Dynamic Mapping and common field types

Original: Dynamic Mapping and common field types

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What is Mapping

• Similar mapping database schema definition, role is as follows:
  • Name defined index fields
  • Field data type definition, such as strings, numbers, Boolean ...
  • Field, inverted index configuration, Analyzed or Not Analyzed, Analyzer
• JSON document mapping will be mapped into the flat form required Lucene
• A mapping belonging to an index of type
  • Each document belongs to a Type
  • Mapping a Type has a defined
  • 7.0, do not need to specify the type of information in the mapping definition

Field data types

• Simple type
  • Text/Keyword
  • Date
  • Integer/Floating
  • Boolean
  • ipv4 & ipv6
• Complex types - objects and nested objects
  • Object Type / nested type
• Special type
  • geo_point & geo_shape & percolator

What is Dynamic Mapping

• In written documents, when, if the index does not exist, it will automatically create an index
• Dynamic Mapping mechanism, so that we do not need to manually define Mappings. Elasticsearch automatically according to the document information, calculate the type of the field
• But sometimes the wrong projections, such as geographic location information
• When the type If not, it will cause some features not work properly, for example: Range query

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Automatic identification of the type

JSON type	Elasticsearch type
String	1, matching log format, provided Date 2, arranged to float or configure the digital long, this option is off by default 3, set to Text, and increase the keyword subfields
Boolean value	boolean
Float	float
Integer	long
Objects	Object
Array	Determined by the type of the first non-null value
Null	ignore

Mapping can change field type

• In both cases
  • New field
    • Dynamic When set to true, if there is a document written in the new field, Mapping also be updated
    • When Dynamic set to false, Mapping will not be updated, new data fields can not be indexed, but the information will appear in the _source
    • Dynamic set to Strict, file write failure
  • Existing field, once the data has been written, it is no longer modify the field definition support
    • Lucene inverted index to achieve, once generated, can not be modified
  • If you want to change the field type, you must Reindex API, rebuild the index
• the reason
  • If you modify the data type of the field, will result has been indexed belongs to can not be searched
  • But if it is to add a new field, there would be no such effects

Control Dynamic Mappings

air	“true”	“false”	“strict”
Documents can be indexed	YES	YES	NO
Fields indexable	YES	NO	NO
Mapping was updated	YES	NO	NO

PUT movies
{
	"mappings":{
		"_doc":{
			"dynamic":"false"
		}
	}
}

   
   

  
  

   
   
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• When dynamic time is set to false, the presence of additional fields into the data, the data may be indexed, but the new field is discarded
• When set to Strict mode when data is written directly Error