Result caching layers in Snowflake - Mini Project: Build & Apply

Result caching layers

📖 Scenario: You work as a data engineer managing a Snowflake data warehouse. Your team wants to improve query performance by using result caching layers effectively. You will create a simple table, configure caching settings, and write queries to observe caching behavior.

🎯 Goal: Build a Snowflake setup that demonstrates how result caching layers work by creating a table, setting a caching configuration variable, running a query that benefits from caching, and finally enabling result caching explicitly.

📋 What You'll Learn

Create a table named sales_data with specified columns and data

Create a variable cache_enabled to control caching behavior

Write a query selecting from sales_data using the caching variable

Enable result caching explicitly in the query using a query hint

💡 Why This Matters

🌍 Real World

Result caching in Snowflake helps speed up repeated queries by storing previous results, reducing compute costs and improving user experience.

💼 Career

Understanding and configuring result caching is important for data engineers and analysts to optimize data warehouse performance and cost.

1

Create the sales_data table

Write a Snowflake SQL statement to create a table called sales_data with columns id (integer), product (string), and amount (integer). Insert three rows with values: (1, 'Pen', 10), (2, 'Notebook', 20), and (3, 'Eraser', 5).

Snowflake

-- Create the sales_data table and insert data
-- Your code here

Hint

Use CREATE OR REPLACE TABLE to define the table and INSERT INTO to add rows.

2

Create a caching control variable

Create a Snowflake session variable named cache_enabled and set it to true to indicate that result caching should be used.

Snowflake

CREATE OR REPLACE TABLE sales_data (id INT, product STRING, amount INT);
INSERT INTO sales_data VALUES (1, 'Pen', 10), (2, 'Notebook', 20), (3, 'Eraser', 5);
-- Create the cache_enabled variable
-- Your code here

Hint

Use the SET command to create a session variable.

3

Write a query using the caching variable

Write a SELECT query to get all columns from sales_data. Use the session variable cache_enabled in a comment to indicate caching is enabled (simulate caching control).

Snowflake

CREATE OR REPLACE TABLE sales_data (id INT, product STRING, amount INT);
INSERT INTO sales_data VALUES (1, 'Pen', 10), (2, 'Notebook', 20), (3, 'Eraser', 5);
SET cache_enabled = true;
-- Write a SELECT query using the cache_enabled variable in a comment
-- Your code here

Hint

Write a simple SELECT query and add a comment referencing cache_enabled.

4

Enable result caching explicitly in the query

Modify the SELECT query to include the Snowflake query hint /*+ RESULT_CACHE */ to explicitly enable result caching.

Snowflake

CREATE OR REPLACE TABLE sales_data (id INT, product STRING, amount INT);
INSERT INTO sales_data VALUES (1, 'Pen', 10), (2, 'Notebook', 20), (3, 'Eraser', 5);
SET cache_enabled = true;
-- cache_enabled is true
-- Add the RESULT_CACHE hint to the SELECT query
-- Your code here

Hint

Add the query hint /*+ RESULT_CACHE */ immediately after SELECT.

Practice

1. What does Snowflake's result caching do when you run the same query multiple times within 24 hours?

easy

A. Deletes the previous result and returns an error

B. Runs the query again and stores a new result

C. Requires manual cache refresh before returning results

D. Returns the cached result instantly without rerunning the query

Solution

1. Step 1: Understand Snowflake's caching behavior

   Snowflake stores query results for 24 hours to speed up repeated queries.

2. Step 2: Identify the effect of caching on repeated queries

   When the same query runs again within 24 hours, Snowflake returns the cached result instantly without rerunning the query.

3. Final Answer:

   Returns the cached result instantly without rerunning the query -> Option D

4. Quick Check:

   Result caching = instant cached return [OK]

Hint: Same query within 24h returns cached result instantly [OK]

Common Mistakes:

• Thinking query always reruns
• Assuming cache expires immediately
• Believing manual refresh is needed

2. Which of the following is the correct way to disable result caching for a single query in Snowflake?

easy

A. ALTER SESSION SET DISABLE_CACHE = TRUE;

B. ALTER SESSION SET USE_CACHED_RESULT = FALSE;

C. ALTER SESSION SET NO_CACHE_RESULT = TRUE;

D. ALTER SESSION SET SKIP_CACHE = TRUE;

Solution

1. Step 1: Recall how to disable result caching

   Snowflake uses ALTER SESSION SET USE_CACHED_RESULT = FALSE to disable caching for the session.

2. Step 2: Match the correct syntax

   The correct syntax is ALTER SESSION SET USE_CACHED_RESULT = FALSE;

3. Final Answer:

   ALTER SESSION SET USE_CACHED_RESULT = FALSE; -> Option B

4. Quick Check:

   Disable cache param = USE_CACHED_RESULT = FALSE [OK]

Hint: Use ALTER SESSION SET USE_CACHED_RESULT = FALSE to disable caching [OK]

Common Mistakes:

• Using wrong parameter names
• Incorrect ALTER SESSION syntax
• Confusing with other cache parameters

3. Consider this sequence of queries run in Snowflake:
SELECT COUNT(*) FROM sales;
Immediately followed by:
SELECT COUNT(*) FROM sales;
What will happen on the second query?

medium

A. Snowflake returns the cached result from the first query

B. Snowflake returns partial results from cache

C. Snowflake returns an error about duplicate queries

D. Snowflake reruns the query and returns fresh results

Solution

1. Step 1: Identify caching behavior for repeated queries

   Snowflake caches query results for 24 hours and returns cached results if the same query runs again.

2. Step 2: Apply to the given queries

   The second SELECT COUNT(*) query is identical and runs immediately, so Snowflake returns the cached result.

3. Final Answer:

   Snowflake returns the cached result from the first query -> Option A

4. Quick Check:

   Repeated query = cached result return [OK]

Hint: Repeated query returns cached result instantly [OK]

Common Mistakes:

• Assuming query always reruns
• Expecting partial or error results
• Confusing cache with data freshness

4. You executed this command in Snowflake:
ALTER SESSION SET USE_CACHED_RESUTL = FALSE;
But you notice subsequent queries still return cached results. What is the likely cause?

medium

A. Result caching cannot be disabled in Snowflake

B. The query is too complex to cache

C. The USE_CACHED_RESULT parameter is misspelled or incorrect

D. The cache expired before the query ran

Solution

1. Step 1: Verify the USE_CACHED_RESULT parameter usage

   The parameter must be spelled exactly USE_CACHED_RESULT and set to FALSE to disable caching.

2. Step 2: Identify why caching still happens

   If caching still occurs, the parameter might be misspelled or incorrectly specified.

3. Final Answer:

   The USE_CACHED_RESULT parameter is misspelled or incorrect -> Option C

4. Quick Check:

   Correct parameter spelling and value disables cache [OK]

Hint: Check parameter spelling and syntax to disable caching [OK]

Common Mistakes:

• Assuming caching can't be disabled
• Misspelling the parameter name
• Ignoring exact parameter syntax

5. You want to ensure a query always returns fresh data and never uses cached results in Snowflake. Which approach correctly achieves this while minimizing cost?

hard

A. Execute ALTER SESSION SET USE_CACHED_RESULT = FALSE; before the query to disable caching

B. Manually clear the entire result cache before running the query

C. Run the query multiple times to refresh the cache

D. Use a different warehouse to bypass caching

Solution

1. Step 1: Identify how to disable result caching per session

   Snowflake allows disabling result caching using ALTER SESSION SET USE_CACHED_RESULT = FALSE before the query.

2. Step 2: Evaluate other options for cost and effectiveness

   Manually clearing cache or switching warehouses is inefficient and costly; running multiple times does not guarantee fresh data.

3. Final Answer:

   Execute ALTER SESSION SET USE_CACHED_RESULT = FALSE; before the query to disable caching -> Option A

4. Quick Check:

   Use USE_CACHED_RESULT = FALSE for fresh data [OK]

Hint: Use ALTER SESSION SET USE_CACHED_RESULT = FALSE for fresh data without extra cost [OK]

Common Mistakes:

• Trying to clear cache manually
• Switching warehouses unnecessarily
• Relying on repeated runs to refresh data