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diff.go
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diff.go
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// Copyright 2021-present The Atlas Authors. All rights reserved.
// This source code is licensed under the Apache 2.0 license found
// in the LICENSE file in the root directory of this source tree.
package sqlx
import (
"fmt"
"reflect"
"sort"
"strconv"
"strings"
"ariga.io/atlas/sql/schema"
)
type (
// A Diff provides a generic schema.Differ for diffing schema elements.
//
// The DiffDriver is required for supporting database/dialect specific
// diff capabilities, like diffing custom types or attributes.
Diff struct {
DiffDriver
}
// A DiffDriver wraps all required methods for diffing elements that may
// have database-specific diff logic. See sql/schema/mysql/diff.go for an
// implementation example.
DiffDriver interface {
// SchemaAttrDiff returns a changeset for migrating schema attributes
// from one state to the other. For example, changing schema collation.
SchemaAttrDiff(from, to *schema.Schema) []schema.Change
// TableAttrDiff returns a changeset for migrating table attributes from
// one state to the other. For example, dropping or adding a `CHECK` constraint.
TableAttrDiff(from, to *schema.Table) ([]schema.Change, error)
// ColumnChange returns the schema changes (if any) for migrating one column to the other.
ColumnChange(fromT *schema.Table, from, to *schema.Column) (schema.ChangeKind, error)
// IndexAttrChanged reports if the index attributes were changed.
// For example, an index type or predicate (for partial indexes).
IndexAttrChanged(from, to []schema.Attr) bool
// IndexPartAttrChanged reports if the index-part attributes were
// changed. For example, an index-part collation.
IndexPartAttrChanged(from, to *schema.IndexPart) 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
}
// A Normalizer wraps the Normalize method for normalizing the from and to tables before
// running diffing. The "from" usually represents the inspected database state (current),
// and the second represents the desired state.
//
// If the DiffDriver implements the Normalizer interface, TableDiff normalizes its table
// inputs before starting the diff process.
Normalizer interface {
Normalize(from, to *schema.Table) error
}
)
// RealmDiff implements the schema.Differ for Realm objects and returns a list of changes
// that need to be applied in order to move a database from the current state to the desired.
func (d *Diff) RealmDiff(from, to *schema.Realm) ([]schema.Change, error) {
var changes []schema.Change
// Drop or modify schema.
for _, s1 := range from.Schemas {
s2, ok := to.Schema(s1.Name)
if !ok {
changes = append(changes, &schema.DropSchema{S: s1})
continue
}
change, err := d.SchemaDiff(s1, s2)
if err != nil {
return nil, err
}
changes = append(changes, change...)
}
// Add schemas.
for _, s1 := range to.Schemas {
if _, ok := from.Schema(s1.Name); ok {
continue
}
changes = append(changes, &schema.AddSchema{S: s1})
for _, t := range s1.Tables {
changes = append(changes, &schema.AddTable{T: t})
}
}
return changes, nil
}
// SchemaDiff implements the schema.Differ interface and returns a list of
// changes that need to be applied in order to move from one state to the other.
func (d *Diff) SchemaDiff(from, to *schema.Schema) ([]schema.Change, error) {
if from.Name != to.Name {
return nil, fmt.Errorf("mismatched schema names: %q != %q", from.Name, to.Name)
}
var changes []schema.Change
// Drop or modify attributes (collations, charset, etc).
if change := d.SchemaAttrDiff(from, to); len(change) > 0 {
changes = append(changes, &schema.ModifySchema{
S: to,
Changes: change,
})
}
// Drop or modify tables.
for _, t1 := range from.Tables {
t2, ok := to.Table(t1.Name)
if !ok {
changes = append(changes, &schema.DropTable{T: t1})
continue
}
change, err := d.TableDiff(t1, t2)
if err != nil {
return nil, err
}
if len(change) > 0 {
changes = append(changes, &schema.ModifyTable{
T: t2,
Changes: change,
})
}
}
// Add tables.
for _, t1 := range to.Tables {
if _, ok := from.Table(t1.Name); !ok {
changes = append(changes, &schema.AddTable{T: t1})
}
}
return changes, nil
}
// TableDiff implements the schema.TableDiffer interface and returns a list of
// changes that need to be applied in order to move from one state to the other.
func (d *Diff) TableDiff(from, to *schema.Table) ([]schema.Change, error) {
if from.Name != to.Name {
return nil, fmt.Errorf("mismatched table names: %q != %q", from.Name, to.Name)
}
// Normalizing tables before starting the diff process.
if n, ok := d.DiffDriver.(Normalizer); ok {
if err := n.Normalize(from, to); err != nil {
return nil, err
}
}
var changes []schema.Change
if from.Name != to.Name {
return nil, fmt.Errorf("mismatched table names: %q != %q", from.Name, to.Name)
}
// PK modification is not supported.
if pk1, pk2 := from.PrimaryKey, to.PrimaryKey; (pk1 != nil) != (pk2 != nil) || (pk1 != nil) && d.pkChange(pk1, pk2) != schema.NoChange {
return nil, fmt.Errorf("changing %q table primary key is not supported", to.Name)
}
// Drop or modify attributes (collations, checks, etc).
change, err := d.TableAttrDiff(from, to)
if err != nil {
return nil, err
}
changes = append(changes, change...)
// Drop or modify columns.
for _, c1 := range from.Columns {
c2, ok := to.Column(c1.Name)
if !ok {
changes = append(changes, &schema.DropColumn{C: c1})
continue
}
change, err := d.ColumnChange(from, c1, c2)
if err != nil {
return nil, err
}
if change != schema.NoChange {
changes = append(changes, &schema.ModifyColumn{
From: c1,
To: c2,
Change: change,
})
}
}
// Add columns.
for _, c1 := range to.Columns {
if _, ok := from.Column(c1.Name); !ok {
changes = append(changes, &schema.AddColumn{C: c1})
}
}
// Index changes.
changes = append(changes, d.indexDiff(from, to)...)
// Drop or modify foreign-keys.
for _, fk1 := range from.ForeignKeys {
fk2, ok := to.ForeignKey(fk1.Symbol)
if !ok {
changes = append(changes, &schema.DropForeignKey{F: fk1})
continue
}
if change := d.fkChange(fk1, fk2); change != schema.NoChange {
changes = append(changes, &schema.ModifyForeignKey{
From: fk1,
To: fk2,
Change: change,
})
}
}
// Add foreign-keys.
for _, fk1 := range to.ForeignKeys {
if _, ok := from.ForeignKey(fk1.Symbol); !ok {
changes = append(changes, &schema.AddForeignKey{F: fk1})
}
}
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)
return change & ^schema.ChangeUnique
}
// indexChange returns the schema changes (if any) for migrating one index to the other.
func (d *Diff) indexChange(from, to *schema.Index) schema.ChangeKind {
var change schema.ChangeKind
if from.Unique != to.Unique {
change |= schema.ChangeUnique
}
if d.IndexAttrChanged(from.Attrs, to.Attrs) {
change |= schema.ChangeAttr
}
change |= d.partsChange(from.Parts, to.Parts)
change |= CommentChange(from.Attrs, to.Attrs)
return change
}
func (d *Diff) partsChange(from, to []*schema.IndexPart) schema.ChangeKind {
if len(from) != len(to) {
return schema.ChangeParts
}
sort.Slice(to, func(i, j int) bool { return to[i].SeqNo < to[j].SeqNo })
sort.Slice(from, func(i, j int) bool { return from[i].SeqNo < from[j].SeqNo })
for i := range from {
switch {
case from[i].Desc != to[i].Desc || d.IndexPartAttrChanged(from[i], to[i]):
return schema.ChangeParts
case from[i].C != nil && to[i].C != nil:
if from[i].C.Name != to[i].C.Name {
return schema.ChangeParts
}
case from[i].X != nil && to[i].X != nil:
x1, x2 := from[i].X.(*schema.RawExpr).X, to[i].X.(*schema.RawExpr).X
if x1 != x2 && x1 != MayWrap(x2) {
return schema.ChangeParts
}
default: // (C1 != nil) != (C2 != nil) || (X1 != nil) != (X2 != nil).
return schema.ChangeParts
}
}
return schema.NoChange
}
// fkChange returns the schema changes (if any) for migrating one index to the other.
func (d *Diff) fkChange(from, to *schema.ForeignKey) schema.ChangeKind {
var change schema.ChangeKind
switch {
case from.Table.Name != to.Table.Name:
change |= schema.ChangeRefTable | schema.ChangeRefColumn
case len(from.RefColumns) != len(to.RefColumns):
change |= schema.ChangeRefColumn
default:
for i := range from.RefColumns {
if from.RefColumns[i].Name != to.RefColumns[i].Name {
change |= schema.ChangeRefColumn
}
}
}
switch {
case len(from.Columns) != len(to.Columns):
change |= schema.ChangeColumn
default:
for i := range from.Columns {
if from.Columns[i].Name != to.Columns[i].Name {
change |= schema.ChangeColumn
}
}
}
if d.ReferenceChanged(from.OnUpdate, to.OnUpdate) {
change |= schema.ChangeUpdateAction
}
if d.ReferenceChanged(from.OnDelete, to.OnDelete) {
change |= schema.ChangeDeleteAction
}
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
if Has(from, &c1) != Has(to, &c2) || c1.Text != c2.Text {
return schema.ChangeComment
}
return schema.NoChange
}
var (
attrsType = reflect.TypeOf(([]schema.Attr)(nil))
clausesType = reflect.TypeOf(([]schema.Clause)(nil))
exprsType = reflect.TypeOf(([]schema.Expr)(nil))
)
// Has finds the first element in the elements list that
// matches target, and if so, sets target to that attribute
// value and returns true.
func Has(elements, target any) bool {
ev := reflect.ValueOf(elements)
if t := ev.Type(); t != attrsType && t != clausesType && t != exprsType {
panic(fmt.Sprintf("unexpected elements type: %T", elements))
}
tv := reflect.ValueOf(target)
if tv.Kind() != reflect.Ptr || tv.IsNil() {
panic("target must be a non-nil pointer")
}
for i := 0; i < ev.Len(); i++ {
idx := ev.Index(i)
if idx.IsNil() {
continue
}
if e := idx.Elem(); e.Type().AssignableTo(tv.Type()) {
tv.Elem().Set(e.Elem())
return true
}
}
return false
}
// UnsupportedTypeError describes an unsupported type error.
type UnsupportedTypeError struct {
schema.Type
}
func (e UnsupportedTypeError) Error() string {
return fmt.Sprintf("unsupported type %T", e.Type)
}
// CommentDiff computes the comment diff between the 2 attribute list.
// Note that, the implementation relies on the fact that both PostgreSQL
// and MySQL treat empty comment as "no comment" and a way to clear comments.
func CommentDiff(from, to []schema.Attr) schema.Change {
var fromC, toC schema.Comment
switch fromHas, toHas := Has(from, &fromC), Has(to, &toC); {
case !fromHas && !toHas:
case !fromHas && toC.Text != "":
return &schema.AddAttr{
A: &toC,
}
case !toHas:
// In MySQL, there is no way to DROP a comment. Instead, setting it to empty ('')
// will remove it from INFORMATION_SCHEMA. We use the same approach in PostgreSQL,
// because comments can be dropped either by setting them to NULL or empty string.
// See: postgres/backend/commands/comment.c#CreateComments.
return &schema.ModifyAttr{
From: &fromC,
To: &toC,
}
default:
v1, err1 := Unquote(fromC.Text)
v2, err2 := Unquote(toC.Text)
if err1 == nil && err2 == nil && v1 != v2 {
return &schema.ModifyAttr{
From: &fromC,
To: &toC,
}
}
}
return nil
}
// CheckDiff computes the change diff between the 2 tables. A compare
// function is provided to check if a Check object was modified.
func CheckDiff(from, to *schema.Table, compare ...func(c1, c2 *schema.Check) bool) []schema.Change {
var changes []schema.Change
// Drop or modify checks.
for _, c1 := range checks(from.Attrs) {
switch c2, ok := similarCheck(to.Attrs, c1); {
case !ok:
changes = append(changes, &schema.DropCheck{
C: c1,
})
case len(compare) == 1 && !compare[0](c1, c2):
changes = append(changes, &schema.ModifyCheck{
From: c1,
To: c2,
})
}
}
// Add checks.
for _, c1 := range checks(to.Attrs) {
if _, ok := similarCheck(from.Attrs, c1); !ok {
changes = append(changes, &schema.AddCheck{
C: c1,
})
}
}
return changes
}
// checks extracts all constraints from table attributes.
func checks(attr []schema.Attr) (checks []*schema.Check) {
for i := range attr {
if c, ok := attr[i].(*schema.Check); ok {
checks = append(checks, c)
}
}
return checks
}
// similarCheck returns a CHECK by its constraints name or expression.
func similarCheck(attrs []schema.Attr, c *schema.Check) (*schema.Check, bool) {
var byName, byExpr *schema.Check
for i := 0; i < len(attrs) && (byName == nil || byExpr == nil); i++ {
check, ok := attrs[i].(*schema.Check)
if !ok {
continue
}
if check.Name != "" && check.Name == c.Name {
byName = check
}
if check.Expr == c.Expr {
byExpr = check
}
}
// Give precedence to constraint name.
if byName != nil {
return byName, true
}
if byExpr != nil {
return byExpr, true
}
return nil, false
}
// Unquote single or double quotes.
func Unquote(s string) (string, error) {
switch {
case IsQuoted(s, '"'):
return strconv.Unquote(s)
case IsQuoted(s, '\''):
return strings.ReplaceAll(s[1:len(s)-1], "''", "'"), nil
default:
return s, nil
}
}
// SingleQuote quotes the given string with single quote.
func SingleQuote(s string) (string, error) {
switch {
case IsQuoted(s, '\''):
return s, nil
case IsQuoted(s, '"'):
v, err := strconv.Unquote(s)
if err != nil {
return "", err
}
s = v
fallthrough
default:
return "'" + strings.ReplaceAll(s, "'", "''") + "'", nil
}
}