fix duplicate foreign key constraint on inline column references

Author: elianddb

server/ast/alter_table.go

@@ -245,7 +245,10 @@ func nodeAlterTableAddColumn(ctx *Context, node *tree.AlterTableAddColumn, table
 		if err != nil {
 			return nil, err
 		}
-		tableSpec.AddConstraint(&vitess.ConstraintDefinition{Details: constraintDef})
+		tableSpec.AddConstraint(&vitess.ConstraintDefinition{
+			Name:    string(node.ColumnDef.References.ConstraintName),
+			Details: constraintDef,
+		})
 	}
 
 	return &vitess.DDL{

server/ast/column_table_def.go

@@ -78,22 +78,12 @@ func nodeColumnTableDef(ctx *Context, node *tree.ColumnTableDef) (*vitess.Column
 		defaultExpr = &vitess.ParenExpr{Expr: defaultExpr}
 	}
 
-	var fkDef *vitess.ForeignKeyDefinition
 	if node.References.Table != nil {
 		if len(node.References.Col) == 0 {
 			return nil, errors.Errorf("implicit primary key matching on column foreign key is not yet supported")
 		}
-		fkDef, err = nodeForeignKeyConstraintTableDef(ctx, &tree.ForeignKeyConstraintTableDef{
-			Name:     node.References.ConstraintName,
-			Table:    *node.References.Table,
-			FromCols: tree.NameList{node.Name},
-			ToCols:   tree.NameList{node.References.Col},
-			Actions:  node.References.Actions,
-			Match:    node.References.Match,
-		})
-		if err != nil {
-			return nil, err
-		}
+		// Callers register the foreign key via the table constraint list, so ForeignKeyDef
+		// is left unset here to avoid creating the same constraint twice.
 	}
 
 	if len(node.Computed.Options) > 0 {
@@ -164,7 +154,6 @@ func nodeColumnTableDef(ctx *Context, node *tree.ColumnTableDef) (*vitess.Column
 			Length:        convertType.Length,
 			Scale:         convertType.Scale,
 			KeyOpt:        keyOpt,
-			ForeignKeyDef: fkDef,
 			GeneratedExpr: generated,
 			Stored:        generated != nil, // postgres generated columns are always stored, never virtual
 		},

server/ast/table_def.go

@@ -61,6 +61,7 @@ func assignTableDef(ctx *Context, node tree.TableDef, target *vitess.DDL) error
 				return err
 			}
 			target.TableSpec.Constraints = append(target.TableSpec.Constraints, &vitess.ConstraintDefinition{
+				Name:    string(node.References.ConstraintName),
 				Details: fkDef,
 			})
 		}

testing/go/foreign_keys_test.go

@@ -88,6 +88,44 @@ func TestForeignKeys(t *testing.T) {
 					},
 				},
 			},
+			{
+				// See https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-FK
+				Name: "inline column REFERENCES enforces a foreign key constraint",
+				SetUpScript: []string{
+					`CREATE TABLE parent (a INT PRIMARY KEY)`,
+					`CREATE TABLE child (id INT PRIMARY KEY, pid INT REFERENCES parent(a))`,
+					`INSERT INTO parent VALUES (1)`,
+				},
+				Assertions: []ScriptTestAssertion{
+					{
+						Query: "INSERT INTO child VALUES (1, 1)",
+					},
+					{
+						Query:       "INSERT INTO child VALUES (2, 999)",
+						ExpectedErr: "Foreign key violation",
+					},
+				},
+			},
+			{
+				// See https://github.com/morenoh149/postgresDBSamples/blob/master/french-towns-communes-francaises/french-towns-communes-francaises.sql
+				Name: "inline column REFERENCES enforces constraints across a chain of related tables",
+				SetUpScript: []string{
+					`CREATE TABLE regions (id SERIAL UNIQUE NOT NULL, code VARCHAR(4) UNIQUE NOT NULL, name TEXT UNIQUE NOT NULL)`,
+					`CREATE TABLE departments (id SERIAL UNIQUE NOT NULL, code VARCHAR(4) UNIQUE NOT NULL, region VARCHAR(4) NOT NULL REFERENCES regions(code), name TEXT UNIQUE NOT NULL)`,
+					`CREATE TABLE towns (id SERIAL UNIQUE NOT NULL, code VARCHAR(10) NOT NULL, name TEXT NOT NULL, department VARCHAR(4) NOT NULL REFERENCES departments(code), UNIQUE (code, department))`,
+					`INSERT INTO regions VALUES (1, '01', 'Region1')`,
+					`INSERT INTO departments VALUES (1, 'D01', '01', 'Department1')`,
+				},
+				Assertions: []ScriptTestAssertion{
+					{
+						Query: "INSERT INTO towns VALUES (1, 'T01', 'Town1', 'D01')",
+					},
+					{
+						Query:       "INSERT INTO towns VALUES (2, 'T02', 'Town2', 'NOPE')",
+						ExpectedErr: "Foreign key violation",
+					},
+				},
+			},
 			{
 				Name: "text foreign key",
 				SetUpScript: []string{