Add a new SPFileHandle class to support gzip compression and writing on a background thread, and integrate for SQL import:

 - Implement streaming reading of gzip-compressed files for SQL import
 - Support exporting SQL dumps into a gzip-compressed file
 - SPFileHandle supports the most-used subset of NSFileHandle commands for easy integration
 - Integrate zlib 1.2.4 for improved gzip streaming performance (and support for custom buffer sizes and file offset positions)
This implements Issue #571 .

7 files changed, 452 insertions, 46 deletions

diff --git a/Source/SPConstants.h b/Source/SPConstants.h
index e6574f31..4bda5116 100644
--- a/Source/SPConstants.h
+++ b/Source/SPConstants.h
@@ -223,7 +223,7 @@ extern NSString *SPFavoritesSortedInReverse;
 extern NSString *SPPrintWarningRowLimit;
 extern NSString *SPDisplayServerVersionInWindowTitle;
 
-// Import
+// Import and export
 extern NSString *SPCSVImportFieldTerminator;
 extern NSString *SPCSVImportLineTerminator;
 extern NSString *SPCSVImportFieldEnclosedBy;
@@ -231,6 +231,7 @@ extern NSString *SPCSVImportFieldEscapeCharacter;
 extern NSString *SPCSVImportFirstLineIsHeader;
 extern NSString *SPCSVFieldImportMappingAlignment;
 extern NSString *SPImportClipboardTempFileNamePrefix;
+extern NSString *SPSQLExportUseCompression;
 
 // Misc
 extern NSString *SPContentFilters;
diff --git a/Source/SPConstants.m b/Source/SPConstants.m
index f0d12e51..da9e6b10 100644
--- a/Source/SPConstants.m
+++ b/Source/SPConstants.m
@@ -137,7 +137,7 @@ NSString *SPFavoritesSortedInReverse             = @"FavoritesSortedInReverse";
 NSString *SPPrintWarningRowLimit                 = @"PrintWarningRowLimit";
 NSString *SPDisplayServerVersionInWindowTitle    = @"DisplayServerVersionInWindowTitle";
 
-// Import
+// Import and export
 NSString *SPCSVImportFieldEnclosedBy             = @"CSVImportFieldEnclosedBy";
 NSString *SPCSVImportFieldEscapeCharacter        = @"CSVImportFieldEscapeCharacter";
 NSString *SPCSVImportFieldTerminator             = @"CSVImportFieldTerminator";
@@ -145,6 +145,7 @@ NSString *SPCSVImportFirstLineIsHeader           = @"CSVImportFirstLineIsHeader"
 NSString *SPCSVImportLineTerminator              = @"CSVImportLineTerminator";
 NSString *SPCSVFieldImportMappingAlignment       = @"CSVFieldImportMappingAlignment";
 NSString *SPImportClipboardTempFileNamePrefix    = @"/tmp/_SP_ClipBoard_Import_File_";
+NSString *SPSQLExportUseCompression              = @"SQLExportUseCompression";
 
 // Misc 
 NSString *SPContentFilters                       = @"ContentFilters";
diff --git a/Source/SPFileHandle.h b/Source/SPFileHandle.h
new file mode 100644
index 00000000..f614d403
--- /dev/null
+++ b/Source/SPFileHandle.h
@@ -0,0 +1,78 @@
+//
+//  SPFileHandle.h
+//  sequel-pro
+//
+//  Created by Rowan Beentje on 05/04/2010.
+//  Copyright 2010 Arboreal. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+@interface SPFileHandle : NSObject {
+	void *wrappedFile;
+	char *wrappedFilePath;
+
+	NSMutableData *buffer;
+	NSUInteger bufferDataLength;
+	NSUInteger bufferPosition;
+	BOOL endOfFile;
+	pthread_mutex_t bufferLock;
+	NSThread *processingThread;
+
+	int fileMode;
+	BOOL dataWritten;
+	BOOL fileIsClosed;
+	BOOL useGzip;
+}
+
+
+#pragma mark -
+#pragma mark Class methods
+
++ (id) fileHandleForReadingAtPath:(NSString *)path;
++ (id) fileHandleForWritingAtPath:(NSString *)path;
++ (id) fileHandleForPath:(NSString *)path mode:(int)mode;
+
+#pragma mark -
+#pragma mark Initialisation
+
+// Returns a file handle initialised with a file
+- (id) initWithFile:(void *)theFile fromPath:(const char *)path mode:(int)mode;
+
+
+#pragma mark -
+#pragma mark Data reading
+
+// Reads data up to a specified number of bytes from the file
+- (NSMutableData *) readDataOfLength:(NSUInteger)length;
+
+// Returns the data to the end of the file
+- (NSMutableData *) readDataToEndOfFile;
+
+// Returns the on-disk (raw) length of data read so far - can be used in progress bars
+- (NSUInteger) realDataReadLength;
+
+#pragma mark -
+#pragma mark Data writing
+
+// Set whether data should be written as gzipped data (defaults to NO on a fresh object)
+- (void) setShouldWriteWithGzipCompression:(BOOL)useGzip;
+
+// Write the provided data to the file
+- (void) writeData:(NSData *)data;
+
+// Ensures any buffers are written to disk
+- (void) synchronizeFile;
+
+// Prevents further access to the file
+- (void) closeFile;
+
+
+#pragma mark -
+#pragma mark File information
+
+// Returns whether gzip compression is enabled on the file
+- (BOOL) isCompressed;
+
+
+@end
diff --git a/Source/SPFileHandle.m b/Source/SPFileHandle.m
new file mode 100644
index 00000000..4b28d4d6
--- /dev/null
+++ b/Source/SPFileHandle.m
@@ -0,0 +1,287 @@
+//
+//  SPFileHandle.m
+//  sequel-pro
+//
+//  Created by Rowan Beentje on 05/04/2010.
+//  Copyright 2010 Arboreal. All rights reserved.
+//
+
+#import "SPFileHandle.h"
+#import "zlib.1.2.4.h"
+
+// Define the size of the background read/write buffer.  This affects speed and memory usage.
+#define SPFH_BUFFER_SIZE 1048576
+
+@interface SPFileHandle (PrivateAPI)
+- (void) _writeBufferToData;
+@end
+
+
+@implementation SPFileHandle
+
+#pragma mark -
+#pragma mark Setup and teardown
+
+/**
+ * Initialises and returns a SPFileHandle with a specified file (FILE or gzFile).
+ * "mode" indicates the file interaction mode - currently only read-only
+ * or write-only are supported.
+ * On reading, theFile should always be a gzFile; on writing, theFile is a FILE
+ * when compression is disabled, or a gzFile when enbled.
+ */
+- (id) initWithFile:(void *)theFile fromPath:(const char *)path mode:(int)mode
+{
+	if (self = [super init]) {
+		fileIsClosed = NO;
+
+		wrappedFile = theFile;
+		wrappedFilePath = malloc(strlen(path) + 1);
+		strcpy(wrappedFilePath, path);
+
+		// Check and set the mode
+		fileMode = mode;
+		if (fileMode != O_RDONLY && fileMode != O_WRONLY) {
+			[NSException raise:NSInvalidArgumentException format:@"SPFileHandle only supports read-only and write-only file modes"];
+		}
+
+		// Instantiate the buffer
+		pthread_mutex_init(&bufferLock, NULL);
+		buffer = [[NSMutableData alloc] init];
+		bufferDataLength = 0;
+		bufferPosition = 0;
+		endOfFile = NO;
+
+		// If in read mode, set up the buffer
+		if (fileMode == O_RDONLY) {
+			gzbuffer(wrappedFile, 131072);
+			useGzip = !gzdirect(wrappedFile);
+			processingThread = nil;
+
+		// In write mode, set up a thread to handle writing in the background
+		} else if (fileMode == O_WRONLY) {
+			useGzip = NO;
+			processingThread = [[NSThread alloc] initWithTarget:self selector:@selector(_writeBufferToData) object:nil];
+			[processingThread start];
+		}
+	}
+
+	return self;
+}
+
+- (void) dealloc
+{
+	[self closeFile];
+	if (processingThread) [processingThread release];
+	free(wrappedFilePath);
+	[buffer release];
+	pthread_mutex_destroy(&bufferLock);
+	[super dealloc];
+}
+
+#pragma mark -
+#pragma mark Class methods
+
+/**
+ * Retrieve and return a SPFileHandle for reading a file at the supplied
+ * path.  Returns nil if the file could not be found or opened.
+ */
++ (id) fileHandleForReadingAtPath:(NSString *)path
+{
+	return [self fileHandleForPath:path mode:O_RDONLY];
+}
+
+/**
+ * Retrieve and return a SPFileHandle for writing a file at the supplied
+ * path.  Returns nil if the file could not be found or opened.
+ */
++ (id) fileHandleForWritingAtPath:(NSString *)path
+{
+	return [self fileHandleForPath:path mode:O_WRONLY];
+}
+
+/**
+ * Retrieve and return a SPFileHandle for a file at the specified path,
+ * using the supplied file status flag.  Returns nil if the file could
+ * not be found or opened.
+ */
++ (id) fileHandleForPath:(NSString *)path mode:(int)mode
+{
+
+	// Retrieves the path in a filesystem-appropriate format and encoding
+	const char *pathRepresentation = [path fileSystemRepresentation];
+	if (!pathRepresentation) return nil;
+
+	// Open the file to get a file descriptor, returning on failure
+	FILE *theFile;
+	const char *theMode;
+	if (mode == O_WRONLY) {
+		theMode = "wb";
+		theFile = fopen(pathRepresentation, theMode);
+	} else {
+		theMode = "rb";
+		theFile = gzopen(pathRepresentation, theMode);
+	}
+	if (theFile == NULL) return nil;
+
+	// Return an autoreleased file handle
+	return [[[self alloc] initWithFile:theFile fromPath:pathRepresentation mode:mode] autorelease];
+}
+
+
+#pragma mark -
+#pragma mark Data reading
+
+// Reads data up to a specified number of bytes from the file
+- (NSMutableData *) readDataOfLength:(NSUInteger)length
+{
+	void *theData = malloc(length);
+	long theDataLength = gzread(wrappedFile, theData, length);
+	return [NSMutableData dataWithBytesNoCopy:theData length:theDataLength freeWhenDone:YES];
+}
+
+// Returns the data to the end of the file
+- (NSMutableData *) readDataToEndOfFile
+{
+	return [self readDataOfLength:NSUIntegerMax];
+}
+
+// Returns the on-disk (raw) length of data read so far - can be used in progress bars
+- (NSUInteger) realDataReadLength
+{
+	if (fileMode == O_WRONLY) return 0;
+	return gzoffset(wrappedFile);
+}
+
+#pragma mark -
+#pragma mark Data writing
+
+/**
+ * Set whether data should be written as gzipped data, defaulting
+ * to NO on a fresh object. If this is called after data has been
+ * written, an exception is thrown.
+ */
+- (void) setShouldWriteWithGzipCompression:(BOOL)shouldUseGzip
+{
+	if (shouldUseGzip == useGzip) return;
+
+	if (dataWritten) [NSException raise:NSInternalInconsistencyException format:@"Cannot change compression settings when data has already been written"];
+
+	if (shouldUseGzip) {
+		fclose(wrappedFile);
+		wrappedFile = gzopen(wrappedFilePath, "wb");
+		gzbuffer(wrappedFile, 131072);
+	} else {
+		gzclose(wrappedFile);
+		wrappedFile = fopen(wrappedFilePath, "wb");
+	}
+	useGzip = shouldUseGzip;
+}
+
+
+// Write the provided data to the file
+- (void) writeData:(NSData *)data
+{
+
+	// Throw an exception if the file is closed
+	if (fileIsClosed) [NSException raise:NSInternalInconsistencyException format:@"Cannot write to a file handle after it has been closed"];
+
+	// Add the data to the buffer
+	pthread_mutex_lock(&bufferLock);
+	[buffer appendData:data];
+	bufferDataLength += [data length];
+
+	// If the buffer is large, wait for some to be written out
+	while (bufferDataLength > SPFH_BUFFER_SIZE) {
+		pthread_mutex_unlock(&bufferLock);
+		usleep(100);
+		pthread_mutex_lock(&bufferLock);
+	}
+	pthread_mutex_unlock(&bufferLock);
+}
+
+// Ensures any buffers are written to disk
+- (void) synchronizeFile
+{
+	pthread_mutex_lock(&bufferLock);
+	while (bufferDataLength) {
+		pthread_mutex_unlock(&bufferLock);
+		usleep(100);
+		pthread_mutex_lock(&bufferLock);
+	}
+	pthread_mutex_unlock(&bufferLock);
+}
+
+// Prevent further access to the file
+- (void)closeFile
+{
+	if (!fileIsClosed) {
+		[self synchronizeFile];
+		if (useGzip || fileMode == O_RDONLY) {
+			gzclose(wrappedFile);
+		} else {
+			fclose(wrappedFile);
+		}
+		if (processingThread) {
+			if ([processingThread isExecuting]) {
+				[processingThread cancel];
+				while ([processingThread isExecuting]) usleep(100);
+			}
+		}
+		fileIsClosed = YES;
+	}
+}
+
+
+#pragma mark -
+#pragma mark File information
+
+/**
+ * Returns whether gzip compression is enabled on the file.
+ */
+- (BOOL) isCompressed
+{
+	return useGzip;
+}
+
+@end
+
+@implementation SPFileHandle (PrivateAPI)
+
+/**
+ * A method to be called on a background thread, allowing write data to build
+ * up in a buffer and write to disk in chunks as the buffer fills.  This allows
+ * background compression of the data when using Gzip compression.
+ */
+- (void) _writeBufferToData
+{
+	NSAutoreleasePool *writePool = [[NSAutoreleasePool alloc] init];
+
+	// Process the buffer in a loop into the file, until cancelled
+	while (![processingThread isCancelled]) {
+
+		// Check whether any data in the buffer needs to be written out - using thread locks for safety
+		pthread_mutex_lock(&bufferLock);
+		if (!bufferDataLength) {
+			pthread_mutex_unlock(&bufferLock);
+			usleep(1000);
+			continue;
+		}
+
+		// Write out the data
+		long bufferLengthWrittenOut;
+		if (useGzip) {
+			bufferLengthWrittenOut = gzwrite(wrappedFile, [buffer bytes], bufferDataLength);
+		} else {
+			bufferLengthWrittenOut = fwrite([buffer bytes], 1, bufferDataLength, wrappedFile);
+		}
+
+		// Update the buffer
+		CFDataDeleteBytes((CFMutableDataRef)buffer, CFRangeMake(0, bufferLengthWrittenOut));
+		bufferDataLength = 0;
+		pthread_mutex_unlock(&bufferLock);
+	}
+
+	[writePool drain];
+}
+
+@end
diff --git a/Source/TableDocument.m b/Source/TableDocument.m
index 990f26a2..de23ba80 100644
--- a/Source/TableDocument.m
+++ b/Source/TableDocument.m
@@ -748,7 +748,6 @@
 				break;
 		}
 	}
-
 }
 
 /**
diff --git a/Source/TableDump.h b/Source/TableDump.h
index af621f68..e506a6d2 100644
--- a/Source/TableDump.h
+++ b/Source/TableDump.h
@@ -27,7 +27,7 @@
 #import <Cocoa/Cocoa.h>
 #import <MCPKit/MCPKit.h>
 
-@class SPFieldMapperController;
+@class SPFieldMapperController, SPFileHandle;
 
 @interface TableDump : NSObject 
 {
@@ -83,6 +83,7 @@
 	IBOutlet id addTableContentSwitch;
 	IBOutlet id addErrorsSwitch;
 	IBOutlet id sqlFullStreamingSwitch;
+	IBOutlet id sqlCompressionSwitch;
 	IBOutlet id csvFullStreamingSwitch;
 	IBOutlet id multiCSVFullStreamingSwitch;
 	IBOutlet id multiXMLFullStreamingSwitch;
@@ -121,6 +122,8 @@
 	NSUInteger exportMode;
 	NSUserDefaults *prefs;
 	BOOL progressCancelled;
+
+	NSSavePanel *currentExportPanel;
 }
 
 // IBAction methods
@@ -148,21 +151,21 @@
 - (NSString *) mappedUpdateSetStatementStringForRowArray:(NSArray *)csvRowArray;
 
 // Export methods
-- (BOOL)dumpSelectedTablesAsSqlToFileHandle:(NSFileHandle *)fileHandle;
-- (BOOL)dumpSchemaAsDotToFileHandle:(NSFileHandle *)fileHandle;
+- (BOOL)dumpSelectedTablesAsSqlToFileHandle:(SPFileHandle *)fileHandle;
+- (BOOL)dumpSchemaAsDotToFileHandle:(SPFileHandle *)fileHandle;
 - (BOOL)writeCsvForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult
-	toFileHandle:(NSFileHandle *)fileHandle
+	toFileHandle:(SPFileHandle *)fileHandle
 	outputFieldNames:(BOOL)firstLine terminatedBy:(NSString *)terminated
 	enclosedBy:(NSString *)enclosed escapedBy:(NSString *)escaped
 	lineEnds:(NSString *)lineEnds withNumericColumns:(NSArray *)tableColumnNumericStatus totalRows:(NSInteger)totalRows silently:(BOOL)silently;
 - (BOOL)writeXmlForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult
-	toFileHandle:(NSFileHandle *)fileHandle
+	toFileHandle:(SPFileHandle *)fileHandle
 	tableName:(NSString *)table withHeader:(BOOL)header totalRows:(NSInteger)totalRows silently:(BOOL)silently;
 - (NSString *)htmlEscapeString:(NSString *)string;
 - (NSString *)createViewPlaceholderSyntaxForView:(NSString *)viewName;
 
-- (BOOL)exportTables:(NSArray *)selectedTables toFileHandle:(NSFileHandle *)fileHandle usingFormat:(NSString *)type usingMulti:(BOOL)multi;
-- (BOOL)exportSelectedTablesToFileHandle:(NSFileHandle *)fileHandle usingFormat:(NSString *)type;
+- (BOOL)exportTables:(NSArray *)selectedTables toFileHandle:(SPFileHandle *)fileHandle usingFormat:(NSString *)type usingMulti:(BOOL)multi;
+- (BOOL)exportSelectedTablesToFileHandle:(SPFileHandle *)fileHandle usingFormat:(NSString *)type;
 
 // New Export methods
 - (IBAction)switchTab:(id)sender;
@@ -174,5 +177,6 @@
 
 // Import/export delegate notifications
 - (void)panelSelectionDidChange:(id)sender;
+- (IBAction)updateExportCompressionSetting:(id)sender;
 
 @end
diff --git a/Source/TableDump.m b/Source/TableDump.m
index 983d7b6d..8d56a1d7 100644
--- a/Source/TableDump.m
+++ b/Source/TableDump.m
@@ -41,6 +41,7 @@
 #import "SPFieldMapperController.h"
 #import "SPMainThreadTrampoline.h"
 #import "SPNotLoaded.h"
+#import "SPFileHandle.h"
 
 @implementation TableDump
 
@@ -156,9 +157,9 @@
 {
 	NSString *file;
 	NSString *contextInfo;
-	NSSavePanel *savePanel = [NSSavePanel savePanel];
-	[savePanel setAllowsOtherFileTypes:YES];
-	[savePanel setExtensionHidden:NO];
+	currentExportPanel = [NSSavePanel savePanel];
+	[currentExportPanel setAllowsOtherFileTypes:YES];
+	[currentExportPanel setExtensionHidden:NO];
 	NSString *currentDate = [[NSDate date] descriptionWithCalendarFormat:@"%Y-%m-%d" timeZone:nil locale:nil];
 	
 	switch ( tag ) {
@@ -166,9 +167,14 @@
 			// export dump
 			exportMode = SPExportingSQL;
 			[self reloadTables:self];
-			file = [NSString stringWithFormat:@"%@_%@.sql", [tableDocumentInstance database], currentDate];
-			[savePanel setRequiredFileType:@"sql"];
-			[savePanel setAccessoryView:exportDumpView];
+			[sqlCompressionSwitch setState:[prefs boolForKey:SPSQLExportUseCompression]?NSOnState:NSOffState];
+			if ([prefs boolForKey:SPSQLExportUseCompression]) {
+				[currentExportPanel setRequiredFileType:@"gz"];
+			} else {
+				[currentExportPanel setRequiredFileType:@"sql"];
+			}
+			file = [NSString stringWithFormat:@"%@_%@.%@", [tableDocumentInstance database], currentDate, [currentExportPanel requiredFileType]];
+			[currentExportPanel setAccessoryView:exportDumpView];
 			contextInfo = @"exportDump";
 			break;
 			
@@ -176,7 +182,7 @@
 		case 6:
 			exportMode = SPExportingCSV;
 			file = [NSString stringWithFormat:@"%@.csv", [tableDocumentInstance table]];
-			[savePanel setAccessoryView:exportCSVView];
+			[currentExportPanel setAccessoryView:exportCSVView];
 			[csvFullStreamingSwitch setEnabled:YES];
 			contextInfo = @"exportTableContentAsCSV";
 			break;
@@ -192,7 +198,7 @@
 		case 8:
 			exportMode = SPExportingCSV;
 			file = [NSString stringWithFormat:@"%@ view.csv", [tableDocumentInstance table]];
-			[savePanel setAccessoryView:exportCSVView];
+			[currentExportPanel setAccessoryView:exportCSVView];
 			[csvFullStreamingSwitch setEnabled:NO];
 			contextInfo = @"exportBrowseViewAsCSV";
 			break;
@@ -208,7 +214,7 @@
 		case 10:
 			exportMode = SPExportingCSV;
 			file = @"customresult.csv";
-			[savePanel setAccessoryView:exportCSVView];
+			[currentExportPanel setAccessoryView:exportCSVView];
 			[csvFullStreamingSwitch setEnabled:NO];
 			contextInfo = @"exportCustomResultAsCSV";
 			break;
@@ -225,7 +231,7 @@
 			exportMode = SPExportingCSV;
 			[self reloadTables:self];
 			file = [NSString stringWithFormat:@"%@.csv", [tableDocumentInstance database]];
-			[savePanel setAccessoryView:exportMultipleCSVView];
+			[currentExportPanel setAccessoryView:exportMultipleCSVView];
 			contextInfo = @"exportMultipleTablesAsCSV";
 			break;
 			
@@ -234,7 +240,7 @@
 			exportMode = SPExportingXML;
 			[self reloadTables:self];
 			file = [NSString stringWithFormat:@"%@.xml", [tableDocumentInstance database]];
-			[savePanel setAccessoryView:exportMultipleXMLView];
+			[currentExportPanel setAccessoryView:exportMultipleXMLView];
 			contextInfo = @"exportMultipleTablesAsXML";
 			break;
 			
@@ -243,7 +249,7 @@
 			exportMode = SPExportingDOT;
 			[self reloadTables:self];
 			file = [NSString stringWithString:[tableDocumentInstance database]];
-			[savePanel setRequiredFileType:@"dot"];
+			[currentExportPanel setRequiredFileType:@"dot"];
 			contextInfo = @"exportDot";
 			break;
 			
@@ -253,12 +259,12 @@
 			break;
 	}
 
-	[savePanel setDelegate:self];
+	[currentExportPanel setDelegate:self];
 
 	// Open the savePanel
-	[savePanel beginSheetForDirectory:[prefs objectForKey:@"savePath"]
-								 file:file modalForWindow:tableWindow modalDelegate:self
-					   didEndSelector:@selector(savePanelDidEnd:returnCode:contextInfo:) contextInfo:contextInfo];
+	[currentExportPanel beginSheetForDirectory:[prefs objectForKey:@"savePath"]
+										  file:file modalForWindow:tableWindow modalDelegate:self
+								didEndSelector:@selector(savePanelDidEnd:returnCode:contextInfo:) contextInfo:contextInfo];
 }
 
 /**
@@ -293,7 +299,7 @@
 	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 	NSString *exportActionName = [exportAction objectForKey:@"action"];
 	NSString *exportFile = [exportAction objectForKey:@"filename"];
-	NSFileHandle *fileHandle = nil;
+	SPFileHandle *fileHandle = nil;
 	BOOL success;	
 
 	// Start the notification timer to allow notifications to be shown even if frontmost for long queries
@@ -305,17 +311,14 @@
 	// Error if the file already exists and is not writable, and get a fileHandle to it.
 	if ( [[NSFileManager defaultManager] fileExistsAtPath:exportFile] ) {
 		if ( ![[NSFileManager defaultManager] isWritableFileAtPath:exportFile]
-			|| !(fileHandle = [NSFileHandle fileHandleForWritingAtPath:exportFile]) ) {
+			|| !(fileHandle = [SPFileHandle fileHandleForWritingAtPath:exportFile]) ) {
 			SPBeginAlertSheet(NSLocalizedString(@"Error", @"error"), NSLocalizedString(@"OK", @"OK button"), nil, nil, tableWindow, self, nil, nil, nil,
 							  NSLocalizedString(@"Couldn't replace the file. Be sure that you have the necessary privileges.", @"message of panel when file cannot be replaced"));
 			[pool release];
 			return;
 		}
 		
-		// Truncate the file to zero bytes
-		[fileHandle truncateFileAtOffset:0];
-		
-		// Otherwise attempt to create a file
+	// Otherwise attempt to create a file
 	} else {
 		if ( ![[NSFileManager defaultManager] createFileAtPath:exportFile contents:[NSData data] attributes:nil] ) {
 			SPBeginAlertSheet(NSLocalizedString(@"Error", @"error"), NSLocalizedString(@"OK", @"OK button"), nil, nil, tableWindow, self, nil, nil, nil,
@@ -325,7 +328,7 @@
 		}
 		
 		// Retrieve a filehandle for the file, attempting to delete it on failure.
-		fileHandle = [NSFileHandle fileHandleForWritingAtPath:exportFile];
+		fileHandle = [SPFileHandle fileHandleForWritingAtPath:exportFile];
 		if ( !fileHandle ) {
 			[[NSFileManager defaultManager] removeFileAtPath:exportFile handler:nil];
 			SPBeginAlertSheet(NSLocalizedString(@"Error", @"error"), NSLocalizedString(@"OK", @"OK button"), nil, nil, tableWindow, self, nil, nil, nil,
@@ -337,6 +340,7 @@
 	
 	// Export the tables selected in the MySQL export sheet to a file
 	if ( [exportActionName isEqualToString:@"exportDump"] ) {
+		[fileHandle setShouldWriteWithGzipCompression:([sqlCompressionSwitch state] == NSOnState)];
 		success = [self dumpSelectedTablesAsSqlToFileHandle:fileHandle];
 		
 		// Export the full resultset for the currently selected table to a file in CSV format
@@ -578,7 +582,7 @@
 - (void) importSQLFile:(NSString *)filename
 {
 	NSAutoreleasePool *importPool;
-	NSFileHandle *sqlFileHandle;
+	SPFileHandle *sqlFileHandle;
 	NSMutableData *sqlDataBuffer;
 	const unsigned char *sqlDataBufferBytes;
 	NSData *fileChunk;
@@ -593,6 +597,7 @@
 	NSInteger dataBufferLength = 0;
 	NSInteger dataBufferPosition = 0;
 	NSInteger dataBufferLastQueryEndPosition = 0;
+	BOOL fileIsCompressed;
 	BOOL importSQLAsUTF8 = YES;
 	BOOL allDataRead = NO;
 	NSStringEncoding sqlEncoding = NSUTF8StringEncoding;
@@ -602,7 +607,7 @@
 	[[SPGrowlController sharedGrowlController] setVisibilityForNotificationName:@"Import Finished"];
 
 	// Open a filehandle for the SQL file
-	sqlFileHandle = [NSFileHandle fileHandleForReadingAtPath:filename];
+	sqlFileHandle = [SPFileHandle fileHandleForReadingAtPath:filename];
 	if (!sqlFileHandle) {
 		SPBeginAlertSheet(NSLocalizedString(@"Import Error title", @"Import Error"),
 						  NSLocalizedString(@"OK button label", @"OK button"),
@@ -612,6 +617,7 @@
 			[[NSFileManager defaultManager] removeItemAtPath:filename error:nil];
 		return;
 	}
+	fileIsCompressed = [sqlFileHandle isCompressed];
 
 	// Grab the file length
 	fileTotalLength = [[[[NSFileManager defaultManager] attributesOfItemAtPath:filename error:NULL] objectForKey:NSFileSize] longLongValue];
@@ -757,9 +763,15 @@
 			queriesPerformed++;
 
 			// Update the progress bar
-			[singleProgressBar setDoubleValue:fileProcessedLength];
-			[singleProgressText setStringValue:[NSString stringWithFormat:NSLocalizedString(@"Imported %@ of %@", @"SQL import progress text"),
-				[NSString stringForByteSize:fileProcessedLength], [NSString stringForByteSize:fileTotalLength]]];
+			if (fileIsCompressed) {
+				[singleProgressBar setDoubleValue:[sqlFileHandle realDataReadLength]];
+				[singleProgressText setStringValue:[NSString stringWithFormat:NSLocalizedString(@"Imported %@ of SQL", @"SQL import progress text where total size is unknown"),
+					[NSString stringForByteSize:fileProcessedLength]]];			
+			} else {
+				[singleProgressBar setDoubleValue:fileProcessedLength];
+				[singleProgressText setStringValue:[NSString stringWithFormat:NSLocalizedString(@"Imported %@ of %@", @"SQL import progress text"),
+					[NSString stringForByteSize:fileProcessedLength], [NSString stringForByteSize:fileTotalLength]]];
+			}
 		}
 		
 		// If all the data has been read, break out of the processing loop
@@ -1594,7 +1606,7 @@
 /*
  Dump the selected tables to a file handle in SQL format.
  */
-- (BOOL)dumpSelectedTablesAsSqlToFileHandle:(NSFileHandle *)fileHandle
+- (BOOL)dumpSelectedTablesAsSqlToFileHandle:(SPFileHandle *)fileHandle
 {
 	NSInteger i,j,t,rowCount, colCount, lastProgressValue, queryLength;
 	NSInteger progressBarWidth;
@@ -2122,7 +2134,7 @@
  See here for language syntax: http://www.graphviz.org/doc/info/lang.html
  (Not the easiest to decode)
  */
-- (BOOL)dumpSchemaAsDotToFileHandle:(NSFileHandle *)fileHandle
+- (BOOL)dumpSchemaAsDotToFileHandle:(SPFileHandle *)fileHandle
 {
 	NSMutableString *metaString = [NSMutableString string];
 	NSInteger  progressBarWidth;
@@ -2267,7 +2279,7 @@
 
 /*
  * Takes an array, or a streaming result set, and writes the appropriate data
- * in CSV format to the supplied NSFileHandle.
+ * in CSV format to the supplied SPFileHandle.
  * The field terminators, quotes and escape characters should all be supplied
  * together with the line terminators; if an array of numeric column types is
  * supplied, processing of rows is significantly sped up as each field does not
@@ -2276,7 +2288,7 @@
  * for arrays, this must be accurate, but for streaming result sets it is only
  * used for drawing the progress bar.
  */
-- (BOOL)writeCsvForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult toFileHandle:(NSFileHandle *)fileHandle
+- (BOOL)writeCsvForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult toFileHandle:(SPFileHandle *)fileHandle
 		outputFieldNames:(BOOL)outputFieldNames
 		terminatedBy:(NSString *)fieldSeparatorString
 		enclosedBy:(NSString *)enclosingString
@@ -2521,14 +2533,14 @@
 
 /*
  * Takes an array, or streaming result reference, and writes it in XML
- * format to the supplied NSFileHandle.  For output, also takes a table
+ * format to the supplied SPFileHandle.  For output, also takes a table
  * name for tag construction, and a toggle to control whether the header
  * is output.
  * Also takes a totalRows parameter, which is used for drawing progress bars -
  * for arrays, this must be accurate, but for streaming result sets it is only
  * used for drawing the progress bar.
  */
-- (BOOL)writeXmlForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult toFileHandle:(NSFileHandle *)fileHandle tableName:(NSString *)table withHeader:(BOOL)header totalRows:(NSInteger)totalRows silently:(BOOL)silently
+- (BOOL)writeXmlForArray:(NSArray *)array orStreamingResult:(MCPStreamingResult *)streamingResult toFileHandle:(SPFileHandle *)fileHandle tableName:(NSString *)table withHeader:(BOOL)header totalRows:(NSInteger)totalRows silently:(BOOL)silently
 {
 	NSAutoreleasePool *xmlExportPool;
 	NSStringEncoding tableEncoding = [MCPConnection encodingForMySQLEncoding:[[tableDocumentInstance connectionEncoding] UTF8String]];
@@ -2693,7 +2705,7 @@
  Processes the selected tables within the multiple table export accessory view and passes them
  to be exported.
  */
-- (BOOL)exportSelectedTablesToFileHandle:(NSFileHandle *)fileHandle usingFormat:(NSString *)type
+- (BOOL)exportSelectedTablesToFileHandle:(SPFileHandle *)fileHandle usingFormat:(NSString *)type
 {
 	NSInteger i;
 	NSMutableArray *selectedTables = [NSMutableArray array];
@@ -2712,7 +2724,7 @@
  Walks through the selected tables and exports them to a file handle.  The export type must be
  "csv" for CSV format, and "xml" for XML format.
  */
-- (BOOL)exportTables:(NSArray *)selectedTables toFileHandle:(NSFileHandle *)fileHandle usingFormat:(NSString *)type usingMulti:(BOOL)multi
+- (BOOL)exportTables:(NSArray *)selectedTables toFileHandle:(SPFileHandle *)fileHandle usingFormat:(NSString *)type usingMulti:(BOOL)multi
 {
 	NSInteger i, j;
 	MCPResult *queryResult;
@@ -3088,6 +3100,14 @@
 	// If a single file is selected and the extension is recognised, change the format dropdown automatically
 	if ( [selectedFilenames count] != 1 ) return;
 	pathExtension = [[[selectedFilenames objectAtIndex:0] pathExtension] uppercaseString];
+
+	// If a file has extension ".gz", indicating gzip, fetch the next extension
+	if ([pathExtension isEqualToString:@"GZ"]) {
+		NSMutableString *pathString = [NSMutableString stringWithString:[selectedFilenames objectAtIndex:0]];
+		[pathString deleteCharactersInRange:NSMakeRange([pathString length]-3, 3)];
+		pathExtension = [[pathString pathExtension] uppercaseString];
+	}
+
 	if ([pathExtension isEqualToString:@"SQL"]) {
 		[importFormatPopup selectItemWithTitle:@"SQL"];
 		[self changeFormat:self];
@@ -3123,6 +3143,22 @@
 	}
 }
 
+/**
+ * When the compression setting on export is altered, update the filename
+ * and if appropriate the required extension.
+ */
+- (IBAction)updateExportCompressionSetting:(id)sender
+{
+	if (exportMode == SPExportingSQL) {
+		if ([sender state] == NSOnState) {
+			[currentExportPanel setAllowedFileTypes:[NSArray arrayWithObject:@"gz"]];
+		} else {
+			[currentExportPanel setAllowedFileTypes:[NSArray arrayWithObject:@"sql"]];
+		}
+		[prefs setBool:([sender state] == NSOnState) forKey:SPSQLExportUseCompression];
+	}
+}
+
 
 #pragma mark -
 #pragma mark Other