Parser hangs on certain input - some signed literals, some parentheticals

[jessestimpson]

Hi, thanks for the library. I've been making continued use of it in my FDB SQL layer, and it's great.

We've found a couple inputs that cause the parser to hang.

Version: commit da69080 (current main), Elixir 1.19.4, OTP 28

sql = "select id from t where a = -5"
{:ok, ctx, tokens} = SQL.Lexer.lex(sql)
task = Task.async(fn -> SQL.Parser.parse(tokens, ctx) end)
Task.yield(task, 5_000) || Task.shutdown(task, :brutal_kill)
#=> nil  (parse never completes)

These examples all display the hang:

select id from t where a = -5
select id from t where a > -5
select id from t where a = +5
select id from t where a = 1 and (b > 2)
select id from t where a = 1 or (b > 2)
select id from t where a = 1 for update

Comparatively, these examples parse fine, no issues:

select id from t where a in (-1, 2)
select id from t where (a > 1 or b < 0)
select -1

For the record, I don't have any use case for for update but found that it also hangs, so provided here for completeness.

[Schultzer]

Thanks, I really need to refactor the parser so it’s more reliable then this, but thats not on the roadmap for the upcoming release, this is very likely to be an issue in

sql/lib/parser.ex

Line 206 in da69080

defp __parse__(tokens) do

I’ll add those cases to the test suite and get a fix for this.