change SQL literal numeric type from Float64 to Decimal128

[kmitchener]

Which issue does this PR close?

Closes #3394 .

Rationale for this change

What changes are included in this PR?

Per issue, switches SQL non-integer literals to Decimal128 instead of Float64.

Are there any user-facing changes?

[kmitchener]

@liukun4515 could you take a look at this conversion?

[liukun4515]

@liukun4515 could you take a look at this conversion?

I will take a look later

@kmitchener

[andygrove]

Thanks for working on this @kmitchener.

We really need to be able to parse numeric literals as either float or decimal. We don't need to do all of this in this PR, but we should make sure we file follow-on issues for anything not included here.

Per the ANSI SQL specification:

<signed numeric literal> ::=
[ <sign> ] <unsigned numeric literal>

<unsigned numeric literal> ::=
<exact numeric literal>
| <approximate numeric literal>

<exact numeric literal> ::=
<unsigned integer> [ <period> [ <unsigned integer> ] ]
| <period> <unsigned integer>

<sign> ::= <plus sign> | <minus sign>

<approximate numeric literal> ::= <mantissa> E <exponent>

<mantissa> ::= <exact numeric literal>

<exponent> ::= <signed integer>

<signed integer> ::= [ <sign> ] <unsigned integer>

<unsigned integer> ::= <digit>..

[kmitchener]

That's extremely helpful, thanks. What source are you using for the SQL specification?

[kmitchener]

In Postgres, these variants all get converted to decimals. https://dbfiddle.uk/CSN4-3op

sqlparser-rs is doing something funky with the "e" notation, so I'll add some follow-on issues for that.

[alamb]

Is this pull request ready for review @kmitchener ? I ask because it is still marked as draft

[kmitchener]

Is this pull request ready for review @kmitchener ? I ask because it is still marked as draft

Hi @alamb, no, it's still draft. I've learned a bit since this PR and am figuring out next steps and also working on other PRs that will make this final PR smaller. I can close this and submit a new PR when the change is finally ready if that's preferable? At this point, I need to make more changes before this is ready for review.

[alamb]

. I've learned a bit since this PR and am figuring out next steps and also working on other PRs that will make this final PR smaller. I can close this and submit a new PR when the change is finally ready if that's preferable? At this point, I need to make more changes before this is ready for review.

Sounds good. I am just trying to keep tabs on PRs in this repo to keep them moving, which is why i asked. I'll close this one to signify it doesn't need any additional attention at this time. Thanks for all your help so far @kmitchener