public void createTable(string tblname, Schema sch, Transaction tx)
{//创建一个新表，有指定的表名称、模式信息
TableInfo ti = new TableInfo(tblname, sch);
//往tblcat表中插入一条记录
RecordFile tcatfile = new RecordFile(tcatInfo, tx);
tcatfile.insert();
tcatfile.setString("tblname", tblname);
tcatfile.setInt("reclength", ti.recordLength());
tcatfile.close();
//往fldcat表中插入记录：每个字段的信息
RecordFile fcatfile = new RecordFile(fcatInfo, tx);
foreach (string fldname in sch.fields())
{
fcatfile.insert();
fcatfile.setString("tblname", tblname);
fcatfile.setString("fldname", fldname);
fcatfile.setInt("type", sch.type(fldname));
fcatfile.setInt("length", sch.length(fldname));
fcatfile.setInt("offset", ti.offset(fldname));
}
fcatfile.close();
}
public TableInfo getTableInfo(string tblname, Transaction tx)
{
RecordFile tcatfile = new RecordFile(tcatInfo, tx);
int reclen = -1;
while (tcatfile.next())
{
if (tcatfile.getString("tblname").Equals(tblname))
{//获取到指定表名称的一条记录长度
reclen = tcatfile.getInt("reclength");
break;
}
}
tcatfile.close();
RecordFile fcatfile = new RecordFile(fcatInfo, tx);
Schema sch = new Schema();
Dictionary <string, int> offsets = new Dictionary <string, int>();
while (fcatfile.next())
{//每次取fcatfile中的一条记录
if (fcatfile.getString("tblname").Equals(tblname))
{
string fldname = fcatfile.getString("fldname");
int fldtype = fcatfile.getInt("type");
int fldlen = fcatfile.getInt("length");
int offset = fcatfile.getInt("offset");
offsets.Add(fldname, offset); //获取一张表中每个字段名称的偏移量
sch.addField(fldname, fldtype, fldlen); //获取一张表的模式信息
}
}
fcatfile.close();
return(new TableInfo(tblname, sch, offsets, reclen));
}
public void createIndex(string idxname, string tblname, string fldname, Transaction tx)
{//在指定表、指定字段上创造一个指定名称的索引
RecordFile rf = new RecordFile(ti, tx);
rf.insert();
rf.setString("indexname", idxname);
rf.setString("tablename", tblname);
rf.setString("fieldname", fldname);
rf.close();
}
public void createView(string vname, string vdef, Transaction tx)
{//创建视图，在内存中创建RecordFile读取类往里面写信息
TableInfo ti = tblMgr.getTableInfo("viewcat", tx);
RecordFile rf = new RecordFile(ti, tx);
rf.insert();
rf.setString("viewname", vname);
rf.setString("viewdef", vdef);
rf.close();
}
private StatInfo calcTableStats(TableInfo ti, Transaction tx)
{
lock (threadLock)
{
int numRecs = 0;
RecordFile rf = new RecordFile(ti, tx);
int numblocks = 0;
while (rf.next())
{
numRecs++;
numblocks = rf.currentRid().blockNumber() + 1;
}
rf.close();
return(new StatInfo(numblocks, numRecs));
}
}
public string getViewDef(string vname, Transaction tx)
{
string result = null;
TableInfo ti = tblMgr.getTableInfo("viewcat", tx);
RecordFile rf = new RecordFile(ti, tx);
while (rf.next())
{
if (rf.getString("viewdef").Equals(vname))
{
result = rf.getString("viewdef");
break;
}
}
rf.close();
return(result);
}
private void refreshStatistics(Transaction tx)
{
lock (threadLock)
{
tablestats = new Dictionary <string, StatInfo>();
numcalls = 0;
TableInfo tcatmd = tblMgr.getTableInfo("tblcat", tx); //获取tblcat表中的信息
RecordFile tcatfile = new RecordFile(tcatmd, tx); //利用这些信息新建一个RecordFile读取类
while (tcatfile.next())
{ //获取每一张表的字段信息，计算出块数和记录数，添加到统计信息管理器中去
string tblname = tcatfile.getString("tblname");
TableInfo md = tblMgr.getTableInfo(tblname, tx);
StatInfo si = calcTableStats(md, tx);
tablestats.Add(tblname, si);
}
tcatfile.close();
}
}
public Dictionary <string, IndexInfo> getIndexInfo(string tblname, Transaction tx)
{//返回一个映射，包含了指定表中所有索引的信息
Dictionary <string, IndexInfo> result = new Dictionary <string, IndexInfo>();
RecordFile rf = new RecordFile(ti, tx);
while (rf.next())
{
if (rf.getString("tablename").Equals(tblname))
{
string idxname = rf.getString("indexname");
string fldname = rf.getString("fieldname");
IndexInfo ii = new IndexInfo(idxname, tblname, fldname, tx);
result.Add(fldname, ii);
}
}
rf.close();
return(result);
}
public void close()
{
rf.close();
}