[branch-50] fix: Implement AggregateUDFImpl::reverse_expr for StringAgg (#17165) (#17473)

datafusion/core/tests/sql/select.rs

@@ -344,3 +344,28 @@ async fn test_version_function() {
 
     assert_eq!(version.value(0), expected_version);
 }
+
+/// Regression test for https://github.com/apache/datafusion/issues/17513
+/// See https://github.com/apache/datafusion/pull/17520
+#[tokio::test]
+async fn test_select_no_projection() -> Result<()> {
+    let tmp_dir = TempDir::new()?;
+    // `create_ctx_with_partition` creates 10 rows per partition and we chose 1 partition
+    let ctx = create_ctx_with_partition(&tmp_dir, 1).await?;
+
+    let results = ctx.sql("SELECT FROM test").await?.collect().await?;
+    // We should get all of the rows, just without any columns
+    let total_rows: usize = results.iter().map(|b| b.num_rows()).sum();
+    assert_eq!(total_rows, 10);
+    // Check that none of the batches have any columns
+    for batch in &results {
+        assert_eq!(batch.num_columns(), 0);
+    }
+    // Sanity check the output, should be just empty columns
+    assert_snapshot!(batches_to_sort_string(&results), @r"
+    ++
+    ++
+    ++
+    ");
+    Ok(())
+}

datafusion/sql/src/select.rs

@@ -665,14 +665,6 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
         let mut prepared_select_exprs = vec![];
         let mut error_builder = DataFusionErrorBuilder::new();
 
-        // Handle the case where no projection is specified but we have a valid FROM clause
-        // In this case, implicitly add a wildcard projection (SELECT *)
-        let projection = if projection.is_empty() && !empty_from {
-            vec![SelectItem::Wildcard(WildcardAdditionalOptions::default())]
-        } else {
-            projection
-        };
-
         for expr in projection {
             match self.sql_select_to_rex(expr, plan, empty_from, planner_context) {
                 Ok(expr) => prepared_select_exprs.push(expr),

datafusion/sqllogictest/test_files/projection.slt

@@ -252,3 +252,31 @@ physical_plan
 
 statement ok
 drop table t;
+
+# Regression test for 
+# https://github.com/apache/datafusion/issues/17513
+
+query I
+COPY (select 1 as a, 2 as b)
+TO 'test_files/scratch/projection/17513.parquet'
+STORED AS PARQUET;
+----
+1
+
+statement ok
+create external table t1 stored as parquet location 'test_files/scratch/projection/17513.parquet';
+
+query TT
+explain format indent
+select from t1 where t1.a > 1;
+----
+logical_plan
+01)Projection:
+02)--Filter: t1.a > Int64(1)
+03)----TableScan: t1 projection=[a], partial_filters=[t1.a > Int64(1)]
+physical_plan
+01)ProjectionExec: expr=[]
+02)--CoalesceBatchesExec: target_batch_size=8192
+03)----FilterExec: a@0 > 1
+04)------RepartitionExec: partitioning=RoundRobinBatch(4), input_partitions=1
+05)--------DataSourceExec: file_groups={1 group: [[WORKSPACE_ROOT/datafusion/sqllogictest/test_files/scratch/projection/17513.parquet]]}, projection=[a], file_type=parquet, predicate=a@0 > 1, pruning_predicate=a_null_count@1 != row_count@2 AND a_max@0 > 1, required_guarantees=[]

docs/source/user-guide/sql/select.md

@@ -75,20 +75,6 @@ Example:
 SELECT t.a FROM table AS t
 ```
 
-The `FROM` clause can also come before the `SELECT` clause.
-Example:
-
-```sql
-FROM table AS t
-SELECT t.a
-```
-
-If the `SELECT` clause is omitted, the `FROM` clause will return all columns from the table.
-
-```sql
-FROM table
-```
-
 ## WHERE clause
 
 Example: