DB Indexes

Q. What's DB indexes ?
A. basically used to sort data in a table.
There are basically 2 types of DB indexes:- Clustered and non-clusterd

Q. What's Mean By Cluster?
A. Oracle cluster supply an optional way of storing table data. In a cluster a group of tables share the same data blocks. The tables are grouped together because they share identical columns and are often used together. For example, the employee and department table use the depth no column. When you cluster the employee and department tables Oracle Database physically stores all rows for each department from both the employee and department tables in the same data blocks.
A cluster is used in database so that to keep all the rows of all data tables together and they can easily be accessed by the help of shared cluster key.

Because clusters store relevant rows of dissimilar tables together in the one data blocks, correctly used clusters offer two primary benefits:
■ Disk I/O is condensed and access time improves for joins of clustered tables.
■ The cluster key is the column, or collection of columns, that the clustered tables have
in same. You identify the columns of the cluster key when creating the cluster.
You next specify the same columns when creating every table added to the cluster. Each cluster key value is saved only single time each in the cluster and the cluster index, no concern how many rows of different tables hold the value.

Q. What's Cluster and Non-Cluster Indexes ?

A clustered Index sort the data in a table physically.
A non-clustered Index doesn't sort the data physically.

As clustered Index sort the data physically, So there can be only one Clustered index per table.
where as there can be many non-clustered index in table.
(with a maximum of 255 such indexes per table a very authentic possibility. i.e. every single column can be utilize for non-cluster indexing )

Q. when you can use a clustered or a non clustered index????
A. The clustered is a safe bet if you are working with a table having a large number of unique data, such as a table containing the employee IDs for the different members of an organization. These IDs are always unique, and using a clustered index is a good way of retrieving this large volume of unique data rapidly. On the other hand, a non clustered index is the best approach if you have a table that does not contain too many such unique values. These are just some of the differences between the two. You can read in detail about these differences by putting a search on the Internet for the differences between the two.

- - - - - -- - - - -- - - -

BST to Doubly Link List

To solve this problem, First we will analyze the different Cases :-
  Case 1: Leaf Node - left & right child is Null
  Case 2: No Left Subtree   - left Child is Null
  Case 2: No Right Subtree  - right Child is Null
  Case 2: No Left Subtree   - left Child is Null

Java 'ArrayList' Pseudocode ....

protected int modCount = 0;

ArrayList(int initialSize)

        IF  initialSize<0  THEN
                       Throw exception "Invalid Size"
       else
             arrayElement= new Object[initialSize];
        

ArrayList() 

  Call ArrayList(defaultSize); // default-size is 10

ArrayList(Collection<? extends E> C)
     arrayElement = C.toArray();
     size = arrayElement.length;
     IF arrayElement.getClass() != Object[].class THEN
                 arrayElement = Arrays.copyOf(arrayElement, size, Object[].class);

ensureCapacity(int newCapacity) 

   modCount++
   oldCapacity  = arrayElement.length;
    IF newCapacity > oldCapacity THEN
         Object[] oldData = arrayElement;
         newCap = (oldCap *3)/2 +1;
         IF newCap < newCapacity THEN
                   newCap=newCapacity;

         ENDIF
    END IF
  arrayElement =Arrays.copyOf(arrayElement, newCap); // My own implementation is at the end.

add(E data)
    ensureCapacity(size + 1);  // Increments modCount!!
    elementData[size++] = data;


add(int index, E element)
 IF index > size OR  index < 0 THEN
        throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);
 ENDIF
 ensureCapacity(size+1);  // Increments modCount!!
 System.arraycopy(elementData, index, elementData, index + 1, size - index); //shifting the right hand side elements by 1.
 elementData[index] = element;
 size++;

RangeCheck(int index)
   IF index >= size THEN
        throw new IndexOutOfBoundsException( "Index: "+index+", Size: "+size);

 remove(int index)

  RangeCheck(index)
  modCount++;   // modification count
  Object oldVal = elementData.get(index);
  int numMoved = size - index - 1;

addAll(Collection<? extends E> c)

Object[] a = c.toArray();
length = a.length;
ensureCapacity(size + numNew);
System.arraycopy(a, 0, elementData, size, numNew);
 size = size + numNew;
return numNew != 0;




  ........... to be continued (will add other details later)