fix: carry ON DELETE SET NULL/SET DEFAULT column list on foreign keys (#589)

internal/diff/constraint.go

@@ -2,6 +2,7 @@ package diff
 
 import (
 	"fmt"
+	"slices"
 	"strings"
 
 	"github.com/pgplex/pgschema/ir"
@@ -59,9 +60,7 @@ func generateConstraintSQL(constraint *ir.Constraint, targetSchema string, quali
 		if constraint.UpdateRule != "" && constraint.UpdateRule != "NO ACTION" {
 			stmt += fmt.Sprintf(" ON UPDATE %s", constraint.UpdateRule)
 		}
-		if constraint.DeleteRule != "" && constraint.DeleteRule != "NO ACTION" {
-			stmt += fmt.Sprintf(" ON DELETE %s", constraint.DeleteRule)
-		}
+		stmt += onDeleteClause(constraint)
 		// Add deferrable clause
 		stmt += deferrableClause(constraint)
 		// Add NOT VALID if needed
@@ -182,6 +181,11 @@ func constraintsEqual(old, new *ir.Constraint) bool {
 	if old.DeleteRule != new.DeleteRule {
 		return false
 	}
+	// The SET NULL/SET DEFAULT column list is a set: PostgreSQL stores it in the
+	// order written, so compare order-independently to avoid a needless recreate.
+	if !slices.Equal(slices.Sorted(slices.Values(old.DeleteSetColumns)), slices.Sorted(slices.Values(new.DeleteSetColumns))) {
+		return false
+	}
 	if old.UpdateRule != new.UpdateRule {
 		return false
 	}
@@ -237,3 +241,21 @@ func constraintsEqual(old, new *ir.Constraint) bool {
 
 	return true
 }
+
+// onDeleteClause renders the ON DELETE action of a foreign key, including the
+// optional column list of SET NULL / SET DEFAULT (PG15+, issue #589). Returns
+// "" for the default NO ACTION.
+func onDeleteClause(constraint *ir.Constraint) string {
+	if constraint.DeleteRule == "" || constraint.DeleteRule == "NO ACTION" {
+		return ""
+	}
+	clause := fmt.Sprintf(" ON DELETE %s", constraint.DeleteRule)
+	if len(constraint.DeleteSetColumns) > 0 {
+		cols := make([]string, len(constraint.DeleteSetColumns))
+		for i, col := range constraint.DeleteSetColumns {
+			cols[i] = ir.QuoteIdentifier(col)
+		}
+		clause += fmt.Sprintf(" (%s)", strings.Join(cols, ", "))
+	}
+	return clause
+}

internal/diff/table.go

@@ -2036,9 +2036,7 @@ func generateForeignKeyClauseMode(constraint *ir.Constraint, targetSchema string
 	if constraint.UpdateRule != "" && constraint.UpdateRule != "NO ACTION" {
 		clause += fmt.Sprintf(" ON UPDATE %s", constraint.UpdateRule)
 	}
-	if constraint.DeleteRule != "" && constraint.DeleteRule != "NO ACTION" {
-		clause += fmt.Sprintf(" ON DELETE %s", constraint.DeleteRule)
-	}
+	clause += onDeleteClause(constraint)
 
 	// Add deferrable clause
 	if constraint.Deferrable {

internal/plan/rewrite.go

@@ -308,6 +308,14 @@ func generateForeignKeyRewrite(constraint *ir.Constraint) []RewriteStep {
 	}
 	if constraint.DeleteRule != "" && constraint.DeleteRule != "NO ACTION" {
 		fkClause += fmt.Sprintf(" ON DELETE %s", constraint.DeleteRule)
+		// SET NULL / SET DEFAULT column list (PG15+, issue #589)
+		if len(constraint.DeleteSetColumns) > 0 {
+			var setCols []string
+			for _, col := range constraint.DeleteSetColumns {
+				setCols = append(setCols, ir.QuoteIdentifier(col))
+			}
+			fkClause += fmt.Sprintf(" (%s)", joinStrings(setCols, ", "))
+		}
 	}
 
 	// Add DEFERRABLE clauses if specified

ir/inspector.go

@@ -3,6 +3,7 @@ package ir
 import (
 	"context"
 	"database/sql"
+	"encoding/json"
 	"fmt"
 	"sort"
 	"strconv"
@@ -557,6 +558,15 @@ func (i *Inspector) buildConstraints(ctx context.Context, schema *IR, targetSche
 				if deleteRule := i.safeInterfaceToString(constraint.DeleteRule); deleteRule != "" && deleteRule != "<nil>" {
 					c.DeleteRule = deleteRule
 				}
+				// ON DELETE SET NULL/SET DEFAULT (column list) arrives as a JSON array of
+				// column names (empty string when absent or on PG14). Issue #589.
+				if setCols := constraint.DeleteSetColumns.String; setCols != "" {
+					var cols []string
+					if err := json.Unmarshal([]byte(setCols), &cols); err != nil {
+						return fmt.Errorf("failed to parse delete set columns for constraint %s.%s.%s: %w", schemaName, tableName, constraintName, err)
+					}
+					c.DeleteSetColumns = cols
+				}
 				if updateRule := i.safeInterfaceToString(constraint.UpdateRule); updateRule != "" && updateRule != "<nil>" {
 					c.UpdateRule = updateRule
 				}

ir/ir.go

@@ -244,6 +244,7 @@ type Constraint struct {
 	CheckClause         string              `json:"check_clause,omitempty"`
 	ExclusionDefinition string              `json:"exclusion_definition,omitempty"` // Full EXCLUDE definition from pg_get_constraintdef()
 	DeleteRule          string              `json:"delete_rule,omitempty"`
+	DeleteSetColumns    []string            `json:"delete_set_columns,omitempty"` // PG15+: column list of ON DELETE SET NULL/SET DEFAULT (confdelsetcols)
 	UpdateRule          string              `json:"update_rule,omitempty"`
 	Deferrable          bool                `json:"deferrable,omitempty"`
 	InitiallyDeferred   bool                `json:"initially_deferred,omitempty"`

ir/queries/queries.sql

@@ -337,14 +337,27 @@ SELECT
     c.condeferred AS initially_deferred,
     c.convalidated AS is_valid,
     COALESCE((to_jsonb(c) ->> 'conperiod')::boolean, false) AS is_period,
-    c.connoinherit AS no_inherit
+    c.connoinherit AS no_inherit,
+    -- ON DELETE SET NULL/SET DEFAULT (column list), PG15+ (pg_constraint.confdelsetcols).
+    -- Rendered as a JSON array of column names so it survives the per-column row fan-out
+    -- and stays a single scalar on PG14 (where the attribute does not exist). Issue #589.
+    COALESCE(ds.delete_set_columns, '') AS delete_set_columns
 FROM pg_constraint c
 JOIN pg_class cl ON c.conrelid = cl.oid
 JOIN pg_namespace n ON cl.relnamespace = n.oid
 LEFT JOIN pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY(c.conkey)
 LEFT JOIN pg_class fcl ON c.confrelid = fcl.oid
 LEFT JOIN pg_namespace fn ON fcl.relnamespace = fn.oid
 LEFT JOIN pg_attribute fa ON fa.attrelid = c.confrelid AND fa.attnum = c.confkey[array_position(c.conkey, a.attnum)]
+LEFT JOIN LATERAL (
+    SELECT jsonb_agg(da.attname ORDER BY e.ord)::text AS delete_set_columns
+    FROM jsonb_array_elements_text(
+        CASE WHEN jsonb_typeof(to_jsonb(c) -> 'confdelsetcols') = 'array'
+             THEN to_jsonb(c) -> 'confdelsetcols'
+             ELSE '[]'::jsonb END
+    ) WITH ORDINALITY AS e(attnum, ord)
+    JOIN pg_attribute da ON da.attrelid = c.conrelid AND da.attnum = e.attnum::int
+) ds ON true
 LEFT JOIN LATERAL (
     SELECT
         -- Render with search_path set to the table's own schema so same-schema
@@ -1054,7 +1067,11 @@ SELECT
     c.connoinherit AS no_inherit,
     -- pg_index.indnullsnotdistinct is PG15+. Use to_jsonb so the column reference
     -- doesn't fail to plan on PG14 (where the attribute does not exist on pg_index).
-    COALESCE((to_jsonb(i) ->> 'indnullsnotdistinct')::boolean, false) AS nulls_not_distinct
+    COALESCE((to_jsonb(i) ->> 'indnullsnotdistinct')::boolean, false) AS nulls_not_distinct,
+    -- ON DELETE SET NULL/SET DEFAULT (column list), PG15+ (pg_constraint.confdelsetcols).
+    -- Rendered as a JSON array of column names so it survives the per-column row fan-out
+    -- and stays a single scalar on PG14 (where the attribute does not exist). Issue #589.
+    COALESCE(ds.delete_set_columns, '') AS delete_set_columns
 FROM pg_constraint c
 JOIN pg_class cl ON c.conrelid = cl.oid
 JOIN pg_namespace n ON cl.relnamespace = n.oid
@@ -1063,6 +1080,15 @@ LEFT JOIN pg_class fcl ON c.confrelid = fcl.oid
 LEFT JOIN pg_namespace fn ON fcl.relnamespace = fn.oid
 LEFT JOIN pg_attribute fa ON fa.attrelid = c.confrelid AND fa.attnum = c.confkey[array_position(c.conkey, a.attnum)]
 LEFT JOIN pg_index i ON i.indexrelid = c.conindid
+LEFT JOIN LATERAL (
+    SELECT jsonb_agg(da.attname ORDER BY e.ord)::text AS delete_set_columns
+    FROM jsonb_array_elements_text(
+        CASE WHEN jsonb_typeof(to_jsonb(c) -> 'confdelsetcols') = 'array'
+             THEN to_jsonb(c) -> 'confdelsetcols'
+             ELSE '[]'::jsonb END
+    ) WITH ORDINALITY AS e(attnum, ord)
+    JOIN pg_attribute da ON da.attrelid = c.conrelid AND da.attnum = e.attnum::int
+) ds ON true
 LEFT JOIN LATERAL (
     SELECT
         -- Render with search_path set to the table's own schema so same-schema

testdata/diff/create_table/add_fk/diff.sql

@@ -1,3 +1,6 @@
+ALTER TABLE audit_log
+ADD CONSTRAINT audit_log_org_id_actor_member_id_fkey FOREIGN KEY (org_id, actor_member_id) REFERENCES members (org_id, id) ON DELETE SET NULL (actor_member_id);
+
 ALTER TABLE books
 ADD CONSTRAINT books_author_id_fkey FOREIGN KEY (author_id) REFERENCES authors (id) ON DELETE CASCADE;
 
@@ -7,6 +10,11 @@ ADD CONSTRAINT employees_department_id_fkey FOREIGN KEY (department_id) REFERENC
 ALTER TABLE nodes
 ADD CONSTRAINT nodes_parent_id_fkey FOREIGN KEY (parent_id) REFERENCES nodes (id);
 
+ALTER TABLE notes DROP CONSTRAINT notes_org_id_author_member_id_fkey;
+
+ALTER TABLE notes
+ADD CONSTRAINT notes_org_id_author_member_id_fkey FOREIGN KEY (org_id, author_member_id) REFERENCES members (org_id, id) ON DELETE SET NULL (author_member_id);
+
 ALTER TABLE orders
 ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customers (id);
 
@@ -25,6 +33,9 @@ ADD CONSTRAINT products_category_code_fkey FOREIGN KEY (category_code) REFERENCE
 ALTER TABLE projects
 ADD CONSTRAINT projects_tenant_id_org_id_fkey FOREIGN KEY (tenant_id, org_id) REFERENCES organizations (tenant_id, org_id);
 
+ALTER TABLE tasks
+ADD CONSTRAINT tasks_org_id_owner_member_id_fkey FOREIGN KEY (org_id, owner_member_id) REFERENCES members (org_id, id) ON DELETE SET DEFAULT (owner_member_id);
+
 ALTER TABLE teams
 ADD CONSTRAINT teams_manager_id_fkey FOREIGN KEY (manager_id) REFERENCES managers (id) ON DELETE SET NULL;
 

testdata/diff/create_table/add_fk/new.sql

@@ -116,6 +116,40 @@ CREATE TABLE public.orders (
     CONSTRAINT orders_manager_id_fkey FOREIGN KEY (manager_id) REFERENCES public.managers(id) ON DELETE SET NULL
 );
 
+-- Composite FK with ON DELETE SET NULL / SET DEFAULT column list (PG15+, issue #589)
+CREATE TABLE public.members (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    CONSTRAINT members_pkey PRIMARY KEY (id),
+    CONSTRAINT members_org_id_id_key UNIQUE (org_id, id)
+);
+
+CREATE TABLE public.audit_log (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    actor_member_id integer,
+    CONSTRAINT audit_log_pkey PRIMARY KEY (id),
+    CONSTRAINT audit_log_org_id_actor_member_id_fkey FOREIGN KEY (org_id, actor_member_id) REFERENCES public.members(org_id, id) ON DELETE SET NULL (actor_member_id)
+);
+
+CREATE TABLE public.tasks (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    owner_member_id integer DEFAULT 0,
+    CONSTRAINT tasks_pkey PRIMARY KEY (id),
+    CONSTRAINT tasks_org_id_owner_member_id_fkey FOREIGN KEY (org_id, owner_member_id) REFERENCES public.members(org_id, id) ON DELETE SET DEFAULT (owner_member_id)
+);
+
+-- Existing composite FK that lacks the column list: the desired state adds it,
+-- so the constraint must be recreated (the column list must be compared).
+CREATE TABLE public.notes (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    author_member_id integer,
+    CONSTRAINT notes_pkey PRIMARY KEY (id),
+    CONSTRAINT notes_org_id_author_member_id_fkey FOREIGN KEY (org_id, author_member_id) REFERENCES public.members(org_id, id) ON DELETE SET NULL (author_member_id)
+);
+
 -- Temporal FK case (PG18+)
 CREATE TABLE public.price_history (
     product_id integer NOT NULL,

testdata/diff/create_table/add_fk/old.sql

@@ -106,6 +106,38 @@ CREATE TABLE public.orders (
     CONSTRAINT orders_pkey PRIMARY KEY (id)
 );
 
+-- Composite FK with ON DELETE SET NULL / SET DEFAULT column list (PG15+, issue #589)
+CREATE TABLE public.members (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    CONSTRAINT members_pkey PRIMARY KEY (id),
+    CONSTRAINT members_org_id_id_key UNIQUE (org_id, id)
+);
+
+CREATE TABLE public.audit_log (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    actor_member_id integer,
+    CONSTRAINT audit_log_pkey PRIMARY KEY (id)
+);
+
+CREATE TABLE public.tasks (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    owner_member_id integer DEFAULT 0,
+    CONSTRAINT tasks_pkey PRIMARY KEY (id)
+);
+
+-- Existing composite FK that lacks the column list: the desired state adds it,
+-- so the constraint must be recreated (the column list must be compared).
+CREATE TABLE public.notes (
+    id integer NOT NULL,
+    org_id integer NOT NULL,
+    author_member_id integer,
+    CONSTRAINT notes_pkey PRIMARY KEY (id),
+    CONSTRAINT notes_org_id_author_member_id_fkey FOREIGN KEY (org_id, author_member_id) REFERENCES public.members(org_id, id) ON DELETE SET NULL
+);
+
 -- Temporal FK case (PG18+)
 CREATE TABLE public.price_history (
     product_id integer NOT NULL,