/**
* Inserts tuples read from child into the tableid specified by the constructor. It returns a one
* field tuple containing the number of inserted records. Inserts should be passed through
* BufferPool. An instances of BufferPool is available via Database.getBufferPool(). Note that
* insert DOES NOT need check to see if a particular tuple is a duplicate before inserting it.
*
* @return A 1-field tuple containing the number of inserted records, or null if called more than
* once.
* @see Database#getBufferPool
* @see BufferPool#insertTuple
*/
protected Tuple fetchNext() throws TransactionAbortedException, DbException {
Tuple result = new Tuple(td); // use to store the insertion result
int count = 0; // use to keep track of numbers of tuple insertion
if (fetchNextNum
> 0) // meaning this is not the first time calling fetchNext(), and should not return any
// tuples
return null;
else {
try {
while (dbIt.hasNext()) {
try {
Database.getBufferPool().insertTuple(tranId, tableId, dbIt.next());
} catch (IOException e) {
e.printStackTrace();
}
count++;
}
result.setField(0, new IntField(count));
fetchNextNum++;
} catch (DbException e) {
e.printStackTrace();
} catch (TransactionAbortedException e) {
e.printStackTrace();
}
}
return result;
}
public static void main(String[] args) {
DbClient client = null;
try {
client = new DbClient();
client.connect();
// client.runUpdate("INSERT INTO DrWeb VALUES(0,null,null,'boogle','worp')");
// ResultSet rs =
// client.runQuery("SELECT LASTNAME FROM DrWeb WHERE FIRSTNAME='worp'"
// );
ResultSet rs = client.runQuery("SELECT LASTNAME FROM DrWeb");
while (rs.next()) {
System.out.println("lastname=" + rs.getString(1));
}
} catch (SQLException e) {
e.printStackTrace();
} catch (DbException e) {
e.printStackTrace();
} finally {
if ((client != null) && client.isConnected()) {
try {
client.disconnect();
} catch (DbException e) {
}
}
}
System.exit(0);
}
public void rewind() throws DbException, TransactionAbortedException {
try {
dbIt.rewind();
} catch (DbException e) {
e.printStackTrace();
} catch (TransactionAbortedException e) {
e.printStackTrace();
}
}
public void open() throws DbException, TransactionAbortedException {
try {
super.open();
dbIt.open();
} catch (DbException e) {
e.printStackTrace();
} catch (TransactionAbortedException e) {
e.printStackTrace();
}
}
// see DbFile.java for javadocs
public DbFileIterator iterator(TransactionId tid) {
try {
return new HeapFileIterator(tid, this);
} catch (DbException dbe) {
dbe.printStackTrace();
} catch (TransactionAbortedException transe) {
transe.printStackTrace();
} catch (NoSuchElementException nosuche) {
nosuche.printStackTrace();
}
return null;
}
/**
* Create a new TableStats object, that keeps track of statistics on each column of a table
*
* @param tableid The table over which to compute statistics
* @param ioCostPerPage The cost per page of IO. This doesn't differentiate between
* sequential-scan IO and disk seeks.
*/
public TableStats(int tableid, int ioCostPerPage) {
// For this function, we use the DbFile for the table in question,
// then scan through its tuples and calculate the values that you
// to build the histograms.
// TODO: Fill out the rest of the constructor.
// Feel free to change anything already written, it's only a guideline
this.ioCostPerPage = ioCostPerPage;
DbFile file = Database.getCatalog().getDbFile(tableid);
tupleDesc = file.getTupleDesc();
numPages = ((HeapFile) file).numPages();
numTuples = 0;
int numFields = tupleDesc.numFields();
// TODO: what goes here?
statistics = new ArrayList<Object>();
for (int i = 0; i < numFields; i++) {
if (Type.INT_TYPE.equals(tupleDesc.getFieldType(i))) {
statistics.add(new IntStatistics(NUM_HIST_BINS));
} else {
statistics.add(new StringHistogram(NUM_HIST_BINS));
}
}
final DbFileIterator iter = file.iterator(null);
try {
iter.open();
while (iter.hasNext()) {
Tuple t = iter.next();
numTuples++;
// TODO: and here?
for (int i = 0; i < numFields; i++) {
if (Type.INT_TYPE.equals(tupleDesc.getFieldType(i))) {
((IntStatistics) statistics.get(i)).addValue(((IntField) t.getField(i)).getValue());
} else {
((StringHistogram) statistics.get(i))
.addValue(((StringField) t.getField(i)).getValue());
}
}
}
iter.close();
} catch (DbException e) {
e.printStackTrace();
} catch (TransactionAbortedException e) {
e.printStackTrace();
}
}