From 7393095f073c6c46d86618b83f8867ee1a8da359 Mon Sep 17 00:00:00 2001
From: Gert-Jan Timmer <gjr.timmer@gmail.com>
Date: Tue, 29 May 2018 12:09:56 +0200
Subject: [PATCH] ADD: PRAGMA defer_foreign_keys

---
 README.md  |  1 +
 sqlite3.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/README.md b/README.md
index 3086586..6b96d67 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,7 @@ Boolean values can be one of:
 | Auto Vacuum | `_vacuum` | <ul><li>`0` \| `none`</li><li>`1` \| `full`</li><li>`2` \| `incremental`</li></ul> | For more information see [PRAGMA auto_vacuum](https://www.sqlite.org/pragma.html#pragma_auto_vacuum) |
 | Busy Timeout | `_busy_timeout` \| `_timeout` | `int` | Specify value for sqlite3_busy_timeout. For more information see [PRAGMA busy_timeout](https://www.sqlite.org/pragma.html#pragma_busy_timeout) |
 | Case Sensitive LIKE | `_cslike` | `boolean` | For more information see [PRAGMA case_sensitive_like](https://www.sqlite.org/pragma.html#pragma_case_sensitive_like) |
+| Defer Foreign Keys | `_defer_foreign_keys` \| `_defer_fk` | `boolean` | For more information see [PRAGMA defer_foreign_keys](https://www.sqlite.org/pragma.html#pragma_defer_foreign_keys) |
 | Foreign Keys | `_foreign_keys` \| `_fk` | `boolean` | For more information see [PRAGMA foreign_keys](https://www.sqlite.org/pragma.html#pragma_foreign_keys) |
 | Mutex Locking | `_mutex` | <ul><li>no</li><li>full</li></ul> | Specify mutex mode. |
 | Recursive Triggers | `_recursive_triggers` \| `_rt` | `boolean` | For more information see [PRAGMA recursive_triggers](https://www.sqlite.org/pragma.html#pragma_recursive_triggers) |
diff --git a/sqlite3.go b/sqlite3.go
index 4de18d6..18a1f51 100644
--- a/sqlite3.go
+++ b/sqlite3.go
@@ -810,6 +810,9 @@ func errorString(err Error) string {
 //     Default or disabled the LIKE operation is case-insensitive.
 //     When enabling this options behaviour of LIKE will become case-sensitive.
 //
+//   _defer_foreign_keys=Boolean | _defer_fk=Boolean
+//     Defer Foreign Keys until outermost transaction is committed.
+//
 //   _foreign_keys=Boolean | _fk=Boolean
 //     Enable or disable enforcement of foreign keys.
 //
@@ -836,6 +839,7 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 	autoVacuum := -1
 	busyTimeout := 5000
 	caseSensitiveLike := -1
+	deferForeignKeys := -1
 	foreignKeys := -1
 	recursiveTriggers := -1
 
@@ -935,6 +939,28 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 			}
 		}
 
+		// Defer Foreign Keys
+		//
+		// https://www.sqlite.org/pragma.html#pragma_defer_foreign_keys
+		//
+		pkey = "" // Reset pkey
+		if _, ok := params["_defer_foreign_keys"]; ok {
+			pkey = "_defer_foreign_keys"
+		}
+		if _, ok := params["_defer_fk"]; ok {
+			pkey = "_defer_fk"
+		}
+		if val := params.Get(pkey); val != "" {
+			switch strings.ToLower(val) {
+			case "0", "no", "false", "off":
+				deferForeignKeys = 0
+			case "1", "yes", "true", "on":
+				deferForeignKeys = 1
+			default:
+				return nil, fmt.Errorf("Invalid _foreign_keys: %v, expecting boolean value of '0 1 false true no yes off on'", val)
+			}
+		}
+
 		// Foreign Keys (_foreign_keys)
 		//
 		// https://www.sqlite.org/pragma.html#pragma_foreign_keys
@@ -1028,6 +1054,14 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 		}
 	}
 
+	// Defer Foreign Keys
+	if deferForeignKeys > -1 {
+		if err := exec(fmt.Sprintf("PRAGMA defer_foreign_keys = %d;", deferForeignKeys)); err != nil {
+			C.sqlite3_close_v2(db)
+			return nil, err
+		}
+	}
+
 	// Forgein Keys
 	if foreignKeys > -1 {
 		if err := exec(fmt.Sprintf("PRAGMA foreign_keys = %d;", foreignKeys)); err != nil {