Add support for CombinedFieldsQuery

See
https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-combined-fields-query.html
for details.

Close #1512

README.md

@@ -340,6 +340,8 @@ Here are a few tips on how to get used to Elastic:
   - [x] Common Terms Query
   - [x] Query String Query
   - [x] Simple Query String Query
+  - [x] Combined Fields Query
+  - [x] Intervals Query
 - Term level queries
   - [x] Term Query
   - [x] Terms Query

search_queries_combined_fields.go

@@ -0,0 +1,110 @@
+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+import "fmt"
+
+// CombinedFieldsQuery supports searching multiple text fields as if their
+// contents had been indexed into one combined field.
+//
+// For more details, see
+// https://www.elastic.co/guide/en/elasticsearch/reference/7.13/query-dsl-combined-fields-query.html
+type CombinedFieldsQuery struct {
+	text                            interface{}
+	fields                          []string
+	fieldBoosts                     map[string]*float64
+	autoGenerateSynonymsPhraseQuery *bool
+	operator                        string // AND or OR
+	minimumShouldMatch              string
+	zeroTermsQuery                  string
+}
+
+// NewCombinedFieldsQuery creates and initializes a new CombinedFieldsQuery.
+func NewCombinedFieldsQuery(text interface{}, fields ...string) *CombinedFieldsQuery {
+	q := &CombinedFieldsQuery{
+		text:        text,
+		fieldBoosts: make(map[string]*float64),
+	}
+	q.fields = append(q.fields, fields...)
+	return q
+}
+
+// Field adds a field to run the multi match against.
+func (q *CombinedFieldsQuery) Field(field string) *CombinedFieldsQuery {
+	q.fields = append(q.fields, field)
+	return q
+}
+
+// FieldWithBoost adds a field to run the multi match against with a specific boost.
+func (q *CombinedFieldsQuery) FieldWithBoost(field string, boost float64) *CombinedFieldsQuery {
+	q.fields = append(q.fields, field)
+	q.fieldBoosts[field] = &boost
+	return q
+}
+
+// AutoGenerateSynonymsPhraseQuery indicates whether phrase queries should be
+// automatically generated for multi terms synonyms. Defaults to true.
+func (q *CombinedFieldsQuery) AutoGenerateSynonymsPhraseQuery(enable bool) *CombinedFieldsQuery {
+	q.autoGenerateSynonymsPhraseQuery = &enable
+	return q
+}
+
+// Operator sets the operator to use when using boolean query.
+// It can be either AND or OR (default).
+func (q *CombinedFieldsQuery) Operator(operator string) *CombinedFieldsQuery {
+	q.operator = operator
+	return q
+}
+
+// MinimumShouldMatch represents the minimum number of optional should clauses
+// to match.
+func (q *CombinedFieldsQuery) MinimumShouldMatch(minimumShouldMatch string) *CombinedFieldsQuery {
+	q.minimumShouldMatch = minimumShouldMatch
+	return q
+}
+
+// ZeroTermsQuery can be "all" or "none".
+func (q *CombinedFieldsQuery) ZeroTermsQuery(zeroTermsQuery string) *CombinedFieldsQuery {
+	q.zeroTermsQuery = zeroTermsQuery
+	return q
+}
+
+// Source returns JSON for the query.
+func (q *CombinedFieldsQuery) Source() (interface{}, error) {
+	source := make(map[string]interface{})
+
+	combinedFields := make(map[string]interface{})
+	source["combined_fields"] = combinedFields
+
+	combinedFields["query"] = q.text
+
+	fields := []string{}
+	for _, field := range q.fields {
+		if boost, found := q.fieldBoosts[field]; found {
+			if boost != nil {
+				fields = append(fields, fmt.Sprintf("%s^%f", field, *boost))
+			} else {
+				fields = append(fields, field)
+			}
+		} else {
+			fields = append(fields, field)
+		}
+	}
+	combinedFields["fields"] = fields
+
+	if q.autoGenerateSynonymsPhraseQuery != nil {
+		combinedFields["auto_generate_synonyms_phrase_query"] = q.autoGenerateSynonymsPhraseQuery
+	}
+	if q.operator != "" {
+		combinedFields["operator"] = q.operator
+	}
+	if q.minimumShouldMatch != "" {
+		combinedFields["minimum_should_match"] = q.minimumShouldMatch
+	}
+	if q.zeroTermsQuery != "" {
+		combinedFields["zero_terms_query"] = q.zeroTermsQuery
+	}
+	return source, nil
+}

search_queries_combined_fields_test.go

@@ -0,0 +1,34 @@
+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestCombinedFieldsQuery(t *testing.T) {
+	q := NewCombinedFieldsQuery("query text", "f1", "f2").
+		Field("f3").
+		FieldWithBoost("f4", 2.0).
+		AutoGenerateSynonymsPhraseQuery(false).
+		Operator("AND").
+		MinimumShouldMatch("3").
+		ZeroTermsQuery("all")
+
+	src, err := q.Source()
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := json.Marshal(src)
+	if err != nil {
+		t.Fatalf("marshaling to JSON failed: %v", err)
+	}
+	got := string(data)
+	expected := `{"combined_fields":{"auto_generate_synonyms_phrase_query":false,"fields":["f1","f2","f3","f4^2.000000"],"minimum_should_match":"3","operator":"AND","query":"query text","zero_terms_query":"all"}}`
+	if got != expected {
+		t.Errorf("expected\n%s\n,got:\n%s", expected, got)
+	}
+}