sql: catch unnamed/implicit indexes in diffing

internal/integration/integration_test.go

@@ -27,6 +27,7 @@ type T interface {
 	loadUsers() *schema.Table
 	posts() *schema.Table
 	loadPosts() *schema.Table
+	loadTable(string) *schema.Table
 	dropTables(...string)
 	migrate(...schema.Change)
 	diff(*schema.Table, *schema.Table) []schema.Change
@@ -97,6 +98,36 @@ func testEntIntegration(t T, dialect string, db *sql.DB) {
 	t.migrate(changes...)
 }
 
+func testImplicitIndexes(t T, db *sql.DB) {
+	const (
+		name = "implicit_indexes"
+		ddl  = "create table implicit_indexes(c1 int unique, c2 int unique, unique(c1,c2), unique(c2,c1))"
+	)
+	t.dropTables(name)
+	_, err := db.Exec(ddl)
+	require.NoError(t, err)
+	current := t.loadTable(name)
+	c1, c2 := schema.NewNullIntColumn("c1", "int"), schema.NewNullIntColumn("c2", "int")
+	desired := schema.NewTable(name).
+		AddColumns(c1, c2).
+		AddIndexes(
+			schema.NewUniqueIndex("").AddColumns(c1),
+			schema.NewUniqueIndex("").AddColumns(c2),
+			schema.NewUniqueIndex("").AddColumns(c1, c2),
+			schema.NewUniqueIndex("").AddColumns(c2, c1),
+		)
+	changes := t.diff(current, desired)
+	require.Empty(t, changes)
+	desired.AddIndexes(
+		schema.NewIndex("c1_key").AddColumns(c1),
+		schema.NewIndex("c2_key").AddColumns(c2),
+	)
+	changes = t.diff(current, desired)
+	require.NotEmpty(t, changes)
+	t.migrate(&schema.ModifyTable{T: desired, Changes: changes})
+	ensureNoChange(t, desired)
+}
+
 func testHCLIntegration(t T, full string, empty string) {
 	t.applyHcl(full)
 	users := t.loadUsers()

internal/integration/mysql_test.go

@@ -950,6 +950,12 @@ create table atlas_types_sanity
 			require.EqualValues(t, &expected, ts)
 		})
 	})
+
+	t.Run("ImplicitIndexes", func(t *testing.T) {
+		myRun(t, func(t *myTest) {
+			testImplicitIndexes(t, t.db)
+		})
+	})
 }
 
 func (t *myTest) dsn() string {
@@ -1109,19 +1115,19 @@ func (t *myTest) loadRealm() *schema.Realm {
 }
 
 func (t *myTest) loadUsers() *schema.Table {
-	realm := t.loadRealm()
-	require.Len(t, realm.Schemas, 1)
-	users, ok := realm.Schemas[0].Table("users")
-	require.True(t, ok)
-	return users
+	return t.loadTable("users")
 }
 
 func (t *myTest) loadPosts() *schema.Table {
+	return t.loadTable("posts")
+}
+
+func (t *myTest) loadTable(name string) *schema.Table {
 	realm := t.loadRealm()
 	require.Len(t, realm.Schemas, 1)
-	posts, ok := realm.Schemas[0].Table("posts")
+	table, ok := realm.Schemas[0].Table(name)
 	require.True(t, ok)
-	return posts
+	return table
 }
 
 func (t *myTest) mariadb() bool { return strings.HasPrefix(t.version, "Maria") }

internal/integration/postgres_test.go

@@ -876,6 +876,12 @@ create table atlas_types_sanity
 		}
 		require.EqualValues(t, &expected, ts)
 	})
+
+	t.Run("ImplicitIndexes", func(t *testing.T) {
+		pgRun(t, func(t *pgTest) {
+			testImplicitIndexes(t, t.db)
+		})
+	})
 }
 
 func (t *pgTest) dsn() string {
@@ -910,19 +916,19 @@ func (t *pgTest) loadRealm() *schema.Realm {
 }
 
 func (t *pgTest) loadUsers() *schema.Table {
-	realm := t.loadRealm()
-	require.Len(t, realm.Schemas, 1)
-	users, ok := realm.Schemas[0].Table("users")
-	require.True(t, ok)
-	return users
+	return t.loadTable("users")
 }
 
 func (t *pgTest) loadPosts() *schema.Table {
+	return t.loadTable("posts")
+}
+
+func (t *pgTest) loadTable(name string) *schema.Table {
 	realm := t.loadRealm()
 	require.Len(t, realm.Schemas, 1)
-	posts, ok := realm.Schemas[0].Table("posts")
+	table, ok := realm.Schemas[0].Table(name)
 	require.True(t, ok)
-	return posts
+	return table
 }
 
 func (t *pgTest) users() *schema.Table {

internal/integration/sqlite_test.go

@@ -689,6 +689,12 @@ create table atlas_types_sanity
 		}
 		require.EqualValues(t, &expected, ts)
 	})
+
+	t.Run("ImplicitIndexes", func(t *testing.T) {
+		liteRun(t, func(t *liteTest) {
+			testImplicitIndexes(t, t.db)
+		})
+	})
 }
 
 func (t *liteTest) applyHcl(spec string) {
@@ -712,19 +718,19 @@ func (t *liteTest) loadRealm() *schema.Realm {
 }
 
 func (t *liteTest) loadUsers() *schema.Table {
-	realm := t.loadRealm()
-	require.Len(t, realm.Schemas, 1)
-	users, ok := realm.Schemas[0].Table("users")
-	require.True(t, ok)
-	return users
+	return t.loadTable("users")
 }
 
 func (t *liteTest) loadPosts() *schema.Table {
+	return t.loadTable("posts")
+}
+
+func (t *liteTest) loadTable(name string) *schema.Table {
 	realm := t.loadRealm()
 	require.Len(t, realm.Schemas, 1)
-	posts, ok := realm.Schemas[0].Table("posts")
+	table, ok := realm.Schemas[0].Table(name)
 	require.True(t, ok)
-	return posts
+	return table
 }
 
 func (t *liteTest) users() *schema.Table {

sql/internal/sqlx/diff.go

@@ -46,6 +46,12 @@ type (
 		// changed. For example, an index-part collation.
 		IndexPartAttrChanged(from, to []schema.Attr) bool
 
+		// IsGeneratedIndexName reports if the index name was generated by the database
+		// for unnamed INDEX or UNIQUE constraints. In such cases, the differ will look
+		// for unnamed schema.Indexes on the desired state, before tagging the index as
+		// a candidate for deletion.
+		IsGeneratedIndexName(*schema.Table, *schema.Index) bool
+
 		// ReferenceChanged reports if the foreign key referential action was
 		// changed. For example, action was changed from RESTRICT to CASCADE.
 		ReferenceChanged(from, to schema.ReferenceOption) bool
@@ -186,27 +192,8 @@ func (d *Diff) TableDiff(from, to *schema.Table) ([]schema.Change, error) {
 		}
 	}
 
-	// Drop or modify indexes.
-	for _, idx1 := range from.Indexes {
-		idx2, ok := to.Index(idx1.Name)
-		if !ok {
-			changes = append(changes, &schema.DropIndex{I: idx1})
-			continue
-		}
-		if change := d.indexChange(idx1, idx2); change != schema.NoChange {
-			changes = append(changes, &schema.ModifyIndex{
-				From:   idx1,
-				To:     idx2,
-				Change: change,
-			})
-		}
-	}
-	// Add indexes.
-	for _, idx1 := range to.Indexes {
-		if _, ok := from.Index(idx1.Name); !ok {
-			changes = append(changes, &schema.AddIndex{I: idx1})
-		}
-	}
+	// Index changes.
+	changes = append(changes, d.indexDiff(from, to)...)
 
 	// Drop or modify foreign-keys.
 	for _, fk1 := range from.ForeignKeys {
@@ -232,6 +219,50 @@ func (d *Diff) TableDiff(from, to *schema.Table) ([]schema.Change, error) {
 	return changes, nil
 }
 
+// indexDiff returns the schema changes (if any) for migrating table
+// indexes from current state to the desired state.
+func (d *Diff) indexDiff(from, to *schema.Table) []schema.Change {
+	var (
+		changes []schema.Change
+		exists  = make(map[*schema.Index]bool)
+	)
+	// Drop or modify indexes.
+	for _, idx1 := range from.Indexes {
+		idx2, ok := to.Index(idx1.Name)
+		// Found directly.
+		if ok {
+			if change := d.indexChange(idx1, idx2); change != schema.NoChange {
+				changes = append(changes, &schema.ModifyIndex{
+					From:   idx1,
+					To:     idx2,
+					Change: change,
+				})
+			}
+			exists[idx2] = true
+			continue
+		}
+		// Found indirectly.
+		if d.IsGeneratedIndexName(from, idx1) {
+			if idx2, ok := d.similarUnnamedIndex(to, idx1); ok {
+				exists[idx2] = true
+				continue
+			}
+		}
+		// Not found.
+		changes = append(changes, &schema.DropIndex{I: idx1})
+	}
+	// Add indexes.
+	for _, idx := range to.Indexes {
+		if exists[idx] {
+			continue
+		}
+		if _, ok := from.Index(idx.Name); !ok {
+			changes = append(changes, &schema.AddIndex{I: idx})
+		}
+	}
+	return changes
+}
+
 // pkChange returns the schema changes (if any) for migrating one primary key to the other.
 func (d *Diff) pkChange(from, to *schema.Index) schema.ChangeKind {
 	change := d.indexChange(from, to)
@@ -311,6 +342,19 @@ func (d *Diff) fkChange(from, to *schema.ForeignKey) schema.ChangeKind {
 	return change
 }
 
+// similarUnnamedIndex searches for an unnamed index with the same index-parts in the table.
+func (d *Diff) similarUnnamedIndex(t *schema.Table, idx1 *schema.Index) (*schema.Index, bool) {
+	for _, idx2 := range t.Indexes {
+		if idx2.Name != "" || len(idx2.Parts) != len(idx1.Parts) || idx2.Unique != idx1.Unique {
+			continue
+		}
+		if d.partsChange(idx1.Parts, idx2.Parts) == schema.NoChange {
+			return idx2, true
+		}
+	}
+	return nil, false
+}
+
 // CommentChange reports if the element comment was changed.
 func CommentChange(from, to []schema.Attr) schema.ChangeKind {
 	var c1, c2 schema.Comment

sql/mysql/diff.go

@@ -78,6 +78,34 @@ func (d *diff) ColumnChange(from, to *schema.Column) (schema.ChangeKind, error)
 	return change, nil
 }
 
+// IsGeneratedIndexName reports if the index name was generated by the database.
+func (d *diff) IsGeneratedIndexName(_ *schema.Table, idx *schema.Index) bool {
+	// Auto-generated index names for functional/expression indexes. See.
+	// mysql-server/sql/sql_table.cc#add_functional_index_to_create_list
+	const f = "functional_index"
+	switch {
+	case d.supportsIndexExpr() && idx.Name == f:
+		return true
+	case d.supportsIndexExpr() && strings.HasPrefix(idx.Name+"_", f):
+		i, err := strconv.ParseInt(strings.TrimLeft(idx.Name, idx.Name+"_"), 10, 64)
+		return err == nil && i > 1
+	case len(idx.Parts) == 0 || idx.Parts[0].C == nil:
+		return false
+	}
+	// Unnamed INDEX or UNIQUE constraints are named by
+	// the first index-part (as column or part of it).
+	// For example, "c", "c_2", "c_3", etc.
+	switch name := idx.Parts[0].C.Name; {
+	case idx.Name == name:
+		return true
+	case strings.HasPrefix(idx.Name, name+"_"):
+		i, err := strconv.ParseInt(strings.TrimPrefix(idx.Name, name+"_"), 10, 64)
+		return err == nil && i > 1
+	default:
+		return false
+	}
+}
+
 // IndexAttrChanged reports if the index attributes were changed.
 func (*diff) IndexAttrChanged(from, to []schema.Attr) bool {
 	return indexType(from).T != indexType(to).T

sql/postgres/diff.go

@@ -7,6 +7,7 @@ package postgres
 import (
 	"fmt"
 	"reflect"
+	"strconv"
 	"strings"
 	"unicode"
 
@@ -79,6 +80,25 @@ func (d *diff) defaultChanged(from, to *schema.Column) (bool, error) {
 	return !equals, nil
 }
 
+// IsGeneratedIndexName reports if the index name was generated by the database.
+func (d *diff) IsGeneratedIndexName(t *schema.Table, idx *schema.Index) bool {
+	names := make([]string, len(idx.Parts))
+	for i, p := range idx.Parts {
+		if p.C == nil {
+			return false
+		}
+		names[i] = p.C.Name
+	}
+	// Auto-generate index names will have the following format: <table>_<c1>_..._key.
+	// In case of conflict, PostgreSQL adds additional index at the end (e.g. "key1").
+	p := fmt.Sprintf("%s_%s_key", t.Name, strings.Join(names, "_"))
+	if idx.Name == p {
+		return true
+	}
+	i, err := strconv.ParseInt(strings.TrimPrefix(idx.Name, p), 10, 64)
+	return err == nil && i > 0
+}
+
 // IndexAttrChanged reports if the index attributes were changed.
 // The default type is BTREE if no type was specified.
 func (*diff) IndexAttrChanged(from, to []schema.Attr) bool {

sql/sqlite/diff.go

@@ -7,6 +7,8 @@ package sqlite
 import (
 	"fmt"
 	"reflect"
+	"strconv"
+	"strings"
 
 	"ariga.io/atlas/sql/internal/sqlx"
 	"ariga.io/atlas/sql/schema"
@@ -84,6 +86,17 @@ func (d *diff) defaultChanged(from, to *schema.Column) bool {
 	return err1 != nil || err2 != nil || x1 != x2
 }
 
+// IsGeneratedIndexName reports if the index name was generated by the database.
+// See: https://github.com/sqlite/sqlite/blob/e937df8/src/build.c#L3583.
+func (d *diff) IsGeneratedIndexName(t *schema.Table, idx *schema.Index) bool {
+	p := fmt.Sprintf("sqlite_autoindex_%s_", t.Name)
+	if !strings.HasPrefix(idx.Name, p) {
+		return false
+	}
+	i, err := strconv.ParseInt(strings.TrimPrefix(idx.Name, p), 10, 64)
+	return err == nil && i > 0
+}
+
 // IndexAttrChanged reports if the index attributes were changed.
 func (*diff) IndexAttrChanged(from, to []schema.Attr) bool {
 	var p1, p2 IndexPredicate