SELECT 
  company_descriptions.*, 
  companies.*, 
  yandex_checkout_shopid, 
  agent_type, 
  tax_number, 
  yandex_tax_code, 
  cscart_vendor_plan_descriptions.plan, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path, 
  AVG(
    cscart_discussion_rating.rating_value
  ) AS average_rating, 
  CONCAT(
    companies.company_id, 
    '_', 
    IF (
      cscart_discussion_rating.thread_id, 
      cscart_discussion_rating.thread_id, 
      '0'
    )
  ) AS company_thread_ids 
FROM 
  cscart_companies AS companies 
  LEFT JOIN cscart_company_descriptions AS company_descriptions ON company_descriptions.company_id = companies.company_id 
  AND company_descriptions.lang_code = 'ru' 
  LEFT JOIN cscart_vendor_plan_descriptions ON companies.plan_id = cscart_vendor_plan_descriptions.plan_id 
  AND cscart_vendor_plan_descriptions.lang_code = 'ru' 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = 9 
  AND cscart_seo_names.type = 'm' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'ru' 
  LEFT JOIN cscart_discussion ON cscart_discussion.object_id = companies.company_id 
  AND cscart_discussion.object_type = 'M' 
  LEFT JOIN cscart_discussion_posts ON cscart_discussion_posts.thread_id = cscart_discussion.thread_id 
  AND cscart_discussion_posts.status = 'A' 
  LEFT JOIN cscart_discussion_rating ON cscart_discussion.thread_id = cscart_discussion_rating.thread_id 
  AND cscart_discussion_rating.post_id = cscart_discussion_posts.post_id 
WHERE 
  companies.company_id = 9

Query time 0.00079

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "table": {
      "table_name": "companies",
      "access_type": "system",
      "possible_keys": ["PRIMARY"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "company_descriptions",
      "access_type": "system",
      "possible_keys": ["PRIMARY"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_vendor_plan_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "10",
      "used_key_parts": ["plan_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_seo_names",
      "access_type": "ref",
      "possible_keys": ["PRIMARY", "dispatch"],
      "key": "PRIMARY",
      "key_length": "206",
      "used_key_parts": ["object_id", "type", "dispatch", "lang_code"],
      "ref": ["const", "const", "const", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(cscart_seo_names.`type` = 'm' and cscart_seo_names.dispatch = '' and cscart_seo_names.lang_code = 'ru')"
    },
    "table": {
      "table_name": "cscart_discussion",
      "access_type": "const",
      "possible_keys": ["object_id"],
      "key": "object_id",
      "key_length": "6",
      "used_key_parts": ["object_id", "object_type"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(cscart_discussion.object_type = 'M')"
    },
    "table": {
      "table_name": "cscart_discussion_posts",
      "access_type": "ALL",
      "possible_keys": ["thread_id", "thread_id_2"],
      "rows": 3,
      "filtered": 100,
      "attached_condition": "trigcond(cscart_discussion_posts.thread_id = cscart_discussion.thread_id and cscart_discussion_posts.`status` = 'A')"
    },
    "table": {
      "table_name": "cscart_discussion_rating",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "thread_id"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["post_id"],
      "ref": ["admin_test.cscart_discussion_posts.post_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(cscart_discussion_rating.thread_id = cscart_discussion.thread_id and trigcond(cscart_discussion_posts.post_id is not null))"
    }
  }
}