destroy.c

linux 下用c++ 开发的一个小型数据库系统

#include "catalog.h"


//
// Destroys a relation. It performs the following steps:
//
// 	removes the catalog entry for the relation
// 	destroys the heap file containing the tuples in the relation
//
// Returns:
// 	OK on success
// 	error code otherwise
//

const Status RelCatalog::destroyRel(const string & relation)
{
  Status status;

  if (relation.empty() || 
      relation == string(RELCATNAME) || 
      relation == string(ATTRCATNAME))
    return BADCATPARM;
  
  if ((status = attrCat->dropRelation(relation)) != OK) return status ;
    
  if ((status = removeInfo(relation)) != OK) return status ;
  
  db.destroyFile(relation) ;
  
  if (strcmp(relation.c_str(), "Tmp_Ubase_Result") != 0)  
    printf("  Table  %s   Destroy!\n", relation.c_str()) ;
  return OK ; 
}


//
// Drops a relation. It performs the following steps:
//
// 	removes the catalog entries for the relation
//
// Returns:
// 	OK on success
// 	error code otherwise
//

const Status AttrCatalog::dropRelation(const string & relation)
{
  Status status;
  AttrDesc *attrs;
  int attrCnt, i;

  if (relation.empty())
    return BADCATPARM;

  if ((status = getRelInfo( relation, attrCnt, attrs)) != OK) return status ;

  for (i = 0; i < attrCnt; i++)
    if ((status = removeInfo(relation, attrs[i].attrName)) != OK) return status ;

  delete [] attrs ;

  return OK ;
}