In the documentation, some types, such as numbers and dates, it specifies that store defaults to no. But that the field can still be retrieved from the json.
Its confusing. Does this mean _source?
Is there a way to not store a field at all, and just have it indexed and searchable?
None of the field types are stored by default. Only the _source field is. That means you can always get back what you sent to the search engine. Even if you ask for specific fields, elasticsearch is going to parse the _source field for you and give you back those fields.
You can disable the _source if you want but then you could only retrieve the fields that you explicitly stored, according to your mapping.
Related
I am posting data so I can search it later in elastic search.
I am posting it like this:
POST https://localhost:9200/superheroes/_doc/27
body:
{
"name": "Flash",
"super_power": "Super Speed"
}
This is automatically stored on a _source object... but I read the _source field itself is not indexed (and thus is not searchable) online, and the entire purpose of this application is quick search by value... like if I wanna know which superheroes have super speed and I write super speed on the search bar.
you are right about the _source field, but if you don't define the mapping for your fields, Elasticsearch generates the default mapping with default param for these fields . You can read more about the mapping param and in your case, if you want field to be searchable it needs to be the part of the inverted index and this is controlled by the index param.
You can override the value of these params by defining your own mapping(recommended otherwise Elasticsearch will guess the field type based on the first data you index in a field).
Hope this helps and clears your doubt, in short if you are not defining your mapping, your text data is searchable by default.
I am using elastic search 7.10.1. I would store and search against my blogs. The blog has id,title and content fields.
I would like to search against id, title and content, but since the content of blog is too big, so that I would like to save the original content text outside of Elastic Search, such as HBase.
I would ask how to achieve this in ES?
If you are using a static mapping then simply don't define your content field in your index mapping, and don't populate it while indexing your document to ES.
Refer to Mapping param for more info, and specifically, store param default false which means you can't retrieve field value if _source(true by default) is also disabled.
index param default true, which controls whether the field is searchable or not, in your case if you don't want to search and retrieve it you have to disable these two params.
I was wondering what is the recommended approach to filter out some of the fields that are sent to Elasticsearch from Store and Index?
I want to filter our some fields from getting indexed in Elasticsearch. You may ask why you are sending them to Elasticsearch from the first place. Unfortunately, it is sent via another application that doesn't accept any filtering mechanism. Hence, filtering should be addressed at the time of indexing. Here is what we have done, but I am not sure what would be the consequences of these steps:
1- Disable dynamic mapping ("dynamic": "false" ) in ES templates.
2- Including only the required fields in _source and excluding the rest.
According to ES website, some of the ES functionalities will be disabled by disabling _source fields. Given I don't need the filtered fields at all, I was wondering whether the mentioned solution will break anything regarding the remaining fields or not?
There are a few mapping parameters that allow you to do what you want:
index: true/false: if true the field value is indexed in order to be searched later on (default: true)
store: true/false: if true the field values are stored in addition to being indexed. Usually, the field values are stored in the source already, but you can choose to not store the source but store the field value itself (default: false)
enabled: true/false: only for the mapping type as a whole or for object types. you can decide whether to only store the value but not index it
So you can use any combination of the above parameters if you don't want to modify the source documents and simple let ES do it for you.
In Elasticsearch all fields of a mapping have a stored property which determines whether the data of the field will be stored on disk (in addition to the storing of the whole _source).
It defaults to false.
However each segment in every shard also has a Docvalues structure per field in the mapping. The structure stores the value of the field for all documents in the segment.
All documents and fields are included in the structured by default.
So on one hand, by default Elasticsearch doesn't store the values for fields. On the other hand, it does store the values in the Docvalues structure.
So which is it? Does Elasticsearch store or not store values by default?
ES stores the same field in multiple formats for different purposes.
For eg. Consider this :
"prop_1":{ "type":"string", "index":"not_analyzed","store":true,"doc_values":true}
prop_1 would be stored on its own as an indexed, doc_values and
stored field. On top of that the prop_1 is stored to into the
_source field together with your other fields.
As explained above, even if stored:false, the field data is still persisted on disk in multiple formats.
Stored fields are designed for optimal storage whereas doc values are
designed the access field values quickly. During the execution of
query many of doc values fields are accessed for candidate hits, so
the access must be fast. This the reason why you should use doc values
in sorting, aggregations and scrips.On the other hand stored fields should be used for return field values for the top matching documents.
Now, you can use doc_values to return fields in response as well :-
GET /_search
{
"query" : {
"match_all": {}
},
"docvalue_fields" : ["test1", "test2"]
}
Doc value fields can work on fields that are not stored. So IMO, stored fields do not have any significance now.
If I create a first document of it's type, or put a mapping, is an index created for each field?
Obviously if i set "index" to "analyzed" or "not analyzed" the field is indexed.
Is there a way to store a field so it can be retrieved but never searched by? I imagine this will save a lot of space? If I set this to "no" will this save space?
Will I still be able to search by this, just take more time, or will this be totally unsearchable?
Is there a way to make a field indexed after some documents are inserted and I change my mind?
For example, I might have a mapping:
{
"book":{"properties":{
"title":{"type":"string", "index":"not_analyzed"},
"shelf":{"type":"long","index":"no"}
}}}
so I want to be able to search by title, but also retrieve the shelf the book is on
index:no will indeed not create an index for that field, so that saves some space. Once you've done that you can't search for that particular field anymore.
Perhaps also useful in this context is to know aboutthe _source field, which is returned by default and includes all fields you've stored. http://www.elasticsearch.org/guide/reference/mapping/source-field/
As to your second question:
you can't change your mind halfway. When you want to index a particular field later on you have to reindex the documents.
That's why you may want to reconsider setting index:no, etc. In fact a good strategy to begin is to don't define a schema for fields at all, unless you're 100% sure you need a non-default analyzer for a particular field for instance. Otherwise ES will use generally usable defaults.