0
我有一個rails應用程序(postgres + postGIS)與一個評級列(整數)後模型。如果我進入控制檯,並做到:Postgres的偏移量/限制與mysql的工作方式不一樣嗎?
Post.order("rating DESC").map(&:id)
=> [9, 15, 19, 6, 17, 5, 4, 16, 1, 3, 13, 20, 14, 10, 8, 12, 7, 2, 18, 11]
然而,如果我通過這些一個嘗試週期在與限制時間和偏移,我得到奇怪的結果。
Post.order("rating DESC").limit(1).offset(0)
=> [#<Post id: 5, body: "Hi", rating: 4, location: #<RGeo::Geographic::SphericalPointImpl:0x81bb34c0 "POINT (-118.495 34.017)">, user_id: 8, created_at: "2012-07-25 22:43:41", updated_at: "2012-07-25 22:43:41">]
爲什麼這篇文章#5?它應該是#9。無論如何,當我申請抵消時,它會變得更加怪異。
>Post.order("rating DESC").limit(1).offset(1)
=> [#<Post id: 5, body: "Hi", rating: 4, location: #<RGeo::Geographic::SphericalPointImpl:0x81bb34c0 "POINT (-118.495 34.017)">, user_id: 8, created_at: "2012-07-25 22:43:41", updated_at: "2012-07-25 22:43:41">]
>Post.order("rating DESC").limit(1).offset(2)
=> [#<Post id: 5, body: "Hi", rating: 4, location: #<RGeo::Geographic::SphericalPointImpl:0x81bb34c0 "POINT (-118.495 34.017)">, user_id: 8, created_at: "2012-07-25 22:43:41", updated_at: "2012-07-25 22:43:41">]
>Post.order("rating DESC").limit(1).offset(3)
=> [#<Post id: 5, body: "Hi", rating: 4, location: #<RGeo::Geographic::SphericalPointImpl:0x81bb34c0 "POINT (-118.495 34.017)">, user_id: 8, created_at: "2012-07-25 22:43:41", updated_at: "2012-07-25 22:43:41">]
>Post.order("rating DESC").limit(1).offset(4)
=> [#<Post id: 15, body: "I luv coffee", rating: 4, flagged: 0, location: #<RGeo::Geographic::SphericalPointImpl:0x82260df4 "POINT (-118.495 34.017)">, user_id: 1, created_at: "2012-07-25 22:43:41", updated_at: "2012-07-25 22:43:41">]