Compound order for histogram aggregations. (#22343)

This commit adds support for histogram and date_histogram agg compound order by refactoring and reusing terms agg order code. The major change is that the Terms.Order and Histogram.Order classes have been replaced/refactored into a new class BucketOrder. This is a breaking change for the Java Transport API. For backward compatibility with previous ES versions the (date)histogram compound order will use the first order. Also the _term and _time aggregation order keys have been deprecated; replaced by _key.

Relates to #20003: now that all these aggregations use the same order code, it should be easier to move validation to parse time (as a follow up PR).

Relates to #14771: histogram and date_histogram aggregation order will now be validated at reduce time.

Closes #23613: if a single BucketOrder that is not a tie-breaker is added with the Java Transport API, it will be converted into a CompoundOrder with a tie-breaker.

2 files changed, 117 insertions, 0 deletions

diff --git a/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/10_histogram.yaml b/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/10_histogram.yaml
index 63deebcd87..4955dcfb4d 100644
--- a/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/10_histogram.yaml
+++ b/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/10_histogram.yaml
@@ -10,6 +10,8 @@ setup:
                 "properties":
                   "number":
                      "type" : "integer"
+                  "date":
+                     "type" : "date"
   - do:
       cluster.health:
         wait_for_status: green
@@ -143,3 +145,64 @@ setup:
   - match: { aggregations.histo.buckets.3.key_as_string: "Value is 150.0" }
   
   - match: { aggregations.histo.buckets.3.doc_count: 1 }
+
+---
+"Deprecated _time order":
+
+  - skip:
+      version: " - 5.99.99"
+      reason:  _time order deprecated in 6.0, replaced by _key
+      features: "warnings"
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 1
+        body: { "date" : "2016-01-01" }
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 2
+        body: { "date" : "2016-01-02" }
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 3
+        body: { "date" : "2016-02-01" }
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 4
+        body: { "date" : "2016-03-01" }
+
+  - do:
+      indices.refresh: {}
+
+  - do:
+      search:
+        body: { "aggs" : { "histo" : { "date_histogram" : { "field" : "date", "interval" : "month", "order" : { "_time" : "desc" } } } } }
+      warnings:
+        - "Deprecated aggregation order key [_time] used, replaced by [_key]"
+
+  - match: { hits.total: 4 }
+
+  - length: { aggregations.histo.buckets: 3 }
+
+  - match: { aggregations.histo.buckets.0.key_as_string: "2016-03-01T00:00:00.000Z" }
+
+  - match: { aggregations.histo.buckets.0.doc_count: 1 }
+
+  - match: { aggregations.histo.buckets.1.key_as_string: "2016-02-01T00:00:00.000Z" }
+
+  - match: { aggregations.histo.buckets.1.doc_count: 1 }
+
+  - match: { aggregations.histo.buckets.2.key_as_string: "2016-01-01T00:00:00.000Z" }
+
+  - match: { aggregations.histo.buckets.2.doc_count: 2 }
diff --git a/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/20_terms.yaml b/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/20_terms.yaml
index c9ba94cf61..9cc30bbcd1 100644
--- a/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/20_terms.yaml
+++ b/rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/20_terms.yaml
@@ -747,3 +747,57 @@ setup:
   - match: { aggregations.number_terms.buckets.2.key: 14.6 }
 
   - match: { aggregations.number_terms.buckets.2.doc_count: 1 }
+
+---
+"Deprecated _term order":
+
+  - skip:
+      version: " - 5.99.99"
+      reason:  _term order deprecated in 6.0, replaced by _key
+      features: "warnings"
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 1
+        body: { "str": "abc" }
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 2
+        body: { "str": "abc" }
+
+  - do:
+      index:
+        index: test_1
+        type: test
+        id: 3
+        body: { "str": "bcd" }
+
+  - do:
+      indices.refresh: {}
+
+  - do:
+      search:
+        body: { "size" : 0, "aggs" : { "str_terms" : { "terms" : { "field" : "str", "order" :  { "_term" : "desc" } } } } }
+      warnings:
+        - "Deprecated aggregation order key [_term] used, replaced by [_key]"
+
+  - match: { hits.total: 3 }
+
+  - length: { aggregations.str_terms.buckets: 2 }
+
+  - match: { aggregations.str_terms.buckets.0.key: "bcd" }
+
+  - is_false: aggregations.str_terms.buckets.0.key_as_string
+
+  - match: { aggregations.str_terms.buckets.0.doc_count: 1 }
+
+  - match: { aggregations.str_terms.buckets.1.key: "abc" }
+
+  - is_false: aggregations.str_terms.buckets.1.key_as_string
+
+  - match: { aggregations.str_terms.buckets.1.doc_count: 2 }