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Copy pathTupleDesc.java
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320 lines (248 loc) · 8.51 KB
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package simpledb;
import java.io.Serializable;
import java.util.*;
/**
* TupleDesc describes the schema of a tuple.
*/
public class TupleDesc implements Serializable {
private TDItem[] schema;
/**
* A help class to facilitate organizing the information of each field
* */
public static class TDItem implements Serializable {
private static final long serialVersionUID = 1L;
/**
* The type of the field
* */
public final Type fieldType;
/**
* The name of the field
* */
public final String fieldName;
public TDItem(Type t, String n) {
this.fieldName = n;
this.fieldType = t;
}
public String toString() {
return fieldName + "(" + fieldType + ")";
}
public boolean equals(Object o){
if(o instanceof TDItem)
{
TDItem item = (TDItem) o;
boolean field_types_eq = item.fieldType.equals(this.fieldType);
/*boolean field_names_eq = false;
if(item.fieldName != null && fieldName !=null)
field_names_eq = item.fieldName.equals(this.fieldName);
else if(item.fieldName == null && fieldName ==null)
field_names_eq = true;
if (field_names_eq && field_types_eq) return true;*/
return field_types_eq;
}
return false;
}
}
/**
* @return
* An iterator which iterates over all the field TDItems
* that are included in this TupleDesc
* */
public Iterator<TDItem> iterator() {
List<TDItem> td_list = Arrays.asList(schema);
return td_list.iterator();
}
private static final long serialVersionUID = 1L;
/**
* Create a new TupleDesc with typeAr.length fields with fields of the
* specified types, with associated named fields.
*
* @param typeAr
* array specifying the number of and types of fields in this
* TupleDesc. It must contain at least one entry.
* @param fieldAr
* array specifying the names of the fields. Note that names may
* be null.
*/
public TupleDesc(Type[] typeAr, String[] fieldAr) {
//System.out.println("TupleDesc()");
this.schema = new TDItem[typeAr.length];
for(int i=0; i< schema.length; i++)
{
//System.out.println("i is: "+i);
TDItem to_add = new TDItem(typeAr[i], fieldAr[i]);
schema[i] = to_add;
//System.out.println(schema[i]);
}
}
/**
* Constructor. Create a new tuple desc with typeAr.length fields with
* fields of the specified types, with anonymous (unnamed) fields.
*
* @param typeAr
* array specifying the number of and types of fields in this
* TupleDesc. It must contain at least one entry.
*/
public TupleDesc(Type[] typeAr) {
this.schema = new TDItem[typeAr.length];
for(int i = 0; i < schema.length; i++)
{
TDItem to_add = new TDItem(typeAr[i], null);
schema[i] = to_add;
}
}
/**
* @return the number of fields in this TupleDesc
*/
public int numFields() {
int output = schema.length;
return output;
}
/**
* Gets the (possibly null) field name of the ith field of this TupleDesc.
*
* @param i
* index of the field name to return. It must be a valid index.
* @return the name of the ith field
* @throws NoSuchElementException
* if i is not a valid field reference.
*/
public String getFieldName(int i) throws NoSuchElementException {
check_range(i); //throws error if out of range
TDItem my_TDItem = schema[i];
String field_name = my_TDItem.fieldName;
return field_name;
}
private int check_range(int i) throws NoSuchElementException {
if(i>=schema.length || i < 0)
{
System.out.println("Error: index: " + i + "-- out of range in schema.length: " + schema.length);
throw new NoSuchElementException();
}
return 0;
}
/**
* Gets the type of the ith field of this TupleDesc.
*
* @param i
* The index of the field to get the type of. It must be a valid
* index.
* @return the type of the ith field
* @throws NoSuchElementException
* if i is not a valid field reference.
*/
public Type getFieldType(int i) throws NoSuchElementException {
check_range(i);
TDItem my_TDItem = schema[i];
Type my_type = my_TDItem.fieldType;
//System.out.println(my_type.toString());
return my_type;
}
/**
* Find the index of the field with a given name.
*
* @param name
* name of the field.
* @return the index of the field that is first to have the given name.
* @throws NoSuchElementException
* if no field with a matching name is found.
*/
public int fieldNameToIndex(String name) throws NoSuchElementException {
for(int i = 0; i < schema.length; i++)
{
TDItem my_TDItem = schema[i];
String field_name = my_TDItem.fieldName;
if(field_name == null)
break;
if(field_name.equals(name))
return i;
}
throw new NoSuchElementException();
}
/**
* @return The size (in bytes) of tuples corresponding to this TupleDesc.
* Note that tuples from a given TupleDesc are of a fixed size.
*/
public int getSize() {
int size = 0;
for(int i = 0; i< schema.length; i++)
{
Type my_type = schema[i].fieldType;
int obj_size = my_type.getLen();
size += obj_size;
}
return size;
}
/**
* Merge two TupleDescs into one, with td1.numFields + td2.numFields fields,
* with the first td1.numFields coming from td1 and the remaining from td2.
*
* @param td1
* The TupleDesc with the first fields of the new TupleDesc
* @param td2
* The TupleDesc with the last fields of the TupleDesc
* @return the new TupleDesc
*/
public static TupleDesc merge(TupleDesc td1, TupleDesc td2) {
int new_len = td1.schema.length + td2.schema.length;
Type[] typeAr = new Type[new_len];
String[] fieldAr = new String[new_len];
for(int i=0; i< td1.schema.length; i++)
{
typeAr[i] = td1.schema[i].fieldType;
fieldAr[i] = td1.schema[i].fieldName;
}
for(int i = 0; i< td2.schema.length; i++)
{
typeAr[i+ td1.schema.length] = td2.schema[i].fieldType;
fieldAr[i+ td1.schema.length] = td2.schema[i].fieldName;
}
return new TupleDesc(typeAr, fieldAr);
}
/**
* Compares the specified object with this TupleDesc for equality. Two
* TupleDescs are considered equal if they are the same size and if the n-th
* type in this TupleDesc is equal to the n-th type in td.
*
* @param o
* the Object to be compared for equality with this TupleDesc.
* @return true if the object is equal to this TupleDesc.
*/
public boolean equals(Object o) {
if(o instanceof TupleDesc)
{
TupleDesc other = (TupleDesc) o;
if(schema.length != other.schema.length)
return false;
for(int i = 0; i < this.schema.length; i++)
{
if(! schema[i].equals(other.schema[i]))
return false;
}
return true;
}
else return false;
}
public int hashCode() {
// If you want to use TupleDesc as keys for HashMap, implement this so
// that equal objects have equals hashCode() results
throw new UnsupportedOperationException("unimplemented");
}
/**
* Returns a String describing this descriptor. It should be of the form
* "fieldType[0](fieldName[0]), ..., fieldType[M](fieldName[M])", although
* the exact format does not matter.
*
* @return String describing this descriptor.
*/
public String toString() {
String output = "";
for(int i= 0; i<schema.length; i++)
{
TDItem my_item = schema[i];
output += my_item.toString();
if(i+1 !=schema.length)
output += ", ";
}
return output;
}
}
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