Check out my Elasticsearch course and get it for only $10: https://www.udemy.com/elasticsearch-complete-guide/?couponCode=SLIDESHARE10&utm_source=slideshare&utm_campaign=slideshare&utm_medium=referral

1. META FIELDSby Bo Andersen - codingexplained.com

2. OUTLINE
➤ Introduction to meta fields
➤ Meta fields categories
➤ Identity
➤ Document source
➤ Indexing
➤ Routing
➤ Other

3. INTRODUCTION TO META FIELDS
➤ Each document has metadata associated with it
➤ E.g. the _index, _type, and _id meta fields.
➤ The behavior of some of these meta-fields can be customized
➤ This is done when creating a mapping type

4. IDENTITY
META FIELDS

5. IDENTITY META FIELDS (PART 1)
➤ _index
➤ Allows matching documents based on their indexes
➤ _index is exposed as a virtual field and is not added to the Lucene index as a real
field
➤ _type
➤ The type of the document
➤ Indexed in order to make searching by type name fast

6. IDENTITY META FIELDS (PART 2)
➤ _id
➤ The ID of the document
➤ Not indexed, because its value can be automatically derived from the _uid field
➤ _uid
➤ The values of _type and _id are combined as {type}#{id} and indexed

7. DOCUMENT
SOURCE
META
FIELDS

8. DOCUMENT SOURCE META FIELDS
➤ _source
➤ Contains the JSON that was passed at index time (unless updated)
➤ The field is not indexed and is therefore not searchable
➤ It is stored so that it can be returned when executing fetch requests
➤ Can be disabled to save storage space
➤ _size
➤ Indexes the size of the _source field in bytes
➤ Available as a plugin that must be installed before the field is available
➤ sudo bin/plugin install mapper-size

9. INDEXING
META
FIELDS

10. _ALL
➤ A special field that concatenates the values of all of the other fields into one string
➤ Uses space as a delimiter
➤ The field is analyzed and indexed, but not stored
➤ This means that it can be searched, but not retrieved
➤ The field allows you to search for values in documents without knowing which field
contains the value

11. _FIELD_NAMES
➤ Indexes the names of every field in a document that contains a value other than
NULL
➤ Used by the exists and missing queries
➤ To find documents that either have or do not have a non-null value for a particular
field

12. ROUTING
META
FIELDS

13. _PARENT
➤ Can be used to establish a parent-child relationship between documents in an index
➤ This is done by making one mapping type the parent of another
"mappings": {
"employee": {
"_parent": {
"type": "person"
}
}
}
When adding an index:

14. _ROUTING
➤ Used to route a document to a particular shard within an index
➤ Enables you to define rules that control in which shards documents are stored
➤ For advanced use cases!

15. OTHER
META
FIELDS

16. _META
➤ Each mapping type can have custom meta data associated with it
➤ Elasticsearch does not use this meta data at all
➤ Can be used to store application-specific meta data
➤ This can be anything you want

17. THANK YOU FOR
WATCHING!