SQLFlow Parser TODO list

[tonyyang-svail]

Design Doc: https://github.com/sql-machine-learning/sqlflow/blob/develop/doc/design/sqlflow_parser.md

Step 1: support arbitrary select statement

• Change TRAIN/PREDICT/ANALYZE to TO TRAIN/TO PREDICT/TO EXPLAIN.
• Connect third party parser.
  • Connect Parser in Go.
  • Connect Parser in Java.
• Update sql.y to remove standardSelect field.
  • Port ALPS to IR.
  • Port EDL to IR.

Step 2: support SQL program

• Split SQL program in package sql instead of package server.
• Update IR to support SQL programs.