Properly Strip Keyspace Table Qualifiers in FK Constraints

go/test/endtoend/vtgate/foreignkey/fk_test.go

@@ -30,9 +30,10 @@ import (
 	"vitess.io/vitess/go/test/endtoend/cluster"
 	"vitess.io/vitess/go/test/endtoend/utils"
 	"vitess.io/vitess/go/vt/log"
+	"vitess.io/vitess/go/vt/vtgate/vtgateconn"
+
 	binlogdatapb "vitess.io/vitess/go/vt/proto/binlogdata"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
-	"vitess.io/vitess/go/vt/vtgate/vtgateconn"
 )
 
 // TestInsertWithFK tests that insertions work as expected when foreign key management is enabled in Vitess.
@@ -1505,6 +1506,45 @@ create table temp2(id bigint auto_increment primary key, col varchar(20) not nul
 	mcmp.ExecAllowAndCompareError(`insert into temp1(col) values('d') `, utils.CompareOptions{})
 }
 
+// TestForeignKeyWithKeyspaceQualifier tests that CREATE TABLE with foreign key references
+// that include keyspace qualifiers work correctly. This addresses bug #18889 where keyspace
+// names were not being stripped before being sent to MySQL, causing failures because MySQL
+// expects database names (vt_<keyspace>) not keyspace names.
+func TestForeignKeyWithKeyspaceQualifier(t *testing.T) {
+	mcmp, closer := start(t)
+	defer closer()
+
+	utils.Exec(t, mcmp.VtConn, `use uks`)
+
+	// Create the parent table.
+	utils.Exec(t, mcmp.VtConn, `create table fk_parent(id bigint primary key)`)
+
+	// Create the child table with keyspace-qualified foreign key reference.
+	utils.Exec(t, mcmp.VtConn, `create table fk_child(id bigint primary key, parent_id bigint, foreign key (parent_id) references uks.fk_parent(id))`)
+
+	// Verify that the foreign key constraint works.
+	utils.Exec(t, mcmp.VtConn, `insert into fk_parent(id) values (1), (2)`)
+	utils.Exec(t, mcmp.VtConn, `insert into fk_child(id, parent_id) values (100, 1)`)
+
+	// This should fail due to FK constraint.
+	_, err := utils.ExecAllowError(t, mcmp.VtConn, `insert into fk_child(id, parent_id) values (101, 999)`)
+	assert.ErrorContains(t, err, "Cannot add or update a child row: a foreign key constraint fails")
+
+	// Test ALTER TABLE with keyspace-qualified foreign key.
+	utils.Exec(t, mcmp.VtConn, `create table fk_child2(id bigint primary key, parent_id bigint)`)
+	utils.Exec(t, mcmp.VtConn, `alter table fk_child2 add foreign key (parent_id) references uks.fk_parent(id)`)
+
+	// Verify the constraint works for the altered table.
+	utils.Exec(t, mcmp.VtConn, `insert into fk_child2(id, parent_id) values (200, 2)`)
+	_, err = utils.ExecAllowError(t, mcmp.VtConn, `insert into fk_child2(id, parent_id) values (201, 888)`)
+	assert.ErrorContains(t, err, "Cannot add or update a child row: a foreign key constraint fails")
+
+	// Clean up.
+	utils.Exec(t, mcmp.VtConn, `drop table fk_child`)
+	utils.Exec(t, mcmp.VtConn, `drop table fk_child2`)
+	utils.Exec(t, mcmp.VtConn, `drop table fk_parent`)
+}
+
 // TestRestrictFkOnNonStandardKey verifies that restrict_fk_on_non_standard_key is set to off
 func TestRestrictFkOnNonStandardKey(t *testing.T) {
 	mcmp, closer := start(t)

go/vt/vtgate/planbuilder/ddl.go

@@ -109,6 +109,8 @@ func buildDDLPlans(ctx context.Context, sql string, ddlStatement sqlparser.DDLSt
 		if err != nil {
 			return nil, nil, err
 		}
+		// Remove keyspace qualifiers from all table references (including foreign key references).
+		sqlparser.RemoveSpecificKeyspace(ddlStatement, keyspace.Name)
 		err = checkFKError(vschema, ddlStatement, keyspace)
 	case *sqlparser.CreateView:
 		destination, keyspace, err = buildCreateViewCommon(ctx, vschema, reservedVars, cfg, ddl.Select, ddl)

go/vt/vtgate/planbuilder/testdata/ddl_cases.json

@@ -683,5 +683,105 @@
         "main.function_default"
       ]
     }
+  },
+  {
+    "comment": "create table with foreign key reference without keyspace qualifier",
+    "query": "create table t1(id bigint, t2_id bigint, primary key(id), foreign key (t2_id) references t2(id))",
+    "plan": {
+      "Type": "DirectDDL",
+      "QueryType": "DDL",
+      "Original": "create table t1(id bigint, t2_id bigint, primary key(id), foreign key (t2_id) references t2(id))",
+      "Instructions": {
+        "OperatorType": "DDL",
+        "Keyspace": {
+          "Name": "main",
+          "Sharded": false
+        },
+        "Query": "create table t1 (\n\tid bigint,\n\tt2_id bigint,\n\tprimary key (id),\n\tforeign key (t2_id) references t2 (id)\n)"
+      },
+      "TablesUsed": [
+        "main.t1"
+      ]
+    }
+  },
+  {
+    "comment": "create table with foreign key reference with keyspace qualifier",
+    "query": "create table user.t1(id bigint, t2_id bigint, primary key(id), foreign key (t2_id) references user.t2(id))",
+    "plan": {
+      "Type": "DirectDDL",
+      "QueryType": "DDL",
+      "Original": "create table user.t1(id bigint, t2_id bigint, primary key(id), foreign key (t2_id) references user.t2(id))",
+      "Instructions": {
+        "OperatorType": "DDL",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "Query": "create table t1 (\n\tid bigint,\n\tt2_id bigint,\n\tprimary key (id),\n\tforeign key (t2_id) references t2 (id)\n)"
+      },
+      "TablesUsed": [
+        "user.t1"
+      ]
+    }
+  },
+  {
+    "comment": "create table with multiple foreign keys with keyspace qualifiers",
+    "query": "create table user.orders(order_id bigint, customer_id bigint, product_id bigint, primary key(order_id), foreign key (customer_id) references user.customers(id), foreign key (product_id) references user.products(id))",
+    "plan": {
+      "Type": "DirectDDL",
+      "QueryType": "DDL",
+      "Original": "create table user.orders(order_id bigint, customer_id bigint, product_id bigint, primary key(order_id), foreign key (customer_id) references user.customers(id), foreign key (product_id) references user.products(id))",
+      "Instructions": {
+        "OperatorType": "DDL",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "Query": "create table orders (\n\torder_id bigint,\n\tcustomer_id bigint,\n\tproduct_id bigint,\n\tprimary key (order_id),\n\tforeign key (customer_id) references customers (id),\n\tforeign key (product_id) references products (id)\n)"
+      },
+      "TablesUsed": [
+        "user.orders"
+      ]
+    }
+  },
+  {
+    "comment": "alter table add foreign key with keyspace qualifier",
+    "query": "alter table user.t1 add foreign key (t2_id) references user.t2(id)",
+    "plan": {
+      "Type": "DirectDDL",
+      "QueryType": "DDL",
+      "Original": "alter table user.t1 add foreign key (t2_id) references user.t2(id)",
+      "Instructions": {
+        "OperatorType": "DDL",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "Query": "alter table t1 add foreign key (t2_id) references t2 (id)"
+      },
+      "TablesUsed": [
+        "user.t1"
+      ]
+    }
+  },
+  {
+    "comment": "create table with foreign key with ON DELETE and ON UPDATE clauses and keyspace qualifier",
+    "query": "create table user.employees(emp_id bigint, dept_id bigint, primary key(emp_id), foreign key (dept_id) references user.departments(dept_id) on delete set null on update cascade)",
+    "plan": {
+      "Type": "DirectDDL",
+      "QueryType": "DDL",
+      "Original": "create table user.employees(emp_id bigint, dept_id bigint, primary key(emp_id), foreign key (dept_id) references user.departments(dept_id) on delete set null on update cascade)",
+      "Instructions": {
+        "OperatorType": "DDL",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "Query": "create table employees (\n\temp_id bigint,\n\tdept_id bigint,\n\tprimary key (emp_id),\n\tforeign key (dept_id) references departments (dept_id) on delete set null on update cascade\n)"
+      },
+      "TablesUsed": [
+        "user.employees"
+      ]
+    }
   }
 ]