Add the SQLITE_FCNTL_CKPT_START file-control and use it to optimize

the cksumvfs extension.

FossilOrigin-Name: efdecb13091316aeac2722f58577cb0314e008e857f2816a2a222bac0a83e9e1

2 files changed, 8 insertions, 4 deletions

diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index f65576a15..5c082623c 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -1111,6 +1111,11 @@ struct sqlite3_io_methods {
 ** happen either internally or externally and that are associated with
 ** a particular attached database.
 **
+** <li>[[SQLITE_FCNTL_CKPT_START]]
+** The [SQLITE_FCNTL_CKPT_START] opcode is invoked from within a checkpoint
+** in wal mode before the client starts to copy pages from the wal
+** file to the database file.
+**
 ** <li>[[SQLITE_FCNTL_CKPT_DONE]]
 ** The [SQLITE_FCNTL_CKPT_DONE] opcode is invoked from within a checkpoint
 ** in wal mode after the client has finished copying pages from the wal
@@ -1155,6 +1160,7 @@ struct sqlite3_io_methods {
 #define SQLITE_FCNTL_SIZE_LIMIT             36
 #define SQLITE_FCNTL_CKPT_DONE              37
 #define SQLITE_FCNTL_RESERVE_BYTES          38
+#define SQLITE_FCNTL_CKPT_START             39
 
 /* deprecated names */
 #define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
diff --git a/src/wal.c b/src/wal.c
index 3e4f4acfd..b23085859 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -1868,6 +1868,7 @@ static int walCheckpoint(
       if( rc==SQLITE_OK ){
         i64 nReq = ((i64)mxPage * szPage);
         i64 nSize;                    /* Current size of database file */
+        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_CKPT_START, 0);
         rc = sqlite3OsFileSize(pWal->pDbFd, &nSize);
         if( rc==SQLITE_OK && nSize<nReq ){
           sqlite3OsFileControlHint(pWal->pDbFd, SQLITE_FCNTL_SIZE_HINT, &nReq);
@@ -1895,6 +1896,7 @@ static int walCheckpoint(
         rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, iOffset);
         if( rc!=SQLITE_OK ) break;
       }
+      sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_CKPT_DONE, 0);
 
       /* If work was actually accomplished... */
       if( rc==SQLITE_OK ){
@@ -1907,10 +1909,6 @@ static int walCheckpoint(
           }
         }
         if( rc==SQLITE_OK ){
-          rc = sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_CKPT_DONE, 0);
-          if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
-        }
-        if( rc==SQLITE_OK ){
           pInfo->nBackfill = mxSafeFrame;
         }
       }