spanner/spannertest: support SELECT * queries

These need special handling in the query evaluator since the expression
list doesn't have a 1:1 mapping to the output.

Change-Id: I38f6226d9b990c0d8ae5b10d4971635aeb9d461f
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/49190
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Knut Olav Løite <koloite@gmail.com>

spanner/spannertest/README.md

@@ -31,7 +31,6 @@ by ascending esotericism:
 - SELECT aliases
 - subselects
 - set operations (UNION, INTERSECT, EXCEPT)
-- SELECT star expressions
 - partition support
 - conditional expressions
 - table sampling (implementation)

spanner/spannertest/db_eval.go

@@ -97,13 +97,21 @@ func (d *database) evalSelect(sel spansql.Select, params queryParams, aux []span
 		params: params,
 	}
 
-	for _, e := range sel.List {
-		ci, err := ec.colInfo(e)
-		if err != nil {
-			return nil, err
+	// Is this a `SELECT *` query?
+	selectStar := len(sel.List) == 1 && sel.List[0] == spansql.Star
+
+	if selectStar {
+		// Every column will appear in the output.
+		ri.Cols = append([]colInfo(nil), ec.table.cols...)
+	} else {
+		for _, e := range sel.List {
+			ci, err := ec.colInfo(e)
+			if err != nil {
+				return nil, err
+			}
+			// TODO: deal with ci.Name == ""?
+			ri.Cols = append(ri.Cols, ci)
 		}
-		// TODO: deal with ci.Name == ""?
-		ri.Cols = append(ri.Cols, ci)
 	}
 	for _, r := range t.rows {
 		ec.row = r
@@ -120,16 +128,27 @@ func (d *database) evalSelect(sel spansql.Select, params queryParams, aux []span
 		}
 
 		// Evaluate SELECT expression list on the row.
-		out, err := ec.evalExprList(sel.List)
-		if err != nil {
-			return nil, err
+		var res resultRow
+		if selectStar {
+			var out []interface{}
+			for i := range r {
+				out = append(out, r.copyDataElem(i))
+			}
+			res.data = out
+		} else {
+			out, err := ec.evalExprList(sel.List)
+			if err != nil {
+				return nil, err
+			}
+			res.data = out
 		}
 		a, err := ec.evalExprList(aux)
 		if err != nil {
 			return nil, err
 		}
+		res.aux = a
 
-		ri.rows = append(ri.rows, resultRow{data: out, aux: a})
+		ri.rows = append(ri.rows, res)
 	}
 
 	return ri, nil

spanner/spannertest/db_test.go

@@ -276,6 +276,15 @@ func TestTableData(t *testing.T) {
 				{int64(4)},
 			},
 		},
+		{
+			`SELECT * FROM Staff WHERE Name LIKE "S%"`,
+			nil,
+			[][]interface{}{
+				// These are returned in table column order.
+				// Note that the primary key columns get sorted first.
+				{"Sam", int64(3), int64(9), false, 1.75, nil},
+			},
+		},
 		{
 			`SELECT Name FROM Staff WHERE FirstSeen >= @min`,
 			queryParams{"min": "1996-01-01"},

spanner/spansql/parser_test.go

@@ -70,6 +70,14 @@ func TestParseQuery(t *testing.T) {
 				},
 			},
 		},
+		{`SELECT * FROM Packages`,
+			Query{
+				Select: Select{
+					List: []Expr{Star},
+					From: []SelectFrom{{Table: "Packages"}},
+				},
+			},
+		},
 	}
 	for _, test := range tests {
 		got, err := ParseQuery(test.in)