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fix: prevent race on duplicate respondent insert #1445

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Merged
kaitoyama merged 5 commits into from
Apr 8, 2026
+13 −1
Merged

fix: prevent race on duplicate respondent insert #1445

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6c3e32b
fix: prevent race on duplicate respondent insert
Eraxyso Feb 11, 2026
0bd83d6
Revert "fix: prevent race on duplicate respondent insert"
Eraxyso Feb 11, 2026
cfd403c
fix: prevent race condition on duplicate respondent insert by locking…
Eraxyso Mar 28, 2026
9c3754a
chore: regenerate generated files [skip ci]
github-actions[bot] Mar 28, 2026
de69525
Merge branch 'fix/openapi' into fix/prevent-race-on-duplicate-respond…
Eraxyso Mar 28, 2026
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14 changes: 13 additions & 1 deletion model/respondents_impl.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ import (

"gopkg.in/guregu/null.v4"
"gorm.io/gorm"
"gorm.io/gorm/clause"
)

// Respondent RespondentRepositoryの実装
Expand Down Expand Up @@ -99,6 +100,18 @@ func (*Respondent) InsertRespondent(ctx context.Context, userID string, question
}

if !questionnaire.IsDuplicateAnswerAllowed {
// Lock the questionnaire row to serialize concurrent insert attempts.
// SELECT ... FOR UPDATE on respondents would not lock non-existent rows,
// allowing both transactions to pass the duplicate check simultaneously.
// By locking the parent questionnaire row (which always exists), we ensure
// only one transaction can proceed through the check+insert at a time.
err = db.
Clauses(clause.Locking{Strength: "UPDATE"}).
Where("id = ?", questionnaireID).
First(&Questionnaires{}).Error
if err != nil {
return 0, fmt.Errorf("failed to lock questionnaire row: %w", err)
}
err = db.
Where("questionnaire_id = ? AND user_traqid = ?", questionnaireID, userID).
First(&Respondents{}).Error
Comment on lines 108 to 117
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Copilot AI Mar 28, 2026

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SELECT ... FOR UPDATE here may not reliably provide the intended per-(questionnaire_id,user_traqid) serialization because the respondents table has no index/unique constraint on these columns (see Respondents struct), so this query will degenerate into a full table scan and can lock far more than intended (or behave DB/optimizer-dependent when no row exists). Consider instead locking a stable row that always exists (e.g., questionnaires row WHERE id = ? FOR UPDATE) before checking/inserting, and/or add a composite index (and preferably a uniqueness constraint if semantics allow) on (questionnaire_id, user_traqid) so the lock is scoped and deterministic.

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Expand All @@ -108,7 +121,6 @@ func (*Respondent) InsertRespondent(ctx context.Context, userID string, question
if !errors.Is(err, gorm.ErrRecordNotFound) {
return 0, fmt.Errorf("failed to check duplicate answer: %w", err)
}

}

err = db.Create(&respondent).Error
Expand Down
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