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Introduction
Hey Ninjas! Do you know the actual definition of a file? A file is a collection of records stored in binary format. A file organization is a logical relationship between different records. It defines how file records are mapped onto disk blocks.
This blog will discuss a type of file organization, that is, B+ tree file organization. It is suggested to go through the Introduction to File Organization blog before diving into this blog.
The B+ tree file organization is a method to organize a file in DBMS (Database Management System). The records are sorted using the primary key to conform with the key-value pair rule. It is in a tree-like structure.
B+ tree file organization is much similar to the BST (Binary Search Tree), but it can have more than two children. The leaf nodes of the B+ tree file organization contain all the records, and the middle nodes contain only pointers to the leaf node. It doesn't carry any records.
Characteristics
Let's discuss some characteristics of B+ tree file organization.
The B+ tree file organization is used to implement multi-level indexing. Multi-level indexing helps break down the index into smaller indices to make the outermost level so small that it can be saved in a single disk block.
The data records in a B+ tree file organization are only stored in the leaf node.
The internal node holds the key value only.
Sample Example
Let's understand this using an example. Suppose we have a data record {3, 5, 8, 11, 18, 22, 29}. Now we will understand the whole process step by step. Let's start.
Step 1: In our first step, we will create a B+ tree with the first 3 data from the data record, as shown in the figure.
Step 2: Now, our task is to insert 11 in the B+ tree. As you can see in the above figure, there is no space to insert any new values. So, we have to split the internal nodes, i.e., {3, 5, 8} in this case. We will take the middle number, i.e., 5.
Note: Left-hand side of k must be less than k, and the right-hand side of k must be equal to or greater than k. In this example, the key value (k) is 5.
Step 3: Next step is to insert 18 in the B+ tree. We have to insert 18 after the value 11 in the last node. The reason is 18 is greater than 8, so it must come on the right-hand side of 8.
Step 4: Now, we have to insert 22. As 22 is greater than 8, it must come on the right-hand side of 8, but there is no space on the right-hand side of 8. So, again we have to split the internal nodes, i.e., {8, 11, 18}. We will take k = 11 in this case.
Some of you might be confused about why we are not inserting the value 22 after 8 in the root. The reason is we have to add the data records in the leaf nodes only.
Step 5: The last step is to insert 29. Again there is no space after 22 in the leaf node. So we will again follow the same process of splitting. Now, 18 will go to the upper node, but there is no space in the upper node too. Here we will first split the upper node to make the space for 18. Then we will split the leaf node.
In the end, we got all the data records, i.e., {3, 5, 8, 11, 18, 22, 29} in the leaf node, as shown in the figure.
The advantages of B+ tree file organization are as follows:
Traversing the tree is easier and faster as the distance of every leaf node is the same from the root.
B+ tree file organization is a balanced tree structure, so any insert, update or delete operation does not affect the performance of the tree.
The only nodes in a sequential linked list that contain records are the leaf nodes, making searching quite efficient.
The size of the B+ tree has no restrictions, which means it can grow or shrink dynamically according to an increase or decrease in the number of records.
Disadvantages
The disadvantages of B+ tree file organization are as follows:
The main drawback of B+ tree file organization is that it is not efficient for static tables (where the number of rows and columns are fixed and cannot be changed).
Space overhead occurs from extra insertion and deletion operations.
Sequential file organization, indexed sequential access method (ISAM), heap file organization, hash file organization, and cluster file organization are some other file organization methods.
What are retrieval operations?
The retrieval operation does not alter the data. It just retrieves them after filtering.
What is sequential file organization?
Records are placed in the file in sequential order based on the unique key field or search key is known as sequential file organization.
Can the B+ tree have duplicates?
Yes, the B+ tree can have multiple records or data in the database.
What are the applications of the B+ tree?
The massive amount of data that cannot be kept in the main memory is saved in B+ Trees.
Conclusion
This article discusses the topic of B+ tree file organization. In detail, we have seen the definition of B+ tree file organization, a sample example with a proper explanation, advantages, and disadvantages.
We hope this blog has helped you enhance your knowledge of B+ tree file organization. If you want to learn more, then check out our articles.
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