Add the SQLITE_DBSTATUS_PROPORTIONAL_CACHE_USED sqlite3_db_status() parameter.

FossilOrigin-Name: 118321c8b9d88b8f439c952436f42838c3fc80cb

src/btree.c

@@ -2337,9 +2337,9 @@ int sqlite3BtreeOpen(
 #if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
     /* Add the new BtShared object to the linked list sharable BtShareds.
     */
+    pBt->nRef = 1;
     if( p->sharable ){
       MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
-      pBt->nRef = 1;
       MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
       if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
         pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
@@ -2410,6 +2410,7 @@ btree_open_out:
     assert( sqlite3_mutex_held(mutexOpen) );
     sqlite3_mutex_leave(mutexOpen);
   }
+  assert( rc!=SQLITE_OK || sqlite3BtreeConnectionCount(*ppBtree)>0 );
   return rc;
 }
 
@@ -9698,4 +9699,14 @@ int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }
 int sqlite3BtreeSharable(Btree *p){
   return p->sharable;
 }
+
+/*
+** Return the number of connections to the BtShared object accessed by
+** the Btree handle passed as the only argument. For private caches 
+** this is always 1. For shared caches it may be 1 or greater.
+*/
+int sqlite3BtreeConnectionCount(Btree *p){
+  testcase( p->sharable );
+  return p->pBt->nRef;
+}
 #endif