Add buffer size for SQLFS writer in Python side (#3047)
Add buffer size for SQLFS writer in Python side (#3047)

* add buffer for SQLFS writer

* refine close

* fix hive ci

* fix max length per row
sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow