Based on antlr sqlite3 grammar-v4

modifications

• ...
• switch SQLite to Postgres
• support postgres style type cast(eg. ::int)
• discard expr [NOT] MATCH expr
• discard expr [NOT] GLOB expr
• discard expr [NOT] REGEXP expr
• discard REPLACE INTO
• discard INSERT OR REPLACE INTO
• discard LIMIT x,y
• discard NATURAL JOIN
• discard TABLE_NAME INDEXED BY INDEX_NAME
• discard TABLE_NAME NOT INDEXED
• discard UPDATE OR (ROLLBACK|ABORT|REPLACE|FAIL|IGNORE)
• discard expr NOT NULL
• change expr IS [NOT] expr to expr IS [NOT] (NULL|TRUE|FALSE); NOTE: if right argument is true/false, expr should also be true/false(Postgres will error), but parser cannot validate this
• discard bitwise operator ~ | & << >> ||
• discard == operator
• change entry RULE of parser to statements
• rename Lexer and Parser to SQLLexer and SQLParser
• refactor expr, reflect Postgres operator precedence
• discard collation in ordering_term
• remove blob literal lexer rule