honeymoose/OpenSearch
1
0
Fork 0
mirror of https://github.com/honeymoose/OpenSearch.git synced 2025-04-06 23:39:05 +00:00
Code Issues Packages Projects Releases Wiki Activity
OpenSearch/docs/reference/mapping/fields/parent-field.asciidoc

57 lines
2.3 KiB
Plaintext
Raw Normal View History

Migrated documentation into the main repo
2013-08-29 01:24:34 +02:00
[[mapping-parent-field]]
=== `_parent`
Parent/child: refactored _parent field mapper and parent/child queries * Cut the `has_child` and `has_parent` queries over to use Lucene's query time global ordinal join. The main benefit of this change is that parent/child queries can now efficiently execute if parent/child queries are wrapped in a bigger boolean query. If the rest of the query only hit a few documents both has_child and has_parent queries don't need to evaluate all parent or child documents any more. * Cut the `_parent` field over to use doc values. This significantly reduces the on heap memory footprint of parent/child, because the parent id values are never loaded into memory. Breaking changes: * The `type` option on the `_parent` field can only point to a parent type that doesn't exist yet, so this means that an existing type/mapping can't become a parent type any longer. * The `has_child` and `has_parent` queries can no longer be use in alias filters. All these changes, improvements and breaks in compatibility only apply for indices created with ES version 2.0 or higher. For indices creates with ES <= 2.0 the older implementation is used. It is highly recommended to re-index all your indices with parent and child documents to benefit from all the improvements that come with this refactoring. The easiest way to achieve this is by using the scan and bulk apis using a simple script. Closes #6107 Closes #8134
2015-03-25 10:42:49 +01:00
TIP: It is highly recommend to reindex all indices with `_parent` field created before version 2.x.
The reason for this is to gain from all the optimizations added with the 2.0 release.
Migrated documentation into the main repo
2013-08-29 01:24:34 +02:00
The parent field mapping is defined on a child mapping, and points to
the parent type this child relates to. For example, in case of a `blog`
type and a `blog_tag` type child document, the mapping for `blog_tag`
should be:
[source,js]
--------------------------------------------------
{
"blog_tag" : {
"_parent" : {
"type" : "blog"
}
}
}
--------------------------------------------------
The mapping is automatically stored and indexed (meaning it can be
searched on using the `_parent` field notation).
Docs: Document that the fielddata loading defaults to eager on the _parent field. Closes #9804
2015-02-22 23:15:37 +01:00
Parent/child: refactored _parent field mapper and parent/child queries * Cut the `has_child` and `has_parent` queries over to use Lucene's query time global ordinal join. The main benefit of this change is that parent/child queries can now efficiently execute if parent/child queries are wrapped in a bigger boolean query. If the rest of the query only hit a few documents both has_child and has_parent queries don't need to evaluate all parent or child documents any more. * Cut the `_parent` field over to use doc values. This significantly reduces the on heap memory footprint of parent/child, because the parent id values are never loaded into memory. Breaking changes: * The `type` option on the `_parent` field can only point to a parent type that doesn't exist yet, so this means that an existing type/mapping can't become a parent type any longer. * The `has_child` and `has_parent` queries can no longer be use in alias filters. All these changes, improvements and breaks in compatibility only apply for indices created with ES version 2.0 or higher. For indices creates with ES <= 2.0 the older implementation is used. It is highly recommended to re-index all your indices with parent and child documents to benefit from all the improvements that come with this refactoring. The easiest way to achieve this is by using the scan and bulk apis using a simple script. Closes #6107 Closes #8134
2015-03-25 10:42:49 +01:00
==== Limitations
The `_parent.type` setting can only point to a type that doesn't exist yet.
This means that a type can't become a parent type after is has been created.
The `parent.type` setting can't point to itself. This means self referential
parent/child isn't supported.
Parent/child queries (`has_child` & `has_parent`) can't be used in index aliases.
==== Global ordinals
Parent-child uses <<index-modules-fielddata-global-ordinals,global ordinals>> to speed up joins and global ordinals need to be rebuilt after any change to a shard.
The more parent id values are stored in a shard, the longer it takes to rebuild global ordinals for the `_parent` field.
Global ordinals, by default, are built lazily: the first parent-child query or aggregation after a refresh will trigger building of global ordinals.
This can introduce a significant latency spike for your users. You can use <<index-modules-fielddata-fielddata-loading,eager_global_ordinals>> to shift the cost of building global ordinals
from query time to refresh time, by mapping the _parent field as follows:
Docs: Document that the fielddata loading defaults to eager on the _parent field. Closes #9804
2015-02-22 23:15:37 +01:00
Parent/child: refactored _parent field mapper and parent/child queries * Cut the `has_child` and `has_parent` queries over to use Lucene's query time global ordinal join. The main benefit of this change is that parent/child queries can now efficiently execute if parent/child queries are wrapped in a bigger boolean query. If the rest of the query only hit a few documents both has_child and has_parent queries don't need to evaluate all parent or child documents any more. * Cut the `_parent` field over to use doc values. This significantly reduces the on heap memory footprint of parent/child, because the parent id values are never loaded into memory. Breaking changes: * The `type` option on the `_parent` field can only point to a parent type that doesn't exist yet, so this means that an existing type/mapping can't become a parent type any longer. * The `has_child` and `has_parent` queries can no longer be use in alias filters. All these changes, improvements and breaks in compatibility only apply for indices created with ES version 2.0 or higher. For indices creates with ES <= 2.0 the older implementation is used. It is highly recommended to re-index all your indices with parent and child documents to benefit from all the improvements that come with this refactoring. The easiest way to achieve this is by using the scan and bulk apis using a simple script. Closes #6107 Closes #8134
2015-03-25 10:42:49 +01:00
==== Memory usage
The only on heap memory used by parent/child is the global ordinals for the `_parent` field.
How much memory is used for the global ordianls for the `_parent` field in the fielddata cache
can be checked via the <<indices-stats,indices stats>> or <<cluster-nodes-stats,nodes stats>>
APIS, eg:
[source,js]
--------------------------------------------------
curl -XGET "http://localhost:9200/_stats/fielddata?pretty&human&fielddata_fields=_parent"
--------------------------------------------------
Reference in New Issue Copy Permalink