When nested objects are present in the mappings, many queries get deoptimized
due to the need to exclude documents that are not in the right space. For
instance, a filter is applied to all queries that prevents them from matching
non-root documents (`+*:* -_type:__*`). Moreover, a filter is applied to all
child queries of `nested` queries in order to make sure that the child query
only matches child documents (`_type:__nested_path`), which is required by
`ToParentBlockJoinQuery` (the Lucene query behing Elasticsearch's `nested`
queries).
These additional filters slow down `nested` queries. In 1.7-, the cost was
somehow amortized by the fact that we cached filters very aggressively. However,
this has proven to be a significant source of slow downs since 2.0 for users
of `nested` mappings and queries, see #20797.
This change makes the filtering a bit smarter. For instance if the query is a
`match_all` query, then we need to exclude nested docs. However, if the query
is `foo: bar` then it may only match root documents since `foo` is a top-level
field, so no additional filtering is required.
Another improvement is to use a `FILTER` clause on all types rather than a
`MUST_NOT` clause on all nested paths when possible since `FILTER` clauses
are more efficient.
Here are some examples of queries and how they get rewritten:
```
"match_all": {}
```
This query gets rewritten to `ConstantScore(+*:* -_type:__*)` on master and
`ConstantScore(_type:AutomatonQuery {\norg.apache.lucene.util.automaton.Automaton@4371da44})`
with this change. The automaton is the complement of `_type:__*` so it matches
the same documents, but is faster since it is now a positive clause. Simplistic
performance testing on a 10M index where each root document has 5 nested
documents on average gave a latency of 420ms on master and 90ms with this change
applied.
```
"term": {
"foo": {
"value": "0"
}
}
```
This query is rewritten to `+foo:0 #(ConstantScore(+*:* -_type:__*))^0.0` on
master and `foo:0` with this change: we do not need to filter nested docs out
since the query cannot match nested docs. While doing performance testing in
the same conditions as above, response times went from 250ms to 50ms.
```
"nested": {
"path": "nested",
"query": {
"term": {
"nested.foo": {
"value": "0"
}
}
}
}
```
This query is rewritten to
`+ToParentBlockJoinQuery (+nested.foo:0 #_type:__nested) #(ConstantScore(+*:* -_type:__*))^0.0`
on master and `ToParentBlockJoinQuery (nested.foo:0)` with this change. The
top-level filter (`-_type:__*`) could be removed since `nested` queries only
match documents of the parent space, as well as the child filter
(`#_type:__nested`) since the child query may only match nested docs since the
`nested` object has both `include_in_parent` and `include_in_root` set to
`false`. While doing performance testing in the same conditions as above,
response times went from 850ms to 270ms.
Set lucene version to 6.4.0-snapshot-ec38570 and update all the sha1s/license
Fix invalid combo after upgrade in query_string query. split_on_whitespace=false is disallowed if auto_generate_phrase_queries=true
Adapt the expectations of some tests to the new format of the Lucene explain output
Lucene 6.2 introduces the new `Analyzer.normalize` API, which allows to apply
only character-level normalization such as lowercasing or accent folding, which
is exactly what is needed to process queries that operate on partial terms such
as `prefix`, `wildcard` or `fuzzy` queries. As a consequence, the
`lowercase_expanded_terms` option is not necessary anymore. Furthermore, the
`locale` option was only needed in order to know how to perform the lowercasing,
so this one can be removed as well.
Closes#9978
This change adds a TypesQuery that checks if the disjunction of types should be rewritten to a MatchAllDocs query. The check is done only if the number of terms is below a threshold (16 by default and configurable via max_boolean_clause).
This change replaces the fields parameter with stored_fields when it makes sense.
This is dictated by the renaming we made in #18943 for the search API.
The following list of endpoint has been changed to use `stored_fields` instead of `fields`:
* get
* mget
* explain
The documentation and the rest API spec has been updated to cope with the changes for the following APIs:
* delete_by_query
* get
* mget
* explain
The `fields` parameter has been deprecated for the following APIs (it is replaced by _source filtering):
* update: the fields are extracted from the _source directly.
* bulk: the fields parameter is used but fields are extracted from the source directly so it is allowed to have non-stored fields.
Some APIs still have the `fields` parameter for various reasons:
* cat.fielddata: the fields paramaters relates to the fielddata fields that should be printed.
* indices.clear_cache: used to indicate which fielddata fields should be cleared.
* indices.get_field_mapping: used to filter fields in the mapping.
* indices.stats: get stats on fields (stored or not stored).
* termvectors: fields are retrieved from the stored fields if possible and extracted from the _source otherwise.
* mtermvectors:
* nodes.stats: the fields parameter is used to concatenate completion_fields and fielddata_fields so it's not related to stored_fields at all.
Fixes#20155
The analysis chain should be used instead of relying on this, as it is
confusing when dealing with different per-field analysers.
The `locale` option was only used for `lowercase_expanded_terms`, which,
once removed, is no longer needed, so it was removed as well.
Fixes#9978
Relates to #9973
- Removed "ok": true from response examples
- Added "created" flag to index response examples
- Replaced exists flag with found in delete response examples
Adrien Grand
Jim Ferenczi
Nik Everett
Isabel Drost-Fromm
Isabel Drost-Fromm
Lee Hinman
Clinton Gormley
Luca Cavanna
Boaz Leskes