is no longer spilled */
+				for (; x < txn->mt_spill_pgs[0]; x++)
+					txn->mt_spill_pgs[x] = txn->mt_spill_pgs[x+1];
+				txn->mt_spill_pgs[0]--;
+			}	/* otherwise, if belonging to a parent txn, the
+				 * page remains spilled until child commits
+				 */
+			mdb_page_dirty(tx0, np);
+			np->mp_flags |= P_DIRTY;
+			*ret = np;
+			break;
+		}
+	}
+	return MDB_SUCCESS;
+}
+
 /** Touch a page: make it dirty and re-insert into tree with updated pgno.
  * @param[in] mc cursor pointing to the page to be touched
  * @return 0 on success, non-zero on failure.
@@ -1548,6 +1751,14 @@ mdb_page_touch(MDB_cursor *mc)
 	int rc;
 
 	if (!F_ISSET(mp->mp_flags, P_DIRTY)) {
+		if (txn->mt_flags & MDB_TXN_SPILLS) {
+			np = NULL;
+			rc = mdb_page_unspill(txn, mp, &np);
+			if (rc)
+				return rc;
+			if (np)
+				goto done;
+		}
 		if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) ||
 			(rc = mdb_page_alloc(mc, 1, &np)))
 			return rc;
@@ -1595,6 +1806,7 @@ mdb_page_touch(MDB_cursor *mc)
 	np->mp_pgno = pgno;
 	np->mp_flags |= P_DIRTY;
 
+done:
 	/* Adjust cursors pointing to mp */
 	mc->mc_pg[mc->mc_top] = np;
 	dbi = mc->mc_dbi;
@@ -1801,6 +2013,7 @@ mdb_txn_renew0(MDB_txn *txn)
 		txn->mt_u.dirty_list[0].mid = 0;
 		txn->mt_free_pgs = env->me_free_pgs;
 		txn->mt_free_pgs[0] = 0;
+		txn->mt_spill_pgs = NULL;
 		env->me_txn = txn;
 	}
 
@@ -1906,6 +2119,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		txn->mt_toggle = parent->mt_toggle;
 		txn->mt_dirty_room = parent->mt_dirty_room;
 		txn->mt_u.dirty_list[0].mid = 0;
+		txn->mt_spill_pgs = NULL;
 		txn->mt_next_pgno = parent->mt_next_pgno;
 		parent->mt_child = txn;
 		txn->mt_parent = parent;
@@ -2008,6 +2222,7 @@ mdb_txn_reset0(MDB_txn *txn, const char *act)
 			txn->mt_parent->mt_child = NULL;
 			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
 			mdb_midl_free(txn->mt_free_pgs);
+			mdb_midl_free(txn->mt_spill_pgs);
 			free(txn->mt_u.dirty_list);
 			return;
 		}
@@ -2210,7 +2425,7 @@ mdb_page_flush(MDB_txn *txn)
 {
 	MDB_env		*env = txn->mt_env;
 	MDB_ID2L	dl = txn->mt_u.dirty_list;
-	unsigned	psize = env->me_psize;
+	unsigned	psize = env->me_psize, j;
 	int			i, pagecount = dl[0].mid, rc;
 	size_t		size = 0, pos = 0;
 	pgno_t		pgno = 0;
@@ -2224,13 +2439,20 @@ mdb_page_flush(MDB_txn *txn)
 	int			n = 0;
 #endif
 
+	j = 0;
 	if (env->me_flags & MDB_WRITEMAP) {
 		/* Clear dirty flags */
 		for (i = pagecount; i; i--) {
 			dp = dl[i].mptr;
+			/* Don't flush this page yet */
+			if (dp->mp_flags & P_KEEP) {
+				dp->mp_flags ^= P_KEEP;
+				dl[++j] = dl[i];
+				continue;
+			}
 			dp->mp_flags &= ~P_DIRTY;
 		}
-		dl[0].mid = 0;
+		dl[0].mid = j;
 		return MDB_SUCCESS;
 	}
 
@@ -2238,6 +2460,12 @@ mdb_page_flush(MDB_txn *txn)
 	for (i = 1;; i++) {
 		if (i <= pagecount) {
 			dp = dl[i].mptr;
+			/* Don't flush this page yet */
+			if (dp->mp_flags & P_KEEP) {
+				dp->mp_flags ^= P_KEEP;
+				dl[i].mid = 0;
+				continue;
+			}
 			pgno = dl[i].mid;
 			/* clear dirty flag */
 			dp->mp_flags &= ~P_DIRTY;
@@ -2309,7 +2537,18 @@ mdb_page_flush(MDB_txn *txn)
 #endif	/* _WIN32 */
 	}
 
-	mdb_dlist_free(txn);
+	j = 0;
+	for (i=1; i<=pagecount; i++) {
+		dp = dl[i].mptr;
+		/* This is a page we skipped above */
+		if (!dl[i].mid) {
+			dl[++j] = dl[i];
+			dl[j].mid = dp->mp_pgno;
+			continue;
+		}
+		mdb_dpage_free(env, dp);
+	}
+	dl[0].mid = j;
 
 	return MDB_SUCCESS;
 }
@@ -2378,6 +2617,37 @@ mdb_txn_commit(MDB_txn *txn)
 
 		dst = parent->mt_u.dirty_list;
 		src = txn->mt_u.dirty_list;
+		/* Remove anything in our dirty list from parent's spill list */
+		if (parent->mt_spill_pgs) {
+			x = parent->mt_spill_pgs[0];
+			len = x;
+			/* zero out our dirty pages in parent spill list */
+			for (i=1; i<=src[0].mid; i++) {
+				if (src[i].mid < parent->mt_spill_pgs[x])
+					continue;
+				if (src[i].mid > parent->mt_spill_pgs[x]) {
+					if (x <= 1)
+						break;
+					x--;
+					continue;
+				}
+				parent->mt_spill_pgs[x] = 0;
+				len--;
+			}
+			/* OK, we had a few hits, squash zeros from the spill list */
+			if (len < parent->mt_spill_pgs[0]) {
+				x=1;
+				for (y=1; y<=parent->mt_spill_pgs[0]; y++) {
+					if (parent->mt_spill_pgs[y]) {
+						if (y != x) {
+							parent->mt_spill_pgs[x] = parent->mt_spill_pgs[y];
+						}
+						x++;
+					}
+				}
+				parent->mt_spill_pgs[0] = len;
+			}
+		}
 		/* Find len = length of merging our dirty list with parent's */
 		x = dst[0].mid;
 		dst[0].mid = 0;		/* simplify loops */
@@ -2409,6 +2679,15 @@ mdb_txn_commit(MDB_txn *txn)
 		dst[0].mid = len;
 		free(txn->mt_u.dirty_list);
 		parent->mt_dirty_room = txn->mt_dirty_room;
+		if (txn->mt_spill_pgs) {
+			if (parent->mt_spill_pgs) {
+				mdb_midl_append_list(&parent->mt_spill_pgs, txn->mt_spill_pgs);
+				mdb_midl_free(txn->mt_spill_pgs);
+				mdb_midl_sort(parent->mt_spill_pgs);
+			} else {
+				parent->mt_spill_pgs = txn->mt_spill_pgs;
+			}
+		}
 
 		parent->mt_child = NULL;
 		mdb_midl_free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pghead);
@@ -3991,6 +4270,19 @@ mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **ret, int *lvl)
 		level = 1;
 		do {
 			MDB_ID2L dl = tx2->mt_u.dirty_list;
+			unsigned x;
+			/* Spilled pages were dirtied in this txn and flushed
+			 * because the dirty list got full. Bring this page
+			 * back in from the map (but don't unspill it here,
+			 * leave that unless page_touch happens again).
+			 */
+			if (tx2->mt_spill_pgs) {
+				x = mdb_midl_search(tx2->mt_spill_pgs, pgno);
+				if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pgno) {
+					p = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno);
+					goto done;
+				}
+			}
 			if (dl[0].mid) {
 				unsigned x = mdb_mid2l_search(dl, pgno);
 				if (x <= dl[0].mid && dl[x].mid == pgno) {
@@ -4091,6 +4383,8 @@ mdb_page_search_root(MDB_cursor *mc, MDB_val *key, int modify)
 
 	DPRINTF("found leaf page %zu for key [%s]", mp->mp_pgno,
 	    key ? DKEY(key) : NULL);
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
 
 	return MDB_SUCCESS;
 }
@@ -4218,11 +4512,21 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
 	int rc;
 
 	DPRINTF("free ov page %zu (%d)", pg, ovpages);
-	/* If the page is dirty we just acquired it, so we should
-	 * give it back to our current free list, if any.
+	/* If the page is dirty or on the spill list we just acquired it,
+	 * so we should give it back to our current free list, if any.
 	 * Not currently supported in nested txns.
 	 * Otherwise put it onto the list of pages we freed in this txn.
 	 */
+	if (!(mp->mp_flags & P_DIRTY) && txn->mt_spill_pgs) {
+		unsigned x = mdb_midl_search(txn->mt_spill_pgs, pg);
+		if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pg) {
+			/* This page is no longer spilled */
+			for (; x < txn->mt_spill_pgs[0]; x++)
+				txn->mt_spill_pgs[x] = txn->mt_spill_pgs[x+1];
+			txn->mt_spill_pgs[0]--;
+			goto release;
+		}
+	}
 	if ((mp->mp_flags & P_DIRTY) && !txn->mt_parent && env->me_pghead) {
 		unsigned j, x;
 		pgno_t *mop;
@@ -4248,6 +4552,7 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
 		}
 		if (!(env->me_flags & MDB_WRITEMAP))
 			mdb_dpage_free(env, mp);
+release:
 		/* Insert in me_pghead */
 		mop = env->me_pghead;
 		j = mop[0] + ovpages;
@@ -4964,6 +5269,9 @@ mdb_cursor_touch(MDB_cursor *mc)
 	return MDB_SUCCESS;
 }
 
+/** Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDB_NOSPILL	0x8000
+
 int
 mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
     unsigned int flags)
@@ -4974,7 +5282,7 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 	MDB_page	*fp;
 	MDB_db dummy;
 	int do_sub = 0, insert = 0;
-	unsigned int mcount = 0, dcount = 0;
+	unsigned int mcount = 0, dcount = 0, nospill;
 	size_t nsize;
 	int rc, rc2;
 	MDB_pagebuf pbuf;
@@ -4992,6 +5300,9 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 			return EINVAL;
 	}
 
+	nospill = flags & MDB_NOSPILL;
+	flags &= ~MDB_NOSPILL;
+
 	if (F_ISSET(mc->mc_txn->mt_flags, MDB_TXN_RDONLY))
 		return EACCES;
 
@@ -5048,7 +5359,17 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 			return rc;
 	}
 
-	/* Cursor is positioned */
+	/* Cursor is positioned, check for room in the dirty list */
+	if (!nospill) {
+		if (flags & MDB_MULTIPLE) {
+			rdata = &xdata;
+			xdata.mv_size = data->mv_size * dcount;
+		} else {
+			rdata = data;
+		}
+		if ((rc2 = mdb_page_spill(mc, key, rdata)))
+			return rc2;
+	}
 
 	if (rc == MDB_NO_ROOT) {
 		MDB_page *np;
@@ -5227,8 +5548,18 @@ current:
 				return rc2;
 			ovpages = omp->mp_pages;
 
-			/* Is the ov page writable and large enough? */
-			if ((omp->mp_flags & P_DIRTY) && ovpages >= dpages) {
+			/* Is the ov page large enough? */
+			if (ovpages >= dpages) {
+			  if (!(omp->mp_flags & P_DIRTY) &&
+				  (level || (mc->mc_txn->mt_env->me_flags & MDB_WRITEMAP)))
+			  {
+				rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
+				if (rc)
+					return rc;
+				level = 0;		/* dirty in this txn or clean */
+			  }
+			  /* Is it dirty? */
+			  if (omp->mp_flags & P_DIRTY) {
 				/* yes, overwrite it. Note in this case we don't
 				 * bother to try shrinking the page if the new data
 				 * is smaller than the overflow threshold.
@@ -5261,10 +5592,10 @@ current:
 				else
 					memcpy(METADATA(omp), data->mv_data, data->mv_size);
 				goto done;
-			} else {
+			  }
+			}
 			if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS)
 				return rc2;
-			}
 		} else if (NODEDSZ(leaf) == data->mv_size) {
 			/* same size, just replace it. Note that we could
 			 * also reuse this node if the new data is smaller,
@@ -5337,10 +5668,11 @@ put_sub:
 			xdata.mv_data = "";
 			leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 			if (flags & MDB_CURRENT) {
-				xflags = MDB_CURRENT;
+				xflags = MDB_CURRENT|MDB_NOSPILL;
 			} else {
 				mdb_xcursor_init1(mc, leaf);
-				xflags = (flags & MDB_NODUPDATA) ? MDB_NOOVERWRITE : 0;
+				xflags = (flags & MDB_NODUPDATA) ?
+					MDB_NOOVERWRITE|MDB_NOSPILL : MDB_NOSPILL;
 			}
 			/* converted, write the original data first */
 			if (dkey.mv_size) {
@@ -5411,6 +5743,10 @@ mdb_cursor_del(MDB_cursor *mc, unsigned int flags)
 	if (!(mc->mc_flags & C_INITIALIZED))
 		return EINVAL;
 
+	if (!(flags & MDB_NOSPILL) && (rc = mdb_page_spill(mc, NULL, NULL)))
+		return rc;
+	flags &= ~MDB_NOSPILL; /* TODO: Or change (flags != MDB_NODUPDATA) to ~(flags & MDB_NODUPDATA), not looking at the logic of that code just now */
+
 	rc = mdb_cursor_touch(mc);
 	if (rc)
 		return rc;
@@ -5422,7 +5758,7 @@ mdb_cursor_del(MDB_cursor *mc, unsigned int flags)
 			if (!F_ISSET(leaf->mn_flags, F_SUBDATA)) {
 				mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
 			}
-			rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, 0);
+			rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, MDB_NOSPILL);
 			/* If sub-DB still has entries, we're done */
 			if (mc->mc_xcursor->mx_db.md_entries) {
 				if (leaf->mn_flags & F_SUBDATA) {

libraries/liblmdb/midl.c

@@ -31,8 +31,7 @@
  */
 #define CMP(x,y)	 ( (x) < (y) ? -1 : (x) > (y) )
 
-#if 0	/* superseded by append/sort */
-static unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id )
+unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id )
 {
 	/*
 	 * binary search of id in ids
@@ -67,6 +66,7 @@ static unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id )
 	return cursor;
 }
 
+#if 0	/* superseded by append/sort */
 int mdb_midl_insert( MDB_IDL ids, MDB_ID id )
 {
 	unsigned x, i;

libraries/liblmdb/midl.h

@@ -74,14 +74,12 @@ typedef MDB_ID *MDB_IDL;
 		xidl[xlen] = (id); \
 	} while (0)
 
-#if 0	/* superseded by append/sort */
-	/** Insert an ID into an IDL.
-	 * @param[in,out] ids	The IDL to insert into.
-	 * @param[in] id	The ID to insert.
-	 * @return	0 on success, -1 if ID was already present, -2 on error.
+	/** Search for an ID in an IDL.
+	 * @param[in] ids	The IDL to search.
+	 * @param[in] id	The ID to search for.
+	 * @return	The index of the first ID greater than or equal to \b id.
 	 */
-int mdb_midl_insert( MDB_IDL ids, MDB_ID id );
-#endif
+unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id );
 
 	/** Allocate an IDL.
 	 * Allocates memory for an IDL of the given size.