You created a B-tree index on column email but notice queries filtering by LOWER(email) are slow. What is the likely problem?

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PostgreSQL - Indexing Strategies

You created a B-tree index on column email but notice queries filtering by LOWER(email) are slow. What is the likely problem?

AB-tree indexes only work on numeric columns

BThe index was created on the wrong table

CB-tree indexes do not support functions like LOWER() by default

DThe database needs to be restarted to use the index

Step-by-Step Solution

Solution:

Step 1: Understand function usage in WHERE clause
Using LOWER(email) means the query filters on a transformed value, not the raw column.
Step 2: Recognize index limitations
Regular B-tree indexes do not support functions unless a functional index is created.
Final Answer:
B-tree indexes do not support functions like LOWER() by default -> Option C
Quick Check:
Function in filter needs functional index [OK]

Quick Trick: Use functional indexes for queries with functions like LOWER() [OK]

Common Mistakes:

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