Given a table users(id SERIAL PRIMARY KEY, name TEXT) with 1 million rows, which scan is PostgreSQL likely to use for this query?

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PostgreSQL - Performance Tuning

Given a table users(id SERIAL PRIMARY KEY, name TEXT) with 1 million rows, which scan is PostgreSQL likely to use for this query?
SELECT * FROM users WHERE id = 500000;

AIndex scan using the primary key index

BSequential scan scanning all 1 million rows

CBitmap heap scan reading random rows

DNo scan, query will fail

Step-by-Step Solution

Solution:

Step 1: Analyze query condition and table size
The query filters by primary key id, which has an index, and the table is large (1 million rows).
Step 2: Determine efficient scan type
PostgreSQL uses an index scan to quickly find the single matching row instead of scanning all rows.
Final Answer:
Index scan using the primary key index -> Option A
Quick Check:
Selective query on indexed column = index scan [OK]

Quick Trick: Selective query on indexed column uses index scan [OK]

Common Mistakes:

Assuming sequential scan for large tables with indexed filter
Confusing bitmap heap scan with index scan
Thinking query fails without reason

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Given a table users(id SERIAL PRIMARY KEY, name TEXT) with 1 million rows, which scan is PostgreSQL likely to use for this query?

Step 1: Analyze query condition and table size

Step 2: Determine efficient scan type

Final Answer:

Quick Check:

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