You created a B-tree index on the user_id column, but queries filtering by user_id remain slow. What is a likely reason?

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SQL - Indexes and Query Performance

You created a B-tree index on the user_id column, but queries filtering by user_id remain slow. What is a likely reason?

AThe queries apply a function or expression on <code>user_id</code>, preventing index use

BThe index was created on the wrong table

CB-tree indexes do not support filtering queries

DThe database automatically disables indexes on numeric columns

Step-by-Step Solution

Solution:

Step 1: Identify index usage conditions
B-tree indexes are used only when the column is referenced directly.
Step 2: Effect of expressions
Applying functions or calculations on the indexed column disables index usage.
Final Answer:
The queries apply a function or expression on user_id, preventing index use -> Option A
Quick Check:
Functions on indexed columns block index use [OK]

Quick Trick: Functions on indexed columns prevent index usage [OK]

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