Validate that FK constraint name is unique (#428)

We can do this in our validation step before even touching the database.

Part of #105

Author: ryanslade

pkg/migrations/op_set_fk.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 
 	"github.com/lib/pq"
+
 	"github.com/xataio/pgroll/pkg/db"
 	"github.com/xataio/pgroll/pkg/schema"
 )
@@ -58,6 +59,18 @@ func (o *OpSetForeignKey) Validate(ctx context.Context, s *schema.Schema) error
 		}
 	}
 
+	table := s.GetTable(o.Table)
+	if table == nil {
+		return TableDoesNotExistError{Name: o.Table}
+	}
+
+	if table.ConstraintExists(o.References.Name) {
+		return ConstraintAlreadyExistsError{
+			Table:      table.Name,
+			Constraint: o.References.Name,
+		}
+	}
+
 	if o.Up == "" {
 		return FieldRequiredError{Name: "up"}
 	}

pkg/migrations/op_set_fk_test.go

@@ -6,9 +6,9 @@ import (
 	"database/sql"
 	"testing"
 
-	"github.com/xataio/pgroll/internal/testutils"
-
 	"github.com/stretchr/testify/assert"
+
+	"github.com/xataio/pgroll/internal/testutils"
 	"github.com/xataio/pgroll/pkg/migrations"
 )
 
@@ -1120,6 +1120,88 @@ func TestSetForeignKey(t *testing.T) {
 				ColumnMustHaveComment(t, db, schema, "posts", "user_id", "the id of the author")
 			},
 		},
+		{
+			name: "validate that foreign key name is unique",
+			migrations: []migrations.Migration{
+				{
+					Name: "01_add_tables",
+					Operations: migrations.Operations{
+						&migrations.OpCreateTable{
+							Name: "users",
+							Columns: []migrations.Column{
+								{
+									Name: "id",
+									Type: "serial",
+									Pk:   ptr(true),
+								},
+								{
+									Name: "name",
+									Type: "text",
+								},
+							},
+						},
+						&migrations.OpCreateTable{
+							Name: "posts",
+							Columns: []migrations.Column{
+								{
+									Name: "id",
+									Type: "serial",
+									Pk:   ptr(true),
+								},
+								{
+									Name: "title",
+									Type: "text",
+								},
+								{
+									Name:     "user_id",
+									Type:     "integer",
+									Nullable: ptr(true),
+								},
+							},
+						},
+					},
+				},
+				{
+					Name: "02_add_fk_constraint",
+					Operations: migrations.Operations{
+						&migrations.OpAlterColumn{
+							Table:  "posts",
+							Column: "user_id",
+							References: &migrations.ForeignKeyReference{
+								Name:   "fk_users_id",
+								Table:  "users",
+								Column: "id",
+							},
+							Up:   "(SELECT CASE WHEN EXISTS (SELECT 1 FROM users WHERE users.id = user_id) THEN user_id ELSE NULL END)",
+							Down: "user_id",
+						},
+					},
+				},
+				{
+					Name: "03_add_fk_constraint_again",
+					Operations: migrations.Operations{
+						&migrations.OpAlterColumn{
+							Table:  "posts",
+							Column: "user_id",
+							References: &migrations.ForeignKeyReference{
+								Name:   "fk_users_id",
+								Table:  "users",
+								Column: "id",
+							},
+							Up:   "(SELECT CASE WHEN EXISTS (SELECT 1 FROM users WHERE users.id = user_id) THEN user_id ELSE NULL END)",
+							Down: "user_id",
+						},
+					},
+				},
+			},
+			wantStartErr: migrations.ConstraintAlreadyExistsError{
+				Table:      "posts",
+				Constraint: "fk_users_id",
+			},
+			afterStart:    func(t *testing.T, db *sql.DB, schema string) {},
+			afterRollback: func(t *testing.T, db *sql.DB, schema string) {},
+			afterComplete: func(t *testing.T, db *sql.DB, schema string) {},
+		},
 	})
 }
 

pkg/roll/execute.go

@@ -155,7 +155,7 @@ func (m *Roll) Complete(ctx context.Context) error {
 	}
 
 	// read the current schema
-	schema, err := m.state.ReadSchema(ctx, m.schema)
+	currentSchema, err := m.state.ReadSchema(ctx, m.schema)
 	if err != nil {
 		return fmt.Errorf("unable to read schema: %w", err)
 	}
@@ -175,7 +175,7 @@ func (m *Roll) Complete(ctx context.Context) error {
 	// execute operations
 	refreshViews := false
 	for _, op := range migration.Operations {
-		err := op.Complete(ctx, m.pgConn, m.sqlTransformer, schema)
+		err := op.Complete(ctx, m.pgConn, m.sqlTransformer, currentSchema)
 		if err != nil {
 			return fmt.Errorf("unable to execute complete operation: %w", err)
 		}
@@ -189,12 +189,12 @@ func (m *Roll) Complete(ctx context.Context) error {
 
 	// recreate views for the new version (if some operations require it, ie SQL)
 	if refreshViews && !m.disableVersionSchemas {
-		schema, err = m.state.ReadSchema(ctx, m.schema)
+		currentSchema, err = m.state.ReadSchema(ctx, m.schema)
 		if err != nil {
 			return fmt.Errorf("unable to read schema: %w", err)
 		}
 
-		err = m.ensureViews(ctx, schema, migration.Name)
+		err = m.ensureViews(ctx, currentSchema, migration.Name)
 		if err != nil {
 			return err
 		}