single quoted default value in create table statements

[jennifersp]

Current Dolt default literal values are stores in double quotes, but MySQL does not parse double quoted default literal value in CREATE TABLE statements for both sql shell and importing dumps.
Fixes dolthub/dolt#3218

Added character set and collation columns for show create view

[fulghum]

Looks pretty close; just a couple questions.

[fulghum]

Do we know how the double-quotes get stored? I noticed in one of the test cases that the input statement used single quotes, but was output wrapped in double-quotes.

[jennifersp]

I think go stores string value like val = "example", and when this gets used with String() method of literal expressions, we use %q for fmt.Sprintf method for string type, which double quotes the double quotes, which makes it "\"example\"".
https://github.com/dolthub/go-mysql-server/blob/main/sql/expression/literal.go#L68

[fulghum]

Is there something we should do at this level to prevent double quotes from being stored? I haven't dug through this code yet to understand it deeply, but I'm curious what you think. Do you see a good reason we're storing the double quotes?

Overall, I think this fix is okay, but just wanted to understand the rest of the code. I'm specifically wondering if there are other problems from storing the double quotes that we could fix if we looked a little deeper here.

[jennifersp]

One issue I've worked on before that is related to this double quoted literal expression was for displaying column default value in information_schema.columns table. Everytime the literal expression .String() method was called, it was adding a pair of double quotes. We use this method in FromDoltSchema method as well as in information_schema.columns table iter, which is why the result in the columns table has at least two pairs of double quotes. To resolve this, Vinai added code where the columns table will go through analyzer and the column default values are resolved accordingly which gets rid of extra double quotes, but still ends up with one extra pair of double quotes that gets trimmed in trimColumnDefaultOutput method in columns_table.go

[fulghum]

Looks good! Thanks for digging deeper into the literal value quoting behavior and finding a cleaner solution for this. Awesome to tidy up information_schema.columns a little more along the way, too. 😄

It would be good to go ahead and run the dolt tests against this GMS code to see if there are any dolt tests to patch up.

[jennifersp]

Added changes for requiring parentheses around default function expressions. To do this,

• we catch some cases of functions expressions without enclosing parentheses in parser such as GEOMETRY DEFAULT POINT(1,2) is returns false for ParenExpr interface check but has children which means it's functions expression.
• the other set of cases are caught during analyzing the query as we need more information on column type, and some exceptions such as allowing NOW() and CURRENT_TIMESTAMP() without enclosing parentheses for datetime and timestamp column types only are validated in analyzer.

[fulghum]

Code changes look good. Just two questions to make sure we've got good test coverage and two really minor suggestions.