ActiveRecordでupdateできない

Question

前提・実現したいこと

Rubyで記述したプログラム上で、ActiveRecordを通してPostgreSQLを操作したい。

teachersテーブルは以下のカラムを持っています。

• id
• name
• subject

require 'active_record'

ActiveRecord::Base.establish_connection(
    adapter: "postgresql",
    host: "",
    username: "kampachi",
    password: "",
    database: "testdb01"
)

class Teacher < ActiveRecord::Base
end

teacher = Teacher.find_by(name: "Kampachi")

p teacher

<Teacher id: 3, name: "Kampachi", subject: "science">

発生している問題・エラーメッセージ

subjectを更新しようと思い、以下のように記述しました。

require 'active_record'

ActiveRecord::Base.establish_connection(
    adapter: "postgresql",
    host: "",
    username: "kampachi",
    password: "",
    database: "testdb01"
)

class Teacher < ActiveRecord::Base
end

teacher = Teacher.find_by(name: "Kampachi")

teacher.update(subject: "English")

Traceback (most recent call last):
        56: from rb_pg_01.rb:30:in `<main>'
        55: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/relation.rb:342:in `update'
        54: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/relation/delegation.rb:71:in `each'
        53: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/relation/delegation.rb:71:in `each'
        52: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/relation.rb:342:in `block in update'
        51: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:426:in `update'
        50: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:385:in `with_transaction_returning_status'
        49: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:212:in `transaction'
        48: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/database_statements.rb:267:in `transaction'
        47: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/transaction.rb:236:in `within_new_transaction'
        46: from /usr/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
        45: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/transaction.rb:239:in `block in within_new_transaction'
        44: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/database_statements.rb:267:in `block in transaction'
        43: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:387:in `block in with_transaction_returning_status'
        42: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:428:in `block in update'
        41: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/suppressor.rb:44:in `save'
        40: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:309:in `save'
        39: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:325:in `rollback_active_record_state!'
        38: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:310:in `block in save'
        37: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:385:in `with_transaction_returning_status'
        36: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:212:in `transaction'
        35: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/database_statements.rb:265:in `transaction'
        34: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:387:in `block in with_transaction_returning_status'
        33: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/transactions.rb:310:in `block (2 levels) in save'
        32: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/validations.rb:46:in `save'
        31: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:275:in `save'
        30: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/callbacks.rb:342:in `create_or_update'
        29: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/callbacks.rb:816:in `_run_save_callbacks'
        28: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/callbacks.rb:98:in `run_callbacks'
        27: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/callbacks.rb:342:in `block in create_or_update'
        26: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:705:in `create_or_update'
        25: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/timestamp.rb:114:in `_update_record'
        24: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/callbacks.rb:350:in `_update_record'
        23: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/callbacks.rb:816:in `_run_update_callbacks'
        22: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/callbacks.rb:98:in `run_callbacks'
        21: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/callbacks.rb:350:in `block in _update_record'
        20: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/attribute_methods/dirty.rb:134:in `_update_record'
        19: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:719:in `_update_record'
        18: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/locking/optimistic.rb:80:in `_update_row'
        17: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:696:in `_update_row'
        16: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/persistence.rb:197:in `_update_record'
        15: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/query_cache.rb:21:in `update'
        14: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract/database_statements.rb:170:in `update'
        13: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql/database_statements.rb:94:in `exec_delete'
        12: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:598:in `execute_and_clear'
        11: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:609:in `exec_no_cache'
        10: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract_adapter.rb:571:in `log'
         9: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/notifications/instrumenter.rb:23:in `instrument'
         8: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract_adapter.rb:580:in `block in log'
         7: from /usr/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
         6: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/abstract_adapter.rb:581:in `block (2 levels) in log'
         5: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:610:in `block in exec_no_cache'
         4: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies/interlock.rb:47:in `permit_concurrent_loads'
         3: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/concurrency/share_lock.rb:187:in `yield_shares'
         2: from /var/lib/gems/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies/interlock.rb:48:in `block in permit_concurrent_loads'
         1: from /var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:611:in `block (2 levels) in exec_no_cache'
/var/lib/gems/2.5.0/gems/activerecord-5.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:611:in `async_exec_params': PG::SyntaxError: ERROR:  zero-length delimited identifier at or near """" (ActiveRecord::StatementInvalid)
LINE 1: ...PDATE "teachers" SET "subject" = $1 WHERE "teachers"."" = $2
                                                                ^
: UPDATE "teachers" SET "subject" = $1 WHERE "teachers"."" = $2

SQLを直接操作するときに書くSQL文は以下のようになると思うのですが、

UPDATE teachers SET subject = 'English' WHERE teachers.name = 'kampachi';

WHERE以下にカラムの指定ができていない原因はなんでしょうか？
詳しい方ご教示願います。

バージョン情報

Ruby 2.5.1
activerecord 5.2.3
PostgreSQL 10.8

Answer 1

teachersテーブルにPRIMARY KEYが設定されていないのが原因でした。

ALTER TABLE teachers ADD PRIMARY KEY (id);

主キー設定後、上手く動作しました。