Implemented support for group by without aggregate function

Author: Amper

lib/logsql/select.go

@@ -1185,11 +1185,18 @@ func (v *selectTranslatorVisitor) buildStatsPipe(stmt *ast.SelectStatement, havi
 
 	if len(aggregates) == 0 {
 		if hasGroup {
-			return nil, false, &TranslationError{
-				Code:    http.StatusBadRequest,
-				Message: "translator: GROUP BY requires aggregate expressions",
+			v.aggResults = make(map[string]string)
+			v.aggTempDeletes = nil
+			var pipe string
+			if len(groupFields) > 0 {
+				pipe = fmt.Sprintf("uniq by (%s)", strings.Join(groupFields, ", "))
+			} else {
+				pipe = "uniq"
 			}
+			pipes := append(preGroupPipes, pipe)
+			return pipes, true, nil
 		}
+		v.aggResults = nil
 		return nil, false, nil
 	}
 
@@ -2561,7 +2568,7 @@ func (v *selectTranslatorVisitor) buildProjectionPipes(columns []ast.SelectItem,
 	if len(renamePairs) > 0 {
 		pipes = append(pipes, "rename "+strings.Join(renamePairs, ", "))
 	}
-	if len(fields) > 0 && !aggregated {
+	if len(fields) > 0 && (!aggregated || len(v.aggResults) == 0) {
 		pipes = append(pipes, "fields "+strings.Join(fields, ", "))
 	}
 	return pipes, fields, nil

lib/logsql/select_test.go

@@ -408,6 +408,11 @@ SELECT * FROM logs WHERE level = 'warn'`,
 			sql:      "SELECT service, SUM(1) AS total FROM logs GROUP BY service",
 			expected: "* | format 1 as __const_1 | stats by (service) sum(__const_1) total",
 		},
+		{
+			name:     "group by without aggregates",
+			sql:      "SELECT kubernetes.container_name FROM logs GROUP BY kubernetes.container_name",
+			expected: "* | uniq by (kubernetes.container_name) | fields kubernetes.container_name",
+		},
 		{
 			name: "having aggregate constant",
 			sql:  "SELECT SUM(1) AS \"cnt_slack_079B451E84304DF1AAA4188E26F02806_ok\" FROM logs HAVING COUNT(1) > 0",