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schemadiff: rich error for unmet view dependencies #10940

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merged 3 commits into from
Aug 15, 2022
Merged

schemadiff: rich error for unmet view dependencies #10940

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schemadiff: rich error for unmet view dependencies
shlomi-noach Aug 4, 2022
a2d3731
grammar
shlomi-noach Aug 4, 2022
ed67ead
typo
shlomi-noach Aug 4, 2022
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2 changes: 1 addition & 1 deletion go/vt/schemadiff/diff_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -560,7 +560,7 @@ func TestDiffSchemas(t *testing.T) {
name: "create view: unresolved dependencies",
from: "create table t(id int)",
to: "create table t(id int); create view v1 as select id from t2",
expectError: ErrViewDependencyUnresolved.Error(),
expectError: (&ApplyViewNotFoundError{View: "v1"}).Error(),
},
{
name: "convert table to view",
Expand Down
9 changes: 8 additions & 1 deletion go/vt/schemadiff/errors.go
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Expand Up @@ -14,7 +14,6 @@ var (
ErrUnexpectedTableSpec = errors.New("unexpected table spec")
ErrExpectedCreateTable = errors.New("expected a CREATE TABLE statement")
ErrExpectedCreateView = errors.New("expected a CREATE VIEW statement")
ErrViewDependencyUnresolved = errors.New("views have unresolved/loop dependencies")
)

type UnsupportedEntityError struct {
Expand Down Expand Up @@ -239,3 +238,11 @@ func (e *InvalidColumnInForeignKeyConstraintError) Error() string {
return fmt.Sprintf("invalid column %s referenced by foreign key constraint %s in table %s",
sqlescape.EscapeID(e.Column), sqlescape.EscapeID(e.Constraint), sqlescape.EscapeID(e.Table))
}

type ViewDependencyUnresolvedError struct {
View string
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Can we also here have a reference to the entity it tries to refer to? Like if a another table / view is missing, we'd also know the name here as well?

We could then further improve the error to "view %s references unknown entity %s" or something along those lines?

And maybe different from having a loop and have a separate error type for that?

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So the way we detect these dependencies is by creating a connected graph, and then looking at "what's outside the graph". We don't explicitly then check which tables/views are referenced by the left-out views. We could definitely do that.

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@dbussink let's iterate on that in a followup PR though, if that's OK

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Yeah, we can improve on a further iteration.

}

func (e *ViewDependencyUnresolvedError) Error() string {
return fmt.Sprintf("view %s has unresolved/loop dependencies", sqlescape.EscapeID(e.View))
}
8 changes: 7 additions & 1 deletion go/vt/schemadiff/schema.go
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Expand Up @@ -230,7 +230,13 @@ func (s *Schema) normalize() error {
// We have leftover views. This can happen if the schema definition is invalid:
// - a view depends on a nonexistent table
// - two views have a circular dependency
return ErrViewDependencyUnresolved
for _, v := range s.views {
if _, ok := dependencyLevels[v.Name()]; !ok {
// We _know_ that in this iteration, at least one view is found unassigned a dependency level.
// We return the first one.
return &ApplyViewNotFoundError{View: v.ViewName.Name.String()}
}
}
}
return nil
}
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6 changes: 3 additions & 3 deletions go/vt/schemadiff/schema_test.go
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Expand Up @@ -110,7 +110,7 @@ func TestNewSchemaFromQueriesUnresolved(t *testing.T) {
)
_, err := NewSchemaFromQueries(queries)
assert.Error(t, err)
assert.ErrorIs(t, err, ErrViewDependencyUnresolved)
assert.EqualError(t, err, (&ApplyViewNotFoundError{View: "v7"}).Error())
}

func TestNewSchemaFromQueriesUnresolvedAlias(t *testing.T) {
Expand All @@ -120,7 +120,7 @@ func TestNewSchemaFromQueriesUnresolvedAlias(t *testing.T) {
)
_, err := NewSchemaFromQueries(queries)
assert.Error(t, err)
assert.ErrorIs(t, err, ErrViewDependencyUnresolved)
assert.EqualError(t, err, (&ApplyViewNotFoundError{View: "v7"}).Error())
}

func TestNewSchemaFromQueriesLoop(t *testing.T) {
Expand All @@ -131,7 +131,7 @@ func TestNewSchemaFromQueriesLoop(t *testing.T) {
)
_, err := NewSchemaFromQueries(queries)
assert.Error(t, err)
assert.ErrorIs(t, err, ErrViewDependencyUnresolved)
assert.EqualError(t, err, (&ApplyViewNotFoundError{View: "v7"}).Error())
}

func TestToSQL(t *testing.T) {
Expand Down