Quoted schema and table names result in double-quoted names in logical plan.

[neumark]

Description

Quoted schema and table names appear double-quoted in the query plan.

Reproduction

My types of SQL statements are affected, CREATE SCHEMA is just one example:

let sql = "CREATE SCHEMA \"quoted_schema_name\"";
let plan = logical_plan(sql).unwrap();
assert_eq!(format!("{plan:?}"), "CREATE SCHEMA \"\"quoted_schema_name\"\"");

Expected behavior

Quoted identifiers should remain single-quoted (or possibly unquoted if they contain no special characters).

Root cause

The sqlparser create uses ast::Ident (often packaged as ast::ObjectName's) to store identifiers such as table, schema, and column names. Ident stores the actualy identifier in its value field, plus an optional quote character in quoting_style. Ident::to_string() applies the quotes when quoteing_style is not None. The result of Ident::to_string() is once-again quoted by datafusion. For non-quoted identifiers only the second quoting is applied, masking the bug.

Since datafusion does it's own quoting, Ident::to_string() calls should be replaced by ident.value.

Example occurance: Ident::toString() usage for CREATE SCHEMA