feat: Support collection group

completer.go

@@ -20,10 +20,11 @@ var rootSuggestions = []prompt.Suggest{
 }
 
 var (
-	selectSuggestion  = prompt.Suggest{Text: "SELECT", Description: "SELECT [field...]"}
-	whereSuggestion   = prompt.Suggest{Text: "WHERE", Description: "WHERE [field] [operator] [value]"}
-	orderBySuggestion = prompt.Suggest{Text: "ORDER BY", Description: "ORDER BY [field] [ASC/DESC]"}
-	limitSuggestion   = prompt.Suggest{Text: "LIMIT", Description: "LIMIT [count]"}
+	selectSuggestion          = prompt.Suggest{Text: "SELECT", Description: "SELECT [field...]"}
+	whereSuggestion           = prompt.Suggest{Text: "WHERE", Description: "WHERE [field] [operator] [value]"}
+	orderBySuggestion         = prompt.Suggest{Text: "ORDER BY", Description: "ORDER BY [field] [ASC/DESC]"}
+	limitSuggestion           = prompt.Suggest{Text: "LIMIT", Description: "LIMIT [count]"}
+	collectionGroupSuggestion = prompt.Suggest{Text: "COLLECTION_GROUP", Description: "COLLECTION_GROUP [collection]"}
 )
 
 var querySuggestions = []prompt.Suggest{
@@ -83,12 +84,24 @@ func (c *Completer) Parse() ([]prompt.Suggest, error) {
 }
 
 func (c *Completer) parseQueryOperation() ([]prompt.Suggest, error) {
-	if !c.expectPeek(IDENT) {
+	if !c.peekTokenIs(IDENT) && !c.peekTokenIs(COLLECTION_GROUP) {
 		return []prompt.Suggest{}, nil
 	}
+	c.nextToken()
+
+	collectionGroupMode := false
+	if c.curTokenIs(COLLECTION_GROUP) {
+		collectionGroupMode = true
+		if !c.expectPeek(IDENT) {
+			return []prompt.Suggest{}, nil
+		}
+	}
 
 	// collection := c.curToken.Literal
 	if c.peekTokenIs(EOF) {
+		if collectionGroupMode {
+			return querySuggestions, nil
+		}
 		collection := normalizeFirestorePath(c.curToken.Literal)
 		parts := strings.Split(collection, "/")
 		if len(parts)%2 == 0 {
@@ -109,6 +122,7 @@ func (c *Completer) parseQueryOperation() ([]prompt.Suggest, error) {
 		for _, col := range collections {
 			suggestions = append(suggestions, newCollectionSuggestion(baseDoc, col))
 		}
+		suggestions = append(suggestions, collectionGroupSuggestion)
 
 		return prompt.FilterHasPrefix(suggestions, c.curToken.Literal, false), nil
 	}
@@ -292,11 +306,23 @@ func (c *Completer) parseGetOperation() ([]prompt.Suggest, error) {
 }
 
 func (c *Completer) parseCountOperation() ([]prompt.Suggest, error) {
-	if !c.expectPeek(IDENT) {
+	if !c.peekTokenIs(IDENT) && !c.peekTokenIs(COLLECTION_GROUP) {
 		return []prompt.Suggest{}, nil
 	}
+	c.nextToken()
+
+	collectionGroupMode := false
+	if c.curTokenIs(COLLECTION_GROUP) {
+		collectionGroupMode = true
+		if !c.expectPeek(IDENT) {
+			return []prompt.Suggest{}, nil
+		}
+	}
 
 	if c.peekTokenIs(EOF) {
+		if collectionGroupMode {
+			return []prompt.Suggest{whereSuggestion}, nil
+		}
 		collection := normalizeFirestorePath(c.curToken.Literal)
 		parts := strings.Split(collection, "/")
 		if len(parts)%2 == 0 {
@@ -317,6 +343,7 @@ func (c *Completer) parseCountOperation() ([]prompt.Suggest, error) {
 		for _, col := range collections {
 			suggestions = append(suggestions, newCollectionSuggestion(baseDoc, col))
 		}
+		suggestions = append(suggestions, collectionGroupSuggestion)
 
 		return prompt.FilterHasPrefix(suggestions, c.curToken.Literal, false), nil
 	}

completer_test.go

@@ -43,6 +43,21 @@ func TestCompleter(t *testing.T) {
 			input: `QUERY us`,
 			want:  []prompt.Suggest{newCollectionSuggestion("", "user")},
 		},
+		{
+			desc:  "middle of query with collection_group keyword",
+			input: `QUERY C`,
+			want:  []prompt.Suggest{collectionGroupSuggestion},
+		},
+		{
+			desc:  "query collection_group with name and where",
+			input: `QUERY COLLECTION_GROUP posts WH`,
+			want:  []prompt.Suggest{whereSuggestion},
+		},
+		{
+			desc:  "query collection_group with name",
+			input: `QUERY COLLECTION_GROUP posts`,
+			want:  querySuggestions,
+		},
 		{
 			desc:  "middle of query with sub collection",
 			input: `QUERY user/1/p`,
@@ -174,6 +189,21 @@ func TestCompleter(t *testing.T) {
 			input: `COUNT us`,
 			want:  []prompt.Suggest{newCollectionSuggestion("", "user")},
 		},
+		{
+			desc:  "middle of count with collection_group keyword",
+			input: `COUNT C`,
+			want:  []prompt.Suggest{collectionGroupSuggestion},
+		},
+		{
+			desc:  "count collection_group with name and where",
+			input: `COUNT COLLECTION_GROUP posts WH`,
+			want:  []prompt.Suggest{whereSuggestion},
+		},
+		{
+			desc:  "count collection_group with name",
+			input: `COUNT COLLECTION_GROUP posts`,
+			want:  []prompt.Suggest{whereSuggestion},
+		},
 		{
 			desc:  "middle of count with sub collection",
 			input: `COUNT user/1/p`,

docs/operations.md

@@ -8,6 +8,7 @@ Query documents in a collection. Supports `SELECT`, `WHERE`, `ORDER BY`, and `LI
 
 ```
 QUERY <collection_path> [SELECT ...] [WHERE ...] [ORDER BY ...] [LIMIT ...]
+QUERY COLLECTION_GROUP <collection_id> [SELECT ...] [WHERE ...] [ORDER BY ...] [LIMIT ...]
 ```
 
 ### Examples
@@ -21,6 +22,9 @@ QUERY users WHERE age = 20
 
 -- Subcollection query
 QUERY users/abc123/posts
+
+-- Collection group query
+QUERY COLLECTION_GROUP posts WHERE title = "post-1-1"
 ```
 
 ## GET
@@ -49,6 +53,7 @@ Count documents in a collection. Supports `WHERE` clause for filtering.
 
 ```
 COUNT <collection_path> [WHERE ...]
+COUNT COLLECTION_GROUP <collection_id> [WHERE ...]
 ```
 
 Returns a single integer.
@@ -61,6 +66,9 @@ COUNT users
 
 -- Count with filter
 COUNT users WHERE name = "takashi"
+
+-- Collection group count
+COUNT COLLECTION_GROUP posts WHERE title = "post-1-1"
 ```
 
 ## Collection Path
@@ -75,3 +83,11 @@ collection/docId/subcollection/docId/subcollection/...
 - **Document path** (odd number of segments): `users/abc123`, `users/abc123/posts/xyz789`
 
 Leading slashes are automatically stripped.
+
+## Collection Group
+
+`COLLECTION_GROUP` targets all collections with the same collection ID across the database hierarchy.
+
+- Use a single collection ID (for example, `posts`)
+- Slash-separated paths are not allowed (for example, `users/posts` is invalid)
+- Supported with `QUERY` and `COUNT`

executor.go

@@ -20,17 +20,25 @@ func NewExecutor(ctx context.Context, fs *firestore.Client) *Executor {
 }
 
 func (exe *Executor) ExecuteQuery(ctx context.Context, op *QueryOperation) ([]*firestore.DocumentSnapshot, error) {
-	collection := exe.fs.Collection(op.Collection())
-	if collection == nil {
-		return nil, ErrInvalidCollection
+	var q firestore.Query
+	if op.IsCollectionGroup() {
+		q = exe.fs.CollectionGroup(op.Collection()).Query
+	} else {
+		collection := exe.fs.Collection(op.Collection())
+		if collection == nil {
+			return nil, ErrInvalidCollection
+		}
+		q = collection.Query
 	}
-	q := collection.Query
+
 	for _, filter := range op.filters {
 		fieldName := filter.FieldName()
 		value := filter.Value()
 		if fieldName == FieldDocumentID {
 			fieldName = firestore.DocumentID
-			value = toDocRefValue(collection, value)
+			if !op.IsCollectionGroup() {
+				value = toDocRefValue(exe.fs.Collection(op.Collection()), value)
+			}
 		}
 		q = q.Where(fieldName, string(filter.Operator()), value)
 	}
@@ -76,17 +84,25 @@ func (exe *Executor) ExecuteGet(ctx context.Context, op *GetOperation) (*firesto
 }
 
 func (exe *Executor) ExecuteCount(ctx context.Context, op *CountOperation) (int64, error) {
-	collection := exe.fs.Collection(op.Collection())
-	if collection == nil {
-		return 0, ErrInvalidCollection
+	var q firestore.Query
+	if op.IsCollectionGroup() {
+		q = exe.fs.CollectionGroup(op.Collection()).Query
+	} else {
+		collection := exe.fs.Collection(op.Collection())
+		if collection == nil {
+			return 0, ErrInvalidCollection
+		}
+		q = collection.Query
 	}
-	q := collection.Query
+
 	for _, filter := range op.filters {
 		fieldName := filter.FieldName()
 		value := filter.Value()
 		if fieldName == FieldDocumentID {
 			fieldName = firestore.DocumentID
-			value = toDocRefValue(collection, value)
+			if !op.IsCollectionGroup() {
+				value = toDocRefValue(exe.fs.Collection(op.Collection()), value)
+			}
 		}
 		q = q.Where(fieldName, string(filter.Operator()), value)
 	}

executor_test.go

@@ -146,6 +146,18 @@ func TestQuery(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "query with collection group",
+			input: NewCollectionGroupQueryOperation("posts", nil, []Filter{
+				NewStringFilter("title", "==", "post-1-1"),
+			}, nil, 0),
+			want: []map[string]any{
+				{
+					"title":       "post-1-1",
+					"publishedAt": time.Date(2025, 1, 2, 0, 0, 0, 0, time.UTC),
+				},
+			},
+		},
 		{
 			desc: "query with not equal",
 			input: &QueryOperation{collection: "users", filters: []Filter{
@@ -448,6 +460,13 @@ func TestCount(t *testing.T) {
 			}),
 			want: 3,
 		},
+		{
+			desc: "count with collection group",
+			input: NewCollectionGroupCountOperation("posts", []Filter{
+				NewStringFilter("title", "==", "post-1-1"),
+			}),
+			want: 1,
+		},
 	}
 
 	for _, tt := range tests {

operation.go

@@ -133,17 +133,22 @@ type OrderBy struct {
 
 type QueryOperation struct {
 	BaseOperation
-	collection string
-	selects    []string
-	filters    []Filter
-	orderBys   []OrderBy
-	limit      int
+	collection      string
+	collectionGroup bool
+	selects         []string
+	filters         []Filter
+	orderBys        []OrderBy
+	limit           int
 }
 
 func NewQueryOperation(collection string, selects []string, filters []Filter, orderBys []OrderBy, limit int) *QueryOperation {
 	return &QueryOperation{collection: collection, selects: selects, filters: filters, orderBys: orderBys, limit: limit}
 }
 
+func NewCollectionGroupQueryOperation(collectionGroup string, selects []string, filters []Filter, orderBys []OrderBy, limit int) *QueryOperation {
+	return &QueryOperation{collection: collectionGroup, collectionGroup: true, selects: selects, filters: filters, orderBys: orderBys, limit: limit}
+}
+
 func (op *QueryOperation) OperationType() OperationType {
 	return OPERATION_TYPE_QUERY
 }
@@ -152,6 +157,10 @@ func (op *QueryOperation) Collection() string {
 	return op.collection
 }
 
+func (op *QueryOperation) IsCollectionGroup() bool {
+	return op.collectionGroup
+}
+
 type GetOperation struct {
 	BaseOperation
 	collection string
@@ -181,18 +190,27 @@ func (op *GetOperation) Selects() []string {
 
 type CountOperation struct {
 	BaseOperation
-	collection string
-	filters    []Filter
+	collection      string
+	collectionGroup bool
+	filters         []Filter
 }
 
 func NewCountOperation(collection string, filters []Filter) *CountOperation {
 	return &CountOperation{collection: collection, filters: filters}
 }
 
+func NewCollectionGroupCountOperation(collectionGroup string, filters []Filter) *CountOperation {
+	return &CountOperation{collection: collectionGroup, collectionGroup: true, filters: filters}
+}
+
 func (op *CountOperation) OperationType() OperationType {
 	return OPERATION_TYPE_COUNT
 }
 
 func (op *CountOperation) Collection() string {
 	return op.collection
 }
+
+func (op *CountOperation) IsCollectionGroup() bool {
+	return op.collectionGroup
+}