Cast Utf8View to Utf8 to support || from StringViewArray (#11796

)

* make query work

* hack string_concat_coercion

* more tests

datafusion/expr/src/type_coercion/binary.rs

@@ -890,15 +890,22 @@ fn dictionary_coercion(
 /// 2. Data type of the other side should be able to cast to string type
 fn string_concat_coercion(lhs_type: &DataType, rhs_type: &DataType) -> Option<DataType> {
     use arrow::datatypes::DataType::*;
-    string_coercion(lhs_type, rhs_type).or(match (lhs_type, rhs_type) {
-        (Utf8, from_type) | (from_type, Utf8) => {
-            string_concat_internal_coercion(from_type, &Utf8)
-        }
-        (LargeUtf8, from_type) | (from_type, LargeUtf8) => {
-            string_concat_internal_coercion(from_type, &LargeUtf8)
+    match (lhs_type, rhs_type) {
+        // If Utf8View is in any side, we coerce to Utf8.
+        // Ref: https://github.com/apache/datafusion/pull/11796
+        (Utf8View, Utf8View | Utf8 | LargeUtf8) | (Utf8 | LargeUtf8, Utf8View) => {
+            Some(Utf8)
         }
-        _ => None,
-    })
+        _ => string_coercion(lhs_type, rhs_type).or(match (lhs_type, rhs_type) {
+            (Utf8, from_type) | (from_type, Utf8) => {
+                string_concat_internal_coercion(from_type, &Utf8)
+            }
+            (LargeUtf8, from_type) | (from_type, LargeUtf8) => {
+                string_concat_internal_coercion(from_type, &LargeUtf8)
+            }
+            _ => None,
+        }),
+    }
 }
 
 fn array_coercion(lhs_type: &DataType, rhs_type: &DataType) -> Option<DataType> {

datafusion/sqllogictest/test_files/string_view.slt

@@ -447,3 +447,56 @@ select t.dt from dates t where arrow_cast('2024-01-01', 'Utf8View') < t.dt;
 
 statement ok
 drop table dates;
+
+statement ok
+create table temp as values
+('value1', arrow_cast('rust', 'Utf8View'), arrow_cast('fast', 'Utf8View')),
+('value2', arrow_cast('datafusion', 'Utf8View'), arrow_cast('cool', 'Utf8View'));
+
+query T
+select column2||' is fast' from temp;
+----
+rust is fast
+datafusion is fast
+
+
+query T
+select column2 || ' is ' || column3 from temp;
+----
+rust is fast
+datafusion is cool
+
+query TT
+explain select column2 || 'is' || column3 from temp;
+----
+logical_plan
+01)Projection: CAST(temp.column2 AS Utf8) || Utf8("is") || CAST(temp.column3 AS Utf8)
+02)--TableScan: temp projection=[column2, column3]
+
+
+query TT
+explain select column2||' is fast' from temp;
+----
+logical_plan
+01)Projection: CAST(temp.column2 AS Utf8) || Utf8(" is fast")
+02)--TableScan: temp projection=[column2]
+
+
+query T
+select column2||column3 from temp;
+----
+rustfast
+datafusioncool
+
+query TT
+explain select column2||column3 from temp;
+----
+logical_plan
+01)Projection: CAST(temp.column2 AS Utf8) || CAST(temp.column3 AS Utf8)
+02)--TableScan: temp projection=[column2, column3]
+
+query T
+select column2|| ' ' ||column3 from temp;
+----
+rust fast
+datafusion cool