ADD: PRAGMA synchronous

Author: gjrtimmer

README.md

@@ -89,6 +89,7 @@ Boolean values can be one of:
 | Recursive Triggers | `_recursive_triggers` \| `_rt` | `boolean` | For more information see [PRAGMA recursive_triggers](https://www.sqlite.org/pragma.html#pragma_recursive_triggers) |
 | Secure Delete | `_secure_delete` | `boolean` \| `FAST` | For more information see [PRAGMA secure_delete](https://www.sqlite.org/pragma.html#pragma_secure_delete) |
 | Shared-Cache Mode | `cache` | <ul><li>shared</li><li>private</li></ul> | Set cache mode for more information see [sqlite.org](https://www.sqlite.org/sharedcache.html) |
+| Synchronous | `_synchronous` \| `_sync` | <ul><li>0 \| OFF</li><li>1 \| NORMAL</li><li>2 \| FULL</li><li>3 \| EXTRA</li></ul> | For more information see [PRAGMA synchronous](https://www.sqlite.org/pragma.html#pragma_synchronous) |
 | Time Zone Location | `_loc` | auto | Specify location of time format. |
 | Transaction Lock | `_txlock` | <ul><li>immediate</li><li>deferred</li><li>exclusive</li></ul> | Specify locking behavior for transactions. |
 

sqlite3.go

@@ -866,6 +866,10 @@ func errorString(err Error) string {
 //     When secure_delete is on, SQLite overwrites deleted content with zeros.
 //     https://www.sqlite.org/pragma.html#pragma_secure_delete
 //
+//   _synchronous=X | _sync=X
+//     Change the setting of the "synchronous" flag.
+//     https://www.sqlite.org/pragma.html#pragma_synchronous
+//
 //   _vacuum=X
 //     0 | none - Auto Vacuum disabled
 //     1 | full - Auto Vacuum FULL
@@ -894,6 +898,7 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 	queryOnly := -1
 	recursiveTriggers := -1
 	secureDelete := "DEFAULT"
+	synchronousMode := "NORMAL"
 
 	pos := strings.IndexRune(dsn, '?')
 	if pos >= 1 {
@@ -1057,8 +1062,14 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 		//
 		if val := params.Get("_journal"); val != "" {
 			switch strings.ToUpper(val) {
-			case "DELETE", "TRUNCATE", "PERSIST", "MEMORY", "WAL", "OFF":
+			case "DELETE", "TRUNCATE", "PERSIST", "MEMORY", "OFF":
+				journalMode = strings.ToUpper(val)
+			case "WAL":
 				journalMode = strings.ToUpper(val)
+
+				// For WAL Mode set Synchronous Mode to 'NORMAL'
+				// See https://www.sqlite.org/pragma.html#pragma_synchronous
+				synchronousMode = "NORMAL"
 			default:
 				return nil, fmt.Errorf("Invalid _journal: %v, expecting value of 'DELETE TRUNCATE PERSIST MEMORY WAL OFF'", val)
 			}
@@ -1131,6 +1142,26 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 			}
 		}
 
+		// Synchronous Mode (_synchronous | _sync)
+		//
+		// https://www.sqlite.org/pragma.html#pragma_synchronous
+		//
+		pkey = "" // Reset pkey
+		if _, ok := params["_synchronous"]; ok {
+			pkey = "_synchronous"
+		}
+		if _, ok := params["_sync"]; ok {
+			pkey = "_sync"
+		}
+		if val := params.Get(pkey); val != "" {
+			switch strings.ToUpper(val) {
+			case "0", "OFF", "1", "NORMAL", "2", "FULL", "3", "EXTRA":
+				synchronousMode = strings.ToUpper(val)
+			default:
+				return nil, fmt.Errorf("Invalid _synchronous: %v, expecting value of '0 OFF 1 NORMAL 2 FULL 3 EXTRA'", val)
+			}
+		}
+
 		if !strings.HasPrefix(dsn, "file:") {
 			dsn = dsn[:pos]
 		}
@@ -1248,6 +1279,14 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 		}
 	}
 
+	// Synchronous Mode
+	//
+	// Because default is NORMAL this statement is always executed
+	if err := exec(fmt.Sprintf("PRAGMA synchronous = %s;", synchronousMode)); err != nil {
+		C.sqlite3_close_v2(db)
+		return nil, err
+	}
+
 	conn := &SQLiteConn{db: db, loc: loc, txlock: txlock}
 
 	if len(d.Extensions) > 0 {