Enum UpsertStrategy 

pub enum UpsertStrategy {
    None,
    OnConflictDoNothing(Vec<String>),
    OnConflictDoUpdate(Vec<String>, Vec<(String, String)>),
    OnDuplicateKeyUpdate(Vec<(String, String)>),
    Replace,
}

Upsert（插入或更新）策略

支持三种主流数据库的冲突处理语法：

• PostgreSQL/SQLite：ON CONFLICT ... DO NOTHING / DO UPDATE
• MySQL/MariaDB/TiDB：ON DUPLICATE KEY UPDATE / REPLACE INTO

方言兼容性

策略	MySQL	PostgreSQL	SQLite
OnConflictDoNothing	✗	✓	✓
OnConflictDoUpdate	✗	✓	✓
OnDuplicateKeyUpdate	✓	✗	✗
Replace	✓	✗	✓（INSERT OR REPLACE）

不兼容的组合会在 build_with_dialect 中跳过 upsert 子句（不报错，由调用方确保方言匹配）。

Variants

None

不使用 upsert（默认）

OnConflictDoNothing(Vec<String>)

PostgreSQL/SQLite：ON CONFLICT (cols) DO NOTHING

OnConflictDoUpdate(Vec<String>, Vec<(String, String)>)

PostgreSQL/SQLite：ON CONFLICT (cols) DO UPDATE SET col = expr, ... (conflict_cols, update_assignments)

OnDuplicateKeyUpdate(Vec<(String, String)>)

MySQL：ON DUPLICATE KEY UPDATE col = expr, ...

Replace

MySQL：REPLACE INTO（先删除冲突行再插入）

Trait Implementations

impl Clone for UpsertStrategy

fn clone(&self) -> UpsertStrategy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for UpsertStrategy

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for UpsertStrategy

fn default() -> UpsertStrategy

Returns the “default value” for a type.