Apparently "pragma synchronous" defaults to "full", and not "normal" …

…as the documentation states. It also appears this needs to be set per-connection. None of this is very well documented in sqlite.

Testing/Benchmarking/BenchmarkYapDatabase.m

@@ -229,7 +229,8 @@ + (void)runTestsWithCompletion:(dispatch_block_t)completionBlock
 
 	// Create database
 	YapDatabaseOptions *options = [[YapDatabaseOptions alloc] init];
-//	options.pragmaSynchronous = YapDatabasePragmaSynchronous_Off; // Uncomment for full speed
+//	options.pragmaSynchronous = YapDatabasePragmaSynchronous_Normal; // Use for faster speed
+//	options.pragmaSynchronous = YapDatabasePragmaSynchronous_Off;    // Use for fastest speed
 
 	database = [[YapDatabase alloc] initWithPath:databasePath
 	                            objectSerializer:NULL

YapDatabase/Extensions/SecondaryIndex/YapDatabaseSecondaryIndexTransaction.m

@@ -146,10 +146,9 @@ - (BOOL)createIfNeeded
 		#if DEBUG
 		if ([oldVersionTag isEqualToString:versionTag])
 		{
-			__unsafe_unretained YapDatabase *database = databaseTransaction->connection->database;
 			sqlite3 *db = databaseTransaction->connection->db;
 
-			NSDictionary *columns = [database columnNamesAndAffinityForTable:[self tableName] using:db];
+			NSDictionary *columns = [YapDatabase columnNamesAndAffinityForTable:[self tableName] using:db];
 
 			YapDatabaseSecondaryIndexSetup *setup = secondaryIndexConnection->secondaryIndex->setup;
 

YapDatabase/Internal/YapDatabasePrivate.h

@@ -84,9 +84,12 @@ extern NSString *const YapDatabaseNotificationKey;
 /**
  * General utility methods.
 **/
-- (BOOL)tableExists:(NSString *)tableName using:(sqlite3 *)aDb;
-- (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb;
-- (NSDictionary *)columnNamesAndAffinityForTable:(NSString *)tableName using:(sqlite3 *)aDb;
++ (int)pragma:(NSString *)pragmaSetting using:(sqlite3 *)db;
++ (NSString *)pragmaValueForAutoVacuum:(int)auto_vacuum;
++ (NSString *)pragmaValueForSynchronous:(int)synchronous;
++ (BOOL)tableExists:(NSString *)tableName using:(sqlite3 *)aDb;
++ (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb;
++ (NSDictionary *)columnNamesAndAffinityForTable:(NSString *)tableName using:(sqlite3 *)aDb;
 
 /**
  * New connections inherit their default values from this structure.
@@ -160,7 +163,7 @@ extern NSString *const YapDatabaseNotificationKey;
 /**
  * Configures database encryption via SQLCipher.
  **/
-- (BOOL)configureEncryptionForDatabase:(sqlite3*)sqlite;
+- (BOOL)configureEncryptionForDatabase:(sqlite3 *)sqlite;
 #endif
 
 @end

YapDatabase/YapDatabase.m

@@ -281,6 +281,8 @@ - (id)initWithPath:(NSString *)inPath objectSerializer:(YapDatabaseSerializer)in
 		databasePath = path;
 		options = inOptions ? [inOptions copy] : [[YapDatabaseOptions alloc] init];
 
+		BOOL isNewDatabaseFile = ![[NSFileManager defaultManager] fileExistsAtPath:databasePath];
+
 		BOOL(^openConfigCreate)(void) = ^BOOL (void) { @autoreleasepool {
 
 			BOOL result = YES;
@@ -289,7 +291,7 @@ - (id)initWithPath:(NSString *)inPath objectSerializer:(YapDatabaseSerializer)in
 #ifdef SQLITE_HAS_CODEC
             if (result) result = [self configureEncryptionForDatabase:db];
 #endif
-			if (result) result = [self configureDatabase];
+			if (result) result = [self configureDatabase:isNewDatabaseFile];
 			if (result) result = [self createTables];
 
 			if (!result && db)
@@ -348,6 +350,7 @@ - (id)initWithPath:(NSString *)inPath objectSerializer:(YapDatabaseSerializer)in
 
 				if (renamed)
 				{
+					isNewDatabaseFile = YES;
 					result = openConfigCreate();
 					if (result) {
 						YDBLogInfo(@"Database corruption resolved. Renamed corrupt file. (newDB=%@) (corruptDB=%@)",
@@ -368,6 +371,7 @@ - (id)initWithPath:(NSString *)inPath objectSerializer:(YapDatabaseSerializer)in
 
 				if (deleted)
 				{
+					isNewDatabaseFile = YES;
 					result = openConfigCreate();
 					if (result) {
 						YDBLogInfo(@"Database corruption resolved. Deleted corrupt file. (name=%@)",
@@ -525,33 +529,38 @@ - (BOOL)openDatabase
  * Configures the database connection.
  * This mainly means enabling WAL mode, and configuring the auto-checkpoint.
 **/
-- (BOOL)configureDatabase
+- (BOOL)configureDatabase:(BOOL)isNewDatabaseFile
 {
 	int status;
 
+	// Set mandatory pragmas
+
 	status = sqlite3_exec(db, "PRAGMA journal_mode = WAL;", NULL, NULL, NULL);
 	if (status != SQLITE_OK)
 	{
 		YDBLogError(@"Error setting PRAGMA journal_mode: %d %s", status, sqlite3_errmsg(db));
 		return NO;
 	}
 
-	if (options.pragmaSynchronous == YapDatabasePragmaSynchronous_Off ||
-	    options.pragmaSynchronous == YapDatabasePragmaSynchronous_Full )
+	// Set synchronous to normal for THIS sqlite instance.
+	//
+	// This does NOT affect normal connections.
+	// That is, this does NOT affect YapDatabaseConnection instances.
+	// The sqlite connections of normal YapDatabaseConnection instances will follow the set pragmaSynchronous value.
+	//
+	// The reason we hardcode normal for this sqlite instance is because
+	// it's only used to write the initial snapshot value.
+	// And this doesn't need to be durable, as it is initialized to zero everytime.
+	//
+	// (This sqlite db is also used to perform checkpoints.
+	//  But a normal value won't affect these operations,
+	//  as they will perform sync operations whether the connection is normal or full.)
+
+	status = sqlite3_exec(db, "PRAGMA synchronous = NORMAL;", NULL, NULL, NULL);
+	if (status != SQLITE_OK)
 	{
-		char *pragma_stmt;
-
-		if (options.pragmaSynchronous == YapDatabasePragmaSynchronous_Off)
-			pragma_stmt = "PRAGMA synchronous = OFF;";
-		else
-			pragma_stmt = "PRAGMA synchronous = FULL;";
-
-		status = sqlite3_exec(db, pragma_stmt, NULL, NULL, NULL);
-		if (status != SQLITE_OK)
-		{
-			YDBLogError(@"Error setting PRAGMA synchronous: %d %s", status, sqlite3_errmsg(db));
-			// This isn't critical, so we can continue.
-		}
+		YDBLogError(@"Error setting PRAGMA synchronous: %d %s", status, sqlite3_errmsg(db));
+		// This isn't critical, so we can continue.
 	}
 
 	// Disable autocheckpointing.
@@ -569,8 +578,8 @@ - (BOOL)configureDatabase
 #ifdef SQLITE_HAS_CODEC
 /**
  * Configures database encryption via SQLCipher.
- **/
-- (BOOL)configureEncryptionForDatabase:(sqlite3*)sqlite
+**/
+- (BOOL)configureEncryptionForDatabase:(sqlite3 *)sqlite
 {
 	int status;
 
@@ -650,10 +659,64 @@ - (BOOL)createTables
 #pragma mark Utilities
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
++ (int)pragma:(NSString *)pragmaSetting using:(sqlite3 *)db
+{
+	if (pragmaSetting == nil) return 0;
+
+	sqlite3_stmt *statement;
+	NSString *pragma = [NSString stringWithFormat:@"PRAGMA %@;", pragmaSetting];
+
+	int status = sqlite3_prepare_v2(db, [pragma UTF8String], -1, &statement, NULL);
+	if (status != SQLITE_OK)
+	{
+		YDBLogError(@"%@: Error creating statement! %d %s", THIS_METHOD, status, sqlite3_errmsg(db));
+		return NO;
+	}
+
+	int result = 0;
+
+	status = sqlite3_step(statement);
+	if (status == SQLITE_ROW)
+	{
+		result = sqlite3_column_int(statement, 0);
+	}
+	else if (status == SQLITE_ERROR)
+	{
+		YDBLogError(@"%@: Error executing statement! %d %s", THIS_METHOD, status, sqlite3_errmsg(db));
+	}
+
+	sqlite3_finalize(statement);
+	statement = NULL;
+
+	return result;
+}
+
++ (NSString *)pragmaValueForAutoVacuum:(int)auto_vacuum
+{
+	switch(auto_vacuum)
+	{
+		case 0 : return @"NONE";
+		case 1 : return @"FULL";
+		case 2 : return @"INCREMENTAL";
+		default: return @"UNKNOWN";
+	}
+}
+
++ (NSString *)pragmaValueForSynchronous:(int)synchronous
+{
+	switch(synchronous)
+	{
+		case 0 : return @"OFF";
+		case 1 : return @"NORMAL";
+		case 2 : return @"FULL";
+		default: return @"UNKNOWN";
+	}
+}
+
 /**
  * Returns whether or not the given table exists.
 **/
-- (BOOL)tableExists:(NSString *)tableName using:(sqlite3 *)aDb
++ (BOOL)tableExists:(NSString *)tableName using:(sqlite3 *)aDb
 {
 	if (tableName == nil) return NO;
 
@@ -692,7 +755,7 @@ - (BOOL)tableExists:(NSString *)tableName using:(sqlite3 *)aDb
 /**
  * Extracts and returns column names from the given table in the database.
 **/
-- (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb
++ (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb
 {
 	if (tableName == nil) return nil;
 
@@ -710,6 +773,8 @@ - (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb
 
 	while ((status = sqlite3_step(statement)) == SQLITE_ROW)
 	{
+		// cid|name|type|notnull|dflt|value|pk
+
 		const unsigned char *text = sqlite3_column_text(statement, 1);
 		int textSize = sqlite3_column_bytes(statement, 1);
 
@@ -737,7 +802,7 @@ - (NSArray *)columnNamesForTable:(NSString *)tableName using:(sqlite3 *)aDb
  *
  * key:(NSString *)columnName -> value:(NSString *)affinity
 **/
-- (NSDictionary *)columnNamesAndAffinityForTable:(NSString *)tableName using:(sqlite3 *)aDb
++ (NSDictionary *)columnNamesAndAffinityForTable:(NSString *)tableName using:(sqlite3 *)aDb
 {
 	if (tableName == nil) return nil;
 

YapDatabase/YapDatabaseConnection.m

@@ -191,6 +191,27 @@ - (id)initWithDatabase:(YapDatabase *)inDatabase
 			}
 			else
 			{
+				// Set configurable pragmas
+
+				YapDatabasePragmaSynchronous pragmaSynchronous = database.options.pragmaSynchronous;
+
+				if (pragmaSynchronous == YapDatabasePragmaSynchronous_Off ||
+				    pragmaSynchronous == YapDatabasePragmaSynchronous_Normal)
+				{
+					char *pragma_stmt = NULL;
+
+					if (pragmaSynchronous == YapDatabasePragmaSynchronous_Off)
+						pragma_stmt = "PRAGMA synchronous = OFF;";
+					else
+						pragma_stmt = "PRAGMA synchronous = NORMAL;";
+
+					status = sqlite3_exec(db, pragma_stmt, NULL, NULL, NULL);
+					if (status != SQLITE_OK)
+					{
+						YDBLogError(@"Error setting PRAGMA synchronous: %d %s", status, sqlite3_errmsg(db));
+					}
+				}
+
 				// Disable autocheckpointing.
 				//
 				// YapDatabase has its own optimized checkpointing algorithm built-in.

YapDatabase/YapDatabaseOptions.h

@@ -59,7 +59,7 @@ typedef NSString* (^YapDatabaseOptionsPassphraseBlock)(void);
  * 
  * Note that YapDatabase uses sqlite in WAL mode.
  *
- * The default value is YapDatabasePragmaSynchronous_Normal.
+ * The default value is YapDatabasePragmaSynchronous_Full.
 **/
 @property (nonatomic, assign, readwrite) YapDatabasePragmaSynchronous pragmaSynchronous;
 

YapDatabase/YapDatabaseOptions.m

@@ -22,7 +22,7 @@ - (id)init
 	if ((self = [super init]))
 	{
 		corruptAction = YapDatabaseCorruptAction_Rename;
-		pragmaSynchronous = YapDatabasePragmaSynchronous_Normal;
+		pragmaSynchronous = YapDatabasePragmaSynchronous_Full;
 	}
 	return self;
 }