From 1ac78aa950d6dadb8ec430675f4e85117a942df0 Mon Sep 17 00:00:00 2001
From: Tobie Morgan Hitchcock <tobie@abcum.com>
Date: Sun, 26 Nov 2017 13:45:48 +0000
Subject: [PATCH] A single *Thing in a subquery is the same as LIMIT 1

---
 db/fetch.go       | 17 +++++++++++++++++
 db/select.go      |  4 ++--
 db/select_test.go | 44 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/db/fetch.go b/db/fetch.go
index c1058183..dfa550a2 100644
--- a/db/fetch.go
+++ b/db/fetch.go
@@ -275,6 +275,23 @@ func (e *executor) fetchVersion(ctx context.Context, val sql.Expr) (int64, error
 
 }
 
+func (e *executor) fetchOutputs(ctx context.Context, stm *sql.SelectStatement) (int, error) {
+
+	l, err := e.fetchLimit(ctx, stm.Limit)
+	if err != nil {
+		return -1, err
+	}
+
+	if len(stm.What) == 1 {
+		if _, ok := stm.What[0].(*sql.Thing); ok {
+			l = 1
+		}
+	}
+
+	return l, nil
+
+}
+
 func calcAsBool(i interface{}) bool {
 
 	switch v := i.(type) {
diff --git a/db/select.go b/db/select.go
index 991e686f..118faf0b 100644
--- a/db/select.go
+++ b/db/select.go
@@ -95,12 +95,12 @@ func (e *executor) fetchSelect(ctx context.Context, stm *sql.SelectStatement, do
 		return nil, err
 	}
 
-	lim, err := e.fetchLimit(ctx, stm.Limit)
+	cnt, err := e.fetchOutputs(ctx, stm)
 	if err != nil {
 		return nil, err
 	}
 
-	switch lim {
+	switch cnt {
 	case 1:
 		switch len(stm.Expr) {
 		case 1:
diff --git a/db/select_test.go b/db/select_test.go
index 12a54801..daace62a 100644
--- a/db/select_test.go
+++ b/db/select_test.go
@@ -159,6 +159,28 @@ func TestSelect(t *testing.T) {
 
 	})
 
+	Convey("Select records using an * subquery, specifying a single record", t, func() {
+
+		setupDB()
+
+		txt := `
+		USE NS test DB test;
+		CREATE person:1 SET name="Tobias";
+		CREATE person:2 SET name="Silvana";
+		CREATE person:3 SET name="Jonathan";
+		CREATE person:4 SET name="Benjamin";
+		CREATE person:5 SET name="Alexander";
+		SELECT * FROM (SELECT * FROM person:5);
+		`
+
+		res, err := Execute(setupKV(), txt, nil)
+		So(err, ShouldBeNil)
+		So(res, ShouldHaveLength, 7)
+		So(res[6].Result, ShouldHaveLength, 1)
+		So(data.Consume(res[6].Result[0]).Get("name").Data(), ShouldEqual, "Alexander")
+
+	})
+
 	Convey("Select records using an id subquery", t, func() {
 
 		setupDB()
@@ -204,6 +226,28 @@ func TestSelect(t *testing.T) {
 
 	})
 
+	Convey("Select records using an id subquery, specifying a single record", t, func() {
+
+		setupDB()
+
+		txt := `
+		USE NS test DB test;
+		CREATE person:1 SET name="Tobias";
+		CREATE person:2 SET name="Silvana";
+		CREATE person:3 SET name="Jonathan";
+		CREATE person:4 SET name="Benjamin";
+		CREATE person:5 SET name="Alexander";
+		SELECT * FROM (SELECT id FROM (SELECT * FROM person:5));
+		`
+
+		res, err := Execute(setupKV(), txt, nil)
+		So(err, ShouldBeNil)
+		So(res, ShouldHaveLength, 7)
+		So(res[6].Result, ShouldHaveLength, 1)
+		So(data.Consume(res[6].Result[0]).Get("name").Data(), ShouldEqual, "Alexander")
+
+	})
+
 	Convey("Select records using a single field subquery", t, func() {
 
 		setupDB()