ubase.c

linux 下用c++ 开发的一个小型数据库系统

#include <stdio.h>
#include <unistd.h>
#include "catalog.h"
#include "query.h"


DB db;
Error error;

BufMgr *bufMgr;
RelCatalog *relCat;
AttrCatalog *attrCat;

JoinType JoinMethod;

int main(int argc, char **argv)
{
  if (argc < 2) {
    cerr << "Usage: " << argv[0] << " dbname" << endl;
    return 1;
  }

  if (chdir(argv[1]) < 0) {
    perror("chdir");
    exit(1);
  }

  JoinMethod = NLJoin;  // default join method
  if (argc == 3) // alternative join method specified
  {
       if (strcmp (argv[2],"SM") == 0) JoinMethod = SMJoin;
       else if (strcmp (argv[2],"HJ") == 0) JoinMethod = HashJoin;
  }

  // create buffer manager
  
  bufMgr = new BufMgr(100);
  
  // open relation and attribute catalogs

  Status status;
  relCat = new RelCatalog(status);
  if (status == OK)
    attrCat = new AttrCatalog(status);
  if (status != OK) {
    error.print(status);
    exit(1);
  }

  cout << "Welcome to Ubase" << endl;
  cout << "    Using ";
  if (JoinMethod == NLJoin) {cout << "Nested Loops Join Method" << endl;}
  else 
  if (JoinMethod == HashJoin) {cout << "Hash Join Method" << endl;}
  else {cout << "Sort Merge Join Method" << endl;}

  extern void parse();
  parse();

  return 0;
}