Dialect-specific parsing and Snowflake JSON support

Hi ,

Currently the lib support different databases (postgresql-sql, mysql , etc .. ) dialect only in the tokenizer.

My question is - if there was any discussions/plans about supporting per-db dialects also in the parser (or do you you think it's good idea to start such discussions )?

Where most of the DB's support ANSI sql , when it's come to more advance features like json-parsing - There is great variability between the different databases.

该 issue 提到了 tokenizer 和 parser，并以现有的 postgresql-sql 和 mysql 方言作为比较对象。首先检查这些方言是如何处理的，并明确必须支持的 Snowflake JSON 语法。完成的要求是确定 parser-dialect 的范围和实现计划；该 issue 没有指定文件或测试。

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