Simplify the way the read-uncommitted flag is handled to facilitate test coverage. (CVS 6841)

FossilOrigin-Name: e2112d6160a82ccd4b6a1c798d2064d0f1b086eb

manifest

@@ -1,5 +1,5 @@
-C Make\sexplicit\sthe\srestrictions\son\sUPDATE,\sDELETE,\sand\sINSERT\sstatement\ssyntax\nwithin\striggers.\s\sTicket\s#3947.\s(CVS\s6840)
-D 2009-07-03T15:37:28
+C Simplify\sthe\sway\sthe\sread-uncommitted\sflag\sis\shandled\sto\sfacilitate\stest\scoverage.\s(CVS\s6841)
+D 2009-07-03T16:25:07
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 8b8fb7823264331210cddf103831816c286ba446
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -106,7 +106,7 @@ F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 97a3859d8585eb4fcb1e81a795cf4b3fdd82f30f
 F src/bitvec.c 0ef0651714728055d43de7a4cdd95e703fac0119
 F src/btmutex.c 9b899c0d8df3bd68f527b0afe03088321b696d3c
-F src/btree.c 8a3f74aeea07833a7dd62ccd60c5486a17b2044c
+F src/btree.c b7f75130f8699903fe3b699d0591493dc26c4454
 F src/btree.h 8cae6364735a5cb2d577ddb23fa6d0e655a4b931
 F src/btreeInt.h b31e5ac04181c7e2892c33ab06228c551df6233c
 F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
@@ -203,7 +203,7 @@ F src/update.c a1bbe774bce495d62dce3df3f42a5f04c1de173a
 F src/utf.c 9541d28f40441812c0b40f00334372a0542c00ff
 F src/util.c 861d5b5c58be4921f0a254489ea94cb15f550ef8
 F src/vacuum.c 3fe0eebea6d2311c1c2ab2962887d11f7a4dcfb0
-F src/vdbe.c 7e5781773b62c4ef1569e58340f2ca9a034a08b5
+F src/vdbe.c bdf25930bddbf57b18a0be7b1127b357306d2094
 F src/vdbe.h 35a648bc3279a120da24f34d9a25213ec15daf8a
 F src/vdbeInt.h 831c254a6eef237ef4664c8381a0137586567007
 F src/vdbeapi.c 0ab8ada7260b32031ca97f338caecf0812460624
@@ -739,7 +739,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P 304c5110ad958b2cc1ddff30e68c8791109128b5
-R 23c00185520dd16e8ecfdeb38c15386d
-U drh
-Z eccd19ba4bfa8e991ddfacf0b5d84154
+P c8bf40df7be728b11bb633516d1988c6064a9d70
+R 736933d9248a6cfe52584a62da904241
+U danielk1977
+Z 07814554177b18b70ae436ac81d295ec

manifest.uuid

@@ -1 +1 @@
-c8bf40df7be728b11bb633516d1988c6064a9d70
+e2112d6160a82ccd4b6a1c798d2064d0f1b086eb

src/btree.c

@@ -9,7 +9,7 @@
 **    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.
@@ -202,6 +202,7 @@ static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
   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 
@@ -223,27 +224,6 @@ static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
     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:
@@ -265,7 +245,6 @@ static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
       return SQLITE_LOCKED_SHAREDCACHE;
     }
   }
-  }
   return SQLITE_OK;
 }
 #endif /* !SQLITE_OMIT_SHARED_CACHE */
@@ -288,6 +267,12 @@ static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
   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;
@@ -295,20 +280,6 @@ static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
 
   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 ){
@@ -395,6 +366,9 @@ static void clearAllSharedCacheTableLocks(Btree *p){
   }
 }
 
+/*
+** 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 ){
@@ -7032,7 +7006,7 @@ void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
 
   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 );
 

src/vdbe.c

@@ -43,7 +43,7 @@
 ** 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"
@@ -5003,11 +5003,9 @@ case OP_Expire: {
 ** 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;
+  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 );
@@ -5016,6 +5014,7 @@ case OP_TableLock: {
       const char *z = pOp->p4.z;
       sqlite3SetString(&p->zErrMsg, db, "database table is locked: %s", z);
     }
+  }
   break;
 }
 #endif /* SQLITE_OMIT_SHARED_CACHE */