MySQL: Support CAST(... AS ... ARRAY) syntax
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MySQL has a special case in `CAST` parsing where the type can be followed by `ARRAY`. This is only used for creating multi-valued indexes in InnoDB, so is only allowed in `CREATE TABLE` and other DDL statements when specifying keys. See the [docs]. Given those restrictions, we could be significantly more restrictive in parsing this, e.g. not parsing `ARRAY` unless we are in a key specification. Or, if there was such a thing as a suffix array type definition, we could parse it as a type. But as far as I know, that doesn't exist in any supported SQL dialects, and encountering `ARRAY` here is unambiguous. So it seemed simplest to be permissive and always parse it. The only downside I can see is we are now adding a field to `Expr::Cast`. [docs]: https://dev.mysql.com/doc/refman/8.4/en/cast-functions.html#function_cast
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MySQL has a special case in
CASTparsing where the type can be followed byARRAY. This is only used for creating multi-valued indexes in InnoDB, so is only allowed inCREATE TABLEand other DDL statements when specifying keys. See the docs.Given those restrictions, we could be significantly more restrictive in parsing this, e.g. not parsing
ARRAYunless we are in a key specification. Or, if there was such a thing as a suffix array type definition, we could parse it as a type. But as far as I know, that doesn't exist in any supported SQL dialects, and encounteringARRAYhere is unambiguous. So it seemed simplest to be permissive and always parse it. The only downside I can see is we are now adding a field toExpr::Cast.