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Use mmap() to read from the database file in rollback mode. This branch is unix only for now.

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FossilOrigin-Name: 6f21d9cbf5d457e63a7282015a89ae785526cf6d
This commit is contained in:
dan
2013-03-14 18:34:37 +00:00
parent 27e6df4e41
commit b2d3de3bf4
8 changed files with 182 additions and 15 deletions
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31
src/btree.c
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@@ -2564,6 +2564,34 @@ int sqlite3BtreeNewDb(Btree *p){
return rc;
}
/*
** If the shared-btree passed as the only argument is holding references
** to mmap pages, replace them with read/write pages. Return SQLITE_OK
** if successful, or an error code otherwise.
*/
static int btreeSwapOutMmap(BtShared *pBt){
BtCursor *pCsr;
for(pCsr=pBt->pCursor; pCsr; pCsr=pCsr->pNext){
int i;
for(i=0; i<=pCsr->iPage; i++){
MemPage *pPg = pCsr->apPage[i];
if( pPg->pDbPage->flags & PGHDR_MMAP ){
int rc;
MemPage *pNew = 0;
rc = btreeGetPage(pBt, pPg->pgno, &pNew, 0);
if( rc==SQLITE_OK && i==pCsr->iPage ){
pCsr->info.pCell = pNew->aData + (pCsr->info.pCell - pPg->aData);
}
pCsr->apPage[i] = pNew;
releasePage(pPg);
if( rc!=SQLITE_OK ) return rc;
}
}
}
return SQLITE_OK;
}
/*
** Attempt to start a new transaction. A write-transaction
** is started if the second argument is nonzero, otherwise a read-
@@ -2670,6 +2698,9 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
rc = SQLITE_READONLY;
}else{
rc = sqlite3PagerBegin(pBt->pPager,wrflag>1,sqlite3TempInMemory(p->db));
if( rc==SQLITE_OK ){
rc = btreeSwapOutMmap(pBt);
}
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}