Strange error PostgreSQL 9.6 + REST adding

Hi. Publish this topic in General Discussions because i think reason not in REST.
I have DB on postgres 9.6 with table

CREATE TABLE public.projects
(
    name character varying(100) COLLATE pg_catalog."default" NOT NULL,
    priority smallint NOT NULL DEFAULT 0,
    id bigint NOT NULL DEFAULT nextval('projects_id_seq'::regclass),
    CONSTRAINT projects_pkey PRIMARY KEY (id),
    CONSTRAINT name UNIQUE (name)
)
WITH (
    OIDS = FALSE
)

Try to create simple REST application by manual. Controller:

class ProjectsController extends ActiveController
{
    public $modelClass = 'app\models\Projects';
}

Model generated by gii:

class Projects extends \yii\db\ActiveRecord
{
    /**
     * {@inheritdoc}
     */
    public static function tableName()
    {
        return 'projects';
    }

    /**
     * {@inheritdoc}
     */
    public function rules()
    {
        return [
            [['name'], 'required'],
            [['priority'], 'default', 'value' => 0],
            [['priority'], 'integer'],
            [['name'], 'string', 'max' => 100],
            [['name'], 'unique'],
        ];
    }

    /**
     * {@inheritdoc}
     */
    public function attributeLabels()
    {
        return [
            'name' => 'Name',
            'priority' => 'Priority',
            'id' => 'ID',
        ];
    }
}

In table already added first record (manually, by pgadmin) with id 1. Try to add second record by REST

curl -i -H "Accept:application/json" -H "Content-Type:application/json" -XPOST "http://localhost/projects" -d '{"name": "testprj2"}'

And get strange error (russian text on english like “Error: not unique value in projects_pkey, key id=1 already exists”):

{
  "name": "Integrity constraint violation",
  "message": "SQLSTATE[23505]: Unique violation: 7 ОШИБКА:  повторяющееся значение ключа нарушает ограничение уникальности \"projects_pkey\"\nDETAIL:  Ключ \"(id)=(1)\" уже существует.\nThe SQL being executed was: INSERT INTO \"projects\" (\"name\", \"priority\") VALUES ('testprj2', 0) RETURNING \"id\"",
  "code": 23505,
  "type": "yii\\db\\IntegrityException",
  "file": "/home/www/cr-ng-web/vendor/yiisoft/yii2/db/Schema.php",
  "line": 664,
  "stack-trace": [
    "#0 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(1263): yii\\db\\Schema->convertException(Object(PDOException), 'INSERT INTO \"pr...')",
    "#1 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(1148): yii\\db\\Command->internalExecute('INSERT INTO \"pr...')",
    "#2 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(413): yii\\db\\Command->queryInternal('fetch', NULL)",
    "#3 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/pgsql/Schema.php(617): yii\\db\\Command->queryOne()",
    "#4 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/ActiveRecord.php(549): yii\\db\\pgsql\\Schema->insert('projects', Array)",
    "#5 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/ActiveRecord.php(515): yii\\db\\ActiveRecord->insertInternal(NULL)",
    "#6 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/BaseActiveRecord.php(670): yii\\db\\ActiveRecord->insert(true, NULL)",
    "#7 /home/www/cr-ng-web/vendor/yiisoft/yii2/rest/CreateAction.php(52): yii\\db\\BaseActiveRecord->save()",
    "#8 [internal function]: yii\\rest\\CreateAction->run()",
    "#9 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Action.php(94): call_user_func_array(Array, Array)",
    "#10 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Controller.php(157): yii\\base\\Action->runWithParams(Array)",
    "#11 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Module.php(528): yii\\base\\Controller->runAction('create', Array)",
    "#12 /home/www/cr-ng-web/vendor/yiisoft/yii2/web/Application.php(103): yii\\base\\Module->runAction('projects/create', Array)",
    "#13 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Application.php(386): yii\\web\\Application->handleRequest(Object(yii\\web\\Request))",
    "#14 /home/www/cr-ng-web/web/index.php(12): yii\\base\\Application->run()",
    "#15 {main}"
  ],
  "error-info": [
    "23505",
    7,
    "ОШИБКА:  повторяющееся значение ключа нарушает ограничение уникальности \"projects_pkey\"\nDETAIL:  Ключ \"(id)=(1)\" уже существует."
  ],
  "previous": {
    "name": "Exception",
    "message": "SQLSTATE[23505]: Unique violation: 7 ОШИБКА:  повторяющееся значение ключа нарушает ограничение уникальности \"projects_pkey\"\nDETAIL:  Ключ \"(id)=(1)\" уже существует.",
    "code": "23505",
    "type": "PDOException",
    "file": "/home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php",
    "line": 1258,
    "stack-trace": [
      "#0 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(1258): PDOStatement->execute()",
      "#1 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(1148): yii\\db\\Command->internalExecute('INSERT INTO \"pr...')",
      "#2 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/Command.php(413): yii\\db\\Command->queryInternal('fetch', NULL)",
      "#3 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/pgsql/Schema.php(617): yii\\db\\Command->queryOne()",
      "#4 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/ActiveRecord.php(549): yii\\db\\pgsql\\Schema->insert('projects', Array)",
      "#5 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/ActiveRecord.php(515): yii\\db\\ActiveRecord->insertInternal(NULL)",
      "#6 /home/www/cr-ng-web/vendor/yiisoft/yii2/db/BaseActiveRecord.php(670): yii\\db\\ActiveRecord->insert(true, NULL)",
      "#7 /home/www/cr-ng-web/vendor/yiisoft/yii2/rest/CreateAction.php(52): yii\\db\\BaseActiveRecord->save()",
      "#8 [internal function]: yii\\rest\\CreateAction->run()",
      "#9 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Action.php(94): call_user_func_array(Array, Array)",
      "#10 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Controller.php(157): yii\\base\\Action->runWithParams(Array)",
      "#11 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Module.php(528): yii\\base\\Controller->runAction('create', Array)",
      "#12 /home/www/cr-ng-web/vendor/yiisoft/yii2/web/Application.php(103): yii\\base\\Module->runAction('projects/create', Array)",
      "#13 /home/www/cr-ng-web/vendor/yiisoft/yii2/base/Application.php(386): yii\\web\\Application->handleRequest(Object(yii\\web\\Request))",
      "#14 /home/www/cr-ng-web/web/index.php(12): yii\\base\\Application->run()",
      "#15 {main}"
    ]
  }
}

It confused me because in trace i see query

INSERT INTO "projects" ("name", "priority") VALUES ('testprj2', 0) 

There is no id field and it must generated automatically by postgres. I get this query and run into pgadmin. Project #2 was successfully added. After that i without problems added project #3 by REST. This strange error is dissapeared.

How you think, this is PostgreSQL problem or some yii bug?

This is postgres bug. If you add some records with manually primary key (1,2,…) you will see it.