替换sql, 让日志中记录真实执行的sql

[ppanphper]

Describe the feature

替换原sql, gorm 追踪记录新的sql内容

Motivation

希望执行分表后生成新的sql记录到日志中，而不是原来的sql。

Related Issues

conn_pool.go

type ConnPool struct {
    // db, This is global db instance
    sharding *Sharding
    gorm.ConnPool
    currentDB *gorm.DB // 记录当前的db实例
}

func (pool ConnPool) ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error) {
// ....
        pool.sharding.querys.Store("last_query", stQuery)
        // 重置sql
    oldSqlCap := pool.currentDB.Statement.SQL.Cap()
    pool.currentDB.Statement.SQL.Reset()
    pool.currentDB.Statement.SQL.Grow(oldSqlCap + 5)
    pool.currentDB.Statement.SQL.WriteString(stQuery)
// ...
}

func (pool ConnPool) QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error) {
// ...
        pool.sharding.querys.Store("last_query", stQuery)
        // 重置sql
    oldSqlCap := pool.currentDB.Statement.SQL.Cap()
    pool.currentDB.Statement.SQL.Reset()
    pool.currentDB.Statement.SQL.Grow(oldSqlCap + 5)
    pool.currentDB.Statement.SQL.WriteString(stQuery)
// ...
}

sharding.go

func (s *Sharding) switchConn(db *gorm.DB) {
    // Support ignore sharding in some case, like:
    // When DoubleWrite is enabled, we need to query database schema
    // information by table name during the migration.
    if _, ok := db.Get(ShardingIgnoreStoreKey); !ok {
        s.ConnPool = &ConnPool{ConnPool: db.Statement.ConnPool, sharding: s, currentDB: db} // 记录当前的db实例
        db.Statement.ConnPool = s.ConnPool
    }
}