[Solved] Given the table users(id INT, email TEXT) and the index:CREATE INDEX idx_lower_email ON users (LOWER(email));What will the query SELECT * FROM users WHERE LOWER(email) = 'test@example.com'; use? | PostgreSQL

PostgreSQL - Indexing Strategies

Given the table users(id INT, email TEXT) and the index:
CREATE INDEX idx_lower_email ON users (LOWER(email));
What will the query SELECT * FROM users WHERE LOWER(email) = 'test@example.com'; use?

AThe expression index idx_lower_email to speed up the search

BA sequential scan ignoring the index

CThe primary key index on id

DAn error because LOWER(email) cannot be indexed

Step-by-Step Solution

Solution:

Step 1: Understand how expression indexes are used in queries
When a query uses the same expression as the index (LOWER(email)), PostgreSQL can use that index to speed up the search.
Step 2: Analyze the query and index
The query filters by LOWER(email), matching the expression index idx_lower_email, so the index will be used.
Final Answer:
The expression index idx_lower_email to speed up the search -> Option A
Quick Check:
Query expression matches index expression = index used [OK]

Quick Trick: Query expression must match index expression exactly to use it [OK]

Common Mistakes:

Assuming expression indexes are ignored in queries
Thinking primary key index will be used instead
Believing expression indexes cause errors

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Given the table users(id INT, email TEXT) and the index:

Step 1: Understand how expression indexes are used in queries

Step 2: Analyze the query and index

Final Answer:

Quick Check:

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