LSM trees in write-heavy systems in Data Structures Theory - Mini Project: Build & Apply

Understanding LSM Trees in Write-Heavy Systems

📖 Scenario: You are working with a database system that needs to handle many writes quickly. To do this, it uses a data structure called a Log-Structured Merge-tree (LSM tree). This helps the system write data fast and organize it efficiently later.

🎯 Goal: Build a simple step-by-step model of how an LSM tree works in a write-heavy system. You will create the initial data storage, set up a threshold for when to organize data, apply the logic to move data from fast storage to slower storage, and complete the process by confirming the data is organized.

📋 What You'll Learn

Create an in-memory dictionary called memtable to hold new writes.

Set a threshold variable called flush_threshold to control when to move data.

Write code to check if memtable size reaches flush_threshold and then move data to a list called sstable.

Add a final step to clear memtable after moving data to sstable.

💡 Why This Matters

🌍 Real World

LSM trees are used in databases and storage systems that handle many writes quickly, like Cassandra, LevelDB, and RocksDB.

💼 Career

Understanding LSM trees helps in roles involving database design, performance tuning, and big data storage solutions.

1

Create the initial in-memory storage

Create a dictionary called memtable that will hold key-value pairs representing new data writes. Initialize it as empty.

Data Structures Theory

# Create an empty dictionary called memtable
# Your code here

Need a hint?

Use curly braces {} to create an empty dictionary in Python.

2

Set the flush threshold

Create a variable called flush_threshold and set it to 3. This number will decide when to move data from memtable to disk storage.

Data Structures Theory

memtable = {}
# Set flush_threshold to 3
# Your code here

Need a hint?

Just assign the number 3 to the variable flush_threshold.

3

Move data from memtable to sstable when threshold is reached

Create a list called sstable to store flushed data. Then write an if statement that checks if the number of items in memtable is equal to or greater than flush_threshold. If yes, append a copy of memtable to sstable.

Data Structures Theory

memtable = {}
flush_threshold = 3
# Create sstable list and add code to flush memtable when threshold is reached
# Your code here

Need a hint?

Use len(memtable) to get the number of items. Use memtable.copy() to add a snapshot to sstable.

4

Clear memtable after flushing data

After moving data to sstable, clear all items from memtable using the clear() method to prepare for new writes.

Data Structures Theory

memtable = {}
flush_threshold = 3
sstable = []
if len(memtable) >= flush_threshold:
    sstable.append(memtable.copy())
# Clear memtable here
# Your code here

Need a hint?

Use memtable.clear() to remove all entries from the dictionary.