SQLite

*/
static void display_scanstats(
  sqlite3 *db,                    /* Database to query */
  ShellState *pArg                /* Pointer to ShellState */
){
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  int i;
  double *arEstLoop = 0;
  int nEstLoop = 0;
  fprintf(pArg->out, "-------- scanstats --------\n");
  for(i=0; 1; i++){
    sqlite3_stmt *p = pArg->pStmt;
    sqlite3_int64 nLoop, nVisit;
    double rEst, rLoop;
    int iSid;
    const char *zExplain;
    if( sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_NLOOP, (void*)&nLoop) ){
      break;
    }
    sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_NVISIT, (void*)&nVisit);
    sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_EST, (void*)&rEst);
    sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_EXPLAIN, (void*)&zExplain);
    sqlite3_stmt_scanstatus(p, i, SQLITE_SCANSTAT_SELECTID, (void*)&iSid);
    if( iSid>=nEstLoop ){
      arEstLoop = sqlite3_realloc(arEstLoop, sizeof(arEstLoop[0])*(iSid+1) );
      while( nEstLoop<=iSid ) arEstLoop[nEstLoop++] = 1.0; 
    }
    if( iSid>=0 ){
      arEstLoop[iSid] *= rEst;
      rLoop = arEstLoop[iSid];
    }else{
      rLoop = rEst;
    }
    fprintf(pArg->out, "Loop %2d: \"%s\"\n", i, zExplain);

    fprintf(pArg->out, "        nLoop=%-8lld nRow=%-8lld estRow=%-8lld estRow/Loop=%-8g\n",
        nLoop, nVisit, (sqlite3_int64)rLoop, rEst
    );
  }
  sqlite3_free(arEstLoop);
#else
  fprintf(pArg->out, "-------- scanstats --------\n");
  fprintf(pArg->out,
      "sqlite3_stmt_scanstatus() unavailable - "
      "rebuild with SQLITE_ENABLE_STMT_SCANSTATUS\n"
  );
#endif

** total number of rows examined by all iterations of the X-th loop.</dd>
**
** [[SQLITE_SCANSTAT_EST]] <dt>SQLITE_SCANSTAT_EST</dt>
** <dd>^The "double" variable pointed to by the T parameter will be set to the
** query planner's estimate for the average number of rows output from each
** iteration of the X-th loop.  If the query planner's estimates was accurate,
** then this value will approximate the quotient NVISIT/NLOOP and the
** product of this value for all prior loops with the same SELECTID will
** be the NLOOP value for the current loop.
**
** [[SQLITE_SCANSTAT_NAME]] <dt>SQLITE_SCANSTAT_NAME</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the name of the index or table used
** for the X-th loop.
**
** [[SQLITE_SCANSTAT_EXPLAIN]] <dt>SQLITE_SCANSTAT_EXPLAIN</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN] description
** for the X-th loop.
**
** [[SQLITE_SCANSTAT_SELECTID]] <dt>SQLITE_SCANSTAT_SELECT</dt>
** <dd>^The "int" variable pointed to by the T parameter will be set to the
** "select-id" for the X-th loop.  The select-id identifies which query or
** subquery the loop is part of.  The main query has a select-id of zero.
** The select-id is the same value as is output in the first column
** of an [EXPLAIN QUERY PLAN] query.
** </dl>
*/
#define SQLITE_SCANSTAT_NLOOP    0
#define SQLITE_SCANSTAT_NVISIT   1
#define SQLITE_SCANSTAT_EST      2
#define SQLITE_SCANSTAT_NAME     3
#define SQLITE_SCANSTAT_EXPLAIN  4
#define SQLITE_SCANSTAT_SELECTID 5

/*
** CAPI3REF: Prepared Statement Scan Status
**
** Return status data for a single loop within query pStmt.
**
** The "iScanStatusOp" parameter determines which status information to return.

typedef unsigned bft;  /* Bit Field Type */

typedef struct ScanStatus ScanStatus;
struct ScanStatus {
  int addrExplain;                /* OP_Explain for loop */
  int addrLoop;                   /* Address of "loops" counter */
  int addrVisit;                  /* Address of "rows visited" counter */
  int iSelectID;                  /* The "Select-ID" for this loop */
  LogEst nEst;                    /* Estimated output rows per loop */
  char *zName;                    /* Name of table or index */
};

/*
** An instance of the virtual machine.  This structure contains the complete
** state of the virtual machine.

    case SQLITE_SCANSTAT_EXPLAIN: {
      if( pScan->addrExplain ){
        *(const char**)pOut = p->aOp[ pScan->addrExplain ].p4.z;
      }else{
        *(const char**)pOut = 0;
      }
      break;
    }
    case SQLITE_SCANSTAT_SELECTID: {
      if( pScan->addrExplain ){
        *(int*)pOut = p->aOp[ pScan->addrExplain ].p1;
      }else{
        *(int*)pOut = -1;
      }
      break;
    }
    default: {
      return 1;
    }
  }
  return 0;
}