fix: composite FK referenced column order when FK order differs from table column order (#266)

ir/inspector.go

@@ -550,15 +550,15 @@ func (i *Inspector) buildConstraints(ctx context.Context, schema *IR, targetSche
 
 				// Add referenced column only if it doesn't exist
 				if !refColumnExists {
-					// Get the foreign ordinal position for proper ordering
-					refPosition := position // Default fallback to source position
-					if constraint.ForeignOrdinalPosition.Valid {
-						refPosition = int(constraint.ForeignOrdinalPosition.Int32)
-					}
-
+					// Use the local column's constraint position for the referenced column.
+					// The local and referenced columns are paired together in the FK definition,
+					// so they must have the same position to maintain correct ordering.
+					// Note: ForeignOrdinalPosition from the query is fa.attnum (column position
+					// in the foreign table's definition), which is wrong - we need the constraint
+					// array position, which is the same as the local column's position.
 					refConstraintCol := &ConstraintColumn{
 						Name:     refColumnName,
-						Position: refPosition, // Use foreign ordinal position for referenced column
+						Position: position, // Use local column's constraint position
 					}
 					c.ReferencedColumns = append(c.ReferencedColumns, refConstraintCol)
 				}

testdata/diff/create_table/composite_fk_column_order/diff.sql

@@ -0,0 +1,2 @@
+ALTER TABLE order_items
+ADD CONSTRAINT fk_order_items_order FOREIGN KEY (customer_id, order_id) REFERENCES orders (customer_id, order_id);

testdata/diff/create_table/composite_fk_column_order/new.sql

@@ -0,0 +1,22 @@
+-- Test case: Composite FK where FK column order differs from table column order
+-- This tests that constraint column ordering is preserved independently of table column order
+
+-- Referenced table with composite primary key
+CREATE TABLE public.orders (
+    order_id integer NOT NULL,
+    customer_id integer NOT NULL,
+    name varchar(255) NOT NULL,
+    CONSTRAINT orders_pkey PRIMARY KEY (customer_id, order_id)
+);
+
+-- Referencing table where columns are defined in OPPOSITE order from how FK references them
+CREATE TABLE public.order_items (
+    id serial PRIMARY KEY,
+    -- Table defines columns in this order: order_id first (lower attnum), then customer_id (higher attnum)
+    order_id integer NOT NULL,
+    customer_id integer NOT NULL,
+    quantity integer NOT NULL,
+    -- FK references columns in DIFFERENT order than table definition
+    -- customer_id is listed first in FK, but has higher attnum in table
+    CONSTRAINT fk_order_items_order FOREIGN KEY (customer_id, order_id) REFERENCES public.orders(customer_id, order_id)
+);

testdata/diff/create_table/composite_fk_column_order/old.sql

@@ -0,0 +1,19 @@
+-- Test case: Composite FK where FK column order differs from table column order
+-- This tests that constraint column ordering is preserved independently of table column order
+
+-- Referenced table with composite primary key
+CREATE TABLE public.orders (
+    order_id integer NOT NULL,
+    customer_id integer NOT NULL,
+    name varchar(255) NOT NULL,
+    CONSTRAINT orders_pkey PRIMARY KEY (customer_id, order_id)
+);
+
+-- Referencing table where columns are defined in OPPOSITE order from how FK references them
+CREATE TABLE public.order_items (
+    id serial PRIMARY KEY,
+    -- Table defines columns in this order: order_id first (lower attnum), then customer_id (higher attnum)
+    order_id integer NOT NULL,
+    customer_id integer NOT NULL,
+    quantity integer NOT NULL
+);

testdata/diff/create_table/composite_fk_column_order/plan.json

@@ -0,0 +1,26 @@
+{
+  "version": "1.0.0",
+  "pgschema_version": "1.6.1",
+  "created_at": "1970-01-01T00:00:00Z",
+  "source_fingerprint": {
+    "hash": "1948e0ca8413d527d01353e9a8b4f4581198c99a5b994959bda5e05beb462153"
+  },
+  "groups": [
+    {
+      "steps": [
+        {
+          "sql": "ALTER TABLE order_items\nADD CONSTRAINT fk_order_items_order FOREIGN KEY (customer_id, order_id) REFERENCES orders (customer_id, order_id) NOT VALID;",
+          "type": "table.constraint",
+          "operation": "create",
+          "path": "public.order_items.fk_order_items_order"
+        },
+        {
+          "sql": "ALTER TABLE order_items VALIDATE CONSTRAINT fk_order_items_order;",
+          "type": "table.constraint",
+          "operation": "create",
+          "path": "public.order_items.fk_order_items_order"
+        }
+      ]
+    }
+  ]
+}

testdata/diff/create_table/composite_fk_column_order/plan.sql

@@ -0,0 +1,4 @@
+ALTER TABLE order_items
+ADD CONSTRAINT fk_order_items_order FOREIGN KEY (customer_id, order_id) REFERENCES orders (customer_id, order_id) NOT VALID;
+
+ALTER TABLE order_items VALIDATE CONSTRAINT fk_order_items_order;

testdata/diff/create_table/composite_fk_column_order/plan.txt

@@ -0,0 +1,16 @@
+Plan: 1 to modify.
+
+Summary by type:
+  tables: 1 to modify
+
+Tables:
+  ~ order_items
+    + fk_order_items_order (constraint)
+
+DDL to be executed:
+--------------------------------------------------
+
+ALTER TABLE order_items
+ADD CONSTRAINT fk_order_items_order FOREIGN KEY (customer_id, order_id) REFERENCES orders (customer_id, order_id) NOT VALID;
+
+ALTER TABLE order_items VALIDATE CONSTRAINT fk_order_items_order;