Added support for immediate transactions and checkpoint

src/fmdb/FMDatabase.h

@@ -695,6 +695,18 @@ typedef int(^FMDBExecuteStatementsCallbackBlock)(NSDictionary *resultsDictionary
 
 - (BOOL)beginDeferredTransaction;
 
+/** Begin an immediate transaction
+
+ @return `YES` on success; `NO` on failure. If failed, you can call `<lastError>`, `<lastErrorCode>`, or `<lastErrorMessage>` for diagnostic information regarding the failure.
+
+ @see commit
+ @see rollback
+ @see beginTransaction
+ @see isInTransaction
+ */
+
+- (BOOL)beginImmediateTransaction;
+
 /** Commit a transaction
 
  Commit a transaction that was initiated with either `<beginTransaction>` or with `<beginDeferredTransaction>`.
@@ -987,6 +999,20 @@ typedef int(^FMDBExecuteStatementsCallbackBlock)(NSDictionary *resultsDictionary
 
 - (NSError * _Nullable)inSavePoint:(__attribute__((noescape)) void (^)(BOOL *rollback))block;
 
+
+///-----------------
+/// @name Checkpoint
+///-----------------
+
+/** Performs a WAL checkpoint
+
+ @param checkpointMode The checkpoint mode for sqlite3_wal_checkpoint_v2
+ @param name The db name for sqlite3_wal_checkpoint_v2
+ @param error The NSError corresponding to the error, if any.
+ @return YES on success, otherwise NO.
+ */
+- (BOOL)checkpoint:(int)checkpointMode dbName:(NSString *)name error:(NSError * _Nullable *)error;
+
 ///----------------------------
 /// @name SQLite library status
 ///----------------------------

src/fmdb/FMDatabase.m

@@ -1322,6 +1322,16 @@ - (BOOL)beginDeferredTransaction {
     return b;
 }
 
+- (BOOL)beginImmediateTransaction {
+
+    BOOL b = [self executeUpdate:@"begin immediate transaction"];
+    if (b) {
+        _isInTransaction = YES;
+    }
+
+    return b;
+}
+
 - (BOOL)beginTransaction {
     
     BOOL b = [self executeUpdate:@"begin exclusive transaction"];
@@ -1423,6 +1433,29 @@ - (NSError*)inSavePoint:(void (^)(BOOL *rollback))block {
 #endif
 }
 
+- (BOOL)checkpoint:(int)checkpointMode dbName:(NSString *)name error:(NSError * __autoreleasing *)error
+{
+    const char* dbName = [name UTF8String];
+#if SQLITE_VERSION_NUMBER >= 3007006
+    int err = sqlite3_wal_checkpoint_v2(_db, dbName, checkpointMode, NULL, NULL);
+#else
+    NSLog(@"sqlite3_wal_checkpoint_v2 unavailable before sqlite 3.7.6. Ignoring checkpoint mode: %d", mode);
+    int err = sqlite3_wal_checkpoint(_db, dbName);
+#endif
+    if(err != SQLITE_OK) {
+        if (error) {
+            *error = [self lastError];
+        }
+        if (self.logsErrors) NSLog(@"%@", [self lastErrorMessage]);
+        if (self.crashOnErrors) {
+            NSAssert(false, @"%@", [self lastErrorMessage]);
+            abort();
+        }
+        return NO;
+    } else {
+        return YES;
+    }
+}
 
 #pragma mark Cache statements
 

src/fmdb/FMDatabasePool.h

@@ -212,6 +212,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)inDeferredTransaction:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block;
 
+/** Synchronously perform database operations on queue, using immediate transactions.
+
+ @param block The code to be run on the queue of `FMDatabaseQueue`
+ */
+
+- (void)inImmediateTransaction:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block;
+
 /** Synchronously perform database operations in pool using save point.
 
  @param block The code to be run on the `FMDatabasePool` pool.

src/fmdb/FMDatabasePool.m

@@ -15,6 +15,12 @@
 #import "FMDatabasePool.h"
 #import "FMDatabase.h"
 
+typedef NS_ENUM(NSInteger, FMDBTransaction) {
+    FMDBTransactionExclusive,
+    FMDBTransactionDeferred,
+    FMDBTransactionImmediate,
+};
+
 @interface FMDatabasePool () {
     dispatch_queue_t    _lockQueue;
     
@@ -244,17 +250,22 @@ - (void)inDatabase:(void (^)(FMDatabase *db))block {
     [self pushDatabaseBackInPool:db];
 }
 
-- (void)beginTransaction:(BOOL)useDeferred withBlock:(void (^)(FMDatabase *db, BOOL *rollback))block {
+- (void)beginTransaction:(FMDBTransaction)transaction withBlock:(void (^)(FMDatabase *db, BOOL *rollback))block {
     
     BOOL shouldRollback = NO;
     
     FMDatabase *db = [self db];
     
-    if (useDeferred) {
-        [db beginDeferredTransaction];
-    }
-    else {
-        [db beginTransaction];
+    switch (transaction) {
+        case FMDBTransactionExclusive:
+            [db beginTransaction];
+            break;
+        case FMDBTransactionDeferred:
+            [db beginDeferredTransaction];
+            break;
+        case FMDBTransactionImmediate:
+            [db beginImmediateTransaction];
+            break;
     }
     
     
@@ -271,11 +282,15 @@ - (void)beginTransaction:(BOOL)useDeferred withBlock:(void (^)(FMDatabase *db, B
 }
 
 - (void)inDeferredTransaction:(void (^)(FMDatabase *db, BOOL *rollback))block {
-    [self beginTransaction:YES withBlock:block];
+    [self beginTransaction:FMDBTransactionDeferred withBlock:block];
 }
 
 - (void)inTransaction:(void (^)(FMDatabase *db, BOOL *rollback))block {
-    [self beginTransaction:NO withBlock:block];
+    [self beginTransaction:FMDBTransactionExclusive withBlock:block];
+}
+
+- (void)inImmediateTransaction:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block {
+    [self beginTransaction:FMDBTransactionImmediate withBlock:block];
 }
 
 - (NSError*)inSavePoint:(void (^)(FMDatabase *db, BOOL *rollback))block {

src/fmdb/FMDatabaseQueue.h

@@ -217,6 +217,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)inDeferredTransaction:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block;
 
+/** Synchronously perform database operations on queue, using immediate transactions.
+
+ @param block The code to be run on the queue of `FMDatabaseQueue`
+ */
+
+- (void)inImmediateTransaction:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block;
+
 ///-----------------------------------------------
 /// @name Dispatching database operations to queue
 ///-----------------------------------------------
@@ -230,6 +237,20 @@ NS_ASSUME_NONNULL_BEGIN
 // If you need to nest, use FMDatabase's startSavePointWithName:error: instead.
 - (NSError * _Nullable)inSavePoint:(__attribute__((noescape)) void (^)(FMDatabase *db, BOOL *rollback))block;
 
+///-----------------
+/// @name Checkpoint
+///-----------------
+
+/** Synchronously performs a WAL checkpoint
+
+ @param checkpointMode The checkpoint mode for sqlite3_wal_checkpoint_v2
+ @param name The db name for sqlite3_wal_checkpoint_v2
+ @param error The NSError corresponding to the error, if any.
+ @return YES on success, otherwise NO.
+ */
+
+- (BOOL)checkpoint:(int)checkpointMode dbName:(NSString *)name error:(NSError * _Nullable *)error;
+
 @end
 
 NS_ASSUME_NONNULL_END

src/fmdb/FMDatabaseQueue.m

@@ -15,6 +15,12 @@
 #import <sqlite3.h>
 #endif
 
+typedef NS_ENUM(NSInteger, FMDBTransaction) {
+    FMDBTransactionExclusive,
+    FMDBTransactionDeferred,
+    FMDBTransactionImmediate,
+};
+
 /*
  
  Note: we call [self retain]; before using dispatch_sync, just incase 
@@ -201,17 +207,22 @@ - (void)inDatabase:(void (^)(FMDatabase *db))block {
     FMDBRelease(self);
 }
 
-- (void)beginTransaction:(BOOL)useDeferred withBlock:(void (^)(FMDatabase *db, BOOL *rollback))block {
+- (void)beginTransaction:(FMDBTransaction)transaction withBlock:(void (^)(FMDatabase *db, BOOL *rollback))block {
     FMDBRetain(self);
     dispatch_sync(_queue, ^() { 
         
         BOOL shouldRollback = NO;
-        
-        if (useDeferred) {
-            [[self database] beginDeferredTransaction];
-        }
-        else {
-            [[self database] beginTransaction];
+
+        switch (transaction) {
+            case FMDBTransactionExclusive:
+                [[self database] beginTransaction];
+                break;
+            case FMDBTransactionDeferred:
+                [[self database] beginDeferredTransaction];
+                break;
+            case FMDBTransactionImmediate:
+                [[self database] beginImmediateTransaction];
+                break;
         }
         
         block([self database], &shouldRollback);
@@ -228,11 +239,15 @@ - (void)beginTransaction:(BOOL)useDeferred withBlock:(void (^)(FMDatabase *db, B
 }
 
 - (void)inDeferredTransaction:(void (^)(FMDatabase *db, BOOL *rollback))block {
-    [self beginTransaction:YES withBlock:block];
+    [self beginTransaction:FMDBTransactionDeferred withBlock:block];
 }
 
 - (void)inTransaction:(void (^)(FMDatabase *db, BOOL *rollback))block {
-    [self beginTransaction:NO withBlock:block];
+    [self beginTransaction:FMDBTransactionExclusive withBlock:block];
+}
+
+- (void)inImmediateTransaction:(void (^)(FMDatabase * _Nonnull, BOOL * _Nonnull))block {
+    [self beginTransaction:FMDBTransactionImmediate withBlock:block];
 }
 
 - (NSError*)inSavePoint:(void (^)(FMDatabase *db, BOOL *rollback))block {
@@ -267,4 +282,21 @@ - (NSError*)inSavePoint:(void (^)(FMDatabase *db, BOOL *rollback))block {
 #endif
 }
 
+- (BOOL)checkpoint:(int)mode dbName:(NSString *)name error:(NSError * __autoreleasing *)error
+{
+    __block BOOL result;
+    __block NSError *blockError;
+
+    FMDBRetain(self);
+    dispatch_sync(_queue, ^() {
+        result = [self.database checkpoint:mode dbName:name error:&blockError];
+    });
+    FMDBRelease(self);
+
+    if (error) {
+        *error = blockError;
+    }
+    return result;
+}
+
 @end