From 9b65f51aac90d2425a540d9bedb0a956cbfd7ae7 Mon Sep 17 00:00:00 2001
From: Ariel Mashraki <ariel@mashraki.co.il>
Date: Mon, 24 Jan 2022 23:36:36 +0200
Subject: [PATCH] sql/sqlite: inspect index sort order

---
 sql/sqlite/inspect.go      | 36 +++++++++++++++++++++++-------------
 sql/sqlite/inspect_test.go | 18 +++++++++---------
 2 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/sql/sqlite/inspect.go b/sql/sqlite/inspect.go
index 80dc9c4dee4..9207e032a49 100644
--- a/sql/sqlite/inspect.go
+++ b/sql/sqlite/inspect.go
@@ -189,7 +189,7 @@ func (i *inspect) indexes(ctx context.Context, t *schema.Table) error {
 		return fmt.Errorf("sqlite: scan %q indexes: %w", t.Name, err)
 	}
 	for _, idx := range t.Indexes {
-		if err := i.indexColumns(ctx, t, idx); err != nil {
+		if err := i.indexInfo(ctx, t, idx); err != nil {
 			return err
 		}
 	}
@@ -233,33 +233,36 @@ func (i *inspect) addIndexes(t *schema.Table, rows *sql.Rows) error {
 	return nil
 }
 
-func (i *inspect) indexColumns(ctx context.Context, t *schema.Table, idx *schema.Index) error {
+func (i *inspect) indexInfo(ctx context.Context, t *schema.Table, idx *schema.Index) error {
 	rows, err := i.QueryContext(ctx, fmt.Sprintf(indexColumnsQuery, idx.Name))
 	if err != nil {
 		return fmt.Errorf("sqlite: querying %q indexes: %w", t.Name, err)
 	}
 	defer rows.Close()
 	for rows.Next() {
-		var name sql.NullString
-		if err := rows.Scan(&name); err != nil {
+		var (
+			desc sql.NullBool
+			name sql.NullString
+		)
+		if err := rows.Scan(&name, &desc); err != nil {
 			return fmt.Errorf("sqlite: scanning index names: %w", err)
 		}
+		part := &schema.IndexPart{SeqNo: len(idx.Parts) + 1}
 		switch c, ok := t.Column(name.String); {
 		case ok:
-			idx.Parts = append(idx.Parts, &schema.IndexPart{
-				SeqNo: len(idx.Parts) + 1,
-				C:     c,
-			})
+			part.C = c
 		// NULL name indicates that the index-part is an expression and we
 		// should extract it from the `CREATE INDEX` statement (not supported atm).
 		case !sqlx.ValidString(name):
-			idx.Parts = append(idx.Parts, &schema.IndexPart{
-				SeqNo: len(idx.Parts) + 1,
-				X:     &schema.RawExpr{X: "<unsupported>"},
-			})
+			part.X = &schema.RawExpr{X: "<unsupported>"}
 		default:
 			return fmt.Errorf("sqlite: column %q was not found for index %q", name.String, idx.Name)
 		}
+		if desc.Bool {
+			// The default sort order is "ASC".
+			part.Attrs = append(part.Attrs, &IndexOrder{Desc: desc.Bool})
+		}
+		idx.Parts = append(idx.Parts, part)
 	}
 	return nil
 }
@@ -441,6 +444,13 @@ type (
 		P string
 	}
 
+	// IndexOrder describes the sort order of an index.
+	// See: https://www.sqlite.org/lang_createindex.html#descending_indexes
+	IndexOrder struct {
+		schema.Attr
+		Desc bool
+	}
+
 	// IndexOrigin describes how the index was created.
 	// See: https://www.sqlite.org/pragma.html#pragma_index_list
 	IndexOrigin struct {
@@ -663,7 +673,7 @@ const (
 	// Query to list table indexes.
 	indexesQuery = "SELECT `il`.`name`, `il`.`unique`, `il`.`origin`, `il`.`partial`, `m`.`sql` FROM pragma_index_list('%s') AS il JOIN sqlite_master AS m ON il.name = m.name"
 	// Query to list index columns.
-	indexColumnsQuery = "SELECT name FROM pragma_index_info('%s') ORDER BY seqno"
+	indexColumnsQuery = "SELECT name, desc FROM pragma_index_xinfo('%s') WHERE key = 1 ORDER BY seqno"
 	// Query to list table foreign-keys.
 	fksQuery = "SELECT `id`, `from`, `to`, `table`, `on_update`, `on_delete` FROM pragma_foreign_key_list('%s') ORDER BY id, seq"
 )
diff --git a/sql/sqlite/inspect_test.go b/sql/sqlite/inspect_test.go
index fadd14e4654..a516cf73f58 100644
--- a/sql/sqlite/inspect_test.go
+++ b/sql/sqlite/inspect_test.go
@@ -105,17 +105,17 @@ func TestDriver_InspectTable(t *testing.T) {
 `))
 				m.ExpectQuery(sqltest.Escape(fmt.Sprintf(indexColumnsQuery, "c1u"))).
 					WillReturnRows(sqltest.Rows(`
- name 
-------
- c1   
- c2
+ name  |   desc |
+-------+--------+
+ c1   |  1      |
+ c2   |  0      |
 `))
 				m.ExpectQuery(sqltest.Escape(fmt.Sprintf(indexColumnsQuery, "c1_c2"))).
 					WillReturnRows(sqltest.Rows(`
- name 
-------
- c1   
- nil
+ name  |   desc |     
+-------+--------+     
+ c1    |  0     |     
+ nil   |  0     |     
 `))
 				m.noFKs("users")
 			},
@@ -131,7 +131,7 @@ func TestDriver_InspectTable(t *testing.T) {
 						Unique: true,
 						Table:  t,
 						Parts: []*schema.IndexPart{
-							{SeqNo: 1, C: columns[0]},
+							{SeqNo: 1, C: columns[0], Attrs: []schema.Attr{&IndexOrder{Desc: true}}},
 							{SeqNo: 2, C: columns[1]},
 						},
 						Attrs: []schema.Attr{