src/status.c

/*
** 2008 June 18
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This module implements the sqlite3_status() interface and related
** functionality.
*/
#include "sqliteInt.h"

/*
** Variables in which to record status information.
*/
typedef struct sqlite3StatType sqlite3StatType;
static SQLITE_WSD struct sqlite3StatType {
  int nowValue[9];         /* Current value */
  int mxValue[9];          /* Maximum value */
} sqlite3Stat = { {0,}, {0,} };


/* The "wsdStat" macro will resolve to the status information
** state vector.  If writable static data is unsupported on the target,
** we have to locate the state vector at run-time.  In the more common
** case where writable static data is supported, wsdStat can refer directly
** to the "sqlite3Stat" state vector declared above.
*/
#ifdef SQLITE_OMIT_WSD
# define wsdStatInit  sqlite3StatType *x = &GLOBAL(sqlite3StatType,sqlite3Stat)
# define wsdStat x[0]
#else
# define wsdStatInit
# define wsdStat sqlite3Stat
#endif

/*
** Return the current value of a status parameter.
*/
int sqlite3StatusValue(int op){
  wsdStatInit;
  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
  return wsdStat.nowValue[op];
}

/*
** Add N to the value of a status record.  It is assumed that the
** caller holds appropriate locks.
*/
void sqlite3StatusAdd(int op, int N){
  wsdStatInit;
  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
  wsdStat.nowValue[op] += N;
  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
    wsdStat.mxValue[op] = wsdStat.nowValue[op];
  }
}

/*
** Set the value of a status to X.
*/
void sqlite3StatusSet(int op, int X){
  wsdStatInit;
  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
  wsdStat.nowValue[op] = X;
  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
    wsdStat.mxValue[op] = wsdStat.nowValue[op];
  }
}

/*
** Query status information.
**
** This implementation assumes that reading or writing an aligned
** 32-bit integer is an atomic operation.  If that assumption is not true,
** then this routine is not threadsafe.
*/
int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag){
  wsdStatInit;
  if( op<0 || op>=ArraySize(wsdStat.nowValue) ){
    return SQLITE_MISUSE_BKPT;
  }
  *pCurrent = wsdStat.nowValue[op];
  *pHighwater = wsdStat.mxValue[op];
  if( resetFlag ){
    wsdStat.mxValue[op] = wsdStat.nowValue[op];
  }
  return SQLITE_OK;
}

/*
** Query status information for a single database connection
*/
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 */
){
  switch( op ){
    case SQLITE_DBSTATUS_LOOKASIDE_USED: {
      *pCurrent = db->lookaside.nOut;
      *pHighwater = db->lookaside.mxOut;
      if( resetFlag ){
        db->lookaside.mxOut = db->lookaside.nOut;
      }
      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;
      for(i=0; i<db->nDb; i++){
        Btree *pBt = db->aDb[i].pBt;
        if( pBt ){
          Pager *pPager = sqlite3BtreePager(pBt);
          totalUsed += sqlite3PagerMemUsed(pPager);
        }
      }
      *pCurrent = totalUsed;
      *pHighwater = 0;
      break;
    }
    default: {
      return SQLITE_ERROR;
    }
  }
  return SQLITE_OK;
}