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.

此 issue 提到 tokenizer 和 parser，並以現有的 postgresql-sql 與 mysql 方言作為比較對象。首先檢視這些方言的處理方式，並釐清必須支援的 Snowflake JSON 語法。完成的要求是確定 parser-dialect 的範圍與實作計畫；此 issue 未指定檔案或測試。

由索引模型根據 Issue 內容生成。