In sprint 4, we plan to support:

• Mod MayPOC (support function mod in TiFlash #2318)
• COALESCE MayPOC (Push down function COALESCE #2334)
• ASCII, length, position, trim (Push down string related functions - ASCII, length, position, trim #2424)
• ADDDATE, DATE, DATE_ADD (Push down date related functions - ADDDATE, DATE, DATE_ADD #2425)
• ROUND() on Decimal (Push down ROUND() on Decimal types #2426)
• INET_NTOA()/ATON(), INET6_ATON/NTOA() (Push down INET functions - INET_NTOA()/ATON(), INET6_ATON/NTOA() #2427)
• set、enum、INET_NTOA()、INET6_NTOA()、+/- INTERVAL X Y used quite a bit【Results Generation】
• Math (Support pushdown mathematics functions #1901): Ln Log Log2 Log10 Exp Pow Radians Degrees Conv CRC32
• Comparison (Support IsTrueWithNull, IsTrue and IsFalseWithNull, IsFalse in TiFlash #1863): IsTrueWithNull, IsTrueWithoutNull, IsFalsity, NullEQ
• Bit op (Support pushdown LeftShift and RightShift bit operations  #1900 and Support pushdown LogicalXor function #1902): LeftShift, RightShift, LogicXor
• Group concat distinct (Support group concat distinct agg function push down #1908)

Sprint 3 done:

• Replace (support function replace in TiFlash #1860)
• Abs (Support abs function push down #1937)
• left/right (Support left/right function push down #1943)
• str_to_date (Support str_to_date function push down #1942)
• concat (Support concat function push down #1940)
• unix_timestamp (Support unix_timestamp function push down #1939)
• cast string as double (Support cast_str_as_double function push down #1936)
• datediff, datesub, year, day, CastStringAsInt, CastTimeAsString, concat_ws, ifnull (Need support more function pushdown in TiFlash #1480)
• Math (Support pushdown mathematics functions #1901): Ceil, Ceiling, Floor, Sqrt

List by PM: https://docs.google.com/spreadsheets/d/1FUoFEhXXVFskkBLtTfGI0XqlgveW_IdFTOgvYD7PNcA/edit#gid=508440363