Re: Need help with tracing how identifiers are parsed; dot-reserved vs dot-space-reserved

[Justin Ng]

I think I just figured it out.

The important bits are,
+ https://github.com/mysql/mysql-server/blob/5c8c085ba96d30d697d0baa54d67b102c232116b/sql/sql_lex.cc#L1610-L1612
+ `MY_LEX_IDENT_START` does not call `find_keyword()`
+ `MY_LEX_START` calls `find_keyword()`

In `.SELECT`, we go to `MY_LEX_IDENT_START`, never call `find_keyword()` and treat `SELECT` as an identifier.

In `. SELECT`, we see a space, which is not a valid identifier character. So, we go to `MY_LEX_IDENT`, call `find_keyword()` and treat `SELECT` as a keyword.

And `ident_map` is populated here, https://github.com/mysql/mysql-server/blob/3e90d07c3578e4da39dc1bce73559bbdf655c28c/mysys/sql_chars.cc#L120

`ident_map` is basically an array of booleans, mapping each character to true/false, depending on whether it could plausibly be an identifier character.