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  • Why do I see a large performance hit with DRBD?

    - by BHS
    I see a much larger performance hit with DRBD than their user manual says I should get. I'm using DRBD 8.3.7 (Fedora 13 RPMs). I've setup a DRBD test and measured throughput of disk and network without DRBD: dd if=/dev/zero of=/data.tmp bs=512M count=1 oflag=direct 536870912 bytes (537 MB) copied, 4.62985 s, 116 MB/s / is a logical volume on the disk I'm testing with, mounted without DRBD iperf: [ 4] 0.0-10.0 sec 1.10 GBytes 941 Mbits/sec According to Throughput overhead expectations, the bottleneck would be whichever is slower, the network or the disk and DRBD should have an overhead of 3%. In my case network and I/O seem to be pretty evenly matched. It sounds like I should be able to get around 100 MB/s. So, with the raw drbd device, I get dd if=/dev/zero of=/dev/drbd2 bs=512M count=1 oflag=direct 536870912 bytes (537 MB) copied, 6.61362 s, 81.2 MB/s which is slower than I would expect. Then, once I format the device with ext4, I get dd if=/dev/zero of=/mnt/data.tmp bs=512M count=1 oflag=direct 536870912 bytes (537 MB) copied, 9.60918 s, 55.9 MB/s This doesn't seem right. There must be some other factor playing into this that I'm not aware of. global_common.conf global { usage-count yes; } common { protocol C; } syncer { al-extents 1801; rate 33M; } data_mirror.res resource data_mirror { device /dev/drbd1; disk /dev/sdb1; meta-disk internal; on cluster1 { address 192.168.33.10:7789; } on cluster2 { address 192.168.33.12:7789; } } For the hardware I have two identical machines: 6 GB RAM Quad core AMD Phenom 3.2Ghz Motherboard SATA controller 7200 RPM 64MB cache 1TB WD drive The network is 1Gb connected via a switch. I know that a direct connection is recommended, but could it make this much of a difference? Edited I just tried monitoring the bandwidth used to try to see what's happening. I used ibmonitor and measured average bandwidth while I ran the dd test 10 times. I got: avg ~450Mbits writing to ext4 avg ~800Mbits writing to raw device It looks like with ext4, drbd is using about half the bandwidth it uses with the raw device so there's a bottleneck that is not the network.

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  • Detecting upload success/failure in a scripted command-line SFTP session?

    - by Will Martin
    I am writing a BASH shell script to upload all the files in a directory to a remote server and then delete them. It'll run every few hours via a CRON job. My complete script is below. The basic problem is that the part that's supposed to figure out whether the file uploaded successfully or not doesn't work. The SFTP command's exit status is always "0" regardless of whether the upload actually succeeded or not. How can I figure out whether a file uploaded correctly or not so that I can know whether to delete it or let it be? #!/bin/bash # First, save the folder path containing the files. FILES=/home/bob/theses/* # Initialize a blank variable to hold messages. MESSAGES="" ERRORS="" # These are for notifications of file totals. COUNT=0 ERRORCOUNT=0 # Loop through the files. for f in $FILES do # Get the base filename BASE=`basename $f` # Build the SFTP command. Note space in folder name. CMD='cd "Destination Folder"\n' CMD="${CMD}put ${f}\nquit\n" # Execute it. echo -e $CMD | sftp -oIdentityFile /home/bob/.ssh/id_rsa [email protected] # On success, make a note, then delete the local copy of the file. if [ $? == "0" ]; then MESSAGES="${MESSAGES}\tNew file: ${BASE}\n" (( COUNT=$COUNT+1 )) # Next line commented out for ease of testing #rm $f fi # On failure, add an error message. if [ $? != "0" ]; then ERRORS="${ERRORS}\tFailed to upload file ${BASE}\n" (( ERRORCOUNT=$ERRORCOUNT+1 )) fi done SUBJECT="New Theses" BODY="There were ${COUNT} files and ${ERRORCOUNT} errors in the latest batch.\n\n" if [ "$MESSAGES" != "" ]; then BODY="${BODY}New files:\n\n${MESSAGES}\n\n" fi if [ "$ERRORS" != "" ]; then BODY="${BODY}Problem files:\n\n${ERRORS}" fi # Send a notification. echo -e $BODY | mail -s $SUBJECT [email protected] Due to some operational considerations that make my head hurt, I cannot use SCP. The remote server is using WinSSHD on windows, and does not have EXEC privileges, so any SCP commands fail with the message "Exec request failed on channel 0". The uploading therefore has to be done via the interactive SFTP command.

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  • Is it reasonable that a random disk seek & read costs ~16ms?

    - by fzhang
    I am frustrated about the latency of random reading from a non-ssd disk. Based on results from following test program, it speeds ~16 ms for a random read of just 512 bytes without help of os cache. I tried changing 512 to larger values, such as 25k, and the latency did not increase as much. I guess it is because the disk seek dominates the time. I understand that random reading is inherently slow, but just want to be sure that ~16ms is reasonable, even for non-ssd disk. #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> #include <sys/unistd.h> #include <fcntl.h> #include <limits.h> #include <stdio.h> #include <string.h> int main(int argc, char** argv) { int fd = open(argv[1], O_RDONLY); if (fd < 0) { fprintf(stderr, "Failed open %s\n", argv[1]); return -1; } const size_t count = 512; const off_t offset = 25990611 / 2; char buffer[count] = { '\0' }; struct timeval start_time; gettimeofday(&start_time, NULL); off_t ret = lseek(fd, offset, SEEK_SET); if (ret != offset) { perror("lseek error"); close(fd); return -1; } ret = read(fd, buffer, count); if (ret != count) { fprintf(stderr, "Failed reading all: %ld\n", ret); close(fd); return -1; } struct timeval end_time; gettimeofday(&end_time, NULL); printf("tv_sec: %ld, tv_usec: %ld\n", end_time.tv_sec - start_time.tv_sec, end_time.tv_usec - start_time.tv_usec); close(fd); return 0; }

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  • Why does my Windows 7 computer wake itself up from sleep mode?

    - by AbuHamzah
    I have XPS9100 DELL desktop computer awakes out of the sleep mode without me prompting it. I have 64 bit OS Before I go to sleep I put that in sleep mode but in the morning I see its awake and I try every setting possible but could not help I have tried this command and here is what I got and I am not sure what to do. C:\Users\NAME>powercfg -lastwake Wake History Count - 1 Wake History [0] Wake Source Count - 1 Wake Source [0] Type: Wake Timer Owner: [SERVICE] \Device\HarddiskVolume3\Windows\System32\svchost.exe (wuauserv)

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  • Why is domU faster than dom0 on IO?

    - by Paco
    I have installed debian 7 on a physical machine. This is the configuration of the machine: 3 hard drives using RAID 5 Strip element size: 1M Read policy: Adaptive read ahead Write policy: Write Through /boot 200 MB ext2 / 15 GB ext3 SWAP 10GB LVM rest (~500GB) emphasized text I installed postgresql, created a big database (over 1GB). I have an SQL request that takes a lot of time to run (a SELECT statement, so it only reads data from the database). This request takes approximately 5.5 seconds to run. Then, I installed XEN, created a domU, with another debian distro. On this OS, I also installed postgresql, with the same database. The same SQL request takes only 2.5 seconds to run. I checked the kernel on both dom0 and domU. uname-a returns "Linux debian 3.2.0-4-amd64 #1 SMP Debian 3.2.41-2+deb7u2 x86_64 GNU/Linux" on both systems. I checked the kernel parameters, which are approximately the same. For those that are relevant, I changed their values to make them match on both systems using sysctl. I saw no changes (the requests still take the same amount of time). After this, I checked the file systems. I used ext3 on domU. Still no changes. I installed hdparm, and ran hdparm -Tt on both systems, on all my partitions on both systems, and I get similar results. Now, I am stuck, I don't know what is different, and what could be the cause of such a big difference. Additional Info: Debian runs on a Dell server PowerEdge 2950 postgresql: 9.1.9 (both dom0 and domU) xen-linux-system: 3.2.0 xen-hypervisor: 4.1 Thanks EDIT: As Krzysztof Ksiezyk suggested, it might be due to some file caching system. I ran the dd command to test both the read and write speed. Here is domU: root@test1:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 18.8289 s, 107 MB/s root@test1:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 15.0549 s, 134 MB/s And here is dom0: root@debian:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 8.87281 s, 191 MB/s root@debian:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 0.501509 s, 3.4 GB/s What can be the cause of this caching system? And how can we "fix" it? Can we apply it to dom0? EDIT 2: I switched my virtual disk type. To do so I followed this article. I did a dd if=/dev/vg0/test1-disk of=/mnt/test1-disk.img bs=16M Then in /etc/xen/test1.cfg, I changed the disk parameter to use file: instead of phy: it should have removed the file caching, but I still get the same numbers (domU being much faster for Postgres)

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  • Sql Server huge tables with no rows

    - by Mike Gates
    I have a Sql Server database that has a few tables with zero row count but take up a combined 10 GB of space. I can see this by doing right-click/properties on the tables in question (data space is huge, between 1 and 6 GB, and row count is zero on these tables). I have no clue what could be causing this as I would assume zero rows would mean nearly zero space taken. Any ideas?

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  • Capturing and Transforming ASP.NET Output with Response.Filter

    - by Rick Strahl
    During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • Syntax error in aggregate argument: Expecting a single column argument with possible 'Child' qualifier.

    - by Rushabh
    DataTable distinctTable = dTable.DefaultView.ToTable(true,"ITEM_NO","ITEM_STOCK"); DataTable dtSummerized = new DataTable("SummerizedResult"); dtSummerized.Columns.Add("ITEM_NO",typeof(string)); dtSummerized.Columns.Add("ITEM_STOCK",typeof(double)); int count=0; foreach(DataRow dRow in distinctTable.Rows) { count++; //string itemNo = Convert.ToString(dRow[0]); double TotalItem = Convert.ToDouble(dRow[1]); string TotalStock = dTable.Compute("sum(" + TotalItem + ")", "ITEM_NO=" + dRow["ITEM_NO"].ToString()).ToString(); dtSummerized.Rows.Add(count,dRow["ITEM_NO"],TotalStock); } Error Message: Syntax error in aggregate argument: Expecting a single column argument with possible 'Child' qualifier. Do anyone can help me out? Thanks.

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  • jquery countdown/countUP with server side values

    - by basit.
    script: http://keith-wood.name/countdown.htm daily json response: items: { fajr: '5:23 am', sharooq: '7:23 am', dhur: '1:34 pm', asr: '4:66 pm': magrib: '6:23 pm', isha: '8:01 pm'} when site loads i make ajax request and get the above response times, these are events that happens daily for everyday, but different timing. i want to get that time and put a count down on how many minitues left or hours or seconds and show that and once the seconds are done, then show how many minitues ago that event took place, after 15 minitues later show new even count down. so following on how it will look on display dhur 2 hours left dhur 2 minutes left (if no longer hours left) dhur 55 seconds left (if no longer minutes left) dhur 5 seconds ago (if count down finished and then show how many seconds ago) dhur 9 minutes ago (if extended more then seconds, then show how many minutes ago) asr 1 hour left (after 15 minutes later time changes to new event) this is kind of very simple for pro in javascript and really complicated for me, so need your guys help, if the script im using not good and you prefer some other script for this kind of task, please share with me, it dont have to be jquery script, but helps if its jquery.

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  • WM_CONCAT use CASE

    - by Ruslan
    i have a select: select substr(acc,1,4),currency, amount, module, count(*), wm_concat(trn_ref_no) trn from all_entries where date = to_date ('01012010','DDMMYYYY') group by substr(acc,1,4),currency, amount, module in this case i have error: *ORA-06502: PL/SQL: : character string buffer too small ... "WMSYS.WM_CONCAT_IMPL"* if i change to: select substr(acc,1,4),currency, amount, module, count(), (case when count() < 10 then wm_concat(trn_ref_no) else null end) trn from fcc.acvw_all_ac_entries where trn_dt = to_date ('05052010','DDMMYYYY') group by substr(acc,1,4),currency, amount, module to avoid buffer limit error. But even in this case i have the same error. How can i avoid this error?

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  • MySql - Get row number on select

    - by George
    Can I run a select statement and get the row number if the items are sorted? I have a table like this: mysql> describe orders; +-------------+---------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+---------------------+------+-----+---------+----------------+ | orderID | bigint(20) unsigned | NO | PRI | NULL | auto_increment | | itemID | bigint(20) unsigned | NO | | NULL | | +-------------+---------------------+------+-----+---------+----------------+ I can then run this query to get the number of orders by ID: SELECT itemID, COUNT(*) as ordercount FROM orders GROUP BY itemID ORDER BY ordercount DESC; This gives me a count of each itemID in the table like this: +--------+------------+ | itemID | ordercount | +--------+------------+ | 388 | 3 | | 234 | 2 | | 3432 | 1 | | 693 | 1 | | 3459 | 1 | +--------+------------+ I want to get the row number as well, so I could tell that itemID 388 is the first row, 234 is second, etc (essentially the ranking of the orders, not just a raw count). I know I can do this in java when I get the result set back, but I was wondering if there was a way to handle it purely in SQL.

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  • Is there a way to get programmatic access to the columns of a ActiveReports detail section?

    - by Seth Spearman
    Hello, I have a report in Data Dynamics ActiveReports for .NET. In this report I am programmatically setting the ColumnCount property of the detail section to X. The detail section has one databound textbox. The ColumnDirection property of the detail section is set to AcrossDown and the and then the data binding mechanism automatically fills across with data after setting the DataSource and DataMember. Here is the code... Public Sub RunReport Dim count As Integer = 0 ' ... get count Detail1.ColumnCount = count Me.DataSource = ds Me.DataMember = ds.Tables(0).TableName End Sub That code works fine and the data is automatically filled across the report. Now I need to alter the report and circle or highlight one of the items that is auto-filled across columns in the report. I cannot find any way to programmatically access the auto-generated columns so I can turn on a border or draw a circle or something. Any ideas how I would do that? Seth

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  • passing json from servlet to dojo

    - by Moev4
    I am currently trying to pass a generated JSON string to dojo for parsing and am having some issues. The servlet simply writes it as a string as so: response.getWriter().append("{ \"data\": {"); response.getWriter().append("\"type\": \"facing\","); response.getWriter().append("\"score\": " + "\"" + score + "\","); response.getWriter().append("\"count\":" + "\"" + count + "\"" ); response.getWriter().append("}}"); which prints as: {"data":{"type":"facing","score":"10","count":"24"}} And the parsing on the dojo end looks as so: dojo.xhrPost({ url: url, handleAs: "json", load: function(data) { alert(data); /* Parse Not working */ alert(data.data[0].type); }, error: function(error) { alert("No dice") } }); The main issue is the data.data[0].type is returning nothing but when i print this out as text the json seems to be correctly formatted. Any help with this would be appreciated.

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  • Charater string buffer too small

    - by Ruslan
    I have select: select v.accs, v.currency,v.amount,v.drcr_ind, count(*) qua,wm_concat(ids) npx_IDS, wm_concat(px_dtct) npx_DTCT from table v group by accs, currency, amount, drcr_ind but i get error ORA-06502: PL/SQL: : character string buffer too small if i'll remove one string, because sometimes (when v.accs= 3570) count(*) = 215 but when i try to skip using wm_concat for v.accs= 3570 for example this way: select v.accs, v.currency,v.amount,v.drcr_ind, count(*) qua,wm_concat(ids) npx_IDS, (case when v.accs = 3570 then wm_concat(px_dtct) else 'too many' end) npx_DTCT from table v group by accs, currency, amount, drcr_ind i still have the same error message. But why? How can i fix it? Thanx

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  • Equality between two enumerables

    - by Berryl
    I have two enumerables with the exact same reference elements, and wondering why Equals wouldn't be true. As a side question, the code below to compare each element works, but there must be a more elegant way Cheers, Berryl var other = (ActivityService) obj; if (!AllAccounts.Count().Equals(other.AllAccounts.Count())) return false; for (int i = 0; i < AllAccounts.Count(); i++) { if (!AllAccounts.ElementAt(i).Equals(other.AllAccounts.ElementAt(i))) { return false; } } return true;

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  • Boost::Interprocess Container Container Resizing No Default Constructor

    - by CuppM
    Hi, After combing through the Boost::Interprocess documentation and Google searches, I think I've found the reason/workaround to my issue. Everything I've found, as I understand it, seems to be hinting at this, but doesn't come out and say "do this because...". But if anyone can verify this I would appreciate it. I'm writing a series of classes that represent a large lookup of information that is stored in memory for fast performance in a parallelized application. Because of the size of data and multiple processes that run at a time on one machine, we're using Boost::Interprocess for shared memory to have a single copy of the structures. I looked at the Boost::Interprocess documentation and examples, and they typedef classes for shared memory strings, string vectors, int vector vectors, etc. And when they "use" them in their examples, they just construct them passing the allocator and maybe insert one item that they've constructed elsewhere. Like on this page: http://www.boost.org/doc/libs/1_42_0/doc/html/interprocess/allocators_containers.html So following their examples, I created a header file with typedefs for shared memory classes: namespace shm { namespace bip = boost::interprocess; // General/Utility Types typedef bip::managed_shared_memory::segment_manager segment_manager_t; typedef bip::allocator<void, segment_manager_t> void_allocator; // Integer Types typedef bip::allocator<int, segment_manager_t> int_allocator; typedef bip::vector<int, int_allocator> int_vector; // String Types typedef bip::allocator<char, segment_manager_t> char_allocator; typedef bip::basic_string<char, std::char_traits<char>, char_allocator> string; typedef bip::allocator<string, segment_manager_t> string_allocator; typedef bip::vector<string, string_allocator> string_vector; typedef bip::allocator<string_vector, segment_manager_t> string_vector_allocator; typedef bip::vector<string_vector, string_vector_allocator> string_vector_vector; } Then for one of my lookup table classes, it's defined something like this: class Details { public: Details(const shm::void_allocator & alloc) : m_Ids(alloc), m_Labels(alloc), m_Values(alloc) { } ~Details() {} int Read(BinaryReader & br); private: shm::int_vector m_Ids; shm::string_vector m_Labels; shm::string_vector_vector m_Values; }; int Details::Read(BinaryReader & br) { int num = br.ReadInt(); m_Ids.resize(num); m_Labels.resize(num); m_Values.resize(num); for (int i = 0; i < num; i++) { m_Ids[i] = br.ReadInt(); m_Labels[i] = br.ReadString().c_str(); int count = br.ReadInt(); m_Value[i].resize(count); for (int j = 0; j < count; j++) { m_Value[i][j] = br.ReadString().c_str(); } } } But when I compile it, I get the error: 'boost::interprocess::allocator<T,SegmentManager>::allocator' : no appropriate default constructor available And it's due to the resize() calls on the vector objects. Because the allocator types do not have a empty constructor (they take a const segment_manager_t &) and it's trying to create a default object for each location. So in order for it to work, I have to get an allocator object and pass a default value object on resize. Like this: int Details::Read(BinaryReader & br) { shm::void_allocator alloc(m_Ids.get_allocator()); int num = br.ReadInt(); m_Ids.resize(num); m_Labels.resize(num, shm::string(alloc)); m_Values.resize(num, shm::string_vector(alloc)); for (int i = 0; i < num; i++) { m_Ids[i] = br.ReadInt(); m_Labels[i] = br.ReadString().c_str(); int count = br.ReadInt(); m_Value[i].resize(count, shm::string(alloc)); for (int j = 0; j < count; j++) { m_Value[i][j] = br.ReadString().c_str(); } } } Is this the best/correct way of doing it? Or am I missing something. Thanks!

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  • Accessing ruby counter cache

    - by Julian
    Hi all, I'm playing around with a fork of acts_as_taggable_on_steroids as a learning exercise. The version I'm looking at does some stuff I don't understand to calculate Tag counts. So I thought I'd do a version using PORC (Plain Old Rails Counters): class Tagging < ActiveRecord::Base #:nodoc: belongs_to :tag, :counter_cache => "tagging_counter_cache" ... I thought tagging_counter_cache was transparently accessed when I access tag.taggings.count but apparently not? Do I really have to access tag.tagging_counter_cache explicitly? >> tag.taggings.count SQL (0.7ms) SELECT count(*) AS count_all FROM `taggings` WHERE (`taggings`.tag_id = 16) Same for size. It's cool if that's the case but just wanted to check.

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  • Help to translate SQL query to Relational Algebra

    - by Mestika
    Hi everyone, I'm having some difficulties with translating some queries to Relational Algebra. I've a great book about Database Design and here is a chapter about Relational Algebra but I still seem to have some trouble creating the right one: Thoes queries I've most difficuelt with is these: SELECT COUNT( cs.student_id ) AS counter FROM course c, course_student cs WHERE c.id = cs.course_id AND c.course_name = 'Introduction to Database Design' SELECT COUNT( cs.student_id ) FROM Course c INNER JOIN course_student cs ON c.id = cs.course_id WHERE c.course_name = 'Introduction to Database Design' and SELECT COUNT( * ) FROM student JOIN grade ON student.f_name = "Andreas" AND student.l_name = "Pedersen" AND student.id = grade.student_id I know the notation can be a bit hard to paste into HTML forum, but maybe just use some common name or the Greek name. Thanks in advance Mestika

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  • Why I am not able to display image using swing worker?

    - by Vimal Basdeo
    I was trying some codes to implement a scheduled task and came up with these codes . import java.util.*; class Task extends TimerTask { int count = 1; // run is a abstract method that defines task performed at scheduled time. public void run() { System.out.println(count+" : Mahendra Singh"); count++; } } class TaskScheduling { public static void main(String[] args) { Timer timer = new Timer(); // Schedule to run after every 3 second(3000 millisecond) timer.schedule( new Task(), 3000); } } My output : 1 : Mahendra Singh I expected the compiler to print a series of Mahendra Singh at periodic interval of 3 s but despite waiting for around 15 minutes, I get only one output...How do I solve this out?

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  • Paging over a lazy-loaded collection with NHibernate

    - by HackedByChinese
    I read this article where Ayende states NHibernate can (compared to EF 4): Collection with lazy=”extra” – Lazy extra means that NHibernate adapts to the operations that you might run on top of your collections. That means that blog.Posts.Count will not force a load of the entire collection, but rather would create a “select count(*) from Posts where BlogId = 1” statement, and that blog.Posts.Contains() will likewise result in a single query rather than paying the price of loading the entire collection to memory. Collection filters and paged collections - this allows you to define additional filters (including paging!) on top of your entities collections, which means that you can easily page through the blog.Posts collection, and not have to load the entire thing into memory. So I decided to put together a test case. I created the cliché Blog model as a simple demonstration, with two classes as follows: public class Blog { public virtual int Id { get; private set; } public virtual string Name { get; set; } public virtual ICollection<Post> Posts { get; private set; } public virtual void AddPost(Post item) { if (Posts == null) Posts = new List<Post>(); if (!Posts.Contains(item)) Posts.Add(item); } } public class Post { public virtual int Id { get; private set; } public virtual string Title { get; set; } public virtual string Body { get; set; } public virtual Blog Blog { get; private set; } } My mappings files look like this: <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true"> <class xmlns="urn:nhibernate-mapping-2.2" name="Model.Blog, TestEntityFramework, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="Blogs"> <id name="Id" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Id" /> <generator class="identity" /> </id> <property name="Name" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Name" /> </property> <property name="Type" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Type" /> </property> <bag lazy="extra" name="Posts"> <key> <column name="Blog_Id" /> </key> <one-to-many class="Model.Post, TestEntityFramework, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </bag> </class> </hibernate-mapping> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true"> <class xmlns="urn:nhibernate-mapping-2.2" name="Model.Post, TestEntityFramework, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="Posts"> <id name="Id" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Id" /> <generator class="identity" /> </id> <property name="Title" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Title" /> </property> <property name="Body" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Body" /> </property> <many-to-one class="Model.Blog, TestEntityFramework, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Blog"> <column name="Blog_id" /> </many-to-one> </class> </hibernate-mapping> My test case looks something like this: using (ISession session = Configuration.Current.CreateSession()) // this class returns a custom ISession that represents either EF4 or NHibernate { blogs = (from b in session.Linq<Blog>() where b.Name.Contains("Test") orderby b.Id select b); Console.WriteLine("# of Blogs containing 'Test': {0}", blogs.Count()); Console.WriteLine("Viewing the first 5 matching Blogs."); foreach (Blog b in blogs.Skip(0).Take(5)) { Console.WriteLine("Blog #{0} \"{1}\" has {2} Posts.", b.Id, b.Name, b.Posts.Count); Console.WriteLine("Viewing first 5 matching Posts."); foreach (Post p in b.Posts.Skip(0).Take(5)) { Console.WriteLine("Post #{0} \"{1}\" \"{2}\"", p.Id, p.Title, p.Body); } } } Using lazy="extra", the call to b.Posts.Count does do a SELECT COUNT(Id)... which is great. However, b.Posts.Skip(0).Take(5) just grabs all Posts for Blog.Id = ?id, and then LINQ on the application side is just taking the first 5 from the resulting collection. What gives?

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  • Error: An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAV

    - by brz dot net
    I have to find the indentid from the status table based on below two conditions: 1. If there are more than one record having same indentid in status table and the same indentID has count1 in feasibilitystatus table then I don't want to display the record. 2. If there is only one record of indentid in status table and the same indentID has count0 in feasibilitystatus table then I don't want to display the record. Query: select distinct s.indentid from status s where s.status='true' and s.indentid not in( select case when count(s.indentid)>1 then (select indentid from feasibilitystatus group by indentid having count(indentid)>1) else (select indentid from feasibilitystatus group by indentid having count(indentid)>0) end as indentid from status) Error: An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.

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  • Java App Engine - ranked counter

    - by Richard
    I understand the sharded counter, here: http://code.google.com/appengine/articles/sharding_counters.html The problem is that a simple counter will not work in my application. I am sorting my entities by a particular variable so I am returned not so much a count, but more of a rank. My current method is: SELECT COUNT(this) FROM Entity.class WHERE value <= ? Result + 1 is then the rank of the parameter in relation to the value variable in the persistent Entity objects. The limitation of this is the highest rank being returned is 1001 because count() can give a maximum of 1000. The reason I cannot store the rank on the Entity object is that the ranks are updated very often, and re-setting this rank variable would be much too costly. Any ideas on the best way to accomplish this?

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  • how to use found_rows in oracle package to avoid two queries

    - by Omnipresent
    I made a package which I can use like this: select * from table(my_package.my_function(99, 'something, something2', 1, 50)) I make use of the package in a stored procedure. Sample stored procedure looks like: insert into something values(...) from (select * from table(my_package.my_function(99, 'something, something2', 1, 50))) a other_table b where b.something1 = a.something1; open cv_1 for select count(*) from table(my_package.my_function(99, 'something, something2', 1, 50)) So I am calling the same package twice. first time to match records with other tables and other stuff and second time to get the count. Is there a way to get the count first time around and put it into a variable and second time around I just pick that variable rather than calling the whole query again? Hope it makes sense.

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