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schemadiff: schema is immutable through Apply() #10190

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merged 2 commits into from
May 3, 2022
Merged

schemadiff: schema is immutable through Apply() #10190

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1b953e7
schemadiff: schema should be immutable through Apply; adding tests to…
shlomi-noach May 2, 2022
1686ef7
schema export/import by queries
shlomi-noach May 2, 2022
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18 changes: 17 additions & 1 deletion go/vt/schemadiff/diff_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,17 @@ func TestDiffSchemas(t *testing.T) {
from: "create table t(id int primary key)",
to: "create table t(id int primary key)",
},
{
name: "change of table column",
from: "create table t(id int primary key, v varchar(10))",
to: "create table t(id int primary key, v varchar(20))",
diffs: []string{
"alter table t modify column v varchar(20)",
},
cdiffs: []string{
"ALTER TABLE `t` MODIFY COLUMN `v` varchar(20)",
},
},
{
name: "change of table columns, added",
from: "create table t(id int primary key)",
Expand Down Expand Up @@ -329,7 +340,7 @@ func TestDiffSchemas(t *testing.T) {
},
},
{
name: "create table (2)",
name: "create table 2",
from: ";;; ; ; ;;;",
to: "create table t(id int primary key)",
diffs: []string{
Expand Down Expand Up @@ -501,11 +512,16 @@ func TestDiffSchemas(t *testing.T) {
// Validate "apply()" on "from" converges with "to"
schema1, err := NewSchemaFromSQL(ts.from)
assert.NoError(t, err)
schema1SQL := schema1.ToSQL()

schema2, err := NewSchemaFromSQL(ts.to)
assert.NoError(t, err)
applied, err := schema1.Apply(diffs)
require.NoError(t, err)

// validate schema1 unaffected by Apply
assert.Equal(t, schema1SQL, schema1.ToSQL())

appliedDiff, err := schema2.Diff(applied, hints)
require.NoError(t, err)
assert.Empty(t, appliedDiff)
Expand Down
6 changes: 5 additions & 1 deletion go/vt/schemadiff/schema.go
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Original file line number Diff line number Diff line change
Expand Up @@ -426,7 +426,11 @@ func (s *Schema) apply(diffs []EntityDiff) error {
// These diffs are CREATE/DROP/ALTER TABLE/VIEW.
// The operation does not modify this object. Instead, if successful, a new (modified) Schema is returned.
func (s *Schema) Apply(diffs []EntityDiff) (*Schema, error) {
dup, err := NewSchemaFromStatements(s.ToStatements())
// we export to queries, then import back.
// The reason we don't just clone this object's fields, or even export/import to Statements,
// is that we want this schema to be immutable an unaffected by the apply() on the duplicate.
// statements/slices/maps will have shared pointers and changes will propagate back to this schema.
dup, err := NewSchemaFromQueries(s.ToQueries())
if err != nil {
return nil, err
}
Expand Down