feat(gdb/gdb_model_lock.go): gdb support lock update skip locked (#4607)

feat(gdb/gdb_model_lock.go): GDB 支持 FOR UPDATE SKIP LOCKED 语法

---------

Co-authored-by: hailaz <739476267@qq.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

database/gdb/gdb_model_lock.go

@@ -6,16 +6,124 @@
 
 package gdb
 
+// Lock clause constants for different databases.
+// These constants provide type-safe and IDE-friendly access to various lock syntaxes.
+const (
+	// Common lock clauses (supported by most databases)
+	LockForUpdate           = "FOR UPDATE"
+	LockForUpdateSkipLocked = "FOR UPDATE SKIP LOCKED"
+
+	// MySQL lock clauses
+	LockInShareMode     = "LOCK IN SHARE MODE" // MySQL legacy syntax
+	LockForShare        = "FOR SHARE"          // MySQL 8.0+ and PostgreSQL
+	LockForUpdateNowait = "FOR UPDATE NOWAIT"  // MySQL 8.0+ and Oracle
+
+	// PostgreSQL specific lock clauses
+	LockForNoKeyUpdate           = "FOR NO KEY UPDATE"
+	LockForKeyShare              = "FOR KEY SHARE"
+	LockForShareNowait           = "FOR SHARE NOWAIT"
+	LockForShareSkipLocked       = "FOR SHARE SKIP LOCKED"
+	LockForNoKeyUpdateNowait     = "FOR NO KEY UPDATE NOWAIT"
+	LockForNoKeyUpdateSkipLocked = "FOR NO KEY UPDATE SKIP LOCKED"
+	LockForKeyShareNowait        = "FOR KEY SHARE NOWAIT"
+	LockForKeyShareSkipLocked    = "FOR KEY SHARE SKIP LOCKED"
+
+	// Oracle specific lock clauses
+	LockForUpdateWait5  = "FOR UPDATE WAIT 5"
+	LockForUpdateWait10 = "FOR UPDATE WAIT 10"
+	LockForUpdateWait30 = "FOR UPDATE WAIT 30"
+
+	// SQL Server lock hints (use with WITH clause)
+	LockWithUpdLock         = "WITH (UPDLOCK)"
+	LockWithHoldLock        = "WITH (HOLDLOCK)"
+	LockWithXLock           = "WITH (XLOCK)"
+	LockWithTabLock         = "WITH (TABLOCK)"
+	LockWithNoLock          = "WITH (NOLOCK)"
+	LockWithUpdLockHoldLock = "WITH (UPDLOCK, HOLDLOCK)"
+)
+
+// Lock sets a custom lock clause for the current operation.
+// This is a generic method that allows you to specify any lock syntax supported by your database.
+// You can use predefined constants or custom strings.
+//
+// Database-specific lock syntax support:
+//
+// PostgreSQL (most comprehensive):
+//   - "FOR UPDATE"                    - Exclusive lock, blocks all access
+//   - "FOR NO KEY UPDATE"            - Weaker exclusive lock, doesn't block FOR KEY SHARE
+//   - "FOR SHARE"                    - Shared lock, allows reads but blocks writes
+//   - "FOR KEY SHARE"                - Weakest lock, only locks key values
+//   - All above can be combined with:
+//   - "NOWAIT"                     - Return immediately if lock cannot be acquired
+//   - "SKIP LOCKED"               - Skip locked rows instead of waiting
+//
+// MySQL:
+//   - "FOR UPDATE"                    - Exclusive lock (all versions)
+//   - "LOCK IN SHARE MODE"           - Shared lock (legacy syntax)
+//   - "FOR SHARE"                    - Shared lock (MySQL 8.0+)
+//   - "FOR UPDATE NOWAIT"            - MySQL 8.0+ only
+//   - "FOR UPDATE SKIP LOCKED"       - MySQL 8.0+ only
+//
+// Oracle:
+//   - "FOR UPDATE"                    - Exclusive lock
+//   - "FOR UPDATE NOWAIT"            - Exclusive lock, no wait
+//   - "FOR UPDATE SKIP LOCKED"       - Exclusive lock, skip locked rows
+//   - "FOR UPDATE WAIT n"            - Exclusive lock, wait n seconds
+//   - "FOR UPDATE OF column_list"    - Lock specific columns
+//
+// SQL Server (uses WITH hints):
+//   - "WITH (UPDLOCK)"               - Update lock
+//   - "WITH (HOLDLOCK)"              - Hold lock until transaction end
+//   - "WITH (XLOCK)"                 - Exclusive lock
+//   - "WITH (TABLOCK)"               - Table lock
+//   - "WITH (NOLOCK)"                - No lock (dirty read)
+//   - "WITH (UPDLOCK, HOLDLOCK)"     - Combined update and hold lock
+//
+// SQLite:
+//   - Limited locking support, database-level locks only
+//   - No row-level lock syntax supported
+//
+// Usage examples:
+//
+//	db.Model("users").Lock("FOR UPDATE NOWAIT").Where("id", 1).One()
+//	db.Model("users").Lock("FOR SHARE SKIP LOCKED").Where("status", "active").All()
+//	db.Model("users").Lock("WITH (UPDLOCK)").Where("id", 1).One() // SQL Server
+//	db.Model("users").Lock("FOR UPDATE OF name, email").Where("id", 1).One() // Oracle
+//	db.Model("users").Lock("FOR UPDATE WAIT 15").Where("id", 1).One() // Oracle custom wait
+//
+// Or use predefined constants for better IDE support:
+//
+//	db.Model("users").Lock(gdb.LockForUpdateNowait).Where("id", 1).One()
+//	db.Model("users").Lock(gdb.LockForShareSkipLocked).Where("status", "active").All()
+func (m *Model) Lock(lockClause string) *Model {
+	model := m.getModel()
+	model.lockInfo = lockClause
+	return model
+}
+
 // LockUpdate sets the lock for update for current operation.
+// This is equivalent to Lock("FOR UPDATE").
 func (m *Model) LockUpdate() *Model {
 	model := m.getModel()
-	model.lockInfo = "FOR UPDATE"
+	model.lockInfo = LockForUpdate
+	return model
+}
+
+// LockUpdateSkipLocked sets the lock for update with skip locked behavior for current operation.
+// It skips the locked rows.
+// This is equivalent to Lock("FOR UPDATE SKIP LOCKED").
+// Note: Supported by PostgreSQL, Oracle, and MySQL 8.0+.
+func (m *Model) LockUpdateSkipLocked() *Model {
+	model := m.getModel()
+	model.lockInfo = LockForUpdateSkipLocked
 	return model
 }
 
 // LockShared sets the lock in share mode for current operation.
+// This is equivalent to Lock("LOCK IN SHARE MODE") for MySQL or Lock("FOR SHARE") for PostgreSQL.
+// Note: For maximum compatibility, this uses MySQL's legacy syntax.
 func (m *Model) LockShared() *Model {
 	model := m.getModel()
-	model.lockInfo = "LOCK IN SHARE MODE"
+	model.lockInfo = LockInShareMode
 	return model
 }