Add experimental mode that uses two wal files. Activated using "PRAGMA

journal_mode = wal2".

FossilOrigin-Name: e2fc5c814cf6862d536aacb9eca66ecd31ba7e3e3033fa4c5564d533f4a18dfc

manifest

@@ -1,5 +1,5 @@
-C Updates\sto\srequirements\smarks.
+C Add\sexperimental\smode\sthat\suses\stwo\swal\sfiles.\sActivated\susing\s"PRAGMA\njournal_mode\s=\swal2".
-D 2017-10-04T18:26:44.610
+D 2017-10-04T20:57:14.949
 F Makefile.in 4bc36d913c2e3e2d326d588d72f618ac9788b2fd4b7efda61102611a6495c3ff
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 6033b51b6aea702ea059f6ab2d47b1d3cef648695f787247dd4fb395fe60673f
@@ -401,7 +401,7 @@ F src/auth.c 6277d63837357549fe14e723490d6dc1a38768d71c795c5eb5c0f8a99f918f73
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c cc88a7fca7287dfc004921bb5e2764893dfe4f6dd33be3570126b3fc37932600
+F src/btree.c c7d94975b015058e6a68278e53d841585552bbc541c1b31b6e024eb9fd888746
 F src/btree.h 32ef5d3f25dc70ef1ee9cecf84a023c21378f06a57cd701d2e866e141b150f09
 F src/btreeInt.h 55b702efce17e5d1941865464227d3802cfc9c7c832fac81d4c94dced47a71fc
 F src/build.c e71e96a67daf3d1dd23188423e66cd6af38017e2ec73fead5d2b57da2d3c7e16
@@ -442,16 +442,16 @@ F src/os.c 93e0979b9b55df29c0c4923f73b48e9d3fe728f01dd8ed4f6a9d2f1d79779bc8
 F src/os.h 8e976e59eb4ca1c0fca6d35ee803e38951cb0343
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
-F src/os_unix.c 3984fc069df59e26f000e30609611cecdb4e93293e6ee52313a473a7e874af1b
+F src/os_unix.c 1f9c3e771557edd248e1fcec0818739826b2a3121b609a6e3372b670236d085a
 F src/os_win.c 6892c3ff23b7886577e47f13d827ca220c0831bae3ce00eea8c258352692f8c6
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c 2aa56a99bb13128d9102e84c7a9f835e546cbb58f0861d481bc3db32973b1628
+F src/pager.c bc2d2b6784cc2b5103e07aff13b012dab30c7efa0abb9bc2bb949ec45cba4326
-F src/pager.h 581698f2177e8bd4008fe4760898ce20b6133d1df22139b9101b5155f900df7a
+F src/pager.h e11e516208a460bea1b95fe3da697642306e7f350d5f96d2c1d21231ee4d2bf2
 F src/parse.y 52ef3cecd0934e9da4a45b585883a03243ad615d338ad94f44501a05891dcdfa
 F src/pcache.c 4bada070456980c3c1f16d58ec2e64e389ad77b935e3d77e0c96e7bbd397289c
 F src/pcache.h 072f94d29281cffd99e46c1539849f248c4b56ae7684c1f36626797fee375170
 F src/pcache1.c 716975564c15eb6679e97f734cec1bfd6c16ac3d4010f05f1f8e509fc7d19880
-F src/pragma.c d04725ac25387d9638919e197fb009f378e13af7bf899516979e54b3164e3602
+F src/pragma.c 49a04b2ec3199b7967c19b3239182d9c4e860726909ed80b7a3e21fe5bb9e6c4
 F src/pragma.h bb83728944b42f6d409c77f5838a8edbdb0fe83046c5496ffc9602b40340a324
 F src/prepare.c 9a141a1b02dca53beaa9771699d390aafcac01f5d1f1c0ae6e23ded8dcdb709a
 F src/printf.c 40aee47ae9be4bd3dbdc8968bd07fddc027be8edec8daddf24d3391d36698a1c
@@ -526,7 +526,7 @@ F src/update.c 5404be9e840717323a69209190cdbc9d0d34adaedaaf1d1a1069babf2c4171c0
 F src/utf.c 810fbfebe12359f10bc2a011520a6e10879ab2a163bcb26c74768eab82ea62a5
 F src/util.c 5168013cfd937a695d23cce8c67cb07a3dda242d4cb812530ba1148b88e0f159
 F src/vacuum.c 90839322fd5f00df9617eb21b68beda9b6e2a2937576b0d65985e4aeb1c53739
-F src/vdbe.c 176c0897af0aedecd3abc9afaf7fa80eaa7cf5eaf62583de256a9961df474373
+F src/vdbe.c c3c3fe95d98df8757570fb265236cfdf31536d1025bf37c232237d1e422ae39b
 F src/vdbe.h d50cadf12bcf9fb99117ef392ce1ea283aa429270481426b6e8b0280c101fd97
 F src/vdbeInt.h 1fe00770144c12c4913128f35262d11527ef3284561baaab59b947a41c08d0d9
 F src/vdbeapi.c 9c670ca0dcc1cd86373aa353b747b26fe531ca5cd4331690c611d1f03842e2a1
@@ -537,8 +537,8 @@ F src/vdbesort.c 731a09e5cb9e96b70c394c1b7cf3860fbe84acca7682e178615eb941a3a0ef2
 F src/vdbetrace.c 48e11ebe040c6b41d146abed2602e3d00d621d7ebe4eb29b0a0f1617fd3c2f6c
 F src/vtab.c 0e4885495172e1bdf54b12cce23b395ac74ef5729031f15e1bc1e3e6b360ed1a
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 839db09792fead5052bb35e533fa485e134913d547d05b5f42e537b73e63f07a
+F src/wal.c 5ca528539a69edd6333dcab1d49e89d4f98efb6a23f0fda85bc52c4ec313db49
-F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
+F src/wal.h b6063e6be1b03389372f3f32240e99b8ab92c32cdd05aa0e31b30a21e4e41654
 F src/walker.c 3ccfa8637f95355bff61144e01a615b8ef26f79c312880848da73f03367da1e6
 F src/where.c 049522adcf5426f1a8c3ed07be15e1ffa3266afd34e8e7bee64b63e2fbfad0b5
 F src/whereInt.h 82c04c5075308abbac59180c8bad5ecb45b07453981f60a53f3c7dee21e1e971
@@ -1097,7 +1097,7 @@ F test/parser1.test 391b9bf9a229547a129c61ac345ed1a6f5eb1854
 F test/pcache.test c8acbedd3b6fd0f9a7ca887a83b11d24a007972b
 F test/pcache2.test af7f3deb1a819f77a6d0d81534e97d1cf62cd442
 F test/percentile.test 4243af26b8f3f4555abe166f723715a1f74c77ff
-F test/permutations.test d911c9ba49088d22054a05dc73743f677872a92ac89288bcdeafa0ebf3f9c531
+F test/permutations.test 5fe80f417441ed6a69acd77f5190305dbf255cc2be214f8e36df4715c4f63f08
 F test/pragma.test c31b5e98998c160a4c85b1e04f590655c67f2daa7f73854640cd120610e3ac15
 F test/pragma2.test e5d5c176360c321344249354c0c16aec46214c9f
 F test/pragma3.test 14c12bc5352b1e100e0b6b44f371053a81ccf8ed
@@ -1142,11 +1142,11 @@ F test/rowvalue9.test d8dd2c6ecac432dadaa79e41dc2434f007be1b6b
 F test/rowvaluefault.test 7cd9ccc6c2fbdd881672984087aad0491bb75504
 F test/rtree.test 0c8d9dd458d6824e59683c19ab2ffa9ef946f798
 F test/run-wordcount.sh 891e89c4c2d16e629cd45951d4ed899ad12afc09
-F test/savepoint.test 1f8a6b1aea9a0d05837adc463d4bf47bd9d0f1c842f1c2a9caccd639baf34bf9
+F test/savepoint.test 69c56b891ce0ff28f1376b5516bf2b6a8b39d0430433216bfc496e72103baaa5
 F test/savepoint2.test 9b8543940572a2f01a18298c3135ad0c9f4f67d7
 F test/savepoint4.test c8f8159ade6d2acd9128be61e1230f1c1edc6cc0
 F test/savepoint5.test 0735db177e0ebbaedc39812c8d065075d563c4fd
-F test/savepoint6.test f41279c5e137139fa5c21485773332c7adb98cd7
+F test/savepoint6.test 48a645a7bb3a59a6fcf06a7364cfe5b655c336760de39068f7c241b0fc80d963
 F test/savepoint7.test cde525ea3075283eb950cdcdefe23ead4f700daa
 F test/savepointfault.test f044eac64b59f09746c7020ee261734de82bf9b2
 F test/scanstatus.test 5253c219e331318a437f436268e0e82345700285
@@ -1261,7 +1261,7 @@ F test/temptable.test d2c9b87a54147161bcd1822e30c1d1cd891e5b30
 F test/temptable2.test cd396beb41117a5302fff61767c35fa4270a0d5e
 F test/temptable3.test d11a0974e52b347e45ee54ef1923c91ed91e4637
 F test/temptrigger.test 38f0ca479b1822d3117069e014daabcaacefffcc
-F test/tester.tcl 9948bd856ce8a1c127f2f7900365387a42a917ce0dc87185bdd128fa5b11aff2
+F test/tester.tcl 71d30287dd22aae0eb9b07e62574336ae6a57e7a50e5dab320a604cfcca4b173
 F test/thread001.test 9f22fd3525a307ff42a326b6bc7b0465be1745a5
 F test/thread002.test e630504f8a06c00bf8bbe68528774dd96aeb2e58
 F test/thread003.test ee4c9efc3b86a6a2767516a37bd64251272560a7
@@ -1520,6 +1520,7 @@ F test/walro.test 4ab7ac01b77c2f894235c699d59e3e3c7f15a160
 F test/walshared.test 0befc811dcf0b287efae21612304d15576e35417
 F test/walslow.test c05c68d4dc2700a982f89133ce103a1a84cc285f
 F test/walthread.test de8dbaf6d9e41481c460ba31ca61e163d7348f8e
+F test/waltwo2.test 6e4d36500a20ff2d19761cf0e9a5d178e83d1798feda157ebc0681e01a35e56e
 F test/where.test f0c325563acde44f2c4ea6ba348e9e29f7121757
 F test/where2.test 478d2170637b9211f593120648858593bf2445a1
 F test/where3.test 54cdeb02157acc979de41530b804ae7b09552bf1
@@ -1655,7 +1656,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 7c69f8f1089c3e3843fbf7ec37a897c849a3df822a4ce3b4fcde586adf991a3f
+P 40964a4ef7565ea0ddf452f48cb22373d068528e07d40eefc008f2231c969422
-R 61b14913c42f4f709d3e3a3845316f97
+R 07b0a272ae21af8e4cb674b6ac44fa89
-U drh
+T *branch * wal2
-Z 37903880ad327c432f24949839963d82
+T *sym-wal2 *
+T +closed f04ded1d9b40d54463162264e37e6d92411d09427eea592ef05681035e2f2e64
+T -sym-trunk *
+U dan
+Z 07422baaaff21d5f15df6853d7e92b06

manifest.uuid

@@ -1 +1 @@
-40964a4ef7565ea0ddf452f48cb22373d068528e07d40eefc008f2231c969422
+e2fc5c814cf6862d536aacb9eca66ecd31ba7e3e3033fa4c5564d533f4a18dfc

src/btree.c

@@ -2993,10 +2993,10 @@ static int lockBtree(BtShared *pBt){
       goto page1_init_failed;
     }
 #else
-    if( page1[18]>2 ){
+    if( page1[18]>3 ){
       pBt->btsFlags |= BTS_READ_ONLY;
     }
-    if( page1[19]>2 ){
+    if( page1[19]>3 ){
       goto page1_init_failed;
     }
 
@@ -3008,9 +3008,9 @@ static int lockBtree(BtShared *pBt){
     ** may not be the latest version - there may be a newer one in the log
     ** file.
     */
-    if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
+    if( page1[19]>=2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
       int isOpen = 0;
-      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
+      rc = sqlite3PagerOpenWal(pBt->pPager, (page1[19]==3), &isOpen);
       if( rc!=SQLITE_OK ){
         goto page1_init_failed;
       }else{
@@ -9866,7 +9866,7 @@ int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
   BtShared *pBt = pBtree->pBt;
   int rc;                         /* Return code */
  
-  assert( iVersion==1 || iVersion==2 );
+  assert( iVersion==1 || iVersion==2 || iVersion==3 );
 
   /* If setting the version fields to 1, do not automatically open the
   ** WAL connection, even if the version fields are currently set to 2.

src/os_unix.c

@@ -4163,7 +4163,7 @@ static int unixShmSystemLock(
   assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
 
   /* Shared locks never span more than one byte */
-  assert( n==1 || lockType!=F_RDLCK );
+  /* assert( n==1 || lockType!=F_RDLCK ); */
 
   /* Locks are within range */
   assert( n>=1 && n<=SQLITE_SHM_NLOCK );
@@ -4609,7 +4609,7 @@ static int unixShmLock(
        || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
        || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
        || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
-  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+  /* assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 ); */
   assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
   assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
 

src/pager.c

@@ -810,20 +810,6 @@ static const unsigned char aJournalMagic[] = {
 */
 #define PAGER_MAX_PGNO 2147483647
 
-/*
-** The argument to this macro is a file descriptor (type sqlite3_file*).
-** Return 0 if it is not open, or non-zero (but not 1) if it is.
-**
-** This is so that expressions can be written as:
-**
-**   if( isOpen(pPager->jfd) ){ ...
-**
-** instead of
-**
-**   if( pPager->jfd->pMethods ){ ...
-*/
-#define isOpen(pFd) ((pFd)->pMethods!=0)
-
 /*
 ** Return true if this pager uses a write-ahead log to read page pgno.
 ** Return false if the pager reads pgno directly from the database.
@@ -944,6 +930,7 @@ static int assert_pager_state(Pager *p){
         assert( isOpen(p->jfd) 
              || p->journalMode==PAGER_JOURNALMODE_OFF 
              || p->journalMode==PAGER_JOURNALMODE_WAL 
+             || p->journalMode==PAGER_JOURNALMODE_WAL2
         );
       }
       assert( pPager->dbOrigSize==pPager->dbFileSize );
@@ -958,6 +945,7 @@ static int assert_pager_state(Pager *p){
       assert( isOpen(p->jfd) 
            || p->journalMode==PAGER_JOURNALMODE_OFF 
            || p->journalMode==PAGER_JOURNALMODE_WAL 
+           || p->journalMode==PAGER_JOURNALMODE_WAL2
            || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
       );
       assert( pPager->dbOrigSize<=pPager->dbHintSize );
@@ -970,6 +958,7 @@ static int assert_pager_state(Pager *p){
       assert( isOpen(p->jfd) 
            || p->journalMode==PAGER_JOURNALMODE_OFF 
            || p->journalMode==PAGER_JOURNALMODE_WAL 
+           || p->journalMode==PAGER_JOURNALMODE_WAL2
            || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
       );
       break;
@@ -2063,7 +2052,7 @@ static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
       }
       pPager->journalOff = 0;
     }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
-      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
+      || (pPager->exclusiveMode && pPager->journalMode<PAGER_JOURNALMODE_WAL)
     ){
       rc = zeroJournalHdr(pPager, hasMaster||pPager->tempFile);
       pPager->journalOff = 0;
@@ -2077,7 +2066,8 @@ static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
       assert( sqlite3JournalIsInMemory(pPager->jfd)==0 );
       assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
            || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
-           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL2
       );
       sqlite3OsClose(pPager->jfd);
       if( bDelete ){
@@ -3344,9 +3334,9 @@ static int pagerOpenWalIfPresent(Pager *pPager){
           rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
         }else{
           testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
-          rc = sqlite3PagerOpenWal(pPager, 0);
+          rc = sqlite3PagerOpenWal(pPager, 0, 0);
         }
-      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+      }else if( pPager->journalMode>=PAGER_JOURNALMODE_WAL ){
         pPager->journalMode = PAGER_JOURNALMODE_DELETE;
       }
     }
@@ -7245,6 +7235,7 @@ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
             || eMode==PAGER_JOURNALMODE_PERSIST
             || eMode==PAGER_JOURNALMODE_OFF 
             || eMode==PAGER_JOURNALMODE_WAL 
+            || eMode==PAGER_JOURNALMODE_WAL2
             || eMode==PAGER_JOURNALMODE_MEMORY );
 
   /* This routine is only called from the OP_JournalMode opcode, and
@@ -7279,9 +7270,12 @@ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
     assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
     assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
     assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+    assert( (PAGER_JOURNALMODE_WAL2 & 5)==4 );
 
     assert( isOpen(pPager->fd) || pPager->exclusiveMode );
-    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 
+     && eMode!=PAGER_JOURNALMODE_WAL2       /* TODO: fix this if possible */
+    ){
 
       /* In this case we would like to delete the journal file. If it is
       ** not possible, then that is not a problem. Deleting the journal file
@@ -7443,7 +7437,7 @@ static int pagerExclusiveLock(Pager *pPager){
 ** lock on the database file and use heap-memory to store the wal-index
 ** in. Otherwise, use the normal shared-memory.
 */
-static int pagerOpenWal(Pager *pPager){
+static int pagerOpenWal(Pager *pPager, int bWal2){
   int rc = SQLITE_OK;
 
   assert( pPager->pWal==0 && pPager->tempFile==0 );
@@ -7464,7 +7458,7 @@ static int pagerOpenWal(Pager *pPager){
   if( rc==SQLITE_OK ){
     rc = sqlite3WalOpen(pPager->pVfs,
         pPager->fd, pPager->zWal, pPager->exclusiveMode,
-        pPager->journalSizeLimit, &pPager->pWal
+        pPager->journalSizeLimit, bWal2, &pPager->pWal
     );
   }
   pagerFixMaplimit(pPager);
@@ -7490,6 +7484,7 @@ static int pagerOpenWal(Pager *pPager){
 */
 int sqlite3PagerOpenWal(
   Pager *pPager,                  /* Pager object */
+  int bWal2,                      /* Open in wal2 mode if not already open */
   int *pbOpen                     /* OUT: Set to true if call is a no-op */
 ){
   int rc = SQLITE_OK;             /* Return code */
@@ -7506,9 +7501,9 @@ int sqlite3PagerOpenWal(
     /* Close any rollback journal previously open */
     sqlite3OsClose(pPager->jfd);
 
-    rc = pagerOpenWal(pPager);
+    rc = pagerOpenWal(pPager, bWal2);
     if( rc==SQLITE_OK ){
-      pPager->journalMode = PAGER_JOURNALMODE_WAL;
+      pPager->journalMode = bWal2?PAGER_JOURNALMODE_WAL2:PAGER_JOURNALMODE_WAL;
       pPager->eState = PAGER_OPEN;
     }
   }else{
@@ -7530,7 +7525,9 @@ int sqlite3PagerOpenWal(
 int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){
   int rc = SQLITE_OK;
 
-  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL 
+       || pPager->journalMode==PAGER_JOURNALMODE_WAL2
+  );
 
   /* If the log file is not already open, but does exist in the file-system,
   ** it may need to be checkpointed before the connection can switch to
@@ -7545,7 +7542,7 @@ int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){
       );
     }
     if( rc==SQLITE_OK && logexists ){
-      rc = pagerOpenWal(pPager);
+      rc = pagerOpenWal(pPager, 0);
     }
   }
     

src/pager.h

@@ -81,6 +81,23 @@ typedef struct PgHdr DbPage;
 #define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
 #define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
 #define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
+#define PAGER_JOURNALMODE_WAL2        6   /* Use write-ahead logging mode 2 */
+
+#define isWalMode(x) ((x)==PAGER_JOURNALMODE_WAL || (x)==PAGER_JOURNALMODE_WAL2)
+
+/*
+** The argument to this macro is a file descriptor (type sqlite3_file*).
+** Return 0 if it is not open, or non-zero (but not 1) if it is.
+**
+** This is so that expressions can be written as:
+**
+**   if( isOpen(pPager->jfd) ){ ...
+**
+** instead of
+**
+**   if( pPager->jfd->pMethods ){ ...
+*/
+#define isOpen(pFd) ((pFd)->pMethods!=0)
 
 /*
 ** Flags that make up the mask passed to sqlite3PagerGet().
@@ -177,7 +194,7 @@ int sqlite3PagerSharedLock(Pager *pPager);
   int sqlite3PagerCheckpoint(Pager *pPager, sqlite3*, int, int*, int*);
   int sqlite3PagerWalSupported(Pager *pPager);
   int sqlite3PagerWalCallback(Pager *pPager);
-  int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
+  int sqlite3PagerOpenWal(Pager *pPager, int, int *pisOpen);
   int sqlite3PagerCloseWal(Pager *pPager, sqlite3*);
 # ifdef SQLITE_DIRECT_OVERFLOW_READ
   int sqlite3PagerUseWal(Pager *pPager, Pgno);

src/pragma.c

@@ -260,7 +260,7 @@ const char *sqlite3JournalModename(int eMode){
   static char * const azModeName[] = {
     "delete", "persist", "off", "truncate", "memory"
 #ifndef SQLITE_OMIT_WAL
-     , "wal"
+     , "wal", "wal2"
 #endif
   };
   assert( PAGER_JOURNALMODE_DELETE==0 );
@@ -269,6 +269,7 @@ const char *sqlite3JournalModename(int eMode){
   assert( PAGER_JOURNALMODE_TRUNCATE==3 );
   assert( PAGER_JOURNALMODE_MEMORY==4 );
   assert( PAGER_JOURNALMODE_WAL==5 );
+  assert( PAGER_JOURNALMODE_WAL2==6 );
   assert( eMode>=0 && eMode<=ArraySize(azModeName) );
 
   if( eMode==ArraySize(azModeName) ) return 0;

src/vdbe.c

@@ -6325,6 +6325,7 @@ case OP_JournalMode: {    /* out2 */
        || eNew==PAGER_JOURNALMODE_OFF
        || eNew==PAGER_JOURNALMODE_MEMORY
        || eNew==PAGER_JOURNALMODE_WAL
+       || eNew==PAGER_JOURNALMODE_WAL2
        || eNew==PAGER_JOURNALMODE_QUERY
   );
   assert( pOp->p1>=0 && pOp->p1<db->nDb );
@@ -6342,16 +6343,25 @@ case OP_JournalMode: {    /* out2 */
   /* Do not allow a transition to journal_mode=WAL for a database
   ** in temporary storage or if the VFS does not support shared memory 
   */
-  if( eNew==PAGER_JOURNALMODE_WAL
+  if( isWalMode(eNew)
    && (sqlite3Strlen30(zFilename)==0           /* Temp file */
        || !sqlite3PagerWalSupported(pPager))   /* No shared-memory support */
   ){
     eNew = eOld;
   }
 
-  if( (eNew!=eOld)
+  if( eNew!=eOld && (isWalMode(eNew) || isWalMode(eOld)) ){
-   && (eOld==PAGER_JOURNALMODE_WAL || eNew==PAGER_JOURNALMODE_WAL)
+
-  ){
+    /* Prevent changing directly to wal2 from wal mode. And vice versa. */
+    if( isWalMode(eNew) && isWalMode(eOld) ){
+      rc = SQLITE_ERROR;
+      sqlite3VdbeError(p, "cannot change from %s to %s mode",
+          sqlite3JournalModename(eOld), sqlite3JournalModename(eNew)
+      );
+      goto abort_due_to_error;
+    }
+
+    /* Prevent switching into or out of wal/wal2 mode mid-transaction */
     if( !db->autoCommit || db->nVdbeRead>1 ){
       rc = SQLITE_ERROR;
       sqlite3VdbeError(p,
@@ -6359,31 +6369,33 @@ case OP_JournalMode: {    /* out2 */
           (eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
       );
       goto abort_due_to_error;
-    }else{
+    }
  
-      if( eOld==PAGER_JOURNALMODE_WAL ){
+    if( isWalMode(eOld) ){
-        /* If leaving WAL mode, close the log file. If successful, the call
+      /* If leaving WAL mode, close the log file. If successful, the call
-        ** to PagerCloseWal() checkpoints and deletes the write-ahead-log 
+      ** to PagerCloseWal() checkpoints and deletes the write-ahead-log 
-        ** file. An EXCLUSIVE lock may still be held on the database file 
+      ** file. An EXCLUSIVE lock may still be held on the database file 
-        ** after a successful return. 
+      ** after a successful return. 
-        */
-        rc = sqlite3PagerCloseWal(pPager, db);
-        if( rc==SQLITE_OK ){
-          sqlite3PagerSetJournalMode(pPager, eNew);
-        }
-      }else if( eOld==PAGER_JOURNALMODE_MEMORY ){
-        /* Cannot transition directly from MEMORY to WAL.  Use mode OFF
-        ** as an intermediate */
-        sqlite3PagerSetJournalMode(pPager, PAGER_JOURNALMODE_OFF);
-      }
-  
-      /* Open a transaction on the database file. Regardless of the journal
-      ** mode, this transaction always uses a rollback journal.
       */
-      assert( sqlite3BtreeIsInTrans(pBt)==0 );
+      rc = sqlite3PagerCloseWal(pPager, db);
       if( rc==SQLITE_OK ){
-        rc = sqlite3BtreeSetVersion(pBt, (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+        sqlite3PagerSetJournalMode(pPager, eNew);
       }
+    }else if( eOld==PAGER_JOURNALMODE_MEMORY ){
+      /* Cannot transition directly from MEMORY to WAL.  Use mode OFF
+      ** as an intermediate */
+      sqlite3PagerSetJournalMode(pPager, PAGER_JOURNALMODE_OFF);
+    }
+
+    /* Open a transaction on the database file. Regardless of the journal
+    ** mode, this transaction always uses a rollback journal.
+    */
+    assert( sqlite3BtreeIsInTrans(pBt)==0 );
+    if( rc==SQLITE_OK ){
+      /* 1==rollback, 2==wal, 3==wal2 */
+      rc = sqlite3BtreeSetVersion(pBt, 
+          1 + isWalMode(eNew) + (eNew==PAGER_JOURNALMODE_WAL2)
+      );
     }
   }
 #endif /* ifndef SQLITE_OMIT_WAL */

src/wal.h

@@ -26,7 +26,7 @@
 #define CKPT_SYNC_FLAGS(X)  (((X)>>2)&0x03)
 
 #ifdef SQLITE_OMIT_WAL
-# define sqlite3WalOpen(x,y,z)                   0
+# define sqlite3WalOpen(w,x,y,z)                 0
 # define sqlite3WalLimit(x,y)
 # define sqlite3WalClose(v,w,x,y,z)              0
 # define sqlite3WalBeginReadTransaction(y,z)     0
@@ -55,7 +55,7 @@
 typedef struct Wal Wal;
 
 /* Open and close a connection to a write-ahead log. */
-int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
+int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *,int,i64,int,Wal**);
 int sqlite3WalClose(Wal *pWal, sqlite3*, int sync_flags, int, u8 *);
 
 /* Set the limiting size of a WAL file. */

test/permutations.test

@@ -1019,6 +1019,23 @@ test_suite "wal" -description {
   fts3c.test   fts3d.test   fts3e.test   fts3query.test 
 }
 
+test_suite "wal2" -description {
+  Run tests with journal_mode=WAL2
+} -initialize {
+  set ::G(savepoint6_iterations) 100
+} -shutdown {
+  unset -nocomplain ::G(savepoint6_iterations)
+} -files {
+  savepoint.test     savepoint2.test     savepoint6.test
+  trans.test         avtrans.test
+
+  fts3aa.test  fts3ab.test  fts3ac.test  fts3ad.test
+  fts3ae.test  fts3af.test  fts3ag.test  fts3ah.test
+  fts3ai.test  fts3aj.test  fts3ak.test  fts3al.test
+  fts3am.test  fts3an.test  fts3ao.test  fts3b.test
+  fts3c.test   fts3d.test   fts3e.test   fts3query.test 
+}
+
 test_suite "rtree" -description {
   All R-tree related tests. Provides coverage of source file rtree.c.
 } -files [glob -nocomplain $::testdir/../ext/rtree/*.test]

test/savepoint.test

@@ -28,6 +28,7 @@ do_test savepoint-1.1 {
     RELEASE sp1;
   }
 } {}
+wal_check_journal_mode savepoint-1.1
 do_test savepoint-1.2 {
   execsql {
     SAVEPOINT sp1;

test/savepoint6.test

@@ -15,6 +15,10 @@ set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 proc sql {zSql} {
+  if {0 && $::debug_op} {
+    puts stderr "$zSql ;"
+    flush stderr
+  }
   uplevel db eval [list $zSql]
   #puts stderr "$zSql ;"
 }
@@ -67,11 +71,13 @@ proc x_to_y {x} {
 #   delete_rows XVALUES
 #
 proc savepoint {zName} {
+  if {$::debug_op} { puts stderr "savepoint $zName" ; flush stderr }
   catch { sql "SAVEPOINT $zName" }
   lappend ::lSavepoint [list $zName [array get ::aEntry]]
 }
 
 proc rollback {zName} {
+  if {$::debug_op} { puts stderr "rollback $zName" ; flush stderr }
   catch { sql "ROLLBACK TO $zName" }
   for {set i [expr {[llength $::lSavepoint]-1}]} {$i>=0} {incr i -1} {
     set zSavepoint [lindex $::lSavepoint $i 0]
@@ -89,6 +95,7 @@ proc rollback {zName} {
 }
 
 proc release {zName} {
+  if {$::debug_op} { puts stderr "release $zName" ; flush stderr }
   catch { sql "RELEASE $zName" }
   for {set i [expr {[llength $::lSavepoint]-1}]} {$i>=0} {incr i -1} {
     set zSavepoint [lindex $::lSavepoint $i 0]
@@ -104,6 +111,7 @@ proc release {zName} {
 }
 
 proc insert_rows {lX} {
+  if {$::debug_op} { puts stderr "insert_rows $lX" ; flush stderr }
   foreach x $lX {
     set y [x_to_y $x]
 
@@ -116,6 +124,7 @@ proc insert_rows {lX} {
 }
 
 proc delete_rows {lX} {
+  if {$::debug_op} { puts stderr "delete_rows $lX" ; flush stderr }
   foreach x $lX {
     # Update database [db]
     sql "DELETE FROM t1 WHERE x = $x"
@@ -164,6 +173,11 @@ proc random_integers {nRes nRange} {
 } 
 #-------------------------------------------------------------------------
 
+set ::debug_op 0
+proc debug_ops {} {
+  set ::debug_op 1
+}
+
 proc database_op {} {
   set i [expr int(rand()*2)] 
   if {$i==0} {
@@ -185,9 +199,6 @@ proc savepoint_op {} {
   set C [lindex $cmds [expr int(rand()*6)]]
   set N [lindex $names [expr int(rand()*5)]]
 
-  #puts stderr "   $C $N ;  "
-  #flush stderr
-
   $C $N
   return ok
 }

test/tester.tcl

@@ -586,6 +586,7 @@ proc reset_db {} {
   forcedelete test.db
   forcedelete test.db-journal
   forcedelete test.db-wal
+  forcedelete test.db-wal2
   sqlite3 db ./test.db
   set ::DB [sqlite3_connection_pointer db]
   if {[info exists ::SETUP_SQL]} {
@@ -2053,17 +2054,32 @@ proc drop_all_indexes {{db db}} {
 #     Returns true if this test should be run in WAL mode. False otherwise.
 #
 proc wal_is_wal_mode {} {
-  expr {[permutation] eq "wal"}
+  if {[permutation] eq "wal"} { return 1 }
+  if {[permutation] eq "wal2"} { return 2 }
+  return 0
 }
 proc wal_set_journal_mode {{db db}} {
-  if { [wal_is_wal_mode] } {
+  switch -- [wal_is_wal_mode] {
-    $db eval "PRAGMA journal_mode = WAL"
+    0 {
+    }
+
+    1 {
+      $db eval "PRAGMA journal_mode = WAL"
+    }
+
+    2 {
+      $db eval "PRAGMA journal_mode = WAL2"
+    }
   }
 }
 proc wal_check_journal_mode {testname {db db}} {
   if { [wal_is_wal_mode] } {
     $db eval { SELECT * FROM sqlite_master }
-    do_test $testname [list $db eval "PRAGMA main.journal_mode"] {wal}
+    set expected "wal"
+    if {[wal_is_wal_mode]==2} {
+      set expected "wal2"
+    }
+    do_test $testname [list $db eval "PRAGMA main.journal_mode"] $expected
   }
 }
 

test/waltwo2.test

@@ -0,0 +1,127 @@
+# 2017 September 19
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    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.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing the operation of the library in
+# "PRAGMA journal_mode=WAL2" mode.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+source $testdir/lock_common.tcl
+source $testdir/malloc_common.tcl
+source $testdir/wal_common.tcl
+
+set testprefix walsimple
+ifcapable !wal {finish_test ; return }
+
+db close
+foreach f [glob -nocomplain test.db*] { forcedelete $f }
+sqlite3 db test.db
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x, y);
+  PRAGMA journal_mode = wal2;
+} {wal2}
+
+do_execsql_test 1.1 {
+  SELECT * FROM t1;
+} {}
+
+do_execsql_test 1.2 {
+  INSERT INTO t1 VALUES(1, 2);
+} {}
+
+do_execsql_test 1.3 {
+  SELECT * FROM t1;
+} {1 2}
+
+do_test 1.4 {
+  sqlite3 db2 test.db
+  execsql { SELECT * FROM t1 } db2
+} {1 2}
+
+do_test 1.5 {
+  lsort [glob test.db*]
+} {test.db test.db-shm test.db-wal test.db-wal2}
+
+do_test 1.6 {
+  db close
+  db2 close
+  sqlite3 db test.db
+  execsql { SELECT * FROM t1 }
+} {1 2}
+
+do_execsql_test 1.7 {
+  PRAGMA journal_size_limit = 4000;
+  INSERT INTO t1 VALUES(3, 4);
+  INSERT INTO t1 VALUES(5, 6);
+  INSERT INTO t1 VALUES(7, 8);
+  INSERT INTO t1 VALUES(9, 10);
+  INSERT INTO t1 VALUES(11, 12);
+  INSERT INTO t1 VALUES(13, 14);
+  INSERT INTO t1 VALUES(15, 16);
+  INSERT INTO t1 VALUES(17, 18);
+  SELECT * FROM t1;
+} {4000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18}
+
+do_test 1.8 {
+  sqlite3 db2 test.db
+  execsql { SELECT * FROM t1 } db2
+} {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18}
+
+do_test 1.9 {
+  db close
+  db2 close
+  lsort [glob test.db*]
+} {test.db}
+
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 2.0 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
+  CREATE INDEX i1 ON t1(b, c);
+  PRAGMA journal_mode = wal2;
+  PRAGMA journal_size_limit = 4000;
+} {wal2 4000}
+
+proc wal_hook {DB nm nFrame} {
+  $DB eval { PRAGMA wal_checkpoint }
+}
+db wal_hook [list wal_hook db]
+
+
+foreach js {4000 8000 12000} {
+  foreach NROW [list 100 200 300 400 500 600 1000] {
+    do_test 2.$js.$NROW.1 {
+      db eval "DELETE FROM t1"
+      db eval "PRAGMA journal_size_limit = $js"
+      set nTotal 0
+      for {set i 0} {$i < $NROW} {incr i} {
+        db eval { INSERT INTO t1 VALUES($i, $i, randomblob(abs(random()%50))) }
+        incr nTotal $i
+      }
+      set {} {}
+    } {}
+
+    do_test 2.$js.$NROW.2 {
+      sqlite3 db2 test.db
+      db2 eval { 
+        PRAGMA integrity_check;
+        SELECT count(*), sum(b) FROM t1;
+      }
+    } [list ok $NROW $nTotal]
+
+    db2 close
+  }
+}
+
+finish_test
+