piki commented on issue #1846:
URL:
https://github.com/apache/datafusion-sqlparser-rs/issues/1846#issuecomment-2869951944
It looks like #1120 is where this changed. `BigQueryDialect` got the
ability to parse `DELETE` statements without the `FROM` keyword.
`GenericDialect` got treated the same way as `BigQueryDialect`, but that broke
its ability to parse some statements from dialects other than `BigQueryDialect`.
The most permissive thing would be for `GenericDialect` to be able to
support both of these `DELETE` formats:
- `DELETE [FROM] table [alias] WHERE condition` (like BigQuery)
- `DELETE tables FROM table WHERE condition` (like all the other dialects)
The challenge is that just making `FROM` optional doesn't work, because
these two statements become a reduce-reduce conflict:
- `DELETE table_list [FROM] table WHERE condition`
- `DELETE [FROM] table alias WHERE condition`
So I think the best approach is to split `parse_delete` into two functions:
one in the `BigQueryDialect` style and one in the all-others style, and let
`GenericDialect` try both.
Supporting the union of many grammars is hard and sometimes undefined, but I
think that 👆 is what makes the most sense for `DELETE`.
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