Golang gorm – 使用gorm预加载深层嵌套模型

huangapple
go评论122阅读模式
英文:

Golang gorm - preload with deeply nested models

问题

我有一个人为的例子：

  1. type Top struct {
  2.   ID     uint `gorm:"primary_key"`
  3.   Name   string
  4.   Middle []*Middle
  5. }
  7. type Middle struct {
  8.   ID    uint `gorm:"primary_key"`
  9.   TopID int
  10.   Name  string
  11.   Low   []*Low
  12. }
  14. type Low struct {
  15.   ID       uint `gorm:"primary_key"`
  16.   MiddleID int
  17.   Name     string
  18.   Bottom   []*Bottom
  19. }
  21. type Bottom struct {
  22.   ID    uint `gorm:"primary_key"`
  23.   LowID int
  24.   Name  string
  25. }
  27. top := Top{
  28.   Name: "Top",
  29.   Middle: []*Middle{
  30.     {
  31.       Name: "Middle",
  32.       Low: []*Low{
  33.         {
  34.           Name: "Low",
  35.           Bottom: []*Bottom{
  36.             {
  37.               Name: "Bottom",
  38.             },
  39.           },
  40.         },
  41.       },
  42.     },
  43.   },
  44. }
  46. if err := db.Save(&top).Error; err != nil {
  47.   log.Fatal("保存计算时出错", err.Error())
  48. }
  50. if err := db.Where("id = 1").
  51.   Preload("Middle.Low.Bottom").
  52.   First(&top).Error; err != nil {
  53.   log.Fatal(err)
  54. }

这给出了以下输出：

  1. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  2. [2016-03-18 01:53:23]  [4.37ms]  INSERT INTO "tops" ("name") VALUES ('Top') RETURNING "tops"."id"
  4. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  5. [2016-03-18 01:53:23]  [3.49ms]  INSERT INTO "middles" ("name","top_id") VALUES ('Middle','1') RETURNING "middles"."id"
  7. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  8. [2016-03-18 01:53:23]  [1.07ms]  INSERT INTO "lows" ("middle_id","name") VALUES ('1','Low') RETURNING "lows"."id"
  10. ()
  11. [2016-03-18 01:53:23]  [9.16ms]  INSERT INTO "bottoms" ("low_id","name") VALUES ('1','Bottom') RETURNING "bottoms"."id"
  13. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:86)
  14. [2016-03-18 01:53:23]  [1.54ms]  SELECT  * FROM "tops"   ORDER BY "tops"."id" ASC LIMIT 1
  16. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  17. [2016-03-18 01:53:23]  [2.63ms]  SELECT  * FROM "tops"  WHERE ("id" = '1') ORDER BY "tops"."id" ASC LIMIT 1
  19. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  20. [2016-03-18 01:53:23]  [1.65ms]  SELECT  * FROM "middles"  WHERE (top_id IN ('1')) ORDER BY "middles"."id" ASC
  22. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  23. [2016-03-18 01:53:23]  [4.20ms]  SELECT  * FROM "lows"  WHERE (middle_id IN ('1')) ORDER BY "lows"."id" ASC
  25. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  26. [2016-03-18 01:53:23]  找不到 []**main.Low 中的 Bottom 字段

如果我只嵌套 Top -> Middle -> Low 并调用 Preload("Middle.Low")，它可以正常工作。线索可能在于双指针引用 []**main.Low，但我无法弄清楚如何正确处理它。

可能不支持到这个层次的嵌套预加载。有人知道吗？

英文:

I have the following contrived example:

  1. type Top struct {
  2.   ID     uint `gorm:"primary_key"`
  3.   Name   string
  4.   Middle []*Middle
  5. }
  7. type Middle struct {
  8.   ID    uint `gorm:"primary_key"`
  9.   TopID int
  10.   Name  string
  11.   Low   []*Low
  12. }
  14. type Low struct {
  15.   ID       uint `gorm:"primary_key"`
  16.   MiddleID int
  17.   Name     string
  18.   Bottom   []*Bottom
  19. }
  21. type Bottom struct {
  22.   ID    uint `gorm:"primary_key"`
  23.   LowID int
  24.   Name  string
  25. }
  26. top := Top{
  27.   Name: "Top",
  28.   Middle: []*Middle{
  29.     {
  30.       Name: "Middle",
  31.       Low: []*Low{
  32.         {
  33.           Name: "Low",
  34.           Bottom: []*Bottom{
  35.             {
  36.               Name: "Bottom",
  37.             },
  38.           },
  39.         },
  40.       },
  41.     },
  42.   },
  43. }
  45. if err := db.Save(&top).Error; err != nil {
  46.   log.Fatal("Got errors when saving calc", err.Error())
  47. }
  49. if err := db.Where("id = 1").
  50.   Preload("Middle.Low.Bottom").
  51.   First(&top).Error; err != nil {
  52.   log.Fatal(err)
  53. }

This gives me the following output:

  1. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  2. [2016-03-18 01:53:23]  [4.37ms]  INSERT INTO "tops" ("name") VALUES ('Top') RETURNING "tops"."id"
  4. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  5. [2016-03-18 01:53:23]  [3.49ms]  INSERT INTO "middles" ("name","top_id") VALUES ('Middle','1') RETURNING "middles"."id"
  7. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:81)
  8. [2016-03-18 01:53:23]  [1.07ms]  INSERT INTO "lows" ("middle_id","name") VALUES ('1','Low') RETURNING "lows"."id"
  10. ()
  11. [2016-03-18 01:53:23]  [9.16ms]  INSERT INTO "bottoms" ("low_id","name") VALUES ('1','Bottom') RETURNING "bottoms"."id"
  13. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:86)
  14. [2016-03-18 01:53:23]  [1.54ms]  SELECT  * FROM "tops"   ORDER BY "tops"."id" ASC LIMIT 1
  16. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  17. [2016-03-18 01:53:23]  [2.63ms]  SELECT  * FROM "tops"  WHERE ("id" = '1') ORDER BY "tops"."id" ASC LIMIT 1
  19. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  20. [2016-03-18 01:53:23]  [1.65ms]  SELECT  * FROM "middles"  WHERE (top_id IN ('1')) ORDER BY "middles"."id" ASC
  22. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  23. [2016-03-18 01:53:23]  [4.20ms]  SELECT  * FROM "lows"  WHERE (middle_id IN ('1')) ORDER BY "lows"."id" ASC
  25. (/host_home/workspace/golang/src/bitbucket.org/cloudgloballog/gormtest/main.go:88)
  26. [2016-03-18 01:53:23]  can't find field Bottom in []**main.Low

If I were to only nest Top -> Middle -> Low and called Preload("Middle.Low") it works fine. The clue is probably in the double pointer reference []**main.Low but I'm unable to work out how to do this properly.

It's possible that nested preloading is not supported to this level. Anyone know?

答案1

得分: 2

这个问题似乎在早期版本的gorm中存在，如下所述：Issue1，Issue2，Issue3，但最新的预加载问题修复在这个链接中。

看起来这个问题已经解决了一段时间，但具体修复的版本没有记录，除非有人搜索git提交日期。

使用最新版本（截至本文撰写时的v1.9.11）设置一个当前示例没有问题。

  1. package main
  3. import (
  4. 	"log"
  6. 	"github.com/davecgh/go-spew/spew"
  7. 	"github.com/jinzhu/gorm"
  8. 	_ "github.com/jinzhu/gorm/dialects/sqlite"
  9. )
  11. type Top struct {
  12. 	ID     uint   `gorm:"primary_key"`
  13. 	Name   string
  14. 	Middle []*Middle
  15. }
  17. type Middle struct {
  18. 	ID    uint   `gorm:"primary_key"`
  19. 	TopID int
  20. 	Name  string
  21. 	Low   []*Low
  22. }
  24. type Low struct {
  25. 	ID       uint   `gorm:"primary_key"`
  26. 	MiddleID int
  27. 	Name     string
  28. 	Bottom   []*Bottom
  29. }
  31. type Bottom struct {
  32. 	ID    uint   `gorm:"primary_key"`
  33. 	LowID int
  34. 	Name  string
  35. }
  37. func main() {
  38. 	db, err := gorm.Open("sqlite3", "test.db")
  39. 	if err != nil {
  40. 		panic("failed to connect database")
  41. 	}
  42. 	defer db.Close()
  43. 	// 启用日志记录，显示详细日志
  44. 	db.LogMode(true)
  45. 	// 迁移模式
  46. 	db.AutoMigrate(&Top{})
  47. 	db.AutoMigrate(&Middle{})
  48. 	db.AutoMigrate(&Low{})
  49. 	db.AutoMigrate(&Bottom{})
  51. 	top := Top{
  52. 		Name: "Top",
  53. 		Middle: []*Middle{
  54. 			{
  55. 				Name: "Middle",
  56. 				Low: []*Low{
  57. 					{
  58. 						Name: "Low",
  59. 						Bottom: []*Bottom{
  60. 							{
  61. 								Name: "Bottom",
  62. 							},
  63. 						},
  64. 					},
  65. 				},
  66. 			},
  67. 		},
  68. 	}
  70. 	if err := db.Save(&top).Error; err != nil {
  71. 		log.Fatal("保存计算时出错", err.Error())
  72. 	}
  73. 	var ntop Top
  74. 	if err := db.Where("id = 1").
  75. 		Preload("Middle.Low.Bottom").
  76. 		First(&ntop).Error; err != nil {
  77. 		log.Fatal(err)
  78. 	}
  80. 	spew.Dump(&ntop)
  81. }
  1. $ ./main.exe
  3. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  4. [2019-10-31 14:44:23]  [2.00ms]  INSERT  INTO "tops" ("name") VALUES ('Top')
  5. [1 rows affected or returned ]
  7. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  8. [2019-10-31 14:44:23]  [0.00ms]  INSERT  INTO "middles" ("top_id","name") VALUES (1,'Middle')
  9. [1 rows affected or returned ]
  11. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  12. [2019-10-31 14:44:23]  [0.99ms]  INSERT  INTO "lows" ("middle_id","name") VALUES (1,'Low')
  13. [1 rows affected or returned ]
  15. ()
  16. [2019-10-31 14:44:23]  [0.00ms]  INSERT  INTO "bottoms" ("low_id","name") VALUES (1,'Bottom')
  17. [1 rows affected or returned ]
  19. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  20. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "tops"  WHERE (id = 1) ORDER BY "tops"."id" ASC LIMIT 1
  21. [1 rows affected or returned ]
  23. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  24. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "middles"  WHERE ("top_id" IN (1)) ORDER BY "middles"."id" ASC
  25. [1 rows affected or returned ]
  27. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  28. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "lows"  WHERE ("middle_id" IN (1)) ORDER BY "lows"."id" ASC
  29. [1 rows affected or returned ]
  31. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  32. [2019-10-31 14:44:23]  [0.99ms]  SELECT * FROM "bottoms"  WHERE ("low_id" IN (1)) ORDER BY "bottoms"."id" ASC
  33. [1 rows affected or returned ]
  34. (*main.Top)(0xc00015f950)({
  35.  ID: (uint) 1,
  36.  Name: (string) (len=3) "Top",
  37.  Middle: ([]*main.Middle) (len=1 cap=1) {
  38.   (*main.Middle)(0xc000150fc0)({
  39.    ID: (uint) 1,
  40.    TopID: (int) 1,
  41.    Name: (string) (len=6) "Middle",
  42.    Low: ([]*main.Low) (len=1 cap=1) {
  43.     (*main.Low)(0xc000151080)({
  44.      ID: (uint) 1,
  45.      MiddleID: (int) 1,
  46.      Name: (string) (len=3) "Low",
  47.      Bottom: ([]*main.Bottom) (len=1 cap=1) {
  48.       (*main.Bottom)(0xc0001929c0)({
  49.        ID: (uint) 1,
  50.        LowID: (int) 1,
  51.        Name: (string) (len=6) "Bottom"
  52.       })
  53.      }
  54.     })
  55.    }
  56.   })
  57.  }
  58. })
英文:

This issue seems to have been present in earlier versions of gorm as described in: Issue1, Issue2, Issue3, but the lastest preload issue fix has been in this one.

It appears it has been resolved for quite some time but the exact version it was fixed is not documented unless someone searches git commit dates.

Setting up a current example with the latest version (v1.9.11 as of this writing) held no issues.

  1. package main
  3. import (
  4. 	"log"
  6. 	"github.com/davecgh/go-spew/spew"
  7. 	"github.com/jinzhu/gorm"
  8. 	_ "github.com/jinzhu/gorm/dialects/sqlite"
  9. )
  11. type Top struct {
  12. 	ID     uint `gorm:"primary_key"`
  13. 	Name   string
  14. 	Middle []*Middle
  15. }
  17. type Middle struct {
  18. 	ID    uint `gorm:"primary_key"`
  19. 	TopID int
  20. 	Name  string
  21. 	Low   []*Low
  22. }
  24. type Low struct {
  25. 	ID       uint `gorm:"primary_key"`
  26. 	MiddleID int
  27. 	Name     string
  28. 	Bottom   []*Bottom
  29. }
  31. type Bottom struct {
  32. 	ID    uint `gorm:"primary_key"`
  33. 	LowID int
  34. 	Name  string
  35. }
  37. func main() {
  38. 	db, err := gorm.Open("sqlite3", "test.db")
  39. 	if err != nil {
  40. 		panic("failed to connect database")
  41. 	}
  42. 	defer db.Close()
  43. 	// Enable Logger, show detailed log
  44. 	db.LogMode(true)
  45. 	// Migrate the schema
  46. 	db.AutoMigrate(&Top{})
  47. 	db.AutoMigrate(&Middle{})
  48. 	db.AutoMigrate(&Low{})
  49. 	db.AutoMigrate(&Bottom{})
  51. 	top := Top{
  52. 		Name: "Top",
  53. 		Middle: []*Middle{
  54. 			{
  55. 				Name: "Middle",
  56. 				Low: []*Low{
  57. 					{
  58. 						Name: "Low",
  59. 						Bottom: []*Bottom{
  60. 							{
  61. 								Name: "Bottom",
  62. 							},
  63. 						},
  64. 					},
  65. 				},
  66. 			},
  67. 		},
  68. 	}
  70. 	if err := db.Save(&top).Error; err != nil {
  71. 		log.Fatal("Got errors when saving calc", err.Error())
  72. 	}
  73. 	var ntop Top
  74. 	if err := db.Where("id = 1").
  75. 		Preload("Middle.Low.Bottom").
  76. 		First(&ntop).Error; err != nil {
  77. 		log.Fatal(err)
  78. 	}
  80. 	spew.Dump(&ntop)
  81. }
  1. $ ./main.exe
  3. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  4. [2019-10-31 14:44:23]  [2.00ms]  INSERT  INTO "tops" ("name") VALUES ('Top')
  5. [1 rows affected or returned ]
  7. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  8. [2019-10-31 14:44:23]  [0.00ms]  INSERT  INTO "middles" ("top_id","name") VALUES (1,'Middle')
  9. [1 rows affected or returned ]
  11. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:70)
  12. [2019-10-31 14:44:23]  [0.99ms]  INSERT  INTO "lows" ("middle_id","name") VALUES (1,'Low')
  13. [1 rows affected or returned ]
  15. ()
  16. [2019-10-31 14:44:23]  [0.00ms]  INSERT  INTO "bottoms" ("low_id","name") VALUES (1,'Bottom')
  17. [1 rows affected or returned ]
  19. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  20. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "tops"  WHERE (id = 1) ORDER BY "tops"."id" ASC LIMIT 1
  21. [1 rows affected or returned ]
  23. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  24. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "middles"  WHERE ("top_id" IN (1)) ORDER BY "middles"."id" ASC
  25. [1 rows affected or returned ]
  27. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  28. [2019-10-31 14:44:23]  [0.00ms]  SELECT * FROM "lows"  WHERE ("middle_id" IN (1)) ORDER BY "lows"."id" ASC
  29. [1 rows affected or returned ]
  31. (C:/Users/fakename/source/stackoverflow/go/gorm-nested/main.go:76)
  32. [2019-10-31 14:44:23]  [0.99ms]  SELECT * FROM "bottoms"  WHERE ("low_id" IN (1)) ORDER BY "bottoms"."id" ASC
  33. [1 rows affected or returned ]
  34. (*main.Top)(0xc00015f950)({
  35.  ID: (uint) 1,
  36.  Name: (string) (len=3) "Top",
  37.  Middle: ([]*main.Middle) (len=1 cap=1) {
  38.   (*main.Middle)(0xc000150fc0)({
  39.    ID: (uint) 1,
  40.    TopID: (int) 1,
  41.    Name: (string) (len=6) "Middle",
  42.    Low: ([]*main.Low) (len=1 cap=1) {
  43.     (*main.Low)(0xc000151080)({
  44.      ID: (uint) 1,
  45.      MiddleID: (int) 1,
  46.      Name: (string) (len=3) "Low",
  47.      Bottom: ([]*main.Bottom) (len=1 cap=1) {
  48.       (*main.Bottom)(0xc0001929c0)({
  49.        ID: (uint) 1,
  50.        LowID: (int) 1,
  51.        Name: (string) (len=6) "Bottom"
  52.       })
  53.      }
  54.     })
  55.    }
  56.   })
  57.  }
  58. })

huangapple
  • 本文由 发表于 2016年3月18日 09:57:23
  • 转载请务必保留本文链接：https://go.coder-hub.com/36074811.html
  • go
  • go-gorm
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定