elasticsearch for beginners part 1: how to create a document

In this Elasticsearch for beginners series, I will give you basics of Elasticsearch with real world examples. The first part is for teaching you how to create -that is index- a document in Elasticsearch.

I assume you managed to download the latest Elasticsearch zip to your local, extracted it and after that installed the marvel plugin and started a new node by running "elasticsearch" under your installation's bin directory.

Now it is time for some action. We can choose to give custom id to our document or leave it to Elasticsearch so we won't bother by generating a new one.

You can choose whatever content you want, but for keeping it simple I'll consider the usual user example. Our user will have a  username, first name, last name and a contact phone.

 {
   "username" : "kimchy",
   "fist_name" : "kimchy",
   "last_name" : "aloevera",
   "phone" : "00905332446578"
 }

Now lets open our Sense plugin. Go to "http://localhost:9200/_plugin/marvel/sense/index.html" after your node is up and running.

Before indexing anything I'll tell you that we will need an index and a type information.
Index is like a database and type is like a table if we use  RDBMS analogies.

Please don't get confused over the meaning of index. Indexing a document is creating a document, index information of a document is its database.

Lets insert our first document with custom id. We will use "elastic_101" as index and "user" as type.

PUT /elastic_101/user/1
 {
   "username" : "kimchy",
   "fist_name" : "kimchy",
   "last_name" : "aloevera",
   "phone" : "00905332446578"
 }

We can check if we are successful in indexing it.

The result to the following query

GET elastic_101/user/_search

is

{
   "took": 16,
   "timed_out": false,
   "_shards": {
      "total": 5,
      "successful": 5,
      "failed": 0
   },
   "hits": {
      "total": 1,
      "max_score": 1,
      "hits": [
         {
            "_index": "elastic_101",
            "_type": "user",
            "_id": "1",
            "_score": 1,
            "_source": {
               "username": "kimchy",
               "fist_name": "kimchy",
               "last_name": "aloevera",
               "phone": "00905332446578"
            }
         }
      ]
   }
}

Now lets index a new document with autogenerated id.

POST /elastic_101/user/
 {
   "username" : "sezinkarli",
   "fist_name" : "sezin",
   "last_name" : "karli",
   "phone" : "00905322426528"
 }

Again let me check the result with

GET elastic_101/user/_search

Result is:

 
{
   "took": 40,
   "timed_out": false,
   "_shards": {
      "total": 5,
      "successful": 5,
      "failed": 0
   },
   "hits": {
      "total": 2,
      "max_score": 1,
      "hits": [
         {
            "_index": "elastic_101",
            "_type": "user",
            "_id": "AVAFxb36kyTg7_oSOIVN",
            "_score": 1,
            "_source": {
               "username": "sezinkarli",
               "fist_name": "sezin",
               "last_name": "karli",
               "phone": "00905322426528"
            }
         },
         {
            "_index": "elastic_101",
            "_type": "user",
            "_id": "1",
            "_score": 1,
            "_source": {
               "username": "kimchy",
               "fist_name": "kimchy",
               "last_name": "aloevera",
               "phone": "00905332446578"
            }
         }
      ]
   }
}

As you can see both users have a username, first name, last name and a phone. Notice that if for kimchy is 1 which is the one we gave it and the other id is "AVAFxb36kyTg7_oSOIVN" which is generated by Elasticsearch.

In this part of my Elasticsearch tutorial, we learnt how to create documents with custom or auto-generated id. You can have more in depth information in my Elasticsearch in Action course and this link will make a discount of 60%.

elastic search crash course

Check this Elasticsearch crash course video out. It's not only for newbies but also for people with Elasticsearch experience.

unknown column 'date' in 'field list'

When working on a project in which we use hibernate, I get

Unknown column 'date' in 'field list'

as exception. The spring exception was:

org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute query; SQL [select this_.ID as ID3010_0_, this_.date as date3010_0_,

The only field I have in my entity named 'date' is not marked with column annotation. So it should not be mapped to database table and thus should not be used in the query right? No, think again. Every field in the entity class is mapped and column annotation is optional. So if you ever want hibernate to ignore a field in your entity (because either this field is not present in the table or you don't want to use it somehow), use transient annotation. So,

@Entity
public class MyEntity implements Serializable
{
    private String date;

    @Id
    @GeneratedValue
    @Column(name = "ID")
    private Long id;

must become this

@Entity
public class MyEntity implements Serializable
{
    @Transient
    private String date;

    @Id
    @GeneratedValue
    @Column(name = "ID")
    private Long id;

mongodb is evil?

NoSQL databases were quite popular (with cloud computing and scala) at this year's devoxx and one of these databases was MongoDB. The way you define your models with json-style and the performance benefits seemed like the real power of MongoDB but the following article states that you should reconsider your choice if you choose MongoDB in something other than a toy project. See if mongoDB is evil.