Add experimental command "PRAGMA wal_blocking_checkpoint", which uses the busy-handler to block until all readers have finished in order to ensure the next writer will be able to wrap around to the start of the log file.

FossilOrigin-Name: 7e3fc2c833a5baa08820c499867b6902bdc2ed5a

1 files changed, 9 insertions, 2 deletions

diff --git a/src/btree.c b/src/btree.c
index 7e8c39feb..94100f48f 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -7935,8 +7935,15 @@ int sqlite3BtreeIsInTrans(Btree *p){
 **
 ** Return SQLITE_LOCKED if this or any other connection has an open 
 ** transaction on the shared-cache the argument Btree is connected to.
+**
+** If parameter bBlock is true, then the layers below invoke the 
+** busy-handler callback while waiting for readers to release locks so
+** that the entire WAL can be checkpointed. If it is false, then as
+** much as possible of the WAL is checkpointed without waiting for readers
+** to finish. bBlock is true for "PRAGMA wal_blocking_checkpoint" and false
+** for "PRAGMA wal_checkpoint".
 */
-int sqlite3BtreeCheckpoint(Btree *p){
+int sqlite3BtreeCheckpoint(Btree *p, int bBlock){
   int rc = SQLITE_OK;
   if( p ){
     BtShared *pBt = p->pBt;
@@ -7944,7 +7951,7 @@ int sqlite3BtreeCheckpoint(Btree *p){
     if( pBt->inTransaction!=TRANS_NONE ){
       rc = SQLITE_LOCKED;
     }else{
-      rc = sqlite3PagerCheckpoint(pBt->pPager);
+      rc = sqlite3PagerCheckpoint(pBt->pPager, bBlock);
     }
     sqlite3BtreeLeave(p);
   }