Auto detect type of condition value in where statement

[DiamondMofeng]

Currently, the condition values from the input of where statement are always treated as the raw string from input.
This means users have to type quotation marks manually, otherwise their string condition would be treated as a variable or a keyword, etc.
Actually, we can easily get its type from column schema.

[DiamondMofeng]

I do not think this is much necessary now. Anyway feel free to tell me if you have any good ideas.