A different fix to [fc62af4523]. When changing from journal_mode=PERSIST or TRINCATE to some other rollback mode, delete the journal file only if a RESERVED lock can be obtained on the database file first.

FossilOrigin-Name: b9b11855e8a9522309dd30e5256bb67d67e1353a

2 files changed, 44 insertions, 5 deletions

diff --git a/src/pager.c b/src/pager.c
index 8869802c5..a902d70ef 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -5898,6 +5898,48 @@ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
 
     /* Change the journal mode. */
     pPager->journalMode = (u8)eMode;
+
+    /* When transistioning from TRUNCATE or PERSIST to any other journal
+    ** mode except WAL (and we are not in locking_mode=EXCLUSIVE) then 
+    ** delete the journal file.
+    */
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+
+      /* 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
+      ** here is an optimization only.
+      **
+      ** Before deleting the journal file, obtain a RESERVED lock on the
+      ** database file. This ensures that the journal file is not deleted
+      ** while it is in use by some other client.
+      */
+      int rc = SQLITE_OK;
+      int state = pPager->state;
+      if( state<PAGER_SHARED ){
+        rc = sqlite3PagerSharedLock(pPager);
+      }
+      if( pPager->state==PAGER_SHARED ){
+        assert( rc==SQLITE_OK );
+        rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
+      }
+      if( rc==SQLITE_OK ){
+        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }
+      if( rc==SQLITE_OK && state==PAGER_SHARED ){
+        sqlite3OsUnlock(pPager->fd, SHARED_LOCK);
+      }else if( state==PAGER_UNLOCK ){
+        pager_unlock(pPager);
+      }
+      assert( state==pPager->state );
+    }
   }
 
   /* Return the new journal mode */
diff --git a/src/vdbe.c b/src/vdbe.c
index 14785d35d..6803beafd 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -5251,9 +5251,6 @@ case OP_JournalMode: {    /* out2-prerelease */
         }else if( rc==SQLITE_BUSY && pOp->p5==0 ){
           goto abort_due_to_error;
         }
-      }else{
-        sqlite3PagerSetJournalMode(pPager, PAGER_JOURNALMODE_DELETE);
-        rc = SQLITE_OK;
       }
   
       /* Open a transaction on the database file. Regardless of the journal
@@ -5261,8 +5258,7 @@ case OP_JournalMode: {    /* out2-prerelease */
       */
       assert( sqlite3BtreeIsInTrans(pBt)==0 );
       if( rc==SQLITE_OK ){
-        rc = sqlite3BtreeSetVersion(pBt, 
-                                    (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+        rc = sqlite3BtreeSetVersion(pBt, (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
         if( rc==SQLITE_BUSY && pOp->p5==0 ) goto abort_due_to_error;
       }
       if( rc==SQLITE_BUSY ){
@@ -5274,6 +5270,7 @@ case OP_JournalMode: {    /* out2-prerelease */
 #endif /* ifndef SQLITE_OMIT_WAL */
 
   eNew = sqlite3PagerSetJournalMode(pPager, eNew);
+
   pOut = &aMem[pOp->p2];
   pOut->flags = MEM_Str|MEM_Static|MEM_Term;
   pOut->z = (char *)sqlite3JournalModename(eNew);