Revert apache#17295 (Support from-first SQL syntax) (apache#17520) (apache#17544)

* Add failing test

* Fix regression in SELECT FROM syntax with WHERE clause

When using 'SELECT FROM table WHERE condition', the query should create
an empty projection (no columns) while still filtering rows. This was
broken by PR apache#17295 which added FROM-first syntax support.

The issue was that both 'FROM table' and 'SELECT FROM table' resulted
in empty projection lists, making them indistinguishable. The fix checks
for the presence of a WHERE clause to differentiate:
- 'FROM table' (no WHERE) -> add wildcard projection (all columns)
- 'SELECT FROM table WHERE ...' -> keep empty projection

Also updates the test expectation to correctly show the empty Projection
node in the query plan.

Fixes apache#17513

* Revert

* Fix regression: SELECT FROM syntax should return empty projection

Removes automatic wildcard projection for empty projections, fixing
the regression where `SELECT FROM table` incorrectly returned all
columns instead of empty projection.

Note: This temporarily breaks FROM-first syntax. A proper fix would
require distinguishing between `FROM table` and `SELECT FROM table`
at the parser level.

Fixes apache#17513

🤖 Generated with [Claude Code](https://claude.ai/code)



* add a better regression test

* remove comment

* fmt

* Update datafusion/sqllogictest/test_files/projection.slt



* Update datafusion/core/tests/sql/select.rs



* revert docs

* fmt

---------

Co-authored-by: Adrian Garcia Badaracco <[email protected]>
Co-authored-by: Claude <[email protected]>
Co-authored-by: Oleks V <[email protected]>

Author: 4 people

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/from-first.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=[]

datafusion/sqllogictest/test_files/projection.slt

@@ -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: