update.c

linux 下用c++ 开发的一个小型数据库系统

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


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

const Status QU_Update(const string & relation,
                       const int attrCnt,
                       const attrInfo attrList[],
                       const string & attrName,
                       const Operator op,
                       const Datatype type,
                       const char *attrValue)

{
    Record		rec ;
    int			intval ;
    float		flval ;
    HeapFileScan	*hfs ;
    AttrDesc		ads ;
    RelDesc		rds ;
    string		astr ;
    int			n, i, len, recNum ;
    char 		*mydata ;
    AttrDesc		*attrs ;
    int			myattrCnt ;
    Status		status ;
    RID			rid ;

    if (relation.empty()) return BADCATPARM;

    status = relCat->getInfo( relation.c_str(), rds) ;
    if (status != OK) return status ;

    astr.append("begin") ;
    for( i = 0; i < attrCnt; i++){
      astr.erase(1) ;
      n = strlen(attrList[i].attrName) ;
      astr.replace( 0, n, attrList[i].attrName) ;
      if((status = attrCat->getInfo( relation, astr, ads)) != OK)
        return status ;
    }
   
    status = attrCat->getRelInfo( relation, myattrCnt, attrs) ;    
    if (status != OK) return status ;
 
    if ((status = attrCat->getInfo( relation, attrName, ads)) != OK){
      delete [] attrs ; 
      return status ;
    }

    len = 0 ;
    for (i = 0; i < myattrCnt; i++)
       len = len + attrs[i].attrLen ;
    
    mydata = new char[len] ;
    
    hfs = new HeapFileScan( relation, status) ;
    if (status != OK){
      delete [] attrs ;
      delete [] mydata ;
      return status ;
    }

    if (type == INTEGER){
      intval = atoi(attrValue) ;
      hfs->startScan( ads.attrOffset, ads.attrLen,
                     (Datatype)ads.attrType, (char *)&intval, op) ;
    }

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

    if (type == STRING){
       hfs->startScan( ads.attrOffset, ads.attrLen,
                       (Datatype)ads.attrType, attrValue, op) ;
    }
    
    int intval1, flval1 ;

    recNum = 0 ;
    while(hfs->scanNext(rid) != FILEEOF){
      for (i = 0; i < len; i++) mydata[i] = 0 ;
      hfs->getRecord(rec) ;

      memcpy( mydata, rec.data, rec.length) ;
      for (i = 0; i < myattrCnt; i++){
         for (n = 0; n < attrCnt; n++){
          if (strcmp(attrs[i].attrName, attrList[n].attrName) == 0){
             if (attrs[i].attrType == INTEGER){
               intval1 = atoi((char *)attrList[n].attrValue) ;
               memcpy( mydata + attrs[i].attrOffset, &intval1,
                        attrs[i].attrLen) ;
             }
             if (attrs[i].attrType == FLOAT){
               flval1 = (float)atof((char *)attrList[n].attrValue) ;
               memcpy( mydata + attrs[i].attrOffset, &flval1,
                       attrs[i].attrLen) ;
            }
             if (attrs[i].attrType == STRING)
               memcpy( mydata + attrs[i].attrOffset, attrList[n].attrValue,
                       attrs[i].attrLen) ;
          }
        }
      }      

      rec.data = mydata ;
      rec.length = len ;
      hfs->updateRecord(rec) ;
      recNum++ ;
    }
    
    delete hfs ;
    delete [] mydata ;
    delete [] attrs ;

    printf("\n  Table (%s)  %d Record (s) Updateed!\n", relation.c_str(), recNum) ;

    return OK;
}