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-rw-r--r--src/wal.c107
1 files changed, 101 insertions, 6 deletions
diff --git a/src/wal.c b/src/wal.c
index 4238ea483..ae6a54849 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -445,6 +445,7 @@ struct Wal {
u8 padToSectorBoundary; /* Pad transactions out to the next sector */
WalIndexHdr hdr; /* Wal-index header for current transaction */
u32 minFrame; /* Ignore wal frames before this one */
+ u32 iReCksum; /* On commit, recalculate checksums from here */
const char *zWalName; /* Name of WAL file */
u32 nCkpt; /* Checkpoint sequence counter in the wal-header */
#ifdef SQLITE_DEBUG
@@ -698,14 +699,16 @@ static void walEncodeFrame(
assert( WAL_FRAME_HDRSIZE==24 );
sqlite3Put4byte(&aFrame[0], iPage);
sqlite3Put4byte(&aFrame[4], nTruncate);
- memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
+ if( pWal->iReCksum==0 ){
+ memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
- nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
- walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
- walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+ nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+ walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+ walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
- sqlite3Put4byte(&aFrame[16], aCksum[0]);
- sqlite3Put4byte(&aFrame[20], aCksum[1]);
+ sqlite3Put4byte(&aFrame[16], aCksum[0]);
+ sqlite3Put4byte(&aFrame[20], aCksum[1]);
+ }
}
/*
@@ -2632,6 +2635,7 @@ int sqlite3WalBeginWriteTransaction(Wal *pWal){
/* Cannot start a write transaction without first holding a read
** transaction. */
assert( pWal->readLock>=0 );
+ assert( pWal->writeLock==0 && pWal->iReCksum==0 );
if( pWal->readOnly ){
return SQLITE_READONLY;
@@ -2667,6 +2671,7 @@ int sqlite3WalEndWriteTransaction(Wal *pWal){
if( pWal->writeLock ){
walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
pWal->writeLock = 0;
+ pWal->iReCksum = 0;
pWal->truncateOnCommit = 0;
}
return SQLITE_OK;
@@ -2885,6 +2890,59 @@ static int walWriteOneFrame(
return rc;
}
+/*
+** This function is called as part of committing a transaction within which
+** one or more frames have been overwritten. It updates the checksums for
+** all frames written to the wal file by the current transaction starting
+** with the earliest to have been overwritten.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
+*/
+static int walRewriteChecksums(Wal *pWal, u32 iLast){
+ const int szPage = pWal->szPage;/* Database page size */
+ int rc = SQLITE_OK; /* Return code */
+ u8 *aBuf; /* Buffer to load data from wal file into */
+ u8 aFrame[WAL_FRAME_HDRSIZE]; /* Buffer to assemble frame-headers in */
+ u32 iRead; /* Next frame to read from wal file */
+ i64 iCksumOff;
+
+ aBuf = sqlite3_malloc(szPage + WAL_FRAME_HDRSIZE);
+ if( aBuf==0 ) return SQLITE_NOMEM;
+
+ /* Find the checksum values to use as input for the recalculating the
+ ** first checksum. If the first frame is frame 1 (implying that the current
+ ** transaction restarted the wal file), these values must be read from the
+ ** wal-file header. Otherwise, read them from the frame header of the
+ ** previous frame. */
+ assert( pWal->iReCksum>0 );
+ if( pWal->iReCksum==1 ){
+ iCksumOff = 24;
+ }else{
+ iCksumOff = walFrameOffset(pWal->iReCksum-1, szPage) + 16;
+ }
+ rc = sqlite3OsRead(pWal->pWalFd, aBuf, sizeof(u32)*2, iCksumOff);
+ pWal->hdr.aFrameCksum[0] = sqlite3Get4byte(aBuf);
+ pWal->hdr.aFrameCksum[1] = sqlite3Get4byte(&aBuf[sizeof(u32)]);
+
+ iRead = pWal->iReCksum;
+ pWal->iReCksum = 0;
+ for(; rc==SQLITE_OK && iRead<=iLast; iRead++){
+ i64 iOff = walFrameOffset(iRead, szPage);
+ rc = sqlite3OsRead(pWal->pWalFd, aBuf, szPage+WAL_FRAME_HDRSIZE, iOff);
+ if( rc==SQLITE_OK ){
+ u32 iPgno, nDbSize;
+ iPgno = sqlite3Get4byte(aBuf);
+ nDbSize = sqlite3Get4byte(&aBuf[4]);
+
+ walEncodeFrame(pWal, iPgno, nDbSize, &aBuf[WAL_FRAME_HDRSIZE], aFrame);
+ rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOff);
+ }
+ }
+
+ sqlite3_free(aBuf);
+ return rc;
+}
+
/*
** Write a set of frames to the log. The caller must hold the write-lock
** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
@@ -2905,6 +2963,8 @@ int sqlite3WalFrames(
int szFrame; /* The size of a single frame */
i64 iOffset; /* Next byte to write in WAL file */
WalWriter w; /* The writer */
+ u32 iFirst = 0; /* First frame that may be overwritten */
+ WalIndexHdr *pLive; /* Pointer to shared header */
assert( pList );
assert( pWal->writeLock );
@@ -2920,6 +2980,11 @@ int sqlite3WalFrames(
}
#endif
+ pLive = (WalIndexHdr*)walIndexHdr(pWal);
+ if( memcmp(&pWal->hdr, (void *)pLive, sizeof(WalIndexHdr))!=0 ){
+ iFirst = pLive->mxFrame+1;
+ }
+
/* See if it is possible to write these frames into the start of the
** log file, instead of appending to it at pWal->hdr.mxFrame.
*/
@@ -2984,6 +3049,27 @@ int sqlite3WalFrames(
/* Write all frames into the log file exactly once */
for(p=pList; p; p=p->pDirty){
int nDbSize; /* 0 normally. Positive == commit flag */
+
+ /* Check if this page has already been written into the wal file by
+ ** the current transaction. If so, overwrite the existing frame and
+ ** set Wal.writeLock to WAL_WRITELOCK_RECKSUM - indicating that
+ ** checksums must be recomputed when the transaction is committed. */
+ if( iFirst && (p->pDirty || isCommit==0) ){
+ u32 iWrite = 0;
+ VVA_ONLY(rc =) sqlite3WalFindFrame(pWal, p->pgno, &iWrite);
+ assert( rc==SQLITE_OK || iWrite==0 );
+ if( iWrite>=iFirst ){
+ i64 iOff = walFrameOffset(iWrite, szPage) + WAL_FRAME_HDRSIZE;
+ if( pWal->iReCksum==0 || iWrite<pWal->iReCksum ){
+ pWal->iReCksum = iWrite;
+ }
+ rc = sqlite3OsWrite(pWal->pWalFd, p->pData, szPage, iOff);
+ if( rc ) return rc;
+ p->flags &= ~PGHDR_WAL_APPEND;
+ continue;
+ }
+ }
+
iFrame++;
assert( iOffset==walFrameOffset(iFrame, szPage) );
nDbSize = (isCommit && p->pDirty==0) ? nTruncate : 0;
@@ -2991,6 +3077,13 @@ int sqlite3WalFrames(
if( rc ) return rc;
pLast = p;
iOffset += szFrame;
+ p->flags |= PGHDR_WAL_APPEND;
+ }
+
+ /* Recalculate checksums within the wal file if required. */
+ if( isCommit && pWal->iReCksum ){
+ rc = walRewriteChecksums(pWal, iFrame);
+ if( rc ) return rc;
}
/* If this is the end of a transaction, then we might need to pad
@@ -3042,6 +3135,7 @@ int sqlite3WalFrames(
*/
iFrame = pWal->hdr.mxFrame;
for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
+ if( (p->flags & PGHDR_WAL_APPEND)==0 ) continue;
iFrame++;
rc = walIndexAppend(pWal, iFrame, p->pgno);
}
@@ -3154,6 +3248,7 @@ int sqlite3WalCheckpoint(
/* Copy data from the log to the database file. */
if( rc==SQLITE_OK ){
+
if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
rc = SQLITE_CORRUPT_BKPT;
}else{
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-21 14:18:37 +0000