update_index.cpp

来自「小型数据库源代码较多」· C++ 代码 · 共 114 行

#include "min.h"

void sql::update_index( Table* table)
{
	try
	{
		
		int number = table->num;
		Col* col;
		col = table->collist;
		int cth = -1;

		while ( col->next )
		{
			col = col->next;
			cth ++;
/*--------------ch-----------*/
			for ( int mm=0; mm<subsbf; mm++ )
				subbuf[mm] = '\0';
/*--------------ch-----------*/
			if ( col->indexname != "" ) 
			{
				istrstream inb( buf[page], sbf );
				fileload = table->name+ "_" + col->indexname + ".idx";
				inb.ignore(1000,'\n');
				int thn;
				int head = 0 ;
				ostrstream out( subbuf,subsbf );
				if ( col->type=='#' ) //属性为int
				{
					int idx = 0;
					int num=number;
					while (num-- )
					{
						for ( ; head<=strlen(buf[page]) ; head++)
						if( buf[page][head]=='\n' )
							break;
						head++;
						for ( thn=cth; thn; thn-- )
							inb.ignore(1000,'\t' );
						string c_idx;
						inb >> c_idx;
						while ( c_idx.at(0)=='*' )
						{
							inb.ignore(1000,'\n');
							for ( thn=cth; thn; thn-- )
								inb.ignore(1000,'\t' );
							inb >> c_idx;
						}
						for ( int p=0; p<c_idx.size(); p++ )
							idx = idx*10 + c_idx.at(p) - '0';

						out << idx << ' ' << head << '\t';
						idx = 0;
						inb.ignore(1000,'\n');
					}		
				}
				else//属性为char；
				{
					char ind[256];
					int num=number;
					while ( num-- )
					{			
						for ( ; head <= strlen(buf[page]) ; head++)
							if( buf[page][head]=='\n' )
								break;
						head++;
						for ( thn=cth; thn; thn-- )
							inb.ignore(1000,'\t' ); 	
						inb >> ind;
						while ( ind[0]=='*' )
						{
							inb.ignore(1000,'\n');
							for ( thn=cth; thn; thn-- )
								inb.ignore(1000,'\t' );
/*---------ch---------*/		inb >> ind;
						}
						out << ind << ' ' << head << '\t';
						for ( int k=0; k<256; k++ )
							ind[k] = '\0';
						inb.ignore(1000,'\n');					
					}			
				}     	
				out << '\0';
				ofstream file;
				file.open( fileload.c_str(),ios::trunc);
				if( !file )
					throw 5;
				file.write(subbuf, strlen(subbuf));	
				file.close();
			}
		}
	}

	catch( int i )
	{
		switch (i)
		{
			
			case 5: cout << "无法更新索引文件" << endl;
					break;
		}

	}
	catch( bool ex )
	{
		if(ex)
			cout << "索引已存在" << endl;
		else
			cout << "表名不存在！" << endl;
	}

}