chore(release): update package version to 1.0.88

- migration writer now emits unique constraints (direct apply and live diff
  previously dropped them); idempotent via the existing DO block
- unique constraint adopts a same-named model unique index with
  ADD CONSTRAINT ... UNIQUE USING INDEX instead of building a second index
- dbml reader names unnamed unique indexes ukey_<table>_<cols> to match the
  unique constraint naming
- foreign key deferral: Constraint.Deferrable/InitiallyDeferred are *bool
  (nil = unspecified, never diffed); writers emit DEFERRABLE, DEFERRABLE
  INITIALLY DEFERRED and NOT DEFERRABLE; live reader reads condeferrable and
  condeferred; dbml reader/writer support deferrable and initially deferred
- tests and README/naming docs updated

VERSION

@@ -1 +1 @@
-1.0.87
+1.0.88

linux/arch/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Hein (Warky Devs) <hein@warky.dev>
 pkgname=relspec
-pkgver=1.0.87
+pkgver=1.0.88
 pkgrel=1
 pkgdesc="RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs."
 arch=('x86_64' 'aarch64')

linux/centos/relspec.spec

@@ -1,5 +1,5 @@
 Name:           relspec
-Version:        1.0.87
+Version:        1.0.88
 Release:        1%{?dist}
 Summary:        RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs.
 

pkg/diff/diff.go

@@ -504,6 +504,9 @@ func compareConstraintDetails(source, target *models.Constraint) map[string]any
 	if normalizeConstraintAction(source.OnUpdate) != normalizeConstraintAction(target.OnUpdate) {
 		changes["on_update"] = map[string]string{"source": source.OnUpdate, "target": target.OnUpdate}
 	}
+	if !models.DeferralMatches(source, target) {
+		changes["deferral"] = map[string]string{"source": source.DeferralClause(), "target": target.DeferralClause()}
+	}
 
 	return changes
 }

pkg/merge/merge.go

@@ -605,8 +605,8 @@ func cloneConstraint(constraint *models.Constraint) *models.Constraint {
 		OnDelete:          constraint.OnDelete,
 		Expression:        constraint.Expression,
 		Name:              constraint.Name,
-		Deferrable:        constraint.Deferrable,
-		InitiallyDeferred: constraint.InitiallyDeferred,
+		Deferrable:        copyBoolPtr(constraint.Deferrable),
+		InitiallyDeferred: copyBoolPtr(constraint.InitiallyDeferred),
 		Sequence:          constraint.Sequence,
 	}
 	copy(newConstraint.Columns, constraint.Columns)
@@ -823,3 +823,11 @@ func min(a, b int) int {
 	}
 	return b
 }
+
+func copyBoolPtr(b *bool) *bool {
+	if b == nil {
+		return nil
+	}
+	v := *b
+	return &v
+}

pkg/models/deferral.go

@@ -0,0 +1,48 @@
+package models
+
+// DeferralClause returns the SQL deferral clause for a foreign key constraint
+// ("DEFERRABLE", "DEFERRABLE INITIALLY DEFERRED" or "NOT DEFERRABLE"), or ""
+// when the model does not specify one. InitiallyDeferred without Deferrable
+// implies DEFERRABLE; InitiallyDeferred=false alone specifies nothing.
+func (d *Constraint) DeferralClause() string {
+	deferrable, initially, set := d.effectiveDeferral()
+	switch {
+	case !set:
+		return ""
+	case !deferrable:
+		return "NOT DEFERRABLE"
+	case initially != nil && *initially:
+		return "DEFERRABLE INITIALLY DEFERRED"
+	default:
+		return "DEFERRABLE"
+	}
+}
+
+// effectiveDeferral resolves the optional flags. set is false when the model says nothing
+// about deferral; initially is nil when the initial mode is unspecified.
+func (d *Constraint) effectiveDeferral() (deferrable bool, initially *bool, set bool) {
+	switch {
+	case d.Deferrable != nil:
+		return *d.Deferrable, d.InitiallyDeferred, true
+	case d.InitiallyDeferred != nil && *d.InitiallyDeferred:
+		return true, d.InitiallyDeferred, true
+	}
+	return false, nil, false
+}
+
+// DeferralMatches reports whether two constraints agree on deferral. An unspecified side
+// matches anything, and the initial mode is only compared when both sides specify it.
+func DeferralMatches(a, b *Constraint) bool {
+	da, ia, aSet := a.effectiveDeferral()
+	db, ib, bSet := b.effectiveDeferral()
+	if !aSet || !bSet {
+		return true
+	}
+	if da != db {
+		return false
+	}
+	if !da || ia == nil || ib == nil {
+		return true
+	}
+	return *ia == *ib
+}

pkg/models/deferral_test.go

@@ -0,0 +1,59 @@
+package models
+
+import "testing"
+
+func boolPtr(b bool) *bool { return &b }
+
+func TestConstraint_DeferralClause(t *testing.T) {
+	tests := []struct {
+		name string
+		c    Constraint
+		want string
+	}{
+		{"unspecified", Constraint{}, ""},
+		{"deferrable", Constraint{Deferrable: boolPtr(true)}, "DEFERRABLE"},
+		{"deferrable initially deferred", Constraint{Deferrable: boolPtr(true), InitiallyDeferred: boolPtr(true)}, "DEFERRABLE INITIALLY DEFERRED"},
+		{"deferrable initially immediate", Constraint{Deferrable: boolPtr(true), InitiallyDeferred: boolPtr(false)}, "DEFERRABLE"},
+		{"initially deferred implies deferrable", Constraint{InitiallyDeferred: boolPtr(true)}, "DEFERRABLE INITIALLY DEFERRED"},
+		{"initially immediate alone is unspecified", Constraint{InitiallyDeferred: boolPtr(false)}, ""},
+		{"explicitly not deferrable", Constraint{Deferrable: boolPtr(false)}, "NOT DEFERRABLE"},
+		{"not deferrable ignores initially deferred", Constraint{Deferrable: boolPtr(false), InitiallyDeferred: boolPtr(true)}, "NOT DEFERRABLE"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.c.DeferralClause(); got != tt.want {
+				t.Errorf("DeferralClause() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestDeferralMatches(t *testing.T) {
+	live := func(def, init bool) *Constraint {
+		return &Constraint{Deferrable: boolPtr(def), InitiallyDeferred: boolPtr(init)}
+	}
+	tests := []struct {
+		name         string
+		model, other *Constraint
+		want         bool
+	}{
+		{"model unspecified vs deferrable live", &Constraint{}, live(true, false), true},
+		{"model unspecified vs not deferrable live", &Constraint{}, live(false, false), true},
+		{"deferrable vs deferrable live", &Constraint{Deferrable: boolPtr(true)}, live(true, true), true},
+		{"deferrable vs not deferrable live", &Constraint{Deferrable: boolPtr(true)}, live(false, false), false},
+		{"not deferrable vs deferrable live", &Constraint{Deferrable: boolPtr(false)}, live(true, false), false},
+		{"initially deferred vs initially immediate live", &Constraint{InitiallyDeferred: boolPtr(true)}, live(true, false), false},
+		{"initially deferred vs initially deferred live", &Constraint{InitiallyDeferred: boolPtr(true)}, live(true, true), true},
+		{"explicit initially immediate vs initially deferred live", &Constraint{Deferrable: boolPtr(true), InitiallyDeferred: boolPtr(false)}, live(true, true), false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := DeferralMatches(tt.model, tt.other); got != tt.want {
+				t.Errorf("DeferralMatches() = %v, want %v", got, tt.want)
+			}
+			if got := DeferralMatches(tt.other, tt.model); got != tt.want {
+				t.Errorf("DeferralMatches() reversed = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

pkg/models/models.go

@@ -329,8 +329,8 @@ type Constraint struct {
 	ReferencedColumns []string       `json:"referenced_columns" yaml:"referenced_columns" xml:"referenced_columns"`
 	OnDelete          string         `json:"on_delete" yaml:"on_delete" xml:"on_delete"` // CASCADE, SET NULL, RESTRICT, etc.
 	OnUpdate          string         `json:"on_update" yaml:"on_update" xml:"on_update"`
-	Deferrable        bool           `json:"deferrable,omitempty" yaml:"deferrable,omitempty" xml:"deferrable,omitempty"`
-	InitiallyDeferred bool           `json:"initially_deferred,omitempty" yaml:"initially_deferred,omitempty" xml:"initially_deferred,omitempty"`
+	Deferrable        *bool          `json:"deferrable,omitempty" yaml:"deferrable,omitempty" xml:"deferrable,omitempty"`                         // nil: unspecified, left as is
+	InitiallyDeferred *bool          `json:"initially_deferred,omitempty" yaml:"initially_deferred,omitempty" xml:"initially_deferred,omitempty"` // nil: unspecified, left as is
 	Sequence          uint           `json:"sequence,omitempty" yaml:"sequence,omitempty" xml:"sequence,omitempty"`
 	GUID              string         `json:"guid" yaml:"guid" xml:"guid"`
 }

pkg/readers/dbml/README.md

@@ -86,16 +86,40 @@ Ref: posts.user_id > users.id [delete: cascade]
 - Table definitions with columns
 - Primary keys (`pk`)
 - Not null constraints (`not null`)
-- Unique constraints (`unique`)
+- Unique constraints (`unique`) → constraint `ukey_<table>_<col>`
 - Default values (`default`)
 - Inline references (`ref`)
 - Standalone `Ref` blocks
+- FK deferral: `deferrable`, `initially deferred` (see below)
 - Commented cross-file refs (`// Ref:` — see below)
 - Indexes and composite indexes
 - Table notes and column notes
 - Enums
 - Dialect directives (`@postgres:` / `@sqlite:` — see below)
 
+## Naming
+
+| Source | Generated name |
+| ------ | -------------- |
+| Column `[unique]` | constraint `ukey_<table>_<col>` |
+| Unnamed unique index | index `ukey_<table>_<cols>` (same name as the constraint on the same columns) |
+| Unnamed index | `idx_<table>_<cols>` |
+
+Explicit `name:` is never changed. Leading `_` in the table name is stripped.
+
+## FK deferral
+
+```
+col int [ref: > t.id, deferrable, initially deferred]
+Ref: a.x > b.id [delete: cascade, deferrable]
+```
+
+| Setting | SQL |
+| ------- | --- |
+| `deferrable` | `DEFERRABLE` |
+| `initially deferred` | `DEFERRABLE INITIALLY DEFERRED` |
+| neither | unspecified (existing FK left as is) |
+
 ## Commented cross-file refs
 
 `// Ref:` / `// ref:` lines (ignored by dbdiagram) become FKs + relationships once both ends are loaded.

pkg/readers/dbml/reader.go

@@ -848,6 +848,13 @@ func (r *Reader) parseColumn(line, tableName, schemaName string) (*models.Column
 		}
 	}
 
+	// "deferrable" / "initially deferred" column settings apply to the inline foreign key
+	if constraint != nil && constraint.Type == models.ForeignKeyConstraint && attrs != "" {
+		for _, attr := range splitColumnAttrs(attrs) {
+			applyDeferralSetting(constraint, attr)
+		}
+	}
+
 	// Parse inline comment
 	if inlineComment != "" {
 		column.Comment = inlineComment
@@ -1081,11 +1088,13 @@ func (r *Reader) parseIndex(line, tableName, schemaName string) *models.Index {
 
 	// Generate name if not provided
 	if index.Name == "" {
-		prefix := "idx"
+		// Unique indexes share the ukey_ naming of unique constraints, so an index and a
+		// constraint on the same columns get the same name and can be merged on write.
+		prefix, name := "idx", tableName
 		if index.Unique {
-			prefix = "uidx"
+			prefix, name = "ukey", strings.TrimLeft(tableName, "_")
 		}
-		index.Name = fmt.Sprintf("%s_%s_%s", prefix, tableName, strings.Join(columns, "_"))
+		index.Name = fmt.Sprintf("%s_%s_%s", prefix, name, strings.Join(columns, "_"))
 	}
 
 	return index
@@ -1182,6 +1191,8 @@ func (r *Reader) parseRef(refStr string) *models.Constraint {
 					constraint.OnDelete = strings.TrimSpace(strings.TrimPrefix(action, "ondelete:"))
 				} else if strings.HasPrefix(action, "onupdate:") {
 					constraint.OnUpdate = strings.TrimSpace(strings.TrimPrefix(action, "onupdate:"))
+				} else {
+					applyDeferralSetting(constraint, action)
 				}
 			}
 		}
@@ -1190,6 +1201,18 @@ func (r *Reader) parseRef(refStr string) *models.Constraint {
 	return constraint
 }
 
+// applyDeferralSetting applies a "deferrable" or "initially deferred" Ref setting to a
+// foreign key constraint. Other settings are ignored.
+func applyDeferralSetting(constraint *models.Constraint, setting string) {
+	yes := true
+	switch strings.Join(strings.Fields(strings.ToLower(setting)), " ") {
+	case "deferrable":
+		constraint.Deferrable = &yes
+	case "initially deferred", "initially_deferred":
+		constraint.InitiallyDeferred = &yes
+	}
+}
+
 // parseTableRef parses a table reference like "schema.table.(column1, column2)" or "schema"."table"."column"
 func (r *Reader) parseTableRef(ref string) (schema, table string, columns []string) {
 	// Extract columns if present in parentheses format

pkg/readers/dbml/reader_test.go

@@ -3,6 +3,7 @@ package dbml
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
@@ -842,9 +843,9 @@ func TestConstraintNaming(t *testing.T) {
 		t.Logf("Available constraints: %v", getKeys(postsTable.Constraints))
 	}
 
-	// Test unique index naming: uidx_table_columns
-	if _, exists := postsTable.Indexes["uidx_posts_slug"]; !exists {
-		t.Error("Expected unique index 'uidx_posts_slug' not found")
+	// Test unique index naming: ukey_table_columns, matching the unique constraint name
+	if _, exists := postsTable.Indexes["ukey_posts_slug"]; !exists {
+		t.Error("Expected unique index 'ukey_posts_slug' not found")
 		t.Logf("Available indexes: %v", getKeys(postsTable.Indexes))
 	}
 
@@ -1121,3 +1122,69 @@ func TestReader_DuplicateIndexNameInTableKept(t *testing.T) {
 		}
 	}
 }
+
+func TestReader_ForeignKeyDeferral(t *testing.T) {
+	dbml := `Table users {
+  id integer [pk]
+}
+
+Table posts {
+  id integer [pk]
+  user_id integer [ref: > users.id, deferrable, initially deferred]
+  editor_id integer
+  plain_id integer [ref: > users.id]
+}
+
+Table comments {
+  id integer [pk]
+  post_id integer
+  author_id integer
+}
+
+Ref: comments.post_id > posts.id [delete: cascade, deferrable]
+Ref: comments.author_id > users.id [deferrable, initially deferred]
+`
+	path := filepath.Join(t.TempDir(), "deferral.dbml")
+	if err := os.WriteFile(path, []byte(dbml), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	db, err := NewReader(&readers.ReaderOptions{FilePath: path}).ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	find := func(table, column string) *models.Constraint {
+		for _, s := range db.Schemas {
+			for _, tb := range s.Tables {
+				if tb.Name != table {
+					continue
+				}
+				for _, c := range tb.Constraints {
+					if c.Type == models.ForeignKeyConstraint && len(c.Columns) == 1 && c.Columns[0] == column {
+						return c
+					}
+				}
+			}
+		}
+		t.Fatalf("FK %s.%s not found", table, column)
+		return nil
+	}
+
+	tests := []struct {
+		table, column string
+		want          string
+	}{
+		{"posts", "user_id", "DEFERRABLE INITIALLY DEFERRED"},
+		{"posts", "plain_id", ""},
+		{"comments", "post_id", "DEFERRABLE"},
+		{"comments", "author_id", "DEFERRABLE INITIALLY DEFERRED"},
+	}
+	for _, tt := range tests {
+		if got := find(tt.table, tt.column).DeferralClause(); got != tt.want {
+			t.Errorf("%s.%s deferral = %q, want %q", tt.table, tt.column, got, tt.want)
+		}
+	}
+	if got := find("comments", "post_id").OnDelete; !strings.EqualFold(got, "cascade") {
+		t.Errorf("delete action lost, got %q", got)
+	}
+}

pkg/readers/pgsql/queries.go

@@ -439,7 +439,9 @@ func (r *Reader) queryForeignKeys(schemaName string) (map[string][]*models.Const
 			fcl.relname AS referenced_table_name,
 			fatt.attname AS referenced_column,
 			` + actionCase("con.confupdtype") + ` AS update_rule,
-			` + actionCase("con.confdeltype") + ` AS delete_rule
+			` + actionCase("con.confdeltype") + ` AS delete_rule,
+			con.condeferrable AS deferrable,
+			con.condeferred AS initially_deferred
 		FROM pg_catalog.pg_constraint con
 		JOIN pg_catalog.pg_class cl ON cl.oid = con.conrelid
 		JOIN pg_catalog.pg_namespace ns ON ns.oid = cl.relnamespace
@@ -470,6 +472,8 @@ func (r *Reader) queryForeignKeys(schemaName string) (map[string][]*models.Const
 		referencedColumns []string
 		updateRule        string
 		deleteRule        string
+		deferrable        bool
+		initiallyDeferred bool
 	}
 
 	fkMap := make(map[string]*fkData)
@@ -479,8 +483,9 @@ func (r *Reader) queryForeignKeys(schemaName string) (map[string][]*models.Const
 		var foreignSchema, foreignTable, foreignColumn string
 		var referencedSchema, referencedTable, referencedColumn string
 		var updateRule, deleteRule string
+		var deferrable, initiallyDeferred bool
 
-		if err := rows.Scan(&schema, &tableName, &constraintName, &foreignSchema, &foreignTable, &foreignColumn, &referencedSchema, &referencedTable, &referencedColumn, &updateRule, &deleteRule); err != nil {
+		if err := rows.Scan(&schema, &tableName, &constraintName, &foreignSchema, &foreignTable, &foreignColumn, &referencedSchema, &referencedTable, &referencedColumn, &updateRule, &deleteRule, &deferrable, &initiallyDeferred); err != nil {
 			return nil, err
 		}
 
@@ -497,6 +502,8 @@ func (r *Reader) queryForeignKeys(schemaName string) (map[string][]*models.Const
 				referencedColumns: []string{},
 				updateRule:        updateRule,
 				deleteRule:        deleteRule,
+				deferrable:        deferrable,
+				initiallyDeferred: initiallyDeferred,
 			}
 		}
 
@@ -517,6 +524,9 @@ func (r *Reader) queryForeignKeys(schemaName string) (map[string][]*models.Const
 		constraint.ReferencedColumns = fk.referencedColumns
 		constraint.OnUpdate = fk.updateRule
 		constraint.OnDelete = fk.deleteRule
+		deferrable, initiallyDeferred := fk.deferrable, fk.initiallyDeferred
+		constraint.Deferrable = &deferrable
+		constraint.InitiallyDeferred = &initiallyDeferred
 
 		tableKey := fk.schema + "." + fk.tableName
 		foreignKeys[tableKey] = append(foreignKeys[tableKey], constraint)

pkg/writers/dbml/writer.go

@@ -273,6 +273,13 @@ func (w *Writer) constraintToDBML(c *models.Constraint, t *models.Table) string
 		actions = append(actions, fmt.Sprintf("update: %s", c.OnUpdate))
 	}
 
+	if c.Deferrable != nil && *c.Deferrable {
+		actions = append(actions, "deferrable")
+	}
+	if c.InitiallyDeferred != nil && *c.InitiallyDeferred {
+		actions = append(actions, "initially deferred")
+	}
+
 	refLine := fmt.Sprintf("Ref: %s %s %s", fromRef, relationship, toRef)
 	if len(actions) > 0 {
 		refLine += fmt.Sprintf(" [%s]", strings.Join(actions, ", "))

pkg/writers/dbml/writer_test.go

@@ -171,3 +171,31 @@ func TestWriter_WriteDatabase_OneToOneRelationship(t *testing.T) {
 
 	assert.Contains(t, output, "Ref: public.profiles.user_id - public.users.id")
 }
+
+func TestWriter_WriteDatabase_ForeignKeyDeferral(t *testing.T) {
+	yes := true
+	db := models.InitDatabase("test_db")
+	schema := models.InitSchema("public")
+	users := models.InitTable("users", "public")
+	users.Columns["id"] = models.InitColumn("id", "users", "public")
+	users.Columns["id"].Type = "bigint"
+	posts := models.InitTable("posts", "public")
+	posts.Columns["user_id"] = models.InitColumn("user_id", "posts", "public")
+	posts.Columns["user_id"].Type = "bigint"
+	fk := models.InitConstraint("fk_posts_user", models.ForeignKeyConstraint)
+	fk.Table, fk.Schema = "posts", "public"
+	fk.Columns = []string{"user_id"}
+	fk.ReferencedTable, fk.ReferencedSchema = "users", "public"
+	fk.ReferencedColumns = []string{"id"}
+	fk.Deferrable = &yes
+	fk.InitiallyDeferred = &yes
+	posts.Constraints[fk.Name] = fk
+	schema.Tables = append(schema.Tables, users, posts)
+	db.Schemas = append(db.Schemas, schema)
+
+	outputPath := filepath.Join(t.TempDir(), "test.dbml")
+	assert.NoError(t, NewWriter(&writers.WriterOptions{OutputPath: outputPath}).WriteDatabase(db))
+	content, err := os.ReadFile(outputPath)
+	assert.NoError(t, err)
+	assert.Contains(t, string(content), "Ref: public.posts.user_id > public.users.id [deferrable, initially deferred]")
+}

pkg/writers/pgsql/NAMING_CONVENTIONS.md

@@ -8,8 +8,8 @@ Standardized naming rules for all database objects in RelSpec PostgreSQL output.
 | ----------------- | ----------- | ---------------------------------- | ------------------------ |
 | Primary Key       | `pk_`       | `pk_<schema>_<table>`              | `pk_public_users`        |
 | Foreign Key       | `fk_`       | `fk_<table>_<referenced_table>`    | `fk_posts_users`         |
-| Unique Constraint | `uk_`       | `uk_<table>_<column>`              | `uk_users_email`         |
-| Unique Index      | `uidx_`     | `uidx_<table>_<column>`            | `uidx_users_email`       |
+| Unique Constraint | `ukey_`     | `ukey_<table>_<column>`            | `ukey_users_email`       |
+| Unique Index      | `ukey_`     | `ukey_<table>_<column>`            | `ukey_users_email`       |
 | Regular Index     | `idx_`      | `idx_<table>_<column>`             | `idx_posts_user_id`      |
 | Check Constraint  | `chk_`      | `chk_<table>_<constraint_purpose>` | `chk_users_age_positive` |
 | Sequence          | `identity_` | `identity_<table>_<column>`        | `identity_users_id`      |
@@ -43,25 +43,25 @@ Standardized naming rules for all database objects in RelSpec PostgreSQL output.
 
 ### Unique Constraints
 
-**Pattern:** `uk_<table>_<column>`
+**Pattern:** `ukey_<table>_<column>`
 
-- Use `uk_` prefix strictly for database constraints (CONSTRAINT type)
+- Generated by the DBML reader for column `[unique]`
 - Include column name for clarity
 - Examples:
-  - `uk_users_email`
-  - `uk_users_username`
-  - `uk_products_sku`
+  - `ukey_users_email`
+  - `ukey_users_username`
+  - `ukey_products_sku`
 
 ### Unique Indexes
 
-**Pattern:** `uidx_<table>_<column>`
+**Pattern:** `ukey_<table>_<column>`
 
-- Use `uidx_` prefix strictly for index type objects
-- Distinguished from constraints for clarity and implementation flexibility
+- Unnamed unique indexes use the same name as a unique constraint on the same columns
+- Writers then build the constraint on the index (`ADD CONSTRAINT ... UNIQUE USING INDEX`), so no duplicate index is created
 - Examples:
-  - `uidx_users_email`
-  - `uidx_sessions_token`
-  - `uidx_api_keys_key`
+  - `ukey_users_email`
+  - `ukey_sessions_token`
+  - `ukey_api_keys_key`
 
 ### Regular Indexes
 

pkg/writers/pgsql/README.md

@@ -154,6 +154,29 @@ When `migration_mode` is enabled, generates migration scripts with:
 - Transactional DDL
 - Rollback support
 
+### Unique constraints and indexes
+
+- Unique constraint → `ADD CONSTRAINT <name> UNIQUE (cols)`, idempotent (checked by name)
+- Migration mode and direct apply both emit them (not only `convert`)
+- Same-named model unique index → `UNIQUE USING INDEX` (no duplicate index). Requires: same name, same columns, btree, non-partial, no `INCLUDE`
+- Otherwise a plain `ADD CONSTRAINT` (second index is built)
+- Naming: unique constraint and unique index both `ukey_<table>_<cols>`; see `NAMING_CONVENTIONS.md`
+- Renaming `uidx_…` → `ukey_…` drops the old index and re-adds the constraint on the next diff
+
+### FK deferral
+
+| Model (`Deferrable` / `InitiallyDeferred`) | SQL |
+| ------------------------------------------ | --- |
+| unset | create: `DEFERRABLE` (migration/apply), none (full DDL constraints); existing FK never diffed |
+| `true` / unset or `false` | `DEFERRABLE` |
+| `true` / `true`, or unset / `true` | `DEFERRABLE INITIALLY DEFERRED` |
+| `false` | `NOT DEFERRABLE` |
+
+- Both fields are `*bool`; `nil` = unspecified
+- Specified value differing from the live DB → FK dropped and re-added
+- Live reader reads `condeferrable` / `condeferred`
+- Initial mode compared only when both sides state it
+
 ### Audit Triggers
 
 When `include_audit` is enabled, adds:

pkg/writers/pgsql/migration_writer.go

@@ -222,6 +222,13 @@ func (w *MigrationWriter) generateSchemaScripts(model, current *models.Schema) (
 	}
 	scripts = append(scripts, indexScripts...)
 
+	// Phase 4.5: Create unique constraints (Priority 185)
+	uniqueScripts, err := w.generateUniqueConstraintScripts(model, current)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate unique constraint scripts: %w", err)
+	}
+	scripts = append(scripts, uniqueScripts...)
+
 	// Phase 5: Create foreign keys (Priority 195)
 	fkScripts, err := w.generateForeignKeyScripts(model, current, droppedFKs)
 	if err != nil {
@@ -751,6 +758,92 @@ func buildIndexColumnExpressionsFiltered(table *models.Table, index *models.Inde
 	return columnExprs
 }
 
+// generateUniqueConstraintScripts generates ADD CONSTRAINT UNIQUE scripts for model unique
+// constraints that are missing from, or differ in, the live schema.
+func (w *MigrationWriter) generateUniqueConstraintScripts(model, current *models.Schema) ([]MigrationScript, error) {
+	scripts := make([]MigrationScript, 0)
+
+	currentTables := make(map[string]*models.Table)
+	if current != nil {
+		for _, table := range current.Tables {
+			currentTables[strings.ToLower(table.Name)] = table
+		}
+	}
+
+	for _, modelTable := range model.Tables {
+		currentTable := currentTables[strings.ToLower(modelTable.Name)]
+
+		for _, constraint := range sortConstraints(modelTable.Constraints) {
+			if constraint.Type != models.UniqueConstraint {
+				continue
+			}
+
+			if currentTable != nil {
+				if currentConstraint, exists := lookupConstraint(currentTable.Constraints, constraint.Name); exists && constraintsEqual(constraint, currentConstraint) {
+					continue
+				}
+			}
+
+			columnExprs := make([]string, 0, len(constraint.Columns))
+			for _, colName := range constraint.Columns {
+				if col, ok := modelTable.Columns[colName]; ok {
+					columnExprs = append(columnExprs, col.SQLName())
+				}
+			}
+			if len(columnExprs) == 0 {
+				continue
+			}
+
+			sql, err := w.executor.ExecuteCreateUniqueConstraint(CreateUniqueConstraintData{
+				SchemaName:     model.Name,
+				TableName:      modelTable.Name,
+				ConstraintName: constraint.Name,
+				Columns:        strings.Join(columnExprs, ", "),
+				UsingIndex:     adoptableUniqueIndex(modelTable, constraint),
+			})
+			if err != nil {
+				return nil, err
+			}
+
+			scripts = append(scripts, MigrationScript{
+				ObjectName: fmt.Sprintf("%s.%s.%s", model.Name, modelTable.Name, constraint.Name),
+				ObjectType: "create unique constraint",
+				Schema:     model.Name,
+				Priority:   185,
+				Sequence:   len(scripts),
+				Body:       sql,
+			})
+		}
+	}
+
+	return scripts, nil
+}
+
+// adoptableUniqueIndex returns the name of the model's unique index that the given unique
+// constraint can be built on with ADD CONSTRAINT ... UNIQUE USING INDEX, so the constraint does
+// not create a second index (or collide with the index's name). The index must carry the
+// constraint's name, be a plain non-partial btree index and cover exactly the constraint's
+// columns. Index creation runs before constraint creation, so this holds whether or not the
+// live database already has the index. Returns "" when none qualifies.
+func adoptableUniqueIndex(table *models.Table, constraint *models.Constraint) string {
+	index, ok := table.Indexes[constraint.Name]
+	if !ok || !index.Unique || index.Where != "" || len(index.Include) > 0 {
+		return ""
+	}
+	if index.Type != "" && !strings.EqualFold(index.Type, "btree") {
+		return ""
+	}
+	if len(index.Columns) != len(constraint.Columns) {
+		return ""
+	}
+	for i, col := range index.Columns {
+		if !strings.EqualFold(col, constraint.Columns[i]) {
+			return ""
+		}
+	}
+	return index.Name
+}
+
 // generateForeignKeyScripts generates ADD CONSTRAINT FOREIGN KEY scripts using templates.
 // forceRecreate is a set of FK constraint keys (schema.table.name) that must be recreated
 // even if unchanged, because their referenced PK was dropped and recreated.
@@ -800,6 +893,12 @@ func (w *MigrationWriter) generateForeignKeyScripts(model, current *models.Schem
 					onUpdate = strings.ToUpper(constraint.OnUpdate)
 				}
 
+				// An unspecified deferral keeps the historical default of DEFERRABLE.
+				deferral := constraint.DeferralClause()
+				if deferral == "" {
+					deferral = "DEFERRABLE"
+				}
+
 				sql, err := w.executor.ExecuteCreateForeignKey(CreateForeignKeyData{
 					SchemaName:     model.Name,
 					TableName:      modelTable.Name,
@@ -810,6 +909,7 @@ func (w *MigrationWriter) generateForeignKeyScripts(model, current *models.Schem
 					TargetColumns:  strings.Join(constraint.ReferencedColumns, ", "),
 					OnDelete:       onDelete,
 					OnUpdate:       onUpdate,
+					Deferral:       deferral,
 				})
 				if err != nil {
 					return nil, err
@@ -1149,6 +1249,9 @@ func constraintsEqual(c1, c2 *models.Constraint) bool {
 		if !fkActionsEqual(c1.OnDelete, c2.OnDelete) || !fkActionsEqual(c1.OnUpdate, c2.OnUpdate) {
 			return false
 		}
+		if !models.DeferralMatches(c1, c2) {
+			return false
+		}
 	}
 
 	return true

pkg/writers/pgsql/migration_writer_test.go

@@ -1027,3 +1027,316 @@ func TestIndexesEqual_OperatorClassAndStorageParameters(t *testing.T) {
 		})
 	}
 }
+
+func uniqueConstraintTestModel() *models.Database {
+	model := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("login", "public")
+	idCol := models.InitColumn("id", "login", "public")
+	idCol.Type = "integer"
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+	guidCol := models.InitColumn("guid", "login", "public")
+	guidCol.Type = "uuid"
+	table.Columns["guid"] = guidCol
+
+	uc := models.InitConstraint("ukey_login_guid", models.UniqueConstraint)
+	uc.Schema = "public"
+	uc.Table = "login"
+	uc.Columns = []string{"guid"}
+	table.Constraints[uc.Name] = uc
+
+	schema.Tables = append(schema.Tables, table)
+	model.Schemas = append(model.Schemas, schema)
+	return model
+}
+
+func TestWriteMigration_UniqueConstraint(t *testing.T) {
+	tests := []struct {
+		name         string
+		current      func() *models.Database
+		wantConstrnt bool
+	}{
+		{
+			name: "new table",
+			current: func() *models.Database {
+				c := models.InitDatabase("testdb")
+				c.Schemas = append(c.Schemas, models.InitSchema("public"))
+				return c
+			},
+			wantConstrnt: true,
+		},
+		{
+			name: "existing table without constraint",
+			current: func() *models.Database {
+				c := uniqueConstraintTestModel()
+				delete(c.Schemas[0].Tables[0].Constraints, "ukey_login_guid")
+				return c
+			},
+			wantConstrnt: true,
+		},
+		{
+			name:         "existing table with constraint",
+			current:      uniqueConstraintTestModel,
+			wantConstrnt: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			writer, err := NewMigrationWriter(&writers.WriterOptions{})
+			if err != nil {
+				t.Fatalf("Failed to create writer: %v", err)
+			}
+			writer.writer = &buf
+
+			if err := writer.WriteMigration(uniqueConstraintTestModel(), tt.current()); err != nil {
+				t.Fatalf("WriteMigration failed: %v", err)
+			}
+
+			output := buf.String()
+			has := strings.Contains(output, "ADD CONSTRAINT") && strings.Contains(output, "ukey_login_guid") && strings.Contains(output, "UNIQUE")
+			if has != tt.wantConstrnt {
+				t.Fatalf("unique constraint present = %v, want %v; output:\n%s", has, tt.wantConstrnt, output)
+			}
+			if strings.Contains(output, "DROP CONSTRAINT") {
+				t.Fatalf("unexpected DROP CONSTRAINT; output:\n%s", output)
+			}
+		})
+	}
+}
+
+func TestWriteMigration_UniqueConstraintAdoptsSameNamedModelIndex(t *testing.T) {
+	newIndex := func(name string, unique bool, where string) *models.Index {
+		idx := models.InitIndex(name, "login", "public")
+		idx.Columns = []string{"guid"}
+		idx.Unique = unique
+		idx.Type = "btree"
+		idx.Where = where
+		return idx
+	}
+
+	tests := []struct {
+		name      string
+		modelIdx  *models.Index
+		liveIdx   *models.Index // nil: fresh table
+		wantAdopt bool
+		wantDrop  bool
+	}{
+		{
+			name:      "fresh table: same-named unique index is promoted",
+			modelIdx:  newIndex("ukey_login_guid", true, ""),
+			wantAdopt: true,
+		},
+		{
+			name:      "existing live unique index is promoted",
+			modelIdx:  newIndex("ukey_login_guid", true, ""),
+			liveIdx:   newIndex("ukey_login_guid", true, ""),
+			wantAdopt: true,
+		},
+		{
+			name:     "live unique index not in model is dropped and constraint built fresh",
+			liveIdx:  newIndex("ukey_login_guid", true, ""),
+			wantDrop: true,
+		},
+		{
+			name:     "partial model index is not promoted",
+			modelIdx: newIndex("ukey_login_guid", true, "guid IS NOT NULL"),
+		},
+		{
+			name:     "non-unique same-named index is not promoted",
+			modelIdx: newIndex("ukey_login_guid", false, ""),
+		},
+		{
+			name:     "differently named index is not promoted",
+			modelIdx: newIndex("idx_login_guid", true, ""),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			model := uniqueConstraintTestModel()
+			if tt.modelIdx != nil {
+				model.Schemas[0].Tables[0].Indexes[tt.modelIdx.Name] = tt.modelIdx
+			}
+
+			current := models.InitDatabase("testdb")
+			current.Schemas = append(current.Schemas, models.InitSchema("public"))
+			if tt.liveIdx != nil {
+				current = uniqueConstraintTestModel()
+				curTable := current.Schemas[0].Tables[0]
+				delete(curTable.Constraints, "ukey_login_guid")
+				curTable.Indexes[tt.liveIdx.Name] = tt.liveIdx
+			}
+
+			var buf bytes.Buffer
+			writer, err := NewMigrationWriter(&writers.WriterOptions{})
+			if err != nil {
+				t.Fatalf("Failed to create writer: %v", err)
+			}
+			writer.writer = &buf
+			if err := writer.WriteMigration(model, current); err != nil {
+				t.Fatalf("WriteMigration failed: %v", err)
+			}
+			output := buf.String()
+
+			if got := strings.Contains(output, "UNIQUE USING INDEX"); got != tt.wantAdopt {
+				t.Errorf("USING INDEX present = %v, want %v; output:\n%s", got, tt.wantAdopt, output)
+			}
+			if got := strings.Contains(output, "UNIQUE (guid)") || strings.Contains(output, "UNIQUE (\"guid\")"); got == tt.wantAdopt {
+				t.Errorf("column-list ADD CONSTRAINT present = %v, want %v; output:\n%s", got, !tt.wantAdopt, output)
+			}
+			if got := strings.Contains(output, "DROP INDEX"); got != tt.wantDrop {
+				t.Errorf("DROP INDEX present = %v, want %v; output:\n%s", got, tt.wantDrop, output)
+			}
+		})
+	}
+}
+
+func TestWriteDatabase_UniqueConstraintAdoptsSameNamedIndex(t *testing.T) {
+	db := uniqueConstraintTestModel()
+	idx := models.InitIndex("ukey_login_guid", "login", "public")
+	idx.Columns = []string{"guid"}
+	idx.Unique = true
+	db.Schemas[0].Tables[0].Indexes[idx.Name] = idx
+
+	var buf bytes.Buffer
+	w := NewWriter(&writers.WriterOptions{})
+	w.writer = &buf
+	if err := w.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+	output := buf.String()
+
+	if !strings.Contains(output, "UNIQUE USING INDEX") {
+		t.Fatalf("expected UNIQUE USING INDEX in output:\n%s", output)
+	}
+	if strings.Index(output, "CREATE UNIQUE INDEX") > strings.Index(output, "UNIQUE USING INDEX") {
+		t.Fatalf("index must be created before the constraint adopts it:\n%s", output)
+	}
+}
+
+func fkDeferralTestModel(def, init *bool) *models.Database {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	users := models.InitTable("users", "public")
+	uid := models.InitColumn("id", "users", "public")
+	uid.Type = "integer"
+	uid.NotNull = true
+	users.Columns["id"] = uid
+
+	posts := models.InitTable("posts", "public")
+	pid := models.InitColumn("id", "posts", "public")
+	pid.Type = "integer"
+	pid.NotNull = true
+	posts.Columns["id"] = pid
+	puid := models.InitColumn("user_id", "posts", "public")
+	puid.Type = "integer"
+	posts.Columns["user_id"] = puid
+
+	fk := models.InitConstraint("fk_posts_user_id", models.ForeignKeyConstraint)
+	fk.Schema = "public"
+	fk.Table = "posts"
+	fk.Columns = []string{"user_id"}
+	fk.ReferencedSchema = "public"
+	fk.ReferencedTable = "users"
+	fk.ReferencedColumns = []string{"id"}
+	fk.Deferrable = def
+	fk.InitiallyDeferred = init
+	posts.Constraints[fk.Name] = fk
+
+	schema.Tables = append(schema.Tables, users, posts)
+	db.Schemas = append(db.Schemas, schema)
+	return db
+}
+
+func migrationOutput(t *testing.T, model, current *models.Database) string {
+	t.Helper()
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+	return buf.String()
+}
+
+func TestWriteMigration_ForeignKeyDeferral(t *testing.T) {
+	yes, no := true, false
+	empty := func() *models.Database {
+		c := models.InitDatabase("testdb")
+		c.Schemas = append(c.Schemas, models.InitSchema("public"))
+		return c
+	}
+
+	tests := []struct {
+		name     string
+		def      *bool
+		init     *bool
+		wantFrag string
+	}{
+		{"unspecified keeps DEFERRABLE default", nil, nil, "ON UPDATE NO ACTION\n  DEFERRABLE;"},
+		{"deferrable", &yes, nil, "DEFERRABLE;"},
+		{"initially deferred", &yes, &yes, "DEFERRABLE INITIALLY DEFERRED;"},
+		{"not deferrable", &no, nil, "NOT DEFERRABLE;"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			out := migrationOutput(t, fkDeferralTestModel(tt.def, tt.init), empty())
+			if !strings.Contains(out, tt.wantFrag) {
+				t.Fatalf("expected %q in output:\n%s", tt.wantFrag, out)
+			}
+		})
+	}
+}
+
+func TestWriteMigration_ForeignKeyDeferralDiff(t *testing.T) {
+	yes, no := true, false
+	live := func(def, init bool) *models.Database {
+		db := fkDeferralTestModel(&def, &init)
+		return db
+	}
+
+	tests := []struct {
+		name         string
+		def, init    *bool
+		liveDef      bool
+		liveInit     bool
+		wantRecreate bool
+	}{
+		{"unspecified vs deferrable live: untouched", nil, nil, true, false, false},
+		{"unspecified vs not deferrable live: untouched", nil, nil, false, false, false},
+		{"deferrable matches live", &yes, nil, true, true, false},
+		{"deferrable vs not deferrable live: recreated", &yes, nil, false, false, true},
+		{"not deferrable vs deferrable live: recreated", &no, nil, true, false, true},
+		{"initially deferred vs initially immediate live: recreated", &yes, &yes, true, false, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			out := migrationOutput(t, fkDeferralTestModel(tt.def, tt.init), live(tt.liveDef, tt.liveInit))
+			got := strings.Contains(out, "ADD CONSTRAINT") && strings.Contains(out, "FOREIGN KEY")
+			if got != tt.wantRecreate {
+				t.Fatalf("FK recreated = %v, want %v; output:\n%s", got, tt.wantRecreate, out)
+			}
+		})
+	}
+}
+
+func TestWriteDatabase_ForeignKeyDeferral(t *testing.T) {
+	yes := true
+	var buf bytes.Buffer
+	w := NewWriter(&writers.WriterOptions{})
+	w.writer = &buf
+	if err := w.WriteDatabase(fkDeferralTestModel(&yes, &yes)); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+	if !strings.Contains(buf.String(), "DEFERRABLE INITIALLY DEFERRED;") {
+		t.Fatalf("expected DEFERRABLE INITIALLY DEFERRED in output:\n%s", buf.String())
+	}
+}

pkg/writers/pgsql/templates.go

@@ -164,6 +164,7 @@ type CreateForeignKeyData struct {
 	TargetColumns  string
 	OnDelete       string
 	OnUpdate       string
+	Deferral       string // DEFERRABLE / DEFERRABLE INITIALLY DEFERRED / NOT DEFERRABLE, or empty
 }
 
 // DropConstraintData contains data for drop constraint template
@@ -238,6 +239,7 @@ type CreateUniqueConstraintData struct {
 	TableName      string
 	ConstraintName string
 	Columns        string
+	UsingIndex     string // when set, promotes this existing unique index instead of building a new one
 }
 
 // CreateCheckConstraintData contains data for create check constraint template
@@ -259,7 +261,7 @@ type CreateForeignKeyWithCheckData struct {
 	TargetColumns  string
 	OnDelete       string
 	OnUpdate       string
-	Deferrable     bool
+	Deferral       string // DEFERRABLE / DEFERRABLE INITIALLY DEFERRED / NOT DEFERRABLE, or empty
 }
 
 // SetSequenceValueData contains data for set sequence value template

pkg/writers/pgsql/templates/create_foreign_key.tmpl

@@ -7,4 +7,4 @@ ALTER TABLE {{qual_table .SchemaName .TableName}}
   REFERENCES {{qual_table .TargetSchema .TargetTable}} ({{.TargetColumns}})
   ON DELETE {{.OnDelete}}
   ON UPDATE {{.OnUpdate}}
-  DEFERRABLE;
+  {{.Deferral}};

pkg/writers/pgsql/templates/create_foreign_key_with_check.tmpl

@@ -11,8 +11,8 @@ BEGIN
       FOREIGN KEY ({{.SourceColumns}})
       REFERENCES {{qual_table .TargetSchema .TargetTable}} ({{.TargetColumns}})
       ON DELETE {{.OnDelete}}
-      ON UPDATE {{.OnUpdate}}{{if .Deferrable}}
-      DEFERRABLE{{end}};
+      ON UPDATE {{.OnUpdate}}{{if .Deferral}}
+      {{.Deferral}}{{end}};
   END IF;
 END;
 $$;

pkg/writers/pgsql/templates/create_unique_constraint.tmpl

@@ -6,7 +6,7 @@ BEGIN
       AND table_name = '{{.TableName}}'
       AND constraint_name = '{{.ConstraintName}}'
   ) THEN
-    ALTER TABLE {{qual_table .SchemaName .TableName}} ADD CONSTRAINT {{quote_ident .ConstraintName}} UNIQUE ({{.Columns}});
+    ALTER TABLE {{qual_table .SchemaName .TableName}} ADD CONSTRAINT {{quote_ident .ConstraintName}} UNIQUE {{if .UsingIndex}}USING INDEX {{quote_ident .UsingIndex}}{{else}}({{.Columns}}){{end}};
   END IF;
 END;
-$$;
+$$;

pkg/writers/pgsql/writer.go

@@ -345,6 +345,7 @@ func (w *Writer) GenerateSchemaStatements(schema *models.Schema) ([]string, erro
 				TableName:      table.Name,
 				ConstraintName: constraint.Name,
 				Columns:        strings.Join(constraint.Columns, ", "),
+				UsingIndex:     adoptableUniqueIndex(table, constraint),
 			}
 
 			stmt, err := w.executor.ExecuteCreateUniqueConstraint(data)
@@ -411,7 +412,7 @@ func (w *Writer) GenerateSchemaStatements(schema *models.Schema) ([]string, erro
 				TargetColumns:  strings.Join(constraint.ReferencedColumns, ", "),
 				OnDelete:       onDelete,
 				OnUpdate:       onUpdate,
-				Deferrable:     false,
+				Deferral:       constraint.DeferralClause(),
 			}
 
 			stmt, err := w.executor.ExecuteCreateForeignKeyWithCheck(data)
@@ -1150,7 +1151,7 @@ func (w *Writer) writeIndexes(schema *models.Schema) error {
 			if indexName == "" {
 				indexType := "idx"
 				if index.Unique {
-					indexType = "uidx"
+					indexType = "ukey"
 				}
 				columnSuffix := strings.Join(index.Columns, "_")
 				indexName = fmt.Sprintf("%s_%s_%s", indexType, table.SQLName(), strings.ToLower(columnSuffix))
@@ -1236,6 +1237,7 @@ func (w *Writer) writeUniqueConstraints(schema *models.Schema) error {
 				TableName:      table.Name,
 				ConstraintName: constraint.Name,
 				Columns:        strings.Join(columnExprs, ", "),
+				UsingIndex:     adoptableUniqueIndex(table, constraint),
 			})
 			if err != nil {
 				return fmt.Errorf("failed to generate unique constraint: %w", err)
@@ -1380,7 +1382,7 @@ func (w *Writer) writeForeignKeys(schema *models.Schema) error {
 				TargetColumns:  strings.Join(targetColumns, ", "),
 				OnDelete:       onDelete,
 				OnUpdate:       onUpdate,
-				Deferrable:     true,
+				Deferral:       "DEFERRABLE",
 			}
 			sql, err := w.executor.ExecuteCreateForeignKeyWithCheck(data)
 			if err != nil {
@@ -1459,7 +1461,7 @@ func (w *Writer) writeForeignKeys(schema *models.Schema) error {
 				TargetColumns:  strings.Join(targetColumns, ", "),
 				OnDelete:       onDelete,
 				OnUpdate:       onUpdate,
-				Deferrable:     false,
+				Deferral:       constraint.DeferralClause(),
 			}
 			sql, err := w.executor.ExecuteCreateForeignKeyWithCheck(data)
 			if err != nil {