* fix invalid count push down Signed-off-by: yisaer <disxiaofei@163.com> fix explaintest Signed-off-by: yisaer <disxiaofei@163.com> * add testcase Signed-off-by: yisaer <disxiaofei@163.com> * fix test Signed-off-by: yisaer <disxiaofei@163.com> * address the comment Signed-off-by: yisaer <disxiaofei@163.com> * address the comment Signed-off-by: yisaer <disxiaofei@163.com> * add testcase Signed-off-by: yisaer <disxiaofei@163.com> Co-authored-by: Ti Chi Robot <ti-community-prow-bot@tidb.io>