To support PG compliant SQL DML statement

[RogueJin]

Description

Since TiDB is Mysql compliant database, we need to adjust DCParser yacc paser files to remove mysql keywords and add pg keywords, and then implement the keywords logic functions in TiDB4PG project.

The things you need to do are :

1. spot statements in parser.y file
2. remove mysql keywords of the statement
3. make sure build successfully
4. correct related unit tests
5. commit PR

Helpful reference: Understand Delete Statement - Chinese

Task List

DCParser:

• [x] Delete Statement:

1. remove mysql keywords
2. correct unit tests

• [ ] Select Statement Parser

1. remove mysql keywords
2. correct unit tests

• [ ] Insert Statement Parser

1. remove mysql keywords
2. correct unit tests

• [ ] Update Statement Parser

1. remove mysql keywords
2. correct unit tests

TiDB4PG:

Please check the issue https://github.com/DigitalChinaOpenSource/TiDB-for-PostgreSQL/issues/40

[pupillord]

At present, we will not delete MySQL syntax unless it conflicts with PgSQL syntax.