Index: src/btree.c
==================================================================
--- src/btree.c
+++ src/btree.c
@@ -7,11 +7,11 @@
 **    May you do good and not evil.
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.649 2009/07/02 17:21:58 danielk1977 Exp $
+** $Id: btree.c,v 1.650 2009/07/03 16:25:07 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
 ** Including a description of file format and an overview of operation.
 */
@@ -200,10 +200,11 @@
   BtLock *pIter;
 
   assert( sqlite3BtreeHoldsMutex(p) );
   assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
   assert( p->db!=0 );
+  assert( !(p->db->flags&SQLITE_ReadUncommitted)||eLock==WRITE_LOCK||iTab==1 );
   
   /* If requesting a write-lock, then the Btree must have an open write
   ** transaction on this file. And, obviously, for this to be so there 
   ** must be an open write transaction on the file itself.
   */
@@ -221,51 +222,29 @@
   if( pBt->pWriter!=p && pBt->isExclusive ){
     sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
     return SQLITE_LOCKED_SHAREDCACHE;
   }
 
-  /* This (along with setSharedCacheTableLock()) is where
-  ** the ReadUncommitted flag is dealt with.
-  ** If the caller is querying for a read-lock on any table
-  ** other than the sqlite_master table (table 1) and if the ReadUncommitted
-  ** flag is set, then the lock granted even if there are write-locks
-  ** on the table. If a write-lock is requested, the ReadUncommitted flag
-  ** is not considered.
-  **
-  ** In function setSharedCacheTableLock(), if a read-lock is demanded and the 
-  ** ReadUncommitted flag is set, no entry is added to the locks list 
-  ** (BtShared.pLock).
-  **
-  ** To summarize: If the ReadUncommitted flag is set, then read cursors
-  ** on non-schema tables do not create or respect table locks. The locking
-  ** procedure for a write-cursor does not change.
-  */
-  if( 
-    0==(p->db->flags&SQLITE_ReadUncommitted) || 
-    eLock==WRITE_LOCK ||
-    iTab==MASTER_ROOT
-  ){
-    for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
-      /* The condition (pIter->eLock!=eLock) in the following if(...) 
-      ** statement is a simplification of:
-      **
-      **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
-      **
-      ** since we know that if eLock==WRITE_LOCK, then no other connection
-      ** may hold a WRITE_LOCK on any table in this file (since there can
-      ** only be a single writer).
-      */
-      assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
-      assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
-      if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
-        sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
-        if( eLock==WRITE_LOCK ){
-          assert( p==pBt->pWriter );
-          pBt->isPending = 1;
-        }
-        return SQLITE_LOCKED_SHAREDCACHE;
-      }
+  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+    /* The condition (pIter->eLock!=eLock) in the following if(...) 
+    ** statement is a simplification of:
+    **
+    **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
+    **
+    ** since we know that if eLock==WRITE_LOCK, then no other connection
+    ** may hold a WRITE_LOCK on any table in this file (since there can
+    ** only be a single writer).
+    */
+    assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
+    assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
+    if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
+      sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
+      if( eLock==WRITE_LOCK ){
+        assert( p==pBt->pWriter );
+        pBt->isPending = 1;
+      }
+      return SQLITE_LOCKED_SHAREDCACHE;
     }
   }
   return SQLITE_OK;
 }
 #endif /* !SQLITE_OMIT_SHARED_CACHE */
@@ -286,31 +265,23 @@
 
   assert( sqlite3BtreeHoldsMutex(p) );
   assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
   assert( p->db!=0 );
 
+  /* A connection with the read-uncommitted flag set will never try to
+  ** obtain a read-lock using this function. The only read-lock obtained
+  ** by a connection in read-uncommitted mode is on the sqlite_master 
+  ** table, and that lock is obtained in BtreeBeginTrans().  */
+  assert( 0==(p->db->flags&SQLITE_ReadUncommitted) || eLock==WRITE_LOCK );
+
   /* This is a no-op if the shared-cache is not enabled */
   if( !p->sharable ){
     return SQLITE_OK;
   }
 
   assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
 
-  /* If the read-uncommitted flag is set and a read-lock is requested on
-  ** a non-schema table, then the lock is always granted.  Return early
-  ** without adding an entry to the BtShared.pLock list. See
-  ** comment in function querySharedCacheTableLock() for more info
-  ** on handling the ReadUncommitted flag.
-  */
-  if( 
-    (p->db->flags&SQLITE_ReadUncommitted) && 
-    (eLock==READ_LOCK) &&
-    iTable!=MASTER_ROOT
-  ){
-    return SQLITE_OK;
-  }
-
   /* First search the list for an existing lock on this table. */
   for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
     if( pIter->iTable==iTable && pIter->pBtree==p ){
       pLock = pIter;
       break;
@@ -393,10 +364,13 @@
     */
     pBt->isPending = 0;
   }
 }
 
+/*
+** This function changes all write-locks held by connection p to read-locks.
+*/
 static void downgradeAllSharedCacheTableLocks(Btree *p){
   BtShared *pBt = p->pBt;
   if( pBt->pWriter==p ){
     BtLock *pLock;
     pBt->pWriter = 0;
@@ -7030,11 +7004,11 @@
 void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
   BtShared *pBt = p->pBt;
 
   sqlite3BtreeEnter(p);
   assert( p->inTrans>TRANS_NONE );
-  assert( SQLITE_OK==querySharedCacheTableLock(p, 1, READ_LOCK) );
+  assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
   assert( pBt->pPage1 );
   assert( idx>=0 && idx<=15 );
 
   *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
 

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -41,11 +41,11 @@
 ** documentation, headers files, or other derived files.  The formatting
 ** of the code in this file is, therefore, important.  See other comments
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.868 2009/07/02 07:47:33 danielk1977 Exp $
+** $Id: vdbe.c,v 1.869 2009/07/03 16:25:07 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
 
 /*
@@ -5001,22 +5001,21 @@
 **
 ** P4 contains a pointer to the name of the table being locked. This is only
 ** used to generate an error message if the lock cannot be obtained.
 */
 case OP_TableLock: {
-  int p1;
-  u8 isWriteLock;
-
-  p1 = pOp->p1; 
-  isWriteLock = (u8)pOp->p3;
-  assert( p1>=0 && p1<db->nDb );
-  assert( (p->btreeMask & (1<<p1))!=0 );
-  assert( isWriteLock==0 || isWriteLock==1 );
-  rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
-  if( (rc&0xFF)==SQLITE_LOCKED ){
-    const char *z = pOp->p4.z;
-    sqlite3SetString(&p->zErrMsg, db, "database table is locked: %s", z);
+  u8 isWriteLock = (u8)pOp->p3;
+  if( isWriteLock || 0==(db->flags&SQLITE_ReadUncommitted) ){
+    int p1 = pOp->p1; 
+    assert( p1>=0 && p1<db->nDb );
+    assert( (p->btreeMask & (1<<p1))!=0 );
+    assert( isWriteLock==0 || isWriteLock==1 );
+    rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
+    if( (rc&0xFF)==SQLITE_LOCKED ){
+      const char *z = pOp->p4.z;
+      sqlite3SetString(&p->zErrMsg, db, "database table is locked: %s", z);
+    }
   }
   break;
 }
 #endif /* SQLITE_OMIT_SHARED_CACHE */