What are the main advantages and disadvantages of using a hash index for data search?

Hash index is a data structure that uses a hash function for fast record lookup by key.

Advantages:

• Very fast search by exact key value (search, insert, and delete operations are usually performed in O(1)).
• Efficient for equality searches (e.g., WHERE key = value).

Disadvantages:

• Does not support range searches (e.g., WHERE key > value).
• Hash indexes may consume more memory due to the need to store the hash table.
• Collisions are possible, requiring additional handling.

Example of usage in Python with a dictionary:

# Dictionary uses a hash index for quick access
data = {'apple': 1, 'banana': 2, 'cherry': 3}
print(data['banana'])  # Fast access by key

Thus, hash indexes are great for quick exact key searches but not suitable for range queries or sorting.