Query optimization with EXPLAIN in Supabase - Mini Project: Build & Apply

Query optimization with EXPLAIN

📖 Scenario: You are working with a Supabase database that stores information about books and their authors. You want to understand how your SQL queries run so you can make them faster and more efficient.

🎯 Goal: Learn how to use the EXPLAIN command in Supabase to see how your queries are executed and identify ways to optimize them.

📋 What You'll Learn

Create a simple SQL SELECT query on the books table

Add an EXPLAIN command to analyze the query

Interpret the EXPLAIN output to find the query plan

Modify the query or database structure based on EXPLAIN insights

💡 Why This Matters

🌍 Real World

Database administrators and developers use EXPLAIN to understand how queries run and find ways to make them faster.

💼 Career

Knowing how to optimize queries with EXPLAIN is a key skill for backend developers, data engineers, and cloud database specialists.

1

Write a basic SELECT query

Write a SQL query called query that selects all columns from the books table.

Supabase

-- Write the SQL query to select all columns from books
-- Your code here

Hint

Use SELECT * FROM books; to get all data from the books table.

2

Add EXPLAIN to the query

Create a new variable called explain_query that adds the EXPLAIN keyword before the query variable to analyze it.

Supabase

query = "SELECT * FROM books;"
-- Add EXPLAIN before the query
-- Your code here

Hint

Use string concatenation to add EXPLAIN before the query string.

3

Run the EXPLAIN query

Write a function called run_explain that takes a SQL string sql and returns the result of running it on the Supabase database client supabase using supabase.rpc('sql', { query: sql }).

Supabase

query = "SELECT * FROM books;"
explain_query = "EXPLAIN " + query

# Write a function to run the EXPLAIN query
# Your code here

Hint

Define a function with def run_explain(sql): and return the result of supabase.rpc('sql', { 'query': sql }).

4

Interpret and optimize the query

Add a comment explaining that you will check the EXPLAIN output to find slow parts and then add an index on the author_id column of the books table using CREATE INDEX idx_author_id ON books(author_id); to speed up queries filtering by author.

Supabase

query = "SELECT * FROM books;"
explain_query = "EXPLAIN " + query

def run_explain(sql):
    return supabase.rpc('sql', { 'query': sql })

# Add a comment about checking EXPLAIN output and creating an index
# Your code here

Hint

Write a comment about using EXPLAIN output and add the exact SQL command to create the index.