expression: cleanup  code (#29459)
expression: cleanup  code (#29459)


kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,c4pt0r/tidb,c4pt0r/tidb,ngaut/tidb,ngaut/tidb,kyle-wang/tidb,ngaut/tidb,c4pt0r/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,ngaut/tidb,c4pt0r/tidb,kyle-wang/tidb,pingcap/tidb,ngaut/tidb,pingcap/tidb,pingcap/tidb,kyle-wang/tidb