CODEWITHSUNDEEP
elasticsearch
Kramer Li
Kramer Li

Reputation: 2476

How to use the elasticsearch type?

Note: it will be very appreciate if you tell me why you think this is a shit question by comment. Please do not just down vote and not telling why..

We know there is the concept called type under index. But I do not know why we need it.

Firstly I thought we use it to organize data. Like we have index like below:

curl -XPOST 'localhost:9200/customer/USA/_bulk?pretty' -d '
{"index":{"_id":"1"}}
{"name": "John Doe" }
{"index":{"_id":"2"}}
{"name": "Jane Doe" }
'

But in the above situation, we can always eliminate the type, move it to the json body like :

curl -XPOST 'localhost:9200/customer/_bulk?pretty' -d '
{"index":{"_id":"1"}}
{"name": "John Doe","country":"USA" }
{"index":{"_id":"2"}}
{"name": "Jane Doe","country":"USA" }
'

In this way we can always add a field to replace the type.

Then I thought it may be performance related. I thought If you split the data into different type, then there is less data under each type. So the performance to query each type should be better. But it is also not like that.

The performance of elasticsearch index is related to the shard. So even you split the data into different type, it still stored under the same sets of shards.

Then why we need type?

Upvotes: 1

Views: 104

Answers (2)

Sachin
Sachin

Reputation: 1715

From my understanding of ES , type is something we can relate to table concept in a relational database. In which a database can be said as group of related tables. Likewise in ES,index is a group of related types each type in index holds documents that share some common property or fields.

In your example,for a index say Customer we can have different employees from different countries like USA,india,UK etc. Customer records from each country can be grouped under different types so that it will be organized. And when we run a search query for customers in a particular country we will need to run that query on type USA only. We don't need to lookup in the whole index to get the data of customers from USA.

Another example : Let’s assume you run a blogging platform and store all your data in a single index. In this index, you may define a type for user data, another type for blog data, and yet another type for comments data. So we are logically organizing the data to different types and looking up to the required type whenever we do a search.

So in general,type is a logical category/partition of your index whose semantics is completely up to you. It can be defined as documents that have a set of common fields.

You may refer to this post for better understanding https://www.elastic.co/blog/index-vs-type

Upvotes: 1

hspandher
hspandher

Reputation: 16743

First of all, although elastic search determine types of fields on runtime, but once it has assigned a particular type to a field it would always expect same type of value for that field. So you need multiple types if you need to store different type of data. Secondly it allows for storing multiple types with difference mappings in single index. Besides it makes querying on a particular type easier if you are sure about its schema.

Upvotes: 1

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