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How can I know the exact meaning of a AST node.#2004

Answeredbymanticore-projects
yszc asked this question inQ&A
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I'm developing a custom SQL processor using the visitor pattern.
How can I know the exact meaning of a AST class, such asAllColumns,AllTableColumns,AllValue.
What's the origin expression it related in a SQL statement.

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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 leasthttps://manticore-projects.com/JSQLParser/syntax_snapshot.html will show you the Grammar and has a searchable side bar.

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

Replies: 2 comments 4 replies

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Greetings.

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

AllColumns refers to the* inSELECT * FROM ...
AllTableColumns withtablename='t' refers to tot.* inSELECT 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 theirtoString() method in order to understand what this class is holding.

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4 replies
@yszc
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Thanks, but I can't usetoString().

The situation is, I need to process all kinds of nodes extended byASTNodeAccessImpl, 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 inJSqlParserCC.jjt and analyze the context. Is there any more efficiency method?

@manticore-projects
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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 leasthttps://manticore-projects.com/JSQLParser/syntax_snapshot.html will show you the Grammar and has a searchable side bar.

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

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

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

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Additionally you can useJSQLFormatter 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
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