描述
用于sqlite3对象的析构函数。
C / C ++语法
int sqlite3_close(sqlite3 *); |
PB语法
FUNCTION sqlite3_close ( _ BYVAL hDbc AS DWORD _ ) AS LONG |
参数
pDb
[in]数据库连接句柄。必须是从sqlite3_open，sqlite3_open16或sqlite3_open_v2获取的NULL指针或sqlite3对象指针，而不是先前关闭。使用NULL指针参数调用sqlite3_close是无害的操作。
返回值
如果sqlite3对象被成功销毁并且所有关联的资源被释放，SQLITE_OK。
备注
在尝试关闭对象之前，应用程序必须完成所有准备好的语句并关闭与sqlite3对象关联的所有BLOB句柄。如果在仍然有未完成的准备语句或BLOB句柄的数据库连接上调用sqlite3_close，则返回SQLITE_BUSY。
如果在事务打开时调用sqlite3_close，则事务将自动回滚。
C ++实现代码
/*
** Close an existing SQLite database
*/
SQLITE_API int sqlite3_close(sqlite3 *db){
HashElem *i; /* Hash table iterator */
int j;
if( !db ){
return SQLITE_OK;
}
if( !sqlite3SafetyCheckSickOrOk(db) ){
return SQLITE_MISUSE_BKPT;
}
sqlite3_mutex_enter(db->mutex);
/* Force xDisconnect calls on all virtual tables */
disconnectAllVtab(db);
/* If a transaction is open, the disconnectAllVtab() call above
** will not have called the xDisconnect() method on any virtual
** tables in the db->aVTrans[] array. The following sqlite3VtabRollback()
** call will do so. We need to do this before the check for active
** SQL statements below, as the v-table implementation may be storing
** some prepared statements internally.
*/
sqlite3VtabRollback(db);
/* If there are any outstanding VMs, return SQLITE_BUSY. */
if( db->pVdbe ){
sqlite3Error(db, SQLITE_BUSY,
"unable to close due to unfinalised statements");
sqlite3_mutex_leave(db->mutex);
return SQLITE_BUSY;
}
assert( sqlite3SafetyCheckSickOrOk(db) );
for(j=0; j<db->nDb; j++){
Btree *pBt = db->aDb[j].pBt;
if( pBt && sqlite3BtreeIsInBackup(pBt) ){
sqlite3Error(db, SQLITE_BUSY,
"unable to close due to unfinished backup operation");
sqlite3_mutex_leave(db->mutex);
return SQLITE_BUSY;
}
}
/* Free any outstanding Savepoint structures. */
sqlite3CloseSavepoints(db);
/* Close all database connections */
for(j=0; j<db->nDb; j++){
struct Db *pDb = &db->aDb[j];
if( pDb->pBt ){
sqlite3BtreeClose(pDb->pBt);
pDb->pBt = 0;
if( j!=1 ){
pDb->pSchema = 0;
}
}
}
/* Clear the TEMP schema separately and last */
if( db->aDb[1].pSchema ){
sqlite3SchemaClear(db->aDb[1].pSchema);
}
sqlite3VtabUnlockList(db);
/* Free up the array of auxiliary databases */
sqlite3CollapseDatabaseArray(db);
assert( db->nDb<=2 );
assert( db->aDb==db->aDbStatic );
/* Tell the code in notify.c that the connection no longer holds any
** locks and does not require any further unlock-notify callbacks.
*/
sqlite3ConnectionClosed(db);
for(j=0; j<ArraySize(db->aFunc.a); j++){
FuncDef *pNext, *pHash, *p;
for(p=db->aFunc.a[j]; p; p=pHash){
pHash = p->pHash;
while( p ){
functionDestroy(db, p);
pNext = p->pNext;
sqlite3DbFree(db, p);
p = pNext;
}
}
}
for(i=sqliteHashFirst(&db->aCollSeq); i; i=sqliteHashNext(i)){
CollSeq *pColl = (CollSeq *)sqliteHashData(i);
/* Invoke any destructors registered for collation sequence user data. */
for(j=0; j<3; j++){
if( pColl[j].xDel ){
pColl[j].xDel(pColl[j].pUser);
}
}
sqlite3DbFree(db, pColl);
}
sqlite3HashClear(&db->aCollSeq);
#ifndef SQLITE_OMIT_VIRTUALTABLE
for(i=sqliteHashFirst(&db->aModule); i; i=sqliteHashNext(i)){
Module *pMod = (Module *)sqliteHashData(i);
if( pMod->xDestroy ){
pMod->xDestroy(pMod->pAux);
}
sqlite3DbFree(db, pMod);
}
sqlite3HashClear(&db->aModule);
#endif
sqlite3Error(db, SQLITE_OK, 0); /* Deallocates any cached error strings. */
if( db->pErr ){
sqlite3ValueFree(db->pErr);
}
sqlite3CloseExtensions(db);
db->magic = SQLITE_MAGIC_ERROR;
/* The temp-database schema is allocated differently from the other schema
** objects (using sqliteMalloc() directly, instead of sqlite3BtreeSchema()).
** So it needs to be freed here. Todo: Why not roll the temp schema into
** the same sqliteMalloc() as the one that allocates the database
** structure?
*/
sqlite3DbFree(db, db->aDb[1].pSchema);
sqlite3_mutex_leave(db->mutex);
db->magic = SQLITE_MAGIC_CLOSED;
sqlite3_mutex_free(db->mutex);
assert( db->lookaside.nOut==0 ); /* Fails on a lookaside memory leak */
if( db->lookaside.bMalloced ){
sqlite3_free(db->lookaside.pStart);
}
sqlite3_free(db);
return SQLITE_OK;
}