delete.c

来自「linux 下用c++ 开发的一个小型数据库系统」· C语言 代码 · 共 78 行

#include "catalog.h"
#include "query.h"


/*
 * Deletes records from a specified relation.
 *
 * Returns:
 * 	OK on success
 * 	an error code otherwise
 */

const Status QU_Delete(const string & relation, 
		       const string & attrName, 
		       const Operator op,
		       const Datatype type, 
		       const char *attrValue)
{
// part 5
  HeapFileScan  *hfs ;
  Status	status ;
  RID		recrid ;
  int		recNum = 0 ;
  AttrDesc	record ;
  int		intval ;
  float		flval ;

  hfs = new HeapFileScan( relation, status) ;
  if (status != OK) return status ;
  
  if (attrName.empty()){
    hfs->startScan( 0, 0, STRING, NULL, EQ) ;
    while(hfs->scanNext(recrid) != FILEEOF){
      hfs->deleteRecord() ;
      recNum++ ;
    }    
    printf("\n Table (%s)  %d  record (s) deleteed!\n", relation.c_str(), recNum) ;
    delete hfs ;
    return OK ;
  }
  
  status = attrCat->getInfo( relation, attrName, record) ;
  if (status != OK){
    delete hfs ;
    return status ;
  }
  
  if (record.attrType == INTEGER){
    intval = atoi(attrValue) ;  
    hfs->startScan( record.attrOffset, record.attrLen,
                    (Datatype)record.attrType,
                    (char *)&intval, op) ;
  }

  if (record.attrType == FLOAT){
    flval =(float)atof(attrValue) ;
    hfs->startScan( record.attrOffset, record.attrLen,
                    (Datatype)record.attrType,
                    (char *)&flval, op) ;
  }

  if (record.attrType == STRING){
     hfs->startScan( record.attrOffset, record.attrLen,
                     (Datatype)record.attrType,
                     attrValue, op) ;
  }

  while (hfs->scanNext(recrid) != FILEEOF){
    hfs->deleteRecord() ;
    recNum++ ;
  }
  printf("\n Table (%s)  %d  record (s) deleteed!\n", relation.c_str(), recNum) ;
  delete hfs ;
  return OK;
}