public Tuple next() throws NoSuchElementException, TransactionAbortedException, DbException {
// some code goes here
if (i == null) {
throw new NoSuchElementException("iterator is closed");
}
if (!i.hasNext()) {
throw new NoSuchElementException("end of seq scan");
}
return i.next();
}
/**
* 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();
}
}
public boolean hasNext() throws TransactionAbortedException, DbException {
// some code goes here
if (fileIt == null) {
return false;
}
return fileIt.hasNext();
}
public void close() {
// some code goes here
if (i != null) {
i.close();
i_pos = i;
i = null;
}
}
public void open() throws DbException, TransactionAbortedException {
// some code goes here
if (i_pos != null) {
i = i_pos;
} else {
Catalog gc = Database.getCatalog();
HeapFile file = (HeapFile) gc.getDbFile(tableid);
i = file.iterator(tid);
}
i.open();
}
public Tuple next() throws NoSuchElementException, TransactionAbortedException, DbException {
// some code goes here
if (fileIt == null) {
throw new NoSuchElementException("No Such Element");
}
Tuple temp = fileIt.next();
if (temp == null) {
throw new NoSuchElementException("No Next Element");
} else {
return temp;
}
}
@Test
public void testIteratorClose() throws Exception {
// make more than 1 page. Previous closed iterator would start fetching
// from page 1.
HeapFile twoPageFile = SystemTestUtil.createRandomHeapFile(2, 520, null, null);
DbFileIterator it = twoPageFile.iterator(tid);
it.open();
assertTrue(it.hasNext());
it.close();
try {
it.next();
fail("expected exception");
} catch (NoSuchElementException e) {
}
// close twice is harmless
it.close();
}
@Test
public void testIteratorBasic() throws Exception {
HeapFile smallFile = SystemTestUtil.createRandomHeapFile(2, 3, null, null);
DbFileIterator it = smallFile.iterator(tid);
// Not open yet
assertFalse(it.hasNext());
try {
it.next();
fail("expected exception");
} catch (NoSuchElementException e) {
}
it.open();
int count = 0;
while (it.hasNext()) {
System.out.println(count);
assertNotNull(it.next());
count += 1;
}
assertEquals(3, count);
it.close();
}
public void rewind() throws DbException, NoSuchElementException, TransactionAbortedException {
dbiter.rewind();
}
public void close() {
dbiter.close();
}
public Tuple next() throws NoSuchElementException, TransactionAbortedException, DbException {
return dbiter.next();
}
public boolean hasNext() throws TransactionAbortedException, DbException {
return dbiter.hasNext();
}
public void open() throws DbException, TransactionAbortedException {
dbiter.open();
}
public void rewind() throws DbException, NoSuchElementException, TransactionAbortedException {
// some code goes here
fileIt.close();
fileIt.open();
}
public void rewind() throws DbException, NoSuchElementException, TransactionAbortedException {
// some code goes here
i.rewind();
i_pos = null;
}
public void open() throws DbException, TransactionAbortedException {
// some code goes here
fileIt = Database.getCatalog().getDbFile(tableid).iterator(tid);
fileIt.open();
}
public static void main(String args[])
throws DbException, TransactionAbortedException, IOException {
// convert a file
if (args[0].equals("convert")) {
try {
if (args.length == 3) {
HeapFileEncoder.convert(
new File(args[1]),
new File(args[1].replaceAll(".txt", ".dat")),
BufferPool.PAGE_SIZE,
Integer.parseInt(args[2]));
} else if (args.length == 4) {
ArrayList<Type> ts = new ArrayList<Type>();
String[] typeStringAr = args[3].split(",");
for (String s : typeStringAr) {
if (s.toLowerCase().equals("int")) ts.add(Type.INT_TYPE);
else if (s.toLowerCase().equals("string")) ts.add(Type.STRING_TYPE);
else {
System.out.println("Unknown type " + s);
return;
}
}
HeapFileEncoder.convert(
new File(args[1]),
new File(args[1].replaceAll(".txt", ".dat")),
BufferPool.PAGE_SIZE,
Integer.parseInt(args[2]),
ts.toArray(new Type[0]));
} else {
System.out.println("Unexpected number of arguments to convert ");
}
} catch (IOException e) {
throw new RuntimeException(e);
}
} else if (args[0].equals("print")) {
File tableFile = new File(args[1]);
int columns = Integer.parseInt(args[2]);
DbFile table = Utility.openHeapFile(columns, tableFile);
TransactionId tid = new TransactionId();
DbFileIterator it = table.iterator(tid);
if (null == it) {
System.out.println(
"Error: method HeapFile.iterator(TransactionId tid) not yet implemented!");
} else {
it.open();
while (it.hasNext()) {
Tuple t = it.next();
System.out.println(t);
}
it.close();
}
} else if (args[0].equals("parser")) {
// Strip the first argument and call the parser
String[] newargs = new String[args.length - 1];
for (int i = 1; i < args.length; ++i) {
newargs[i - 1] = args[i];
}
try {
// dynamically load Parser -- if it doesn't exist, print error message
Class<?> c = Class.forName("simpledb.Parser");
Class<?> s = String[].class;
java.lang.reflect.Method m = c.getMethod("main", s);
m.invoke(null, (java.lang.Object) newargs);
} catch (ClassNotFoundException cne) {
System.out.println(
"Class Parser not found -- perhaps you are trying to run the parser as a part of lab1?");
} catch (Exception e) {
System.out.println("Error in parser.");
e.printStackTrace();
}
} else {
System.err.println("Unknown command: " + args[0]);
System.exit(1);
}
}
public boolean hasNext() throws TransactionAbortedException, DbException {
// some code goes here
return i != null && i.hasNext();
}