Add solution for gorm challenge-1-crud-operations by grozdovk #771
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WalkthroughAdds three new Go submissions: a palindrome checker (challenge-17), a generics utilities package (challenge-27) with multiple data structures, and two GORM-backed services for challenges (challenge-1 CRUD and challenge-2 associations) including models, relations, and transactional operations. Changes
Sequence Diagram(s)Simple flow for the palindrome checker (normalize → reverse → compare): sequenceDiagram
participant CLI as User/CLI
participant App as PalindromeApp
CLI->>App: input string
App->>App: normalize (lowercase, keep a-z0-9)
App->>App: reverse runes (two-pointer)
App->>App: compare normalized == reversed
App-->>CLI: print result (palindrome / not palindrome)
High-level transactional flow for CreatePostWithTags / AddTagsToPost (GORM many-to-many with transaction): sequenceDiagram
autonumber
participant Caller as Caller
participant DB as GORM (sqlite)
Caller->>DB: Begin Transaction
DB-->>Caller: tx
Caller->>DB: ensure/create Tag rows (for each tag)
DB-->>Caller: tags persisted
Caller->>DB: create Post (or find Post)
DB-->>Caller: post persisted
Caller->>DB: associate Tags <-> Post (Append to many2many)
DB-->>Caller: associations persisted
alt success
Caller->>DB: Commit
DB-->>Caller: Commit OK
else error
Caller->>DB: Rollback
DB-->>Caller: Rollback OK
end
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~25 minutes
Possibly related PRs
Pre-merge checks❌ Failed checks (1 warning, 1 inconclusive)
✅ Passed checks (1 passed)
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Actionable comments posted: 0
🧹 Nitpick comments (10)
challenge-17/submissions/grozdovk/solution-template.go (3)
8-21: Consider using a more flexible input method.
fmt.Scanlnstops reading at the first whitespace, so multi-word inputs like "A man a plan a canal Panama" would only process "A". For comprehensive palindrome testing, consider usingbufio.Scannerorfmt.Scanwith a full line read.Example refactor:
+import ( + "bufio" "fmt" + "os" "strings" +) func main() { // Get input from the user var input string fmt.Print("Enter a string to check if it's a palindrome: ") - fmt.Scanln(&input) + scanner := bufio.NewScanner(os.Stdin) + if scanner.Scan() { + input = scanner.Text() + }
26-27: Remove the TODO comment.The function is fully implemented, so the TODO comment should be removed.
- // TODO: Implement this function - // 1. Clean the string (remove spaces, punctuation, and convert to lowercase)
28-42: Implementation is correct.The palindrome logic correctly handles case insensitivity and filters non-alphanumeric characters. The two-step approach (clean then reverse-and-compare) works well.
Optional: You could optimize by using a two-pointer comparison instead of creating a reversed copy:
// After getting cleanedString and runes: for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 { if runes[i] != runes[j] { return false } } return trueThis avoids allocating memory for the reversed string.
challenge-27/submissions/grozdovk/solution-template.go (6)
12-34: Pair implementation looks good.The generic Pair struct and its methods are correctly implemented. Remember to remove the TODO comments on lines 20 and 29 since the implementation is complete.
40-97: Stack implementation is correct.All Stack methods (Push, Pop, Peek, Size, IsEmpty) are properly implemented with appropriate error handling for empty stack operations.
Minor formatting inconsistencies on lines 65, 79, and 96: add spaces around the
==operator for consistency with Go conventions (e.g.,len(s.elements) == 0). Also, remove the TODO comments since the implementation is complete.
103-158: Queue implementation is functionally correct.All Queue methods work as expected with proper error handling for empty queue operations.
Optional improvements:
- Add spaces around
==operators (lines 128, 141, 157) for consistency- Remove TODO comments since implementation is complete
- Consider that
Dequeueat line 132 usingq.elements[1:]can lead to memory retention in long-running scenarios, as the underlying array keeps references to dequeued elements. For production code, periodically copying to a fresh slice when the queue is smaller than the capacity would help, but for a learning exercise this is fine.
164-211: Set implementation and operations are correct.The Set data structure and all its methods work properly. Union, Intersection, and Difference operations are implemented correctly.
Optional improvements:
- Consider using
map[T]struct{}instead ofmap[T]any(line 167) to save memory, as you only need the keys- In
Elements()(line 206), preallocate the slice with capacity:make([]T, 0, len(s.elements))for better performance- Add spaces around comparison operators for consistency with Go style
- Remove TODO comments
213-254: Set operations are correctly implemented.Union, Intersection, and Difference operations correctly handle the set algebra. The logic for each operation is sound.
Remember to remove the TODO comments on lines 215, 230, and 244.
260-325: Generic utility functions are well implemented.All utility functions (Filter, Map, Reduce, Contains, FindIndex, RemoveDuplicates) correctly implement their expected behaviors. The use of generics makes these reusable across different types.
Minor items:
- Remove TODO comments (lines 262, 274, 284, 293, 304, 315)
- Add spaces around comparison operators for consistency
packages/gorm/challenge-1-crud-operations/submissions/grozdovk/solution.go (1)
38-84: CRUD helpers are correct; consider simplifying existence checks usingRowsAffectedThe CRUD functions are logically correct and propagate errors cleanly.
CreateUser,GetUserByID, andGetAllUsersare already minimal and fine.For
UpdateUserandDeleteUser, you’re doing aFirstfollowed bySave/Delete. That enforces a “must exist” contract but costs an extra query and still has a small time‑of‑check/time‑of‑use gap. If you don’t strictly need a separate pre‑check, you could instead rely onRowsAffectedto detect missing rows after a single operation, e.g.:
- For updates: run a single
Update/Updatesand returngorm.ErrRecordNotFound(or similar) whenRowsAffected == 0.- For deletes: run a single
Deleteand treatRowsAffected == 0as “user not found”.This would reduce DB round‑trips while keeping clear not‑found semantics, at the cost of slightly different GORM behavior (e.g.,
UpdatesvsSaveregarding zero‑values), so worth aligning with the challenge requirements before changing.
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📒 Files selected for processing (3)
challenge-17/submissions/grozdovk/solution-template.go(1 hunks)challenge-27/submissions/grozdovk/solution-template.go(1 hunks)packages/gorm/challenge-1-crud-operations/submissions/grozdovk/solution.go(1 hunks)
🔇 Additional comments (2)
packages/gorm/challenge-1-crud-operations/submissions/grozdovk/solution.go (2)
12-20: User model definition is clear and appropriately constrainedThe struct captures primary key, uniqueness, not‑null, and positive age constraints cleanly and is a good fit for the CRUD exercise.
22-36: Proposed fix is unsafe and introduces new bugs — revise error handling strategyThe web search reveals critical issues with the proposed fix:
GORM ownership model: When you pass
*sql.DBviasqlite.Dialector{Conn: sqlDB}, you (the caller) remain responsible for its lifecycle; GORM does not take ownership.Unsafe to close sqlDB while gorm.DB is active: Closing the underlying
*sql.DBwhile the returned*gorm.DBstill references it shuts down the connection pool and causes GORM operations to fail. With SQLite, this can also trigger SQLITE_BUSY errors.Critical flaw in the proposed fix: The diff closes
sqlDBin theAutoMigrate()error branch (_ = sqlDB.Close(); return nil, err), but the original code returnsdb, erron that failure. This means closingsqlDBwhile the caller expects to receive a live*gorm.DB— the connection will be unusable.The actual resource leak occurs only on
gorm.Open()failure, wheresqlDBis opened but never closed. TheAutoMigrate()failure case is not a leak because the function returnsdbto the caller, who owns cleanup responsibility viadb.DB().Close()at shutdown.Corrected approach: Close
sqlDBonly ongorm.Open()failure:func ConnectDB() (*gorm.DB, error) { sqlDB, err := sql.Open("sqlite", "test.db") if err != nil { return nil, err } db, err := gorm.Open(sqlite.Dialector{Conn: sqlDB}, &gorm.Config{}) if err != nil { + _ = sqlDB.Close() return nil, err } err = db.AutoMigrate(&User{}) return db, err }The caller must ensure
db.DB().Close()is called at graceful shutdown; do not closesqlDBhere onAutoMigrate()failure.Likely an incorrect or invalid review comment.
| func ConnectDB() (*gorm.DB, error) { | ||
| sqlDB, err := sql.Open("sqlite", "test.db") | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| db, err := gorm.Open(sqlite.Dialector{Conn: sqlDB}, &gorm.Config{}) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| err = db.AutoMigrate(&User{},&Post{},&Tag{}) | ||
| return db, err | ||
| } |
There was a problem hiding this comment.
Fix resource leak when GORM initialization fails.
If gorm.Open fails at line 48, the sqlDB connection opened at line 43 is never closed, leading to a resource leak.
Apply this diff to properly handle the resource:
func ConnectDB() (*gorm.DB, error) {
sqlDB, err := sql.Open("sqlite", "test.db")
if err != nil {
return nil, err
}
db, err := gorm.Open(sqlite.Dialector{Conn: sqlDB}, &gorm.Config{})
if err != nil {
+ sqlDB.Close()
return nil, err
}
- err = db.AutoMigrate(&User{},&Post{},&Tag{})
+ err = db.AutoMigrate(&User{}, &Post{}, &Tag{})
return db, err
}📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| func ConnectDB() (*gorm.DB, error) { | |
| sqlDB, err := sql.Open("sqlite", "test.db") | |
| if err != nil { | |
| return nil, err | |
| } | |
| db, err := gorm.Open(sqlite.Dialector{Conn: sqlDB}, &gorm.Config{}) | |
| if err != nil { | |
| return nil, err | |
| } | |
| err = db.AutoMigrate(&User{},&Post{},&Tag{}) | |
| return db, err | |
| } | |
| func ConnectDB() (*gorm.DB, error) { | |
| sqlDB, err := sql.Open("sqlite", "test.db") | |
| if err != nil { | |
| return nil, err | |
| } | |
| db, err := gorm.Open(sqlite.Dialector{Conn: sqlDB}, &gorm.Config{}) | |
| if err != nil { | |
| sqlDB.Close() | |
| return nil, err | |
| } | |
| err = db.AutoMigrate(&User{}, &Post{}, &Tag{}) | |
| return db, err | |
| } |
🤖 Prompt for AI Agents
In packages/gorm/challenge-2-associations/submissions/grozdovk/solution.go
around lines 42 to 55, if gorm.Open fails the previously opened sqlDB is never
closed; update the error path so that when gorm.Open returns an error you call
sqlDB.Close() before returning the error (optionally capture/ignore Close
error), ensuring the SQL connection is not leaked. Keep the rest of the flow the
same (open sql, attempt gorm.Open, on gorm.Open error close sqlDB and return
nil, err; on success continue to AutoMigrate).
| func CreateUserWithPosts(db *gorm.DB, user *User) error { | ||
|
|
||
| result := db.Create(&user) | ||
|
|
||
| return result.Error | ||
| } |
There was a problem hiding this comment.
Fix double-pointer bug in Create call.
Line 60 takes the address of user, which is already a *User pointer. This creates a **User (pointer to pointer), which will cause GORM to fail or behave incorrectly.
Apply this diff:
func CreateUserWithPosts(db *gorm.DB, user *User) error {
- result := db.Create(&user)
+ result := db.Create(user)
return result.Error
}📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| func CreateUserWithPosts(db *gorm.DB, user *User) error { | |
| result := db.Create(&user) | |
| return result.Error | |
| } | |
| func CreateUserWithPosts(db *gorm.DB, user *User) error { | |
| result := db.Create(user) | |
| return result.Error | |
| } |
🤖 Prompt for AI Agents
In packages/gorm/challenge-2-associations/submissions/grozdovk/solution.go
around lines 58 to 63, db.Create is called with &user which makes a **User
(pointer-to-pointer); change the call to pass the existing *User directly
(db.Create(user)) so GORM receives a *User, not **User, and return result.Error
as before.
| // CreatePostWithTags creates a new post with specified tags | ||
| func CreatePostWithTags(db *gorm.DB, post *Post, tagNames []string) error { | ||
| tx := db.Begin() | ||
| if tx.Error != nil { | ||
| return tx.Error | ||
| } | ||
| ShouldRollback := true | ||
| defer func(){ | ||
| if ShouldRollback{ | ||
| tx.Rollback() | ||
| } | ||
| }() | ||
| var tags []Tag | ||
| for _, tagName := range tagNames{ | ||
| var tag Tag | ||
| if err:= tx.Where("name = ?", tagName).First(&tag).Error; err!= nil{ | ||
| if errors.Is(err, gorm.ErrRecordNotFound){ | ||
| tag = Tag{Name: tagName} | ||
| if err:= tx.Create(&tag).Error; err!=nil{ | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| } else { | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| } | ||
| tags = append(tags, tag) | ||
| } | ||
| post.Tags = tags | ||
| if err:= tx.Create(post).Error; err!= nil{ | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| if err:= tx.Commit().Error; err!=nil{ | ||
| return err | ||
| } | ||
| ShouldRollback = false | ||
| return nil | ||
| } |
There was a problem hiding this comment.
🛠️ Refactor suggestion | 🟠 Major
Simplify transaction error handling and fix naming inconsistency.
The manual tx.Rollback() calls at lines 94, 98, and 106 are redundant since the deferred function will handle rollback when ShouldRollback is true. Additionally, the variable ShouldRollback (line 81) uses uppercase naming, which is inconsistent with shouldRollback (lowercase) used in AddTagsToPost at line 139.
Apply this diff to remove redundancy and ensure consistent naming:
func CreatePostWithTags(db *gorm.DB, post *Post, tagNames []string) error {
tx := db.Begin()
if tx.Error != nil {
return tx.Error
}
- ShouldRollback := true
+ shouldRollback := true
defer func(){
- if ShouldRollback{
+ if shouldRollback{
tx.Rollback()
}
}()
var tags []Tag
for _, tagName := range tagNames{
var tag Tag
if err:= tx.Where("name = ?", tagName).First(&tag).Error; err!= nil{
if errors.Is(err, gorm.ErrRecordNotFound){
tag = Tag{Name: tagName}
if err:= tx.Create(&tag).Error; err!=nil{
- tx.Rollback()
return err
}
} else {
- tx.Rollback()
return err
}
}
tags = append(tags, tag)
}
post.Tags = tags
if err:= tx.Create(post).Error; err!= nil{
- tx.Rollback()
return err
}
if err:= tx.Commit().Error; err!=nil{
return err
}
- ShouldRollback = false
+ shouldRollback = false
return nil
}🤖 Prompt for AI Agents
In packages/gorm/challenge-2-associations/submissions/grozdovk/solution.go
around lines 75 to 114, remove the redundant explicit tx.Rollback() calls inside
the loop and error branches (lines ~94, ~98, ~106) and rename the
exported-looking variable ShouldRollback to shouldRollback to match the naming
used elsewhere; keep the deferred rollback logic (defer func(){ if
shouldRollback { tx.Rollback() } }()), return errors immediately without calling
tx.Rollback() when an error occurs, and set shouldRollback = false only after a
successful Commit() so the defer can handle rollbacks consistently.
| // AddTagsToPost adds tags to an existing post | ||
| func AddTagsToPost(db *gorm.DB, postID uint, tagNames []string) error { | ||
| tx := db.Begin() | ||
| if tx.Error != nil { | ||
| return tx.Error | ||
| } | ||
| shouldRollback:= true | ||
| defer func(){ | ||
| if shouldRollback{ | ||
| tx.Rollback() | ||
| } | ||
| }() | ||
| var tags []Tag | ||
| for _, tagName := range tagNames{ | ||
| var tag Tag | ||
| if err:= tx.Where("name = ?", tagName).First(&tag).Error; err!= nil{ | ||
| if errors.Is(err, gorm.ErrRecordNotFound){ | ||
| tag = Tag{Name: tagName} | ||
| if err:= tx.Create(&tag).Error; err!=nil{ | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| } else { | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| } | ||
| tags = append(tags, tag) | ||
| } | ||
| var post Post | ||
| if err:= tx.First(&post, postID).Error; err!= nil{ | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| if err:= tx.Model(&post).Association("Tags").Append(tags); err!=nil{ | ||
| tx.Rollback() | ||
| return err | ||
| } | ||
| if err:= tx.Commit().Error; err!=nil{ | ||
| return err | ||
| } | ||
| shouldRollback = false | ||
| return nil | ||
| } |
There was a problem hiding this comment.
🛠️ Refactor suggestion | 🟠 Major
Remove redundant rollback calls.
The manual tx.Rollback() calls at lines 152, 156, 164, and 168 are redundant since the deferred function will automatically handle rollback when shouldRollback is true.
Apply this diff to simplify error handling:
func AddTagsToPost(db *gorm.DB, postID uint, tagNames []string) error {
tx := db.Begin()
if tx.Error != nil {
return tx.Error
}
shouldRollback:= true
defer func(){
if shouldRollback{
tx.Rollback()
}
}()
var tags []Tag
for _, tagName := range tagNames{
var tag Tag
if err:= tx.Where("name = ?", tagName).First(&tag).Error; err!= nil{
if errors.Is(err, gorm.ErrRecordNotFound){
tag = Tag{Name: tagName}
if err:= tx.Create(&tag).Error; err!=nil{
- tx.Rollback()
return err
}
} else {
- tx.Rollback()
return err
}
}
tags = append(tags, tag)
}
var post Post
if err:= tx.First(&post, postID).Error; err!= nil{
- tx.Rollback()
return err
}
if err:= tx.Model(&post).Association("Tags").Append(tags); err!=nil{
- tx.Rollback()
return err
}
if err:= tx.Commit().Error; err!=nil{
return err
}
shouldRollback = false
return nil
}🤖 Prompt for AI Agents
In packages/gorm/challenge-2-associations/submissions/grozdovk/solution.go
around lines 133 to 176, remove the redundant explicit tx.Rollback() calls
inside the error branches (lines ~152, ~156, ~164, ~168) and simply return the
error; keep the initial tx.Begin() error check and the deferred rollback that
checks shouldRollback, and only set shouldRollback = false after a successful
tx.Commit(); this simplifies error handling by letting the defer handle rollback
consistently while preserving current return semantics.
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