Downloadify Stopped Working in Google Chrome

Downloadify uses Flash's download functionality to enable client side download. It saves server side roundtrip.  There is also nice user extensions using Downloadify to export ExtJS grid on the client side. HTML 5 does have some limited support of client side download, but it suffers inconsistent support between browsers.

Ok, after all the justification for using it, Downloadify stopped working for Google Chrome recently. And here are the observations:

• Environment: Windows, Google Chrome is up-to-date
• Download still works in IE and Firefox;
• Download only works in Chrome if I'm testing using Intranet URL. But it does not work if the URL looks like Internet address (i.e. http://localhost works, but http://10.10.10.1 won't work);
• IE, Firefox are on Flash 11.3, and Chrome is running Flash 11.4

Solution:
Not really a solution. It's more like a workaround.

1. In Chrome address bar type: "about:plugins"
2. Click on "Details" button to expand into more detailed view
3. Find "Flash" section, and disable the Flash player 11.4 (something called "PepperFlash"\"pepflashplayer.dll")
4. Make sure there is another Flash player listed here, which should be Adobe's distribution

Root Cause?
I can only guess. Still not sure why and how to fix it properly.
Turns out Google Chrome has it's own Flash distribution. (Only guessing) It seems to be different from Adobe's official one, and somehow has higher default security settings.

itemId and id in ExtJS

The story: 
Here is a lesson for not reading document thoroughly. My very first ExtJS project goes smoothly until one day I created multiple tabs, and then closed some of them. All of sudden the layout completely messed up. In the debug console, there is null reference error. Call stack is deep in the ExtJS library.

Fast forward, after several hours of digging around, I found out I was using "id" config for several ExtJS controls. Then, close tab action will cause all the controls on the other tabs with the same "id" got deleted from DOM.

Solution:
Use "itemId" instead of "id" config for controls.

Comparison to ASP.NET
Came from ASP.NET world, I guess that is why I was using "id" config without any second thought. Below is a comparison of similar concepts in ASP.NET

ExtJS	ASP.NET	_
itemId	ID	(Recommended) HTML element's ID is automatically generated to ensure uniqueness, usually by concatenating ID of the container hierarchy. Programmer only need to ensure ID is unique within it's container.
id	ClientID	(Not recommended) Rendered HTML element will use this property as their ID. It's programmer's responsibility to ensure it is unique across the whole page (think when you starting to have multiple instances of the same control on a page).

(To check out more ExtJS related posts from me, click here: http://developertips.blogspot.com/search/label/ExtJS)

SQL Performance Sample Queries

	-----------------------------------------------------------------------
	-- Collection of queries that helps in performance tuning
	--grant permission to user
	GRANT VIEW SERVER STATE TO [user_name]
	------------ based on http://msdn.microsoft.com/en-us/magazine/cc135978.aspx
	---------- Uncover hidden data to optimize application performance -----------------------
	-- * Number of missing indexes
	SELECT
	DatabaseName = DB_NAME(database_id)
	,[Number Indexes Missing] = count(*)
	FROM sys.dm_db_missing_index_details
	GROUP BY DB_NAME(database_id)
	ORDER BY 2 DESC;
	-- * top costly missing indexes
	SELECT TOP 10
	[Total Cost] = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0)
	, avg_user_impact
	, TableName = statement
	, [EqualityUsage] = equality_columns
	, [InequalityUsage] = inequality_columns
	, [Include Cloumns] = included_columns
	, s.unique_compiles
	,s.last_user_seek
	,s.user_seeks
	FROM sys.dm_db_missing_index_groups g
	INNER JOIN sys.dm_db_missing_index_group_stats s
	ON s.group_handle = g.index_group_handle
	INNER JOIN sys.dm_db_missing_index_details d
	ON d.index_handle = g.index_handle
	ORDER BY [Total Cost] DESC;
	-- * top costly unused indexes (does not seem to work)
	-- Create required table structure only.
	-- Note: this SQL must be the same as in the Database loop given in the following step.
	SELECT TOP 1
	DatabaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	,user_updates
	,system_updates
	-- Useful fields below:
	--, *
	INTO #TempUnusedIndexes
	FROM sys.dm_db_index_usage_stats s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.database_id = DB_ID()
	AND OBJECTPROPERTY(s.[object_id], 'IsMsShipped') = 0
	AND user_seeks = 0
	AND user_scans = 0
	AND user_lookups = 0
	AND s.[object_id] = -999 -- Dummy value to get table structure.
	;
	-- Loop around all the databases on the server.
	EXEC sp_MSForEachDB 'USE [?];
	-- Table already exists.
	INSERT INTO #TempUnusedIndexes
	SELECT TOP 10
	DatabaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	,user_updates
	,system_updates
	FROM sys.dm_db_index_usage_stats s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.database_id = DB_ID()
	AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
	AND user_seeks = 0
	AND user_scans = 0
	AND user_lookups = 0
	AND i.name IS NOT NULL -- Ignore HEAP indexes.
	ORDER BY user_updates DESC
	;
	'
	-- Select records.
	SELECT TOP 10 * FROM #TempUnusedIndexes ORDER BY [user_updates] DESC
	-- Tidy up.
	DROP TABLE #TempUnusedIndexes
	-- * most costly used indexes
	-- Create required table structure only.
	-- Note: this SQL must be the same as in the Database loop given in the following step.
	SELECT TOP 1
	[Maintenance cost] = (user_updates + system_updates)
	,[Retrieval usage] = (user_seeks + user_scans + user_lookups)
	,DatabaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	INTO #TempMaintenanceCost
	FROM sys.dm_db_index_usage_stats s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.database_id = DB_ID()
	AND OBJECTPROPERTY(s.[object_id], 'IsMsShipped') = 0
	AND (user_updates + system_updates) > 0 -- Only report on active rows.
	AND s.[object_id] = -999 -- Dummy value to get table structure.
	;
	-- Loop around all the databases on the server.
	EXEC sp_MSForEachDB 'USE [?];
	-- Table already exists.
	INSERT INTO #TempMaintenanceCost
	SELECT TOP 10
	[Maintenance cost] = (user_updates + system_updates)
	,[Retrieval usage] = (user_seeks + user_scans + user_lookups)
	,DatabaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	FROM sys.dm_db_index_usage_stats s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.database_id = DB_ID()
	AND i.name IS NOT NULL -- Ignore HEAP indexes.
	AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
	AND (user_updates + system_updates) > 0 -- Only report on active rows.
	ORDER BY [Maintenance cost] DESC
	;
	'
	-- Select records.
	SELECT TOP 10 * FROM #TempMaintenanceCost
	ORDER BY [Maintenance cost] DESC
	-- Tidy up.
	DROP TABLE #TempMaintenanceCost
	-- * most fragmented indexes
	-- Create required table structure only.
	-- Note: this SQL must be the same as in the Database loop given in the -- following step.
	SELECT TOP 1
	DatbaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	,[Fragmentation %] = ROUND(avg_fragmentation_in_percent,2)
	INTO #TempFragmentation
	FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.[object_id] = -999 -- Dummy value just to get table structure.
	;
	-- Loop around all the databases on the server.
	EXEC sp_MSForEachDB 'USE [?];
	-- Table already exists.
	INSERT INTO #TempFragmentation
	SELECT TOP 10
	DatbaseName = DB_NAME()
	,TableName = OBJECT_NAME(s.[object_id])
	,IndexName = i.name
	,[Fragmentation %] = ROUND(avg_fragmentation_in_percent,2)
	FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s
	INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]
	AND s.index_id = i.index_id
	WHERE s.database_id = DB_ID()
	AND i.name IS NOT NULL -- Ignore HEAP indexes.
	AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0
	ORDER BY [Fragmentation %] DESC
	;
	'
	-- Select records.
	SELECT TOP 10 * FROM #TempFragmentation ORDER BY [Fragmentation %] DESC
	-- Tidy up.
	DROP TABLE #TempFragmentation
	-- * Find top server waits (CLR_AUTO_EVENT, CHECKPOINT_QUEUE, PAGEIOLATCH_SH, ...)
	SELECT TOP 10
	[Wait type] = wait_type,
	[Wait time (s)] = wait_time_ms / 1000,
	[% waiting] = CONVERT(DECIMAL(12,2), wait_time_ms * 100.0
	/ SUM(wait_time_ms) OVER())
	FROM sys.dm_os_wait_stats
	WHERE wait_type NOT LIKE '%SLEEP%'
	ORDER BY wait_time_ms DESC;
	-- * Find top queries by average time blocked
	SELECT TOP 100
	[Average Time Blocked (s)] = (total_elapsed_time - total_worker_time) / (qs.execution_count * 1000000)
	,[Total Time Blocked (s)] = total_elapsed_time - total_worker_time / 1000000
	,[Execution count] = qs.execution_count
	-- quote text into CSV friendly format
	,[Individual Query] = '"' + SUBSTRING (qt.text,qs.statement_start_offset/2 + 1,
	(CASE WHEN qs.statement_end_offset = -1
	THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
	ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
	+ '"'
	-- quote text into CSV friendly format
	,[Parent Query] = '"' + qt.text + '"'
	,DatabaseName = DB_NAME(qt.dbid)
	FROM sys.dm_exec_query_stats qs
	CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
	ORDER BY [Average Time Blocked (s)] DESC;
	-- * Find most executed queries by number of executions (repetitions)
	SELECT TOP 10
	[Execution count] = execution_count
	,[Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2 + 1,
	(CASE WHEN qs.statement_end_offset = -1
	THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
	ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
	,[Parent Query] = qt.text
	,DatabaseName = DB_NAME(qt.dbid)
	FROM sys.dm_exec_query_stats qs
	CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
	ORDER BY [Execution count] DESC;
	-- * Find top queries by average CPU
	SELECT TOP 100
	[Average CPU (s)] = total_worker_time / (qs.execution_count * 1000000) --Unit: sec
	,[Total CPU (s)] = total_worker_time / 1000000
	,[Execution count] = qs.execution_count
	,qs.last_execution_time
	-- quote text into CSV friendly format
	,[Individual Query] = '"' + SUBSTRING (qt.text,qs.statement_start_offset/2 + 1,
	(CASE WHEN qs.statement_end_offset = -1
	THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
	ELSE qs.statement_end_offset END -
	qs.statement_start_offset)/2) + '"'
	-- quote text into CSV friendly format
	,[Parent Query] = '"' + qt.text + '"'
	,DatabaseName = DB_NAME(qt.dbid)
	FROM sys.dm_exec_query_stats qs
	CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
	where last_execution_time > '2012-03-10 7:00AM'
	ORDER BY [Average CPU (s)] DESC;
	-- * Find top queries by total CPU
	SELECT TOP 100
	[Average CPU (s)] = total_worker_time / (qs.execution_count * 1000000)
	,[Total CPU (s)] = total_worker_time / 1000000
	,[Execution count] = qs.execution_count
	-- quote text into CSV friendly format
	,[Individual Query] = '"' + SUBSTRING (qt.text,qs.statement_start_offset/2 + 1,
	(CASE WHEN qs.statement_end_offset = -1
	THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
	ELSE qs.statement_end_offset END -
	qs.statement_start_offset)/2) + '"'
	-- quote text into CSV friendly format
	,[Parent Query] = '"' + qt.text + '"'
	,DatabaseName = DB_NAME(qt.dbid)
	FROM sys.dm_exec_query_stats qs
	CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qt
	ORDER BY [Total CPU (s)] DESC;
	-- * list of all current traces
	select * from sys.traces
	-- * list all categories, classes and columns available to SQL trace
	/*
	Script: CH10 Trace View.sql
	Author: James Rowland-Jones
	Title: Professional SQL Server 2008: Internals and Performance Tuning
	*/
	SELECT cat.name AS category_name
	,ev.name AS event_name
	,col.name AS column_name
	,col.is_filterable AS column_is_filterable
	,col.max_size AS column_max_size
	,col.[type_name] AS column_type_name
	,sub.subclass_name AS subclass_name
	,sub.subclass_value AS subclass_value
	FROM sys.trace_categories cat
	JOIN sys.trace_events ev
	ON cat.category_id = ev.category_id
	JOIN sys.trace_event_bindings bi
	ON bi.trace_event_id = ev.trace_event_id
	JOIN sys.trace_columns col
	ON bi.trace_column_id = col.trace_column_id
	LEFT JOIN sys.trace_subclass_values sub
	ON sub.trace_column_id = bi.trace_column_id
	AND sub.trace_event_id = bi.trace_event_id
	ORDER BY cat.name
	,ev.name
	,col.name
	,sub.subclass_value
	-- * List definition of defatul SQL trace
	/*
	Script: CH10 Trace Definition.sql
	Author: James Rowland-Jones
	Title: Professional SQL Server 2008: Internals and Performance Tuning
	*/
	DECLARE @vTraceID INT;
	SET @vTraceID = 1;
	WITH filter AS
	( SELECT columnid
	,CASE logical_operator
	WHEN 0 THEN 'AND'
	WHEN 1 THEN 'OR'
	ELSE 'err'
	END AS logical_operator
	,CASE comparison_operator
	WHEN 0 THEN ' = '
	WHEN 1 THEN ' <> '
	WHEN 2 THEN ' > '
	WHEN 3 THEN ' < '
	WHEN 4 THEN ' >= '
	WHEN 5 THEN ' <= '
	WHEN 6 THEN ' LIKE '
	WHEN 7 THEN ' NOT LIKE '
	END AS comparison_operator
	,value
	FROM ::fn_trace_getfilterinfo(@vTraceID)
	)
	SELECT cat.name AS CategoryName
	,evt.name AS EventName
	,col.name AS ColumnName
	,STUFF ( ( SELECT ' | ' + child_fil.logical_operator
	+ child_fil.comparison_operator
	+ CAST(child_fil.value AS VARCHAR(MAX)
	)
	FROM filter child_fil
	WHERE parent_fil.columnid = child_fil.columnid
	FOR XML PATH ('')
	),1,1,''
	) AS ColFilters
	FROM fn_trace_geteventinfo(@vTraceID) evi
	JOIN sys.trace_events evt
	ON evi.eventid = evt.trace_event_id
	JOIN sys.trace_categories cat
	ON evt.category_id = cat.category_id
	JOIN sys.trace_columns col
	ON evi.columnid = col.trace_column_id
	LEFT JOIN filter parent_fil
	ON col.trace_column_id = parent_fil.columnid
	GROUP BY cat.name
	,evt.name
	,col.name
	,parent_fil.columnid
	ORDER BY cat.name
	,evt.name
	,col.name

view raw SQL hosted with ❤ by GitHub

ASP.NET Exception: "Session state has created a session id, but cannot save it ..."

Symptom:

• Only happens for new session
• Exception Message:
  A first chance exception of type 'System.Web.HttpException' occurred in System.Web.dll Additional information: Session state has created a session id, but cannot save it because the response was already flushed by the application.

•  Stack Trace: 

[HttpException (0x80004005): Session state has created a session id, but cannot save it because the response was already flushed by the application.]   System.Web.SessionState.SessionIDManager.SaveSessionID(HttpContext context, String id, Boolean& redirected, Boolean& cookieAdded) +3691007   System.Web.SessionState.SessionStateModule.DelayedGetSessionId() +199   System.Web.SessionState.SessionStateModule.ReleaseStateGetSessionID() +25   System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) +874   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +270 

Cause:

• I was able to narrow down the cause of this problem to setting page's Buffer="false"
• Reasoning would be that without buffering, all content are pushed to client immediately, and somehow, ASP.NET decided to set cookie at a very late stage where it can no longer write to HTTP header to set SessionID cookie

Solution:
Set Buffer to true is not a solution for me, because I will need to flush content to deliver real-time progress information.
Based on some understanding, a solution quickly came up with some Google search. Simply add the following line to Global.asax.cs > Session_Start, the problem is resolved.
string sessionID = Session.SessionID;

Faster Flex Builder Compile Time

To increase Flex Builder compile time during development, the following tweak helped my Flex 3 builder to go from 30 seconds to just a few seconds for a medium sized project.
Open project property, under Flex Compiler -> Additional compiler arguments, add " -incremental -keep-generated-actionscript"

It definitely helps me go from compile once every hour, to every few minutes. Such that I can get immediate feedback through compiler errors or warnings.

file 'lib' not found

When installing Ruby on Rails using command: gem install rails
Got this error message: file 'lib' not found
Seems like it's fixed by running gem instal rdoc followed by gem install rails again.

Cross Site XMLHttpRequest

• IE8 and above:
  • use XDomainRequest instead
  • Can only cross from HTTP to HTTP or HTTPS to HTTPS (i.e. if web page is served from HTTP, then cannot cross-site access HTTPS. Or web page served over SSL cannot cross site access HTTP content. Will get "Access Denied" error.)
• Cross site request server must send this response header:  Access-Control-Allow-Orig *