SELECT 
  company_descriptions.*, 
  companies.*, 
  vendor_plan_descriptions.plan, 
  seo_names.name as seo_name, 
  seo_names.path as seo_path, 
  vendor_ga_tracking_code, 
  vendor_fb_tracking_code, 
  AVG(discussion_rating.rating_value) AS average_rating, 
  CONCAT(
    companies.company_id, 
    '_', 
    IF (
      discussion_rating.thread_id, discussion_rating.thread_id, 
      '0'
    )
  ) AS company_thread_ids 
FROM 
  companies AS companies 
  LEFT JOIN company_descriptions AS company_descriptions ON company_descriptions.company_id = companies.company_id 
  AND company_descriptions.lang_code = 'en' 
  LEFT JOIN vendor_plan_descriptions ON companies.plan_id = vendor_plan_descriptions.plan_id 
  AND vendor_plan_descriptions.lang_code = 'en' 
  LEFT JOIN seo_names ON seo_names.object_id = 539 
  AND seo_names.type = 'm' 
  AND seo_names.dispatch = '' 
  AND seo_names.lang_code = 'en' 
  LEFT JOIN discussion as discussionA ON discussionA.object_id = companies.company_id 
  AND discussionA.object_type = 'M' 
  LEFT JOIN discussion_posts ON discussion_posts.thread_id = discussionA.thread_id 
  AND discussion_posts.status = 'A' 
  LEFT JOIN discussion_rating ON discussionA.thread_id = discussion_rating.thread_id 
  AND discussion_rating.post_id = discussion_posts.post_id 
WHERE 
  companies.company_id = 539

Query time 0.00099

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.79"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "companies",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "company_id"
          ],
          "key_length": "4",
          "ref": [
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.10",
            "prefix_cost": "0.00",
            "data_read_per_join": "14K"
          },
          "used_columns": [
            "company_id",
            "status",
            "company",
            "lang_code",
            "address",
            "city",
            "state",
            "country",
            "zipcode",
            "email",
            "phone",
            "url",
            "storefront",
            "secure_storefront",
            "entry_page",
            "redirect_customer",
            "countries_list",
            "timestamp",
            "shippings",
            "logos",
            "request_user_id",
            "request_account_name",
            "request_account_data",
            "plan_id",
            "stripe_connect_account_id",
            "identifier_facebook_pixel",
            "featured_products",
            "sd_ga_tracking_code",
            "paypal_commerce_platform_account_id",
            "tagline",
            "url_facebook",
            "url_instagram",
            "url_twitter",
            "url_pinterest",
            "announcement",
            "shippo_api_token",
            "shippo_carrier",
            "shippo_service_type",
            "vendor_ga_tracking_code",
            "vendor_fb_tracking_code",
            "custom_domain",
            "custom_domain_status",
            "taxjar_key",
            "taxjar_export_statuses",
            "taxjar_export_csv_data",
            "ag_hide_city",
            "updated_timestamp",
            "suspend_date",
            "grace_period_start",
            "last_time_suspended",
            "last_debt_notification_time",
            "tax_number",
            "stripe_connect_account_type",
            "registered_from_storefront_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "company_descriptions",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "company_id",
            "lang_code"
          ],
          "key_length": "10",
          "ref": [
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.10",
            "prefix_cost": "0.00",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "company_id",
            "lang_code",
            "company_description",
            "terms",
            "subdomain_colors",
            "i18n_company",
            "i18n_address",
            "i18n_city"
          ]
        }
      },
      {
        "table": {
          "table_name": "vendor_plan_descriptions",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "plan_id",
            "lang_code"
          ],
          "key_length": "10",
          "ref": [
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.10",
            "prefix_cost": "0.00",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "plan_id",
            "lang_code",
            "plan"
          ]
        }
      },
      {
        "table": {
          "table_name": "seo_names",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY",
            "dispatch"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "object_id",
            "type",
            "dispatch",
            "lang_code"
          ],
          "key_length": "206",
          "ref": [
            "const",
            "const",
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.84",
            "eval_cost": "0.10",
            "prefix_cost": "0.94",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "name",
            "object_id",
            "type",
            "dispatch",
            "path",
            "lang_code"
          ]
        }
      },
      {
        "table": {
          "table_name": "discussionA",
          "access_type": "const",
          "possible_keys": [
            "object_id"
          ],
          "key": "object_id",
          "used_key_parts": [
            "object_id",
            "object_type"
          ],
          "key_length": "6",
          "ref": [
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "0.71",
            "eval_cost": "0.10",
            "prefix_cost": "1.75",
            "data_read_per_join": "24"
          },
          "used_columns": [
            "thread_id",
            "object_id",
            "object_type"
          ]
        }
      },
      {
        "table": {
          "table_name": "discussion_posts",
          "access_type": "ref",
          "possible_keys": [
            "thread_id",
            "thread_id_2"
          ],
          "key": "thread_id_2",
          "used_key_parts": [
            "thread_id",
            "status"
          ],
          "key_length": "6",
          "ref": [
            "goimagine.discussionA.thread_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "0.25",
            "eval_cost": "0.18",
            "prefix_cost": "2.17",
            "data_read_per_join": "787"
          },
          "used_columns": [
            "post_id",
            "thread_id",
            "status"
          ]
        }
      },
      {
        "table": {
          "table_name": "discussion_rating",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "thread_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "post_id"
          ],
          "key_length": "3",
          "ref": [
            "goimagine.discussion_posts.post_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.44",
            "eval_cost": "0.18",
            "prefix_cost": "2.79",
            "data_read_per_join": "28"
          },
          "used_columns": [
            "rating_value",
            "post_id",
            "thread_id"
          ],
          "attached_condition": "<if>(is_not_null_compl(discussion_rating), (`goimagine`.`discussion_rating`.`thread_id` = `goimagine`.`discussionA`.`thread_id`), true)"
        }
      }
    ]
  }
}