schemadiff: EntityDiff.Clone() utility function

Signed-off-by: Shlomi Noach <[email protected]>

go/vt/schemadiff/diff_test.go

@@ -569,6 +569,11 @@ func TestDiffViews(t *testing.T) {
 				diff := dq.StatementString()
 				assert.Equal(t, ts.diff, diff)
 			}
+			if d != nil && !d.IsEmpty() {
+				// Validate Clone() works
+				clone := d.Clone()
+				assert.Equal(t, d.Statement(), clone.Statement())
+			}
 		})
 	}
 }
@@ -1061,6 +1066,22 @@ func TestDiffSchemas(t *testing.T) {
 					_, err := env.Parser().ParseStrictDDL(s)
 					assert.NoError(t, err)
 				}
+				// Validate Clone() works
+				for _, d := range diffs {
+					if d.IsEmpty() {
+						continue
+					}
+					dFrom, dTo := d.Entities()
+					clone := d.Clone()
+					clonedFrom, clonedTo := clone.Entities()
+					assert.Equal(t, d.CanonicalStatementString(), clone.CanonicalStatementString())
+					if dFrom != nil {
+						assert.Equal(t, dFrom.Name(), clonedFrom.Name())
+					}
+					if dTo != nil {
+						assert.Equal(t, dTo.Name(), clonedTo.Name())
+					}
+				}
 
 				if ts.annotated != nil {
 					// Optional test for assorted scenarios.

go/vt/schemadiff/table.go

@@ -139,6 +139,29 @@ func (d *AlterTableEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return d.instantDDLCapability
 }
 
+// Clone implements EntityDiff
+func (d *AlterTableEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	ann := *d.annotations
+	clone := &AlterTableEntityDiff{
+		alterTable:           sqlparser.CloneRefOfAlterTable(d.alterTable),
+		instantDDLCapability: d.instantDDLCapability,
+		annotations:          &ann,
+	}
+	if d.from != nil {
+		clone.from = d.from.Clone().(*CreateTableEntity)
+	}
+	if d.to != nil {
+		clone.to = d.to.Clone().(*CreateTableEntity)
+	}
+	if d.subsequentDiff != nil {
+		clone.subsequentDiff = d.subsequentDiff.Clone().(*AlterTableEntityDiff)
+	}
+	return clone
+}
+
 type CreateTableEntityDiff struct {
 	to          *CreateTableEntity
 	createTable *sqlparser.CreateTable
@@ -216,6 +239,20 @@ func (d *CreateTableEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *CreateTableEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	clone := &CreateTableEntityDiff{
+		createTable: sqlparser.CloneRefOfCreateTable(d.createTable),
+	}
+	if d.to != nil {
+		clone.to = d.to.Clone().(*CreateTableEntity)
+	}
+	return clone
+}
+
 type DropTableEntityDiff struct {
 	from      *CreateTableEntity
 	dropTable *sqlparser.DropTable
@@ -293,6 +330,20 @@ func (d *DropTableEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *DropTableEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	clone := &DropTableEntityDiff{
+		dropTable: sqlparser.CloneRefOfDropTable(d.dropTable),
+	}
+	if d.from != nil {
+		clone.from = d.from.Clone().(*CreateTableEntity)
+	}
+	return clone
+}
+
 type RenameTableEntityDiff struct {
 	from        *CreateTableEntity
 	to          *CreateTableEntity
@@ -371,6 +422,23 @@ func (d *RenameTableEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *RenameTableEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	clone := &RenameTableEntityDiff{
+		renameTable: sqlparser.CloneRefOfRenameTable(d.renameTable),
+	}
+	if d.from != nil {
+		clone.from = d.from.Clone().(*CreateTableEntity)
+	}
+	if d.to != nil {
+		clone.to = d.to.Clone().(*CreateTableEntity)
+	}
+	return clone
+}
+
 // CreateTableEntity stands for a TABLE construct. It contains the table's CREATE statement.
 type CreateTableEntity struct {
 	*sqlparser.CreateTable

go/vt/schemadiff/types.go

@@ -69,7 +69,8 @@ type EntityDiff interface {
 	SetSubsequentDiff(EntityDiff)
 	// InstantDDLCapability returns the ability of this diff to run with ALGORITHM=INSTANT
 	InstantDDLCapability() InstantDDLCapability
-
+	// Clone returns a deep copy of the entity diff, and of all referenced entities.
+	Clone() EntityDiff
 	Annotated() (from *TextualAnnotations, to *TextualAnnotations, unified *TextualAnnotations)
 }
 

go/vt/schemadiff/view.go

@@ -100,6 +100,23 @@ func (d *AlterViewEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *AlterViewEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	clone := &AlterViewEntityDiff{
+		alterView: sqlparser.CloneRefOfAlterView(d.alterView),
+	}
+	if d.from != nil {
+		clone.from = d.from.Clone().(*CreateViewEntity)
+	}
+	if d.to != nil {
+		clone.to = d.to.Clone().(*CreateViewEntity)
+	}
+	return clone
+}
+
 type CreateViewEntityDiff struct {
 	createView *sqlparser.CreateView
 
@@ -177,6 +194,16 @@ func (d *CreateViewEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *CreateViewEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	return &CreateViewEntityDiff{
+		createView: sqlparser.CloneRefOfCreateView(d.createView),
+	}
+}
+
 type DropViewEntityDiff struct {
 	from     *CreateViewEntity
 	dropView *sqlparser.DropView
@@ -254,6 +281,20 @@ func (d *DropViewEntityDiff) InstantDDLCapability() InstantDDLCapability {
 	return InstantDDLCapabilityIrrelevant
 }
 
+// Clone implements EntityDiff
+func (d *DropViewEntityDiff) Clone() EntityDiff {
+	if d == nil {
+		return nil
+	}
+	clone := &DropViewEntityDiff{
+		dropView: sqlparser.CloneRefOfDropView(d.dropView),
+	}
+	if d.from != nil {
+		clone.from = d.from.Clone().(*CreateViewEntity)
+	}
+	return clone
+}
+
 // CreateViewEntity stands for a VIEW construct. It contains the view's CREATE statement.
 type CreateViewEntity struct {
 	*sqlparser.CreateView

go/vt/schemadiff/view_test.go

@@ -196,6 +196,15 @@ func TestCreateViewDiff(t *testing.T) {
 						require.NoError(t, err)
 						assert.True(t, appliedDiff.IsEmpty(), "expected empty diff, found changes: %v", appliedDiff.CanonicalStatementString())
 					}
+					// Validate Clone() works
+					{
+						clone := alter.Clone()
+						alterClone, ok := clone.(*AlterViewEntityDiff)
+						require.True(t, ok)
+						assert.Equal(t, eFrom.Create().CanonicalStatementString(), alterClone.from.Create().CanonicalStatementString())
+						alterClone.from.CreateView.ViewName.Name = sqlparser.NewIdentifierCS("something_else")
+						assert.NotEqual(t, eFrom.Create().CanonicalStatementString(), alterClone.from.Create().CanonicalStatementString())
+					}
 				}
 				{
 					cdiff := alter.CanonicalStatementString()