Fix a problem with rolling back to a savepoint opened before the writer decided to wrap the log file.

FossilOrigin-Name: 6b4aed6aae7dc9e92807d27375cbe1e83c15841b

2 files changed, 15 insertions, 3 deletions

diff --git a/src/wal.c b/src/wal.c
index 807622774..bc2d6ff46 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -2110,6 +2110,7 @@ void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
   aWalData[0] = pWal->hdr.mxFrame;
   aWalData[1] = pWal->hdr.aFrameCksum[0];
   aWalData[2] = pWal->hdr.aFrameCksum[1];
+  aWalData[3] = pWal->nCkpt;
 }
 
 /* 
@@ -2120,9 +2121,19 @@ void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
 */
 int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
   int rc = SQLITE_OK;
+
   assert( pWal->writeLock );
+  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
+
+  if( aWalData[3]!=pWal->nCkpt ){
+    /* This savepoint was opened immediately after the write-transaction
+    ** was started. Right after that, the writer decided to wrap around
+    ** to the start of the log. Update the savepoint values to match.
+    */
+    aWalData[0] = 0;
+    aWalData[3] = pWal->nCkpt;
+  }
 
-  assert( aWalData[0]<=pWal->hdr.mxFrame );
   if( aWalData[0]<pWal->hdr.mxFrame ){
     rc = walIndexMap(pWal, walMappingSize(pWal->hdr.mxFrame));
     pWal->hdr.mxFrame = aWalData[0];
@@ -2130,9 +2141,10 @@ int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
     pWal->hdr.aFrameCksum[1] = aWalData[2];
     if( rc==SQLITE_OK ){
       walCleanupHash(pWal);
-      walIndexUnmap(pWal);
     }
   }
+
+  walIndexUnmap(pWal);
   return rc;
 }
 
diff --git a/src/wal.h b/src/wal.h
index 32aade1d0..34710a408 100644
--- a/src/wal.h
+++ b/src/wal.h
@@ -36,7 +36,7 @@
 # define sqlite3WalCallback(z)                 0
 #else
 
-#define WAL_SAVEPOINT_NDATA 3
+#define WAL_SAVEPOINT_NDATA 4
 
 /* Connection to a write-ahead log (WAL) file. 
 ** There is one object of this type for each pager.