Creating an index in Elasticsearch - Quick Revision & Summary

Recall & Review

beginner

What is an index in Elasticsearch?

An index in Elasticsearch is like a folder where documents are stored. It helps organize and quickly find data, similar to how a library index helps find books.

beginner

Which HTTP method is used to create an index in Elasticsearch?

The PUT method is used to create an index in Elasticsearch. You send a PUT request to the server with the index name.

intermediate

What is the purpose of the 'mappings' section when creating an index?

Mappings define the structure of the documents in the index, like what fields exist and their data types. It helps Elasticsearch understand how to store and search the data.

beginner

Show a simple example of creating an index named 'library' in Elasticsearch.

Use this command:

PUT /library

This creates an empty index called 'library' ready to store documents.

intermediate

Why should you define settings like number_of_shards when creating an index?

Settings like number_of_shards control how data is split and stored across servers. This affects speed and reliability, like dividing a big book into chapters for easier reading.

Which HTTP method creates a new index in Elasticsearch?

A POST

B GET

C PUT

D DELETE

PUT is used to create or update an index in Elasticsearch.

What does the 'mappings' section define when creating an index?

A The server location

B The document structure and field types

C The user permissions

D The network protocol

Mappings define the structure and data types of documents in the index.

What is the default number of shards when creating an index if not specified?

A 5

B 10

C 1

D 3

By default, Elasticsearch creates 5 primary shards per index (before version 7.0). Since version 7.0, the default is 1 primary shard.

Which of these is a valid command to create an index named 'books'?

A DELETE /books

B POST /books

C GET /books

D PUT /books

PUT /books creates a new index named 'books'.

Why might you want to customize index settings when creating it?

A To control data distribution and performance

B To set user passwords

C To change the color of the interface

D To install plugins

Custom settings help control how data is stored and how fast searches run.

Explain how to create a basic index in Elasticsearch and why it is important.

Think about how you organize files in folders.

Describe the role of mappings and settings when creating an Elasticsearch index.

Consider how a blueprint and building materials affect a house.

Practice

1. What is the main purpose of creating an index in Elasticsearch?

easy

A. To encrypt data for security

B. To delete data permanently

C. To backup data automatically

D. To organize data for fast searching

Solution

1. Step 1: Understand the role of an index

   An index in Elasticsearch is like a folder that organizes documents to make searching fast and efficient.

2. Step 2: Compare options with index purpose

   Deleting, backing up, or encrypting data are not the main functions of an index.

3. Final Answer:

   To organize data for fast searching -> Option D

4. Quick Check:

   Index = Organize data for search [OK]

Hint: Index means organizing data for quick search [OK]

Common Mistakes:

• Confusing index with backup or encryption
• Thinking index deletes data
• Assuming index automatically secures data

2. Which is the correct syntax to create an index named products in Elasticsearch?

easy

A. PUT /products

B. POST /products

C. GET /products

D. DELETE /products

Solution

1. Step 1: Recall HTTP methods for index creation

   Elasticsearch uses the PUT method to create an index with a specific name.

2. Step 2: Match method with index name

   PUT /products correctly creates the index named 'products'. POST is used for adding documents, GET for retrieving, DELETE for removing.

3. Final Answer:

   PUT /products -> Option A

4. Quick Check:

   PUT creates index [OK]

Hint: Use PUT to create an index by name [OK]

Common Mistakes:

• Using POST instead of PUT for index creation
• Confusing GET with creation
• Trying DELETE to create index

3. Given this request to create an index:

{
  "settings": {"number_of_shards": 1},
  "mappings": {
    "properties": {
      "name": {"type": "text"},
      "price": {"type": "float"}
    }
  }
}

What will be the type of the price field in the index?

medium

A. keyword

B. float

C. integer

D. text

Solution

1. Step 1: Read the mapping for the price field

   The mapping defines "price" with "type": "float" which means it stores decimal numbers.

2. Step 2: Understand field types

   Float is a number with decimals, integer is whole number, text is for full text search, keyword is for exact matches.

3. Final Answer:

   float -> Option B

4. Quick Check:

   price type = float [OK]

Hint: Check mapping 'type' for field data type [OK]

Common Mistakes:

• Confusing float with integer
• Assuming text type for numbers
• Mixing keyword with numeric types

4. Identify the error in this index creation request:

PUT /library
{
  "settings": {
    "number_of_shards": "two"
  },
  "mappings": {
    "properties": {
      "title": {"type": "text"}
    }
  }
}

medium

A. number_of_shards should be a number, not a string

B. title field type should be keyword, not text

C. PUT method cannot be used to create index

D. Missing index name in URL

Solution

1. Step 1: Check the settings syntax

   number_of_shards must be a numeric value, but "two" is a string, causing an error.

2. Step 2: Validate other parts

   Field type 'text' is valid for title, PUT is correct method, index name 'library' is present.

3. Final Answer:

   number_of_shards should be a number, not a string -> Option A

4. Quick Check:

   number_of_shards = number [OK]

Hint: Settings values must match expected data types [OK]

Common Mistakes:

• Using string instead of number for shards
• Confusing field types for text fields
• Using wrong HTTP method for index creation

5. You want to create an index users with a field age that should only accept whole numbers and be searchable. Which mapping is correct?

hard

A. { "mappings": { "properties": { "age": { "type": "float" } } } }

B. { "mappings": { "properties": { "age": { "type": "text" } } } }

C. { "mappings": { "properties": { "age": { "type": "integer" } } } }

D. { "mappings": { "properties": { "age": { "type": "keyword" } } } }

Solution

1. Step 1: Understand the data type needed for age

   Age is a whole number, so integer type is appropriate to store numeric whole values.

2. Step 2: Check searchability and field types

   Text is for full text search, float allows decimals, keyword is for exact matches but not numeric operations.

3. Final Answer:

   { "mappings": { "properties": { "age": { "type": "integer" } } } } -> Option C

4. Quick Check:

   Whole number field = integer type [OK]

Hint: Use integer type for whole number searchable fields [OK]

Common Mistakes:

• Using text type for numeric fields
• Choosing float when decimals not needed
• Using keyword for numeric data