alamb commented on code in PR #11505:
URL: https://github.com/apache/datafusion/pull/11505#discussion_r1683380691
##########
datafusion/sql/src/unparser/plan.rs:
##########
@@ -611,6 +607,67 @@ impl Unparser<'_> {
}
}
+// This logic is to work out the columns and inner query for SubqueryAlias
plan for both types of
+// subquery
+// - `(SELECT column_a as a from table) AS A`
+// - `(SELECT column_a from table) AS A (a)`
+//
+// A roundtrip example for table alias with columns
+//
+// query: SELECT id FROM (SELECT j1_id from j1) AS c (id)
+//
+// LogicPlan:
+// Projection: c.id
+// SubqueryAlias: c
+// Projection: j1.j1_id AS id
+// Projection: j1.j1_id
+// TableScan: j1
+//
+// Before introducing this logic, the unparsed query would be `SELECT c.id
FROM (SELECT j1.j1_id AS
+// id FROM (SELECT j1.j1_id FROM j1)) AS c`.
+// The query is invalid as `j1.j1_id` is not a valid identifier in the derived
table
+// `(SELECT j1.j1_id FROM j1)`
+//
+// With this logic, the unparsed query will be:
+// `SELECT c.id FROM (SELECT j1.j1_id FROM j1) AS c (id)`
+//
+// Caveat: this won't handle the case like `select * from (select 1, 2) AS a
(b, c)`
+// as the parser gives a wrong plan which has mismatch `Int(1)` types: Literal
and
+// Column in the Projections. Once the parser side is fixed, this logic should
work
Review Comment:
Thank you for the comments
##########
datafusion/sql/tests/cases/plan_to_sql.rs:
##########
@@ -240,6 +240,35 @@ fn roundtrip_statement_with_dialect() -> Result<()> {
parser_dialect: Box::new(GenericDialect {}),
unparser_dialect: Box::new(UnparserDefaultDialect {}),
},
+ // more tests around subquery/derived table roundtrip
+ TestStatementWithDialect {
+ sql: "SELECT string_count FROM (
+ SELECT
Review Comment:
I recommend you add a query that has an additional test that selects more
than one column and an expression
something like
```sql
select string_count * 100, id FROM ...
```
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