描述
检索有关单个数据库连接的运行时状态信息。
C / C ++语法
int sqlite3_db_status( sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg ); |
PB语法
FUNCTION sqlite3_db_status ( _ BYVAL hDbc AS DWORD, _ BYVAL op AS LONG, _ BYREF pCur AS LONG, _ BYREF pHiwtr AS LONG, _ BYVAL resetFlag AS LONG _ ) AS LONG |
参数
pDb
[in]要查询的数据库连接对象。必须是从sqlite3_open，sqlite3_open16或sqlite3_open_v2获取的sqlite3对象指针。 数据库连接不能关闭。
op
[in]一组整数常数，取自SQLITE_DBSTATUS选项集，用于确定要查询的参数。
%SQLITE_DBSTATUS_LOOKASIDE_USED = 0
%SQLITE_DBSTATUS_CACHE_USED = 1
%SQLITE_DBSTATUS_SCHEMA_USED = 2
%SQLITE_DBSTATUS_STMT_USED = 3
%SQLITE_DBSTATUS_LOOKASIDE_HIT = 4
%SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE = 5
%SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL = 6
%SQLITE_DBSTATUS_CACHE_HIT = 7
%SQLITE_DBSTATUS_CACHE_MISS = 8
%SQLITE_DBSTATUS_CACHE_WRITE = 9
pCur
[out]请求参数的当前值。
pHiwtr
[out]最高瞬时值。
resetFlag
[out]TRUE或FALSE。如果为真，那么最高瞬时值将被复位回当前值。
返回值
SQLITE_OK成功，失败时出现非零错误代码。
C ++实现代码
/*
** Query status information for a single database connection
*/
SQLITE_API int sqlite3_db_status(
sqlite3 *db, /* The database connection whose status is desired */
int op, /* Status verb */
int *pCurrent, /* Write current value here */
int *pHighwater, /* Write high-water mark here */
int resetFlag /* Reset high-water mark if true */
){
int rc = SQLITE_OK; /* Return code */
sqlite3_mutex_enter(db->mutex);
switch( op ){
case SQLITE_DBSTATUS_LOOKASIDE_USED: {
*pCurrent = db->lookaside.nOut;
*pHighwater = db->lookaside.mxOut;
if( resetFlag ){
db->lookaside.mxOut = db->lookaside.nOut;
}
break;
}
case SQLITE_DBSTATUS_LOOKASIDE_HIT:
case SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE:
case SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL: {
testcase( op==SQLITE_DBSTATUS_LOOKASIDE_HIT );
testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE );
testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL );
assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)>=0 );
assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)<3 );
*pCurrent = 0;
*pHighwater = db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT];
if( resetFlag ){
db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT] = 0;
}
break;
}
/*
** Return an approximation for the amount of memory currently used
** by all pagers associated with the given database connection. The
** highwater mark is meaningless and is returned as zero.
*/
case SQLITE_DBSTATUS_CACHE_USED: {
int totalUsed = 0;
int i;
sqlite3BtreeEnterAll(db);
for(i=0; i<db->nDb; i++){
Btree *pBt = db->aDb[i].pBt;
if( pBt ){
Pager *pPager = sqlite3BtreePager(pBt);
totalUsed += sqlite3PagerMemUsed(pPager);
}
}
sqlite3BtreeLeaveAll(db);
*pCurrent = totalUsed;
*pHighwater = 0;
break;
}
/*
** *pCurrent gets an accurate estimate of the amount of memory used
** to store the schema for all databases (main, temp, and any ATTACHed
** databases. *pHighwater is set to zero.
*/
case SQLITE_DBSTATUS_SCHEMA_USED: {
int i; /* Used to iterate through schemas */
int nByte = 0; /* Used to accumulate return value */
sqlite3BtreeEnterAll(db);
db->pnBytesFreed = &nByte;
for(i=0; i<db->nDb; i++){
Schema *pSchema = db->aDb[i].pSchema;
if( ALWAYS(pSchema!=0) ){
HashElem *p;
nByte += sqlite3GlobalConfig.m.xRoundup(sizeof(HashElem)) * (
pSchema->tblHash.count
+ pSchema->trigHash.count
+ pSchema->idxHash.count
+ pSchema->fkeyHash.count
);
nByte += sqlite3MallocSize(pSchema->tblHash.ht);
nByte += sqlite3MallocSize(pSchema->trigHash.ht);
nByte += sqlite3MallocSize(pSchema->idxHash.ht);
nByte += sqlite3MallocSize(pSchema->fkeyHash.ht);
for(p=sqliteHashFirst(&pSchema->trigHash); p; p=sqliteHashNext(p)){
sqlite3DeleteTrigger(db, (Trigger*)sqliteHashData(p));
}
for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
sqlite3DeleteTable(db, (Table *)sqliteHashData(p));
}
}
}
db->pnBytesFreed = 0;
sqlite3BtreeLeaveAll(db);
*pHighwater = 0;
*pCurrent = nByte;
break;
}
/*
** *pCurrent gets an accurate estimate of the amount of memory used
** to store all prepared statements.
** *pHighwater is set to zero.
*/
case SQLITE_DBSTATUS_STMT_USED: {
struct Vdbe *pVdbe; /* Used to iterate through VMs */
int nByte = 0; /* Used to accumulate return value */
db->pnBytesFreed = &nByte;
for(pVdbe=db->pVdbe; pVdbe; pVdbe=pVdbe->pNext){
sqlite3VdbeDeleteObject(db, pVdbe);
}
db->pnBytesFreed = 0;
*pHighwater = 0;
*pCurrent = nByte;
break;
}
/*
** Set *pCurrent to the total cache hits or misses encountered by all
** pagers the database handle is connected to. *pHighwater is always set
** to zero.
*/
case SQLITE_DBSTATUS_CACHE_HIT:
case SQLITE_DBSTATUS_CACHE_MISS:
case SQLITE_DBSTATUS_CACHE_WRITE:{
int i;
int nRet = 0;
assert( SQLITE_DBSTATUS_CACHE_MISS==SQLITE_DBSTATUS_CACHE_HIT+1 );
assert( SQLITE_DBSTATUS_CACHE_WRITE==SQLITE_DBSTATUS_CACHE_HIT+2 );
for(i=0; i<db->nDb; i++){
if( db->aDb[i].pBt ){
Pager *pPager = sqlite3BtreePager(db->aDb[i].pBt);
sqlite3PagerCacheStat(pPager, op, resetFlag, &nRet);
}
}
*pHighwater = 0;
*pCurrent = nRet;
break;
}
default: {
rc = SQLITE_ERROR;
}
}
sqlite3_mutex_leave(db->mutex);
return rc;
}