Rails PG::UndefinedTable:错误:缺少表的 FROM 子句条目 [英] Rails PG::UndefinedTable: ERROR: missing FROM-clause entry for table

问题描述

我有模型

class Offer < ActiveRecord::Base
  belongs_to :agency
end

class Agency < ActiveRecord::Base
  has_many :offers
end

当我提出这样的要求时 - 一切正常

When I do such request - everything is OK

@offers = Offer.with_state(:confirmed).
  includes(:destination, :cruise_line, :ship).
  paginate(per_page: 10, page: params[:page]).decorate

但我只想选择属于 active 机构的优惠(agencies 表中的 state 列)，所以我尝试这样做这个:

But I want to select only offers that belong to active agencies (column state from agencies table), so I try to do like this:

@offers = Offer.with_state(:confirmed).
  includes(:destination, :cruise_line, :ship).
  joins(:agency).
  where(agency: {state: 'active'}).
  paginate(per_page: 10, page: params[:page]).decorate

完成此操作后，我收到错误 PG::UndefinedTable: ERROR: missing FROM-clause entry for table "agency".我的代码有什么问题?

Having done this I get error PG::UndefinedTable: ERROR: missing FROM-clause entry for table "agency". What is wrong with my code?

查询给了我这个错误和 sql:

The query gives me this error and sql:

PG::UndefinedTable: ERROR: missing FROM-clause entry for table "agency" LINE 1: ...id" WHERE ("offers"."state" IN ('confirmed')) AND "agency"."... ^ : 
SELECT "offers"."id" AS t0_r0, "offers"."name" AS t0_r1, "offers"."destination_id" AS t0_r2, "offers"."cruise_line_id" AS t0_r3, "offers"."ship_id" AS t0_r4, "offers"."departure_date" AS t0_r5, "offers"."departure_port_id" AS t0_r6, "offers"."arrival_date" AS t0_r7, "offers"."arrival_port_id" AS t0_r8, "offers"."flight_price" AS t0_r9, "offers"."bonus" AS t0_r10, "offers"."itinerary" AS t0_r11, "offers"."board_language_id" AS t0_r12, "offers"."agency_landing_page" AS t0_r13, "offers"."benefits" AS t0_r14, "offers"."inner_price" AS t0_r15, "offers"."inner_price_normal" AS t0_r16, "offers"."outer_price" AS t0_r17, "offers"."outer_price_normal" AS t0_r18, "offers"."balcony_price" AS t0_r19, "offers"."balcony_price_normal" AS t0_r20, "offers"."suite_price" AS t0_r21, "offers"."suite_price_normal" AS t0_r22, "offers"."lucky_price" AS t0_r23, "offers"."lucky_price_normal" AS t0_r24, "offers"."valid_from" AS t0_r25, "offers"."valid_till" AS t0_r26, "offers"."created_at" AS t0_r27, "offers"."updated_at" AS t0_r28, "offers"."description" AS t0_r29, "offers"."agency_id" AS t0_r30, "offers"."state" AS t0_r31, "destinations"."id" AS t1_r0, "destinations"."name" AS t1_r1, "destinations"."created_at" AS t1_r2, "destinations"."updated_at" AS t1_r3, "cruise_lines"."id" AS t2_r0, "cruise_lines"."name" AS t2_r1, "cruise_lines"."created_at" AS t2_r2, "cruise_lines"."updated_at" AS t2_r3, "ships"."id" AS t3_r0, "ships"."name" AS t3_r1, "ships"."picture" AS t3_r2, "ships"."cruise_line_id" AS t3_r3, "ships"."created_at" AS t3_r4, "ships"."updated_at" AS t3_r5 
FROM "offers" 
INNER JOIN "agencies" ON "agencies"."id" = "offers"."agency_id" 
LEFT OUTER JOIN "destinations" ON "destinations"."id" = "offers"."destination_id" 
LEFT OUTER JOIN "cruise_lines" ON "cruise_lines"."id" = "offers"."cruise_line_id" 
LEFT OUTER JOIN "ships" ON "ships"."id" = "offers"."ship_id" 
WHERE ("offers"."state" IN ('confirmed')) AND "agency"."state" = 'active' 
LIMIT 10 OFFSET 0

推荐答案

您添加的唯一内容是 where 子句.好像有问题:

The only thing you've added is a where-clause. Seems like it's problematic:

where(agency: {state: 'active'})

...并产生错误的条件，因为在这种情况下，散列键应表示表名.你可能应该有这个:

...and produces a wrong condition because hash key in this case is expected to mean a table name. You should probably have this:

where(agencies: {state: 'active'})

更新

看到这吸引了相当多的注意力，我想我也应该建议一种不同的方式来做同样的事情，稍微更可组合:

Update

Seeing this attract quite a lot of attention, I think I should also suggest a different way of doing the same, slightly more composable:

merge( Agency.where(state: 'active') )

这个如何更好?它不对模型的表名做任何假设(大多数时候这并不重要)并允许您使用范围:

How is this one better? It makes no assumptions about the table name of the model (not that it matters most of the time) and allows you to use scopes:

# Inside Agency
scope :active, -> { where(state: 'active') }

# Somewhere else
merge(Agency.active)

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