How can I know the exact meaning of a AST node.

[yszc]

I'm developing a custom SQL processor using the visitor pattern.
How can I know the exact meaning of a AST class, such as AllColumns, AllTableColumns, AllValue.
What's the origin expression it related in a SQL statement.

[manticore-projects]

Greetings.

I understand what you mean, this kind of documentation is missing:

AllColumns refers to the * in SELECT * FROM ...
AllTableColumns with tablename='t' refers to to t.* in SELECT t.* FROM ...

A strong volunteer would need to write that as Java-Doc into each AST class.
In the meantime, your best bet was to go through those AST classes and study their toString() method in order to understand what this class is holding.

[yszc]

Thanks, but I can't use toString().

The situation is, I need to process all kinds of nodes extended by ASTNodeAccessImpl, so there are some grammer beyond my knowledge, so I need to get SQL snippet directly from the class (have no object).

Now I have a method which is searching for the class name in JSqlParserCC.jjt and analyze the context. Is there any more efficiency method?

[manticore-projects]

I am sorry to tell you that exactly this kind of documentation is missing, because nobody has the time and resources to write it.
Of course you are most welcome to submit PRs with JavaDoc when you are on this job now.

Btw, IntelliJ has an excellent JavaCC plugin which makes it easy to find the production for each AST class.
Also, you could parse the grammar with javaCC itself to get the BNF of each production and last but not least https://manticore-projects.com/JSQLParser/syntax_snapshot.html will show you the Grammar and has a searchable side bar.

Example for AllTableColumns: https://manticore-projects.com/JSQLParser/syntax_snapshot.html#alltablecolumns

[yszc]

Thank you, I wasn't expecting a documentation-based answer. The Syntax Snapshot is very useful. 😀

[manticore-projects]

You are welcome and I am glad to be of assistance. If anything else comes up, please don't hesitate to ask. Cheers!

[manticore-projects]

Additionally you can use JSQLFormatter online

to get this kind of AST illustration:

SQL Text
 └─Statements: statement.select.PlainSelect
    ├─selectItems: statement.select.SelectItem
    │  └─expression: statement.select.AllTableColumns
    │     └─Table: t
    └─Table: dual