35 lines
823 B
Go
35 lines
823 B
Go
package model
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import (
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"errors"
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"gorm.io/gorm"
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"gorm.io/gorm/clause"
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)
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var ErrSessionNotFound = errors.New("会话不存在")
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// CreateMessage 在会话行锁保护下分配消息序号，避免并发写入出现重复序号。
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func CreateMessage(message *Message) error {
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return DB.Transaction(func(tx *gorm.DB) error {
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var session Session
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if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&session, message.SessionID).Error; err != nil {
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if errors.Is(err, gorm.ErrRecordNotFound) {
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return ErrSessionNotFound
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}
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return err
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}
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var maxSeq int
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if err := tx.Model(&Message{}).
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Where("session_id = ?", message.SessionID).
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Select("COALESCE(MAX(seq), 0)").
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Scan(&maxSeq).Error; err != nil {
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return err
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}
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message.Seq = maxSeq + 1
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return tx.Create(message).Error
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})
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}
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