Merge latest changes from wal2 branch.

FossilOrigin-Name: b451bb724ea73367a27c51fcf6e48d02d774c7c5b5b8ec0bd3726a6e4689e591

src/btreeInt.h

@@ -357,6 +357,9 @@ struct Btree {
   u32 iDataVersion;  /* Combines with pBt->pPager->iDataVersion */
   Btree *pNext;      /* List of other sharable Btrees from the same db */
   Btree *pPrev;      /* Back pointer of the same list */
+#ifdef SQLITE_DEBUG
+  u64 nSeek;         /* Calls to sqlite3BtreeMovetoUnpacked() */
+#endif
 #ifndef SQLITE_OMIT_SHARED_CACHE
   BtLock lock;       /* Object used to lock page 1 */
 #endif
@@ -368,11 +371,25 @@ struct Btree {
 ** If the shared-data extension is enabled, there may be multiple users
 ** of the Btree structure. At most one of these may open a write transaction,
 ** but any number may have active read transactions.
+**
+** These values must match SQLITE_TXN_NONE, SQLITE_TXN_READ, and
+** SQLITE_TXN_WRITE
 */
 #define TRANS_NONE  0
 #define TRANS_READ  1
 #define TRANS_WRITE 2
 
+#if TRANS_NONE!=SQLITE_TXN_NONE
+# error wrong numeric code for no-transaction
+#endif
+#if TRANS_READ!=SQLITE_TXN_READ
+# error wrong numeric code for read-transaction
+#endif
+#if TRANS_WRITE!=SQLITE_TXN_WRITE
+# error wrong numeric code for write-transaction
+#endif
+
+
 /*
 ** An instance of this object represents a single database file.
 **