187 lines
5.4 KiB
Plaintext
187 lines
5.4 KiB
Plaintext
=== Query DSL changes
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==== Queries and filters merged
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Queries and filters have been merged -- all filter clauses are now query
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clauses. Instead, query clauses can now be used in _query context_ or in
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_filter context_:
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Query context::
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A query used in query context will caculated relevance scores and will not be
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cacheable. Query context is used whenever filter context does not apply.
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Filter context::
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+
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--
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A query used in filter context will not calculate relevance scores, and will
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be cacheable. Filter context is introduced by:
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* the `constant_score` query
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* the `must_not` and (newly added) `filter` parameter in the `bool` query
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* the `filter` and `filters` parameters in the `function_score` query
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* any API called `filter`, such as the `post_filter` search parameter, or in
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aggregations or index aliases
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--
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As a result of this change, he `execution` option of the `terms` filter is now
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deprecated and ignored if provided.
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==== `or` and `and` now implemented via `bool`
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The `or` and `and` filters previously had a different execution pattern to the
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`bool` filter. It used to be important to use `and`/`or` with certain filter
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clauses, and `bool` with others.
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This distinction has been removed: the `bool` query is now smart enough to
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handle both cases optimally. As a result of this change, the `or` and `and`
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filters are now sugar syntax which are executed internally as a `bool` query.
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These filters may be removed in the future.
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==== `filtered` query and `query` filter deprecated
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The `query` filter is deprecated as is it no longer needed -- all queries can
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be used in query or filter context.
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The `filtered` query is deprecated in favour of the `bool` query. Instead of
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the following:
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[source,js]
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-------------------------
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GET _search
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{
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"query": {
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"filtered": {
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"query": {
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"match": {
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"text": "quick brown fox"
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}
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},
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"filter": {
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"term": {
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"status": "published"
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}
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}
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}
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}
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}
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-------------------------
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move the query and filter to the `must` and `filter` parameters in the `bool`
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query:
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[source,js]
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-------------------------
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GET _search
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{
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"query": {
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"bool": {
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"must": {
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"match": {
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"text": "quick brown fox"
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}
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},
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"filter": {
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"term": {
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"status": "published"
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}
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}
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}
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}
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}
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-------------------------
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==== Filter auto-caching
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It used to be possible to control which filters were cached with the `_cache`
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option and to provide a custom `_cache_key`. These options are deprecated
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and, if present, will be ignored.
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Query clauses used in filter context are now auto-cached when it makes sense
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to do so. The algorithm takes into account the frequency of use, the cost of
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query execution, and the cost of building the filter.
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The `terms` filter lookup mechanism no longer caches the values of the
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document containing the terms. It relies on the filesystem cache instead. If
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the lookup index is not too large, it is recommended to replicate it to all
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nodes by setting `index.auto_expand_replicas: 0-all` in order to remove the
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network overhead as well.
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==== Numeric queries use IDF for scoring
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Previously, term queries on numeric fields were deliberately prevented from
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using the usual Lucene scoring logic and this behaviour was undocumented and,
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to some, unexpected.
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Single `term` queries on numeric fields now score in the same way as string
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fields, using IDF and norms (if enabled).
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To query numeric fields without scoring, the query clause should be used in
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filter context, e.g. in the `filter` parameter of the `bool` query, or wrapped
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in a `constant_score` query:
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[source,js]
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----------------------------
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GET _search
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{
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"query": {
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"bool": {
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"must": [
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{
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"match": { <1>
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"numeric_tag": 5
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}
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}
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],
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"filter": [
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{
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"match": { <2>
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"count": 5
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}
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}
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]
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}
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}
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}
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----------------------------
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<1> This clause would include IDF in the relevance score calculation.
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<2> This clause would have no effect on the relevance score.
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==== Fuzziness and fuzzy-like-this
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Fuzzy matching used to calculate the score for each fuzzy alternative, meaning
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that rare misspellings would have a higher score than the more common correct
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spellings. Now, fuzzy matching blends the scores of all the fuzzy alternatives
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to use the IDF of the most frequently occurring alternative.
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Fuzziness can no longer be specified using a percentage, but should instead
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use the number of allowed edits:
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* `0`, `1`, `2`, or
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* `AUTO` (which chooses `0`, `1`, or `2` based on the length of the term)
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The `fuzzy_like_this` and `fuzzy_like_this_field` queries used a very
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expensive approach to fuzzy matching and have been removed.
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==== More Like This
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The More Like This (`mlt`) API and the `more_like_this_field` (`mlt_field`)
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query have been removed in favor of the
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<<query-dsl-mlt-query, `more_like_this`>> query.
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The parameter `percent_terms_to_match` has been removed in favor of
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`minimum_should_match`.
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==== `limit` filter deprecated
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The `limit` filter is deprecated and becomes a no-op. You can achieve similar
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behaviour using the <<search-request-body,terminate_after>> parameter.
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==== Java plugins registering custom queries
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Java plugins that register custom queries can do so by using the
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`IndicesQueriesModule#addQuery(Class<? extends QueryParser>)` method. Other
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ways to register custom queries are not supported anymore.
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