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Summary - Index tuning

Speed up a query with a covering index.

Summary - Index tuning

Index tuning: B-tree as base, covering index for index-only scan, partial index for few rows, selectivity should be high, maintenance with REINDEX. The right index speeds the right query.

-- CREATE INDEX ... INCLUDE ... WHERE ...
-- ANALYZE -> REINDEX

Index design and maintenance go together.

Practice Summary - Index tuning

Summary task: create a covering index on orders: customer_id as key, amount in INCLUDE.

Starter code

query.sql
-- summary index
CREATE INDEX idx_orders_cust ON orders(customer_id)

Sample solution

query.sql
CREATE INDEX idx_orders_cust ON orders(customer_id) INCLUDE (amount);

Expected output

CREATE INDEX

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Index maintenance

Question 
REINDEX INDEX ____
Answer 
REINDEX INDEX idx_products_name

Explanation: idx_products_name is the right answer.

2 What does a covering index enable?

  • Full scan
  • Index-only scan Correct answer
  • Seq scan
  • Cross join

Explanation: A covering index enables index-only scan.

3 Summary - Index tuning: match the terms

Term Meaning
B-tree balanced
covering covering
partial partial
REINDEX rebuild

All lessons in Expert

1 Database design

  1. ER model
  2. Cardinality
  3. Surrogate keys
  4. Natural keys
  5. Denormalization
  6. Summary - Design

2 Index tuning

  1. B-tree structure
  2. Covering index
  3. Partial index
  4. Index selectivity
  5. Index maintenance
  6. Summary - Index tuning

3 Query optimizer

  1. What is an optimizer?
  2. Statistics
  3. Cost model
  4. Join strategies
  5. Plan cache
  6. Summary - Optimizer

4 Project: Performance tuning

  1. Scenario design
  2. Reading plans
  3. Adding indexes
  4. Rewriting queries
  5. Comparing results

5 Replication and sharding

  1. What is replication?
  2. Master-slave
  3. Sync vs async
  4. What is sharding?
  5. Shard key
  6. Summary - Replication and sharding

6 Distributed and big data

  1. Distributed queries
  2. MPP
  3. Columnar storage
  4. SQL on Hadoop
  5. SQL vs NoSQL
  6. Summary - Distributed and big data

7 Security and backup

  1. SQL injection
  2. Parameterised queries
  3. Authorisation
  4. Backup
  5. Recovery
  6. Summary - Security and backup

8 Expert final

  1. Design challenge
  2. Optimization challenge
  3. Security challenge
  4. Backup challenge