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Fix for #2854. "BEGIN EXCLUSIVE" excludes other shared cache users from using the database. (CVS 4642)

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FossilOrigin-Name: 2e59b1d07ee422bd799b5b7aeea44ebc998d9481
This commit is contained in:
danielk1977
2007-12-21 04:47:25 +00:00
parent 9892c5d1f4
commit 641b0f4ffa
5 changed files with 185 additions and 12 deletions
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35
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.433 2007/12/13 21:54:11 drh Exp $
** $Id: btree.c,v 1.434 2007/12/21 04:47:26 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -103,6 +103,13 @@ static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
return SQLITE_OK;
}
/* If some other connection is holding an exclusive lock, the
** requested lock may not be obtained.
*/
if( pBt->pExclusive && pBt->pExclusive!=p ){
return SQLITE_LOCKED;
}
/* This (along with lockTable()) is where the ReadUncommitted flag is
** dealt with. If the caller is querying for a read-lock and the flag is
** set, it is unconditionally granted - even if there are write-locks
@@ -212,13 +219,15 @@ static int lockTable(Btree *p, Pgno iTable, u8 eLock){
** procedure) held by Btree handle p.
*/
static void unlockAllTables(Btree *p){
BtLock **ppIter = &p->pBt->pLock;
BtShared *pBt = p->pBt;
BtLock **ppIter = &pBt->pLock;
assert( sqlite3BtreeHoldsMutex(p) );
assert( p->sharable || 0==*ppIter );
while( *ppIter ){
BtLock *pLock = *ppIter;
assert( pBt->pExclusive==0 || pBt->pExclusive==pLock->pBtree );
if( pLock->pBtree==p ){
*ppIter = pLock->pNext;
sqlite3_free(pLock);
@@ -226,6 +235,10 @@ static void unlockAllTables(Btree *p){
ppIter = &pLock->pNext;
}
}
if( pBt->pExclusive==p ){
pBt->pExclusive = 0;
}
}
#endif /* SQLITE_OMIT_SHARED_CACHE */
@@ -1850,6 +1863,18 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
goto trans_begun;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
if( wrflag>1 ){
BtLock *pIter;
for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
if( pIter->pBtree!=p ){
rc = SQLITE_BUSY;
goto trans_begun;
}
}
}
#endif
do {
if( pBt->pPage1==0 ){
rc = lockBtree(pBt);
@@ -1882,6 +1907,12 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
if( p->inTrans>pBt->inTransaction ){
pBt->inTransaction = p->inTrans;
}
#ifndef SQLITE_OMIT_SHARED_CACHE
if( wrflag>1 ){
assert( !pBt->pExclusive );
pBt->pExclusive = p;
}
#endif
}