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• iPhone SDK / Core Data usage scenario, similar to GAE data store?

  - by boliva

  Hi all, I am currently rewriting a map based App which I wrote in the past, specifically for 2.2.1 devices. Originally I wrote it to make use of SQLite databases but I would like to try and migrate it over Core Data, now that it's available on 3.X (for which I am rewriting to). I am fairly experienced in iPhone/Obj-C development, SQL and server backend technologies, but I have never had the chance to work with Core Data so IDK really if it's the appropiate tool for what I am trying to accomplish. The App works on a limited area in a map over which there are about 4000 placemarks, with different kinds of icons and sizes. Of course not all 4000 placemarks are shown at once but only those currently visible in the map viewport, and depending on the zoom level. What I am doing right now is, after the user moves the map in any way (panning or zooming) I am requesting from the backend server the required information for the placemarks that would be visible given the viewport coordinates boundaries and zoom level, however the process isn't as smooth as I'd like (the backend is sending its response in XML and I am compressing it using gzip), it takes anywhere from 1 to 3 seconds to update the display of the placemarks after the user ends moving the map. What I would like to do is to prefetch all the placemarks data at the App launch and use it all through the app life time - I don't mind storing it for later use because the data should be dynamic. The way I would do it right now is, after retrieving all the data, to store it on an SQLite db which I would query later, whenever the user moves the map, to return only the placemarks inside the viewport coordinate boundaries and specific to a given zoom level. Now, the question itself is, if is it possible to use some more 'native', object driven way to carry this queries process, which got me thinking about Core Data and if it is in any way similar to what Google App Engine offers through its datastore where you can fetch a number of objects from the backend given a certain query or criteria, without resorting to an SQL query itself. Like I said before I don't have any experience on Core Data but I have a pretty deep understanding of Obj-C and iPhone development, as well as SQL databases. Any guides on how to achieve what I'm trying (if possible at all) would be greatly appreciated.

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• System.Net.Dns.GetHostAddresses("")

  - by dbasnett

  Yesterday s**ked, and today ain't (sic) looking better. I have an application I have been working on and it can be slow to start when my ISP is down because of DNS. My ISP was down for 3 hours yesterday, so I didn't think much about this piece of code I had added, until I found that it is always slow to start. This code is supposed to return your IP address and my reading of the link suggests that should be immediate, but it isn't, at least on my machine. Oh, and yesterday before the internet went down, I upgraded (oymoron) to XP SP3, and have had other problems. So my questions / request: 1. Am I doing this right? 2. If you run this on your machine does it take 39 seconds to return your IP address? It does on mine. One other note, I did a packet capture and the first request did NOT go on the wire, but the second did, and was answered quickly. So the question is what happened in XP SP3 that I am missing, besides a brain. One last note. If I resolve a FQDN all is well. Public Class Form1 'http://msdn.microsoft.com/en-us/library/system.net.dns.gethostaddresses.aspx ' 'excerpt 'The GetHostAddresses method queries a DNS server 'for the IP addresses associated with a host name. ' 'If hostNameOrAddress is an IP address, this address 'is returned without querying the DNS server. ' 'When an empty string is passed as the host name, 'this method returns the IPv4 addresses of the local host Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button1.Click Dim stpw As New Stopwatch stpw.Reset() stpw.Start() 'originally Dns.GetHostEntry, but slow also Dim myIPs() As System.Net.IPAddress = System.Net.Dns.GetHostAddresses("") stpw.Stop() Debug.WriteLine("'" & stpw.Elapsed.TotalSeconds) If myIPs.Length > 0 Then Debug.WriteLine("'" & myIPs(0).ToString) 'debug '39.8990525 '192.168.1.2 stpw.Reset() stpw.Start() 'originally Dns.GetHostEntry, but slow also myIPs = System.Net.Dns.GetHostAddresses("www.vbforums.com") stpw.Stop() Debug.WriteLine("'" & stpw.Elapsed.TotalSeconds) If myIPs.Length > 0 Then Debug.WriteLine("'" & myIPs(0).ToString) 'debug '0.042212 '63.236.73.220 End Sub End Class

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• NHibernate criteria query question

  - by Chris

  I have 3 related objects (Entry, GamePlay, Prize) and I'm trying to find the best way to query them for what I need using NHibernate. When a request comes in, I need to query the Entries table for a matching entry and, if found, get a) the latest game play along with the first game play that has a prize attached. Prize is a child of GamePlay and each Entry object has a GamePlays property (IList). Currently, I'm working on a method that pulls the matching Entry and eagerly loads all game plays and associated prizes, but it seems wasteful to load all game plays just to find the latest one and any that contain a prize. Right now, my query looks like this: var entry = session.CreateCriteria<Entry>() .Add(Restrictions.Eq("Phone", phone)) .AddOrder(Order.Desc("Created")) .SetFetchMode("GamePlays", FetchMode.Join) .SetMaxResults(1).UniqueResult<Entry>(); Two problems with this: It loads all game plays up front. With 365 days of data, this could easily balloon to 300k of data per query. It doesn't eagerly load the Prize child property for each game. Therefore, my code that loops through the GamePlays list looking for a non-null Prize must make a call to load each Prize property I check. I'm not an nhibernate expert, but I know there has to be a better way to do this. Ideally, I'd like to do the following (pseudocode): entry = findEntry(phoneNumber) lastPlay = getLatestGamePlay(Entry) firstWinningPlay = getFirstWinningGamePlay(Entry) The end result of course is that I have the entry details, the latest game play, and the first winning game play. The catch is that I want to do this in as few database calls as possible, otherwise I'd just execute 3 separate queries. The object definitions look like: public class Entry { public Guid Id {get;set;} public string Phone {get;set;} public IList<GamePlay> GamePlays {get;set;} // ... other properties } public class GamePlay { public Guid Id {get;set;} public Entry Entry {get;set;} public Prize Prize {get;set;} // ... other properties } public class Prize { public Guid Id {get;set;} // ... other properties } The proper NHibernate mappings are in place, so I just need help figuring out how to set up the criteria query (not looking for HQL, don't use it).

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• Sysadmin 101: How can I figure out why my server crashes and monitor performance?

  - by bflora

  I have a Drupal-powered site that seems to have neverending performance problems. It was butt-slow about 5 months ago. I brought in some guys who installed nginx for anonymous visitors, ajaxified a few queries so they wouldn't fire during page load, and helped me find a few bottlenecks in the code. For about a month, the site was significantly faster, though not "fast" by any stretch of the word. Meanwhile, I'm now shelling out $400/month to Slicehost to host a site that gets less than 5,000/uniques a day. Yes, you read that right. Go Drupal. Recently the site started crashing again and is slow again. I can't afford to hire people to come in, study my code from top to bottom, and make changes that may or may not help anymore. And I can't afford to throw more hardware at the problem. So I need to figure out what the problem is myself. Questions: When apache crashes, is it possible to find out what caused it to crash? There has to be a way, right? If so, how can I do this? Is there software I can use that will tell me which process caused my server to die? (e.g. "Apache crashed because someone visited page X." or "Apache crashed because you were importing too many RSS items from feed X.") There's got to be a way to learn this, right? What's a good, noob-friendly way to monitor my current apache performance? My developer friends tell me to "just use Top, dude," but Top shows me a bunch of numbers without any context. I have no clue what qualifies as a bad number or a good number in Top, or which processes are relevant and which aren't. Are there any noob-friendly server monitoring tools out there? Ideally, I could have a page that would give me a color-coded indicator about how apache is performing and then show me a list of processes or pages that are sucking right now. This way, I could know when performance is bad and then what's causing it to be so bad. Why does PHP memory matter? My apparently has a 30MB memory foot print. Will it run faster if I bring that number down? Thanks for any advice. I spent a year or so trying to boost my advertising income so I could hire a contractor to solve my performance woes. I didn't want to have to learn all this sysadmin voodoo. I'm now resigned to the fact that might not have a choice.

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• iPhone: Speeding up a search that's polling 17,000 Core Data objects

  - by randombits

  I have a class that conforms to UISearchDisplayDelegate and contains a UISearchBar. This view is responsible for allowing the user to poll a store of about 17,000 objects that are currently managed by Core Data. Everytime the user types in a character, I created an instance of a SearchOperation (subclasses NSOperation) that queries Core Data to find results that might match the search. The code in the search controller looks something like: - (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope { // Update the filtered array based on the search text and scope in a secondary thread if ([searchText length] < 3) { [filteredList removeAllObjects]; // First clear the filtered array. [self setFilteredList:NULL]; [self.tableView reloadData]; return; } NSDictionary *searchdict = [NSDictionary dictionaryWithObjectsAndKeys:scope, @"scope", searchText, @"searchText", nil]; [aSearchQueue cancelAllOperations]; SearchOperation *searchOp = [[SearchOperation alloc] initWithDelegate:self dataDict:searchdict]; [aSearchQueue addOperation:searchOp]; } And my search is rather straight forward. SearchOperation is a subclass of NSOperation. I overwrote the main method with the following code: - (void)main { if ([self isCancelled]) { return; } NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:entity]; NSPredicate *predicate = NULL; predicate = [NSPredicate predicateWithFormat:@"(someattr contains[cd] %@)", searchText]; [fetchRequest setPredicate:predicate]; NSError *error = NULL; NSArray *fetchResults = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; if (self.delegate != nil) [self.delegate didFinishSearching:fetchResults]; [pool drain]; } This code works, but it has several issues. It's slow. Even though I have the search happening in a separate thread other than the UI thread, querying 17,000 objects is clearly not optimal. If I'm not careful, crashes can happen. I set the max concurrent searches in my NSOperationQueue to 1 to avoid this. What else can I do to make this search faster? I think preloading all 17,000 objects into memory might be risky. There has to be a smarter way to conduct this search to give results back to the user faster.

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• Any tool(s) for knowing the layout (segments) of running process in Windows?

  - by claws

  I've always been curious about How exactly the process looks in memory? What are the different segments(parts) in it? How exactly will be the program (on the disk) & process (in the memory) are related? My previous question: http://stackoverflow.com/questions/1966920/more-info-on-memory-layout-of-an-executable-program-process In my quest, I finally found a answer. I found this excellent article that cleared most of my queries: http://www.linuxforums.org/articles/understanding-elf-using-readelf-and-objdump_125.html In the above article, author shows how to get different segments of the process (LINUX) & he compares it with its corresponding ELF file. I'm quoting this section here: Courious to see the real layout of process segment? We can use /proc//maps file to reveal it. is the PID of the process we want to observe. Before we move on, we have a small problem here. Our test program runs so fast that it ends before we can even dump the related /proc entry. I use gdb to solve this. You can use another trick such as inserting sleep() before it calls return(). In a console (or a terminal emulator such as xterm) do: $ gdb test (gdb) b main Breakpoint 1 at 0x8048376 (gdb) r Breakpoint 1, 0x08048376 in main () Hold right here, open another console and find out the PID of program "test". If you want the quick way, type: $ cat /proc/`pgrep test`/maps You will see an output like below (you might get different output): [1] 0039d000-003b2000 r-xp 00000000 16:41 1080084 /lib/ld-2.3.3.so [2] 003b2000-003b3000 r--p 00014000 16:41 1080084 /lib/ld-2.3.3.so [3] 003b3000-003b4000 rw-p 00015000 16:41 1080084 /lib/ld-2.3.3.so [4] 003b6000-004cb000 r-xp 00000000 16:41 1080085 /lib/tls/libc-2.3.3.so [5] 004cb000-004cd000 r--p 00115000 16:41 1080085 /lib/tls/libc-2.3.3.so [6] 004cd000-004cf000 rw-p 00117000 16:41 1080085 /lib/tls/libc-2.3.3.so [7] 004cf000-004d1000 rw-p 004cf000 00:00 0 [8] 08048000-08049000 r-xp 00000000 16:06 66970 /tmp/test [9] 08049000-0804a000 rw-p 00000000 16:06 66970 /tmp/test [10] b7fec000-b7fed000 rw-p b7fec000 00:00 0 [11] bffeb000-c0000000 rw-p bffeb000 00:00 0 [12] ffffe000-fffff000 ---p 00000000 00:00 0 Note: I add number on each line as reference. Back to gdb, type: (gdb) q So, in total, we see 12 segment (also known as Virtual Memory Area--VMA). But I want to know about Windows Process & PE file format. Any tool(s) for getting the layout (segments) of running process in Windows? Any other good resources for learning more on this subject? EDIT: Are there any good articles which shows the mapping between PE file sections & VA segments?

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• LINQ aggregate left join on SQL CE

  - by P Daddy

  What I need is such a simple, easy query, it blows me away how much work I've done just trying to do it in LINQ. In T-SQL, it would be: SELECT I.InvoiceID, I.CustomerID, I.Amount AS AmountInvoiced, I.Date AS InvoiceDate, ISNULL(SUM(P.Amount), 0) AS AmountPaid, I.Amount - ISNULL(SUM(P.Amount), 0) AS AmountDue FROM Invoices I LEFT JOIN Payments P ON I.InvoiceID = P.InvoiceID WHERE I.Date between @start and @end GROUP BY I.InvoiceID, I.CustomerID, I.Amount, I.Date ORDER BY AmountDue DESC The best equivalent LINQ expression I've come up with, took me much longer to do: var invoices = ( from I in Invoices where I.Date >= start && I.Date <= end join P in Payments on I.InvoiceID equals P.InvoiceID into payments select new{ I.InvoiceID, I.CustomerID, AmountInvoiced = I.Amount, InvoiceDate = I.Date, AmountPaid = ((decimal?)payments.Select(P=>P.Amount).Sum()).GetValueOrDefault(), AmountDue = I.Amount - ((decimal?)payments.Select(P=>P.Amount).Sum()).GetValueOrDefault() } ).OrderByDescending(row=>row.AmountDue); This gets an equivalent result set when run against SQL Server. Using a SQL CE database, however, changes things. The T-SQL stays almost the same. I only have to change ISNULL to COALESCE. Using the same LINQ expression, however, results in an error: There was an error parsing the query. [ Token line number = 4, Token line offset = 9,Token in error = SELECT ] So we look at the generated SQL code: SELECT [t3].[InvoiceID], [t3].[CustomerID], [t3].[Amount] AS [AmountInvoiced], [t3].[Date] AS [InvoiceDate], [t3].[value] AS [AmountPaid], [t3].[value2] AS [AmountDue] FROM ( SELECT [t0].[InvoiceID], [t0].[CustomerID], [t0].[Amount], [t0].[Date], COALESCE(( SELECT SUM([t1].[Amount]) FROM [Payments] AS [t1] WHERE [t0].[InvoiceID] = [t1].[InvoiceID] ),0) AS [value], [t0].[Amount] - (COALESCE(( SELECT SUM([t2].[Amount]) FROM [Payments] AS [t2] WHERE [t0].[InvoiceID] = [t2].[InvoiceID] ),0)) AS [value2] FROM [Invoices] AS [t0] ) AS [t3] WHERE ([t3].[Date] >= @p0) AND ([t3].[Date] <= @p1) ORDER BY [t3].[value2] DESC Ugh! Okay, so it's ugly and inefficient when run against SQL Server, but we're not supposed to care, since it's supposed to be quicker to write, and the performance difference shouldn't be that large. But it just doesn't work against SQL CE, which apparently doesn't support subqueries within the SELECT list. In fact, I've tried several different left join queries in LINQ, and they all seem to have the same problem. Even: from I in Invoices join P in Payments on I.InvoiceID equals P.InvoiceID into payments select new{I, payments} generates: SELECT [t0].[InvoiceID], [t0].[CustomerID], [t0].[Amount], [t0].[Date], [t1].[InvoiceID] AS [InvoiceID2], [t1].[Amount] AS [Amount2], [t1].[Date] AS [Date2], ( SELECT COUNT(*) FROM [Payments] AS [t2] WHERE [t0].[InvoiceID] = [t2].[InvoiceID] ) AS [value] FROM [Invoices] AS [t0] LEFT OUTER JOIN [Payments] AS [t1] ON [t0].[InvoiceID] = [t1].[InvoiceID] ORDER BY [t0].[InvoiceID] which also results in the error: There was an error parsing the query. [ Token line number = 2, Token line offset = 5,Token in error = SELECT ] So how can I do a simple left join on a SQL CE database using LINQ? Am I wasting my time?

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• How to create Query syntax for multiple DataTable for implementing IN operator of Sql Server

  - by Shantanu Gupta

  I have fetched 3-4 tables by executing my stored procedure. Now they resides on my dataset. I have to maintain this dataset for multiple forms and I am not doing any DML operation on this dataset. Now this dataset contains 4 tables out of which i have to fetch some records to display data. Data stored in tables are in form of one to many relationship. i.e. In case of transactions. N records per record. Then these N records are further mapped to M records of 3rd table. Table 1 MAP_ID GUEST_ID DEPARTMENT_ID PARENT_ID PREFERENCE_ID -------------------- -------------------- -------------------- -------------------- -------------------- 19 61 1 1 5 14 61 1 5 15 15 61 2 4 10 18 61 2 13 23 17 61 2 20 26 16 61 40 40 41 20 62 1 5 14 21 62 1 5 15 22 62 1 6 16 24 62 2 3 4 23 62 2 4 9 27 62 2 13 23 25 62 2 20 24 26 62 2 20 25 28 63 1 1 5 29 63 1 1 8 34 63 1 5 15 30 63 2 4 10 33 63 2 4 11 31 63 2 13 23 32 63 40 40 41 35 65 1 NULL 1 36 65 1 NULL 1 38 68 2 13 22 37 68 2 20 25 39 68 2 23 27 40 92 1 NULL 1 Table 2 Department_ID Department_Name Parent_Id Parent_Name -------------------- ----------------------- --------------- ---------------------------------------------------------------------------------- 1 Food 1, 5, 6 Food, North Indian, South Indian 2 Lodging 3, 4, 13, 20, 23 Room, Floor, Non Air Conditioned, With Balcony, Without Balcony 40 New 40 SubNew TABLE 3 Parent_Id Parent_Name Preference_ID Preference_Name -------------------- ----------------------------------------------- ----------------------- ------------------- NULL NULL NULL NULL 1 Food 5, 8 North Indian, Italian 3 Room 4 Floor 4 Floor 9, 10, 11 First, Second, Third 5 North Indian 14, 15 X, Y 6 South Indian 16 Dosa 13 Non Air Conditioned 22, 23 With Balcony, Without Balcony 20 With Balcony 24, 25, 26 Mountain View, Ocean View, Garden View 23 Without Balcony 27 Mountain View 40 New 41 SubNew I have these 3 tables that are related in some fashion like this. Table 1 will be the master for these 2 tables i.e. table 2 and table 3. I need to query on them as SELECT Department_Id, Department_Name, Parent_Name FROM Table2 WHERE Department_Id in ( SELECT Department_Id FROM Table1 WHERE guest_id=65 ) SELECT Parent_Id, Parent_Name, Preference_Name FROM Table3 WHERE PARENT_ID in ( SELECT parent_id FROM Table1 WHERE guest_id=65 ) Now I need to use these queries on DataTables. So I am using Query Syntax for this and reached up to this point. var dept_list= from dept in DtMapGuestDepartment.AsEnumerable() where dept.Field<long>("PK_GUEST_ID")==long.Parse(63) select dept; This should give me the list of all departments that has guest id =63 Now I want to select all departments_name and parent_name from Table 2 where guest_id=63 i.e. departments that i fetched above. This same case will be followed for Table3. Please suggest how to do this. Thanks for keeping up patience for reading my question.

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• OneToOne JPA / Hibernate eager loading cause N+1 select

  - by Alexandre Lavoie

  I created a method to have multilingual text on different objects without creating field for each languages or tables for each objects types. Now the only problem I've got is N+1 select queries when doing a simple loading. Tables schema : CREATE TABLE `testentities` ( `keyTestEntity` int(11) NOT NULL, `keyMultilingualText` int(11) NOT NULL, PRIMARY KEY (`keyTestEntity`) ) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8; CREATE TABLE `common_multilingualtexts` ( `keyMultilingualText` int(11) NOT NULL auto_increment, PRIMARY KEY (`keyMultilingualText`) ) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8; CREATE TABLE `common_multilingualtexts_values` ( `languageCode` varchar(5) NOT NULL, `keyMultilingualText` int(11) NOT NULL, `value` text, PRIMARY KEY (`languageCode`,`keyMultilingualText`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; MultilingualText.java @Entity @Table(name = "common_multilingualtexts") public class MultilingualText implements Serializable { private Integer m_iKeyMultilingualText; private Map<String, String> m_lValues = new HashMap<String, String>(); public void setKeyMultilingualText(Integer p_iKeyMultilingualText) { m_iKeyMultilingualText = p_iKeyMultilingualText; } @Id @GeneratedValue @Column(name = "keyMultilingualText") public Integer getKeyMultilingualText() { return m_iKeyMultilingualText; } public void setValues(Map<String, String> p_lValues) { m_lValues = p_lValues; } @ElementCollection(fetch = FetchType.EAGER) @CollectionTable(name = "common_multilingualtexts_values", joinColumns = @JoinColumn(name = "keyMultilingualText")) @MapKeyColumn(name = "languageCode") @Column(name = "value") public Map<String, String> getValues() { return m_lValues; } public void put(String p_sLanguageCode, String p_sValue) { m_lValues.put(p_sLanguageCode,p_sValue); } public String get(String p_sLanguageCode) { if(m_lValues.containsKey(p_sLanguageCode)) { return m_lValues.get(p_sLanguageCode); } return null; } } And it is used like this on a object (having a foreign key to the multilingual text) : @Entity @Table(name = "testentities") public class TestEntity implements Serializable { private Integer m_iKeyEntity; private MultilingualText m_oText; public void setKeyEntity(Integer p_iKeyEntity) { m_iKeyEntity = p_iKeyEntity; } @Id @GeneratedValue @Column(name = "keyEntity") public Integer getKeyEntity() { return m_iKeyEntity; } public void setText(MultilingualText p_oText) { m_oText = p_oText; } @OneToOne(cascade = CascadeType.ALL) @JoinColumn(name = "keyText") public MultilingualText getText() { return m_oText; } } Now, when doing a simple HQL query : from TestEntity, I get a query selecting TestEntity's and one query for each MultilingualText that need to be loaded on each TestEntity. I've searched a lot and found absolutely no solutions. I have tested : @Fetch(FetchType.JOIN) optional = false @ManyToOne instead of @OneToOne Now I am out of idea!

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• Stumbleupon type query...

  - by Chris Denman

  Wow, makes your head spin! I am about to start a project, and although my mySql is OK, I can't get my head around what required for this: I have a table of web addresses. id,url 1,http://www.url1.com 2,http://www.url2.com 3,http://www.url3.com 4,http://www.url4.com I have a table of users. id,name 1,fred bloggs 2,john bloggs 3,amy bloggs I have a table of categories. id,name 1,science 2,tech 3,adult 4,stackoverflow I have a table of categories the user likes as numerical ref relating to the category unique ref. For example: user,category 1,4 1,6 1,7 1,10 2,3 2,4 3,5 . . . I have a table of scores relating to each website address. When a user visits one of these sites and says they like it, it's stored like so: url_ref,category 4,2 4,3 4,6 4,2 4,3 5,2 5,3 . . . So based on the above data, URL 4 would score (in it's own right) as follows: 2=2 3=2 6=1 What I was hoping to do was pick out a random URL from over 2,000,000 records based on the current users interests. So if the logged in user likes categories 1,2,3 then I would like to ORDER BY a score generated based on their interest. If the logged in user likes categories 2 3 and 6 then the total score would be 5. However, if the current logged in user only like categories 2 and 6, the URL score would be 3. So the order by would be in context of the logged in users interests. Think of stumbleupon. I was thinking of using a set of VIEWS to help with sub queries. I'm guessing that all 2,000,000 records will need to be looked at and based on the id of the url it will look to see what scores it has based on each selected category of the current user. So we need to know the user ID and this gets passed into the query as a constant from the start. Ain't got a clue! Chris Denman

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• JDBC CommunicationsException with MySQL Database

  - by Dominik Siebel

  I'm having a little trouble with my MySQL- Connection- Pooling. This is the case: Different jobs are scheduled via Quartz. All jobs connect to different databases which works fine the whole day while the nightly scheduled jobs fail with a CommunicationsException... Quartz-Jobs: Job1 runs 0 0 6,10,14,18 * * ? Job2 runs 0 30 10,18 * * ? Job3 runs 0 0 5 * * ? As you can see the last job runs at 18 taking about 1 hour to run. The first job at 5am is the one that fails. I already tried all kinds of parameter-combinations in my resource config this is the one I am running right now: <!-- Database 1 (MySQL) --> <Resource auth="Container" driverClassName="com.mysql.jdbc.Driver" maxActive="100" maxIdle="30" maxWait="10000" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" type="javax.sql.DataSource" name="jdbc/appDbProd" username="****" password="****" url="jdbc:mysql://127.0.0.1:3306/appDbProd?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> <!-- Database 2 (MySQL) --> <Resource auth="Container" driverClassName="com.mysql.jdbc.Driver" maxActive="100" maxIdle="30" maxWait="10000" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" type="javax.sql.DataSource" name="jdbc/prodDbCopy" username="****" password="****" url="jdbc:mysql://127.0.0.1:3306/prodDbCopy?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> <!-- Database 3 (MSSQL)--> <Resource auth="Container" driverClassName="net.sourceforge.jtds.jdbc.Driver" maxActive="30" maxIdle="30" maxWait="100" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" name="jdbc/catalogDb" username="****" password="****" type="javax.sql.DataSource" url="jdbc:jtds:sqlserver://127.0.0.1:1433;databaseName=catalog;useNdTLMv2=false" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> For obvious reasons I changed IPs, Usernames and Passwords but they can be assumed to be correct, seeing that the application runs successfully the whole day. The most annoying thing is: The first job that runs first queries Database2 successfully but fails to query Database1 for some reason (CommunicationsException): Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 39,376,539 milliseconds ago. The last packet sent successfully to the server was 39,376,539 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. Any ideas? Thanks!

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• .NET JIT Code Cache leaking?

  - by pitchfork

  We have a server component written in .Net 3.5. It runs as service on a Windows Server 2008 Standard Edition. It works great but after some time (days) we notice massive slowdowns and an increased working set. We expected some kind of memory leak and used WinDBG/SOS to analyze dumps of the process. Unfortunately the GC Heap doesn’t show any leak but we noticed that the JIT code heap has grown from 8MB after the start to more than 1GB after a few days. We don’t use any dynamic code generation techniques by our own. We use Linq2SQL which is known for dynamic code generation but we don’t know if it can cause such a problem. The main question is if there is any technique to analyze the dump and check where all this Host Code Heap blocks that are shown in the WinDBG dumps come from? [Update] In the mean time we did some more analysis and had Linq2SQL as probable suspect, especially since we do not use precompiled queries. The following example program creates exactly the same behaviour where more and more Host Code Heap blocks are created over time. using System; using System.Linq; using System.Threading; namespace LinqStressTest { class Program { static void Main(string[] args) { for (int i = 0; i < 100; ++ i) ThreadPool.QueueUserWorkItem(Worker); while(runs < 1000000) { Thread.Sleep(5000); } } static void Worker(object state) { for (int i = 0; i < 50; ++i) { using (var ctx = new DataClasses1DataContext()) { long id = rnd.Next(); var x = ctx.AccountNucleusInfos.Where(an => an.Account.SimPlayers.First().Id == id).SingleOrDefault(); } } var localruns = Interlocked.Add(ref runs, 1); System.Console.WriteLine("Action: " + localruns); ThreadPool.QueueUserWorkItem(Worker); } static Random rnd = new Random(); static long runs = 0; } } When we replace the Linq query with a precompiled one, the problem seems to disappear.

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• Advice for Architecture Design Logic for software application

  - by Prasad

  Hi, I have a framework of basic to complex set of objects/classes (C++) running into around 500. With some rules and regulations - all these objects can communicate with each other and hence can cover most of the common queries in the domain. My Dream: I want to provide these objects as icons/glyphs (as I learnt recently) on a workspace. All these objects can be dragged/dropped into the workspace. They have to communicate only through their methods(interface) and in addition to few iterative and conditional statements. All these objects are arranged finally to execute a protocol/workflow/dataflow/process. After drawing the flow, the user clicks the Execute/run button. All the user interaction should be multi-touch enabled. The best way to show my dream is : Jeff Han's Multitouch Video. consider Jeff is playing with my objects instead of the google maps. :-) it should be like playing a jigsaw puzzle. Objective: how can I achieve the following while working on this final product: a) the development should be flexible to enable provision for web services b) the development should enable easy web application development c) The development should enable client-server architecture - d) further it should also enable mouse based drag/drop desktop application like Adobe programs etc. I mean to say: I want to economize on investments. Now I list my efforts till now in design : a) Created an Editor (VB) where the user writes (manually) the object / class code b) On Run/Execute, the code is copied into a main() function and passed to interpreter. c) Catch the output and show it in the console. The interpreter can be separated to become a server and the Editor can become the client. This needs lot of standard client-server architecture work. But some how I am not comfortable in the tightness of this system. Without interpreter is there much faster and better embeddable solution to this? - other than writing a special compiler for these objects. Recently learned about AXIS-C++ can help me - looks like - a friend suggested. Is that the way to go ? Here are my questions: (pl. consider me a self taught programmer and NOT my domain) a) From the stage of C++ objects to multi-touch product, how can I make sure I will develop the parallel product/service models as well.? What should be architecture aspects I should consider ? b) What technologies are best suited for this? c) If I am thinking of moving to Cloud Computing, how difficult/ how redundant / how unnecessary my efforts will be ? d) How much time in months would it take to get the first beta ? I take the liberty to ask if any of the experts here are interested in this project, please email me: [email protected] Thank you for any help. Looking forward.

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• What are the types and inner workings of a query optimizer?

  - by Frank Developer

  As I understand it, most query optimizers are cost-based. Some can be influenced by hints like FIRST_ROWS(). Others are tailored for OLAP. Is it possible to know more detailed logic about how Informix IDS and SE's optimizers decide what's the best route for processing a query, other than SET EXPLAIN? Is there any documentation which illustrates the ranking of SELECT statements? I would imagine that "SELECT col FROM table WHERE ROWID = n" ranks 1st. What are the rest of them?.. If I'm not mistaking, Informix's ROWID is a SERIAL(INT) which allows for a max. of 2GB nrows, or maybe it uses INT9 for TB's nrows?.. However, I think Oracle uses HEX values for ROWID. Too bad ROWID can't be oftenly used, since a rows ROWID can change. So maybe ROWID is used by the optimizer as a counter? Perhaps, it could be used for implementing the query progress idea I mentioned in my "Begin viewing query results before query completes" question? For some reason, I feel it wouldn't be that difficult to report a query's progress while being processed, perhaps at the expense of some slight overhead, but it would be nice to know ahead of time: A "Google-like" estimate of how many rows meet a query's criteria, display it's progress every 100, 200, 500 or 1,000 rows, give users the ability to cancel it at anytime and start displaying the qualifying rows as they are being put into the current list, while it continues searching?.. This is just one example, perhaps we could think other neat/useful features, the ingridients are more or less there. Perhaps we could fine-tune each query with more granularity than currently available? OLTP queries tend to be mostly static and pre-defined. The "what-if's" are more OLAP, so let's try to add more control and intelligence to it? So, therefore, being able to more precisely control, not "hint-influence" a query is what's needed and therefore it would be necessary to know how the optimizers logic is programmed. We can then have Dynamic SELECT and other statements for specific situations! Maybe even tell IDS to read blocks of indexes nodes at-a-time instead of one-by-one, etc. etc.

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• Arguments for moving from LINQtoSQL to Nhibernate?

  - by sah302

  Backstory: Hi all, I just spent a lot of time reading many of the LINQ vs Nhibernate threads here and on other sites. I work in a small development team of 4 people and we don't even have really any super experienced developers. We work for a small company that has a lot of technical needs but not enough developers to implement them (and hiring more is out of the question right now). Typically our projects (which individually are fairly small) have been coded separately and weren't really layered in anyway, code wasn't re-used, no class libraries, and we just use the LINQtoSQL .dbml files for our pojects, we really don't even use objects but pass around values and stuff, the only time we use objects is when inserting to a database (heck not even querying since you don't need to assign it to a type and can just bind to gridview). Despite all this as I said our company has a lot of technical needs, no one could come to us for a year and we would have plenty of work to implement requested features. Well I have decided to change that a bit first by creating class libraries and actually adding layers to our applications. I am trying to meet these guys halfway by still using LINQtoSQL as the ORM yet and still use VB as the language. However I am finding it a b***h of a time dealing with so many thing in LINQtoSQL that I found easy in Nhibernate (automatic handling of the session, criteria creation easier than expression trees, generic an dynamic querying easier etc.) So... Question: How can I convince my lead developers and other senior programmers that switching to Nhibernate is a good thing? That being in control of our domain objects is a good thing? That being able to implement interfaces is a good? I've tried exlpaining the advantages of this before but it's not understood by them because they've never programmed in a true OO & layered way. Also one of the counter arguments to this I can see is sqlMetal generates those classes automatically and therefore it saves a lot of time. I can't really counter that other than saying spending more time on infrastructure to make it more scalable and flexible is good, but they can't see how. Again, I know the features and advantages (somewhat enough I believe) of each, but I need arguments applicable to my context, hence why I provided the context. I just am not a very good arguer I guess. (Caveat: For all the LINQtoSQL lovers, I may just not be super proficient as LINQ, but I find it very cumbersome that you are required to download some extra library for dynamic queries which don't by default support guid comparisons, and I also find the way of updating entitites to be cumbersome as well in terms of data context managing, so it could just be that I suck hehe.)

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• WordPress: Display Online Users' Avatars

  - by Wade D Ouellet

  Hi, I'm using version 2.7.0 of this WordPress plugin to display which users are currently online (the latest version doesn't work): http://wordpress.org/extend/plugins/wp-useronline/ It's working great but I would love to be able to alter it quickly to display the users' avatars instead of their names. Hoping someone with pretty good knowledge of WordPress queries and functions can help. The part below seems to be the part that handles all this. If this isn't enough, here is the link to download the version I am using with the full php files: http://downloads.wordpress.org/plugin/wp-useronline.2.70.zip // If No Bot Is Found, Then We Check Members And Guests if ( !$bot_found ) { if ( $current_user->ID ) { // Check For Member $user_id = $current_user->ID; $user_name = $current_user->display_name; $user_type = 'member'; $where = $wpdb->prepare("WHERE user_id = %d", $user_id); } elseif ( !empty($_COOKIE['comment_author_'.COOKIEHASH]) ) { // Check For Comment Author (Guest) $user_id = 0; $user_name = trim(strip_tags($_COOKIE['comment_author_'.COOKIEHASH])); $user_type = 'guest'; } else { // Check For Guest $user_id = 0; $user_name = __('Guest', 'wp-useronline'); $user_type = 'guest'; } } // Check For Page Title if ( is_admin() && function_exists('get_admin_page_title') ) { $page_title = ' &raquo; ' . __('Admin', 'wp-useronline') . ' &raquo; ' . get_admin_page_title(); } else { $page_title = wp_title('&raquo;', false); if ( empty($page_title) ) $page_title = ' &raquo; ' . strip_tags($_SERVER['REQUEST_URI']); elseif ( is_singular() ) $page_title = ' &raquo; ' . __('Archive', 'wp-useronline') . ' ' . $page_title; } $page_title = get_bloginfo('name') . $page_title; // Delete Users $delete_users = $wpdb->query($wpdb->prepare(" DELETE FROM $wpdb->useronline $where OR timestamp < CURRENT_TIMESTAMP - %d ", self::$options->timeout)); // Insert Users $data = compact('user_type', 'user_id', 'user_name', 'user_ip', 'user_agent', 'page_title', 'page_url', 'referral'); $data = stripslashes_deep($data); $insert_user = $wpdb->insert($wpdb->useronline, $data); // Count Users Online self::$useronline = intval($wpdb->get_var("SELECT COUNT(*) FROM $wpdb->useronline"));

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• Issue with RegConnectRegistry connecting to 64 bit machines

  - by RA

  I'm seeing a weird thing when connecting to the performance registry on 64 bit editions of Windows. The whole program stalls and callstacks becomes unreadable. After a long timeout, the connection attempts aborts and everything goes back to normal. The only solution is to make sure that only one thread at the time queries the remote registry, unless the remote machine is a 32 bit Windows XP, 2003, 2000 , then you can use as many threads as you like. Have anyone a technical explanation why this might be happening ? I've spent 2-3 days searching the web without coming up with anything. Here is a test program, run it first with one thread (connecting to a 64 bit Windows), then remove the comment in tmain and run it with 4 threads. Running it with one thread works as expected, running with 4, returns ERROR_BUSY (dwRet == 170) after stalling for a while. Remember to set a remote machine correctly in RegConnectRegistry before running the program. #define TOTALBYTES 8192 #define BYTEINCREMENT 4096 void PerfmonThread(void *pData) { DWORD BufferSize = TOTALBYTES; DWORD cbData; DWORD dwRet; PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize ); cbData = BufferSize; printf("\nRetrieving the data..."); HKEY hKey; DWORD dwAccessRet = RegConnectRegistry(L"REMOTE_MACHINE",HKEY_PERFORMANCE_DATA,&hKey); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData, &cbData ); while( dwRet == ERROR_MORE_DATA ) { // Get a buffer that is big enough. BufferSize += BYTEINCREMENT; PerfData = (PPERF_DATA_BLOCK) realloc( PerfData, BufferSize ); cbData = BufferSize; printf("."); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData,&cbData ); } if( dwRet == ERROR_SUCCESS ) printf("\n\nFinal buffer size is %d\n", BufferSize); else printf("\nRegQueryValueEx failed (%d)\n", dwRet); RegCloseKey(hKey); } int _tmain(int argc, _TCHAR* argv[]) { _beginthread(PerfmonThread,0,NULL); /* _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); */ while(1) { Sleep(2000); } }

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• Multiple Connection Types for one Designer Generated TableAdapter

  - by Tim

  I have a Windows Forms application with a DataSet (.xsd) that is currently set to connect to a Sql Ce database. Compact Edition is being used so the users can use this application in the field without an internet connection, and then sync their data at day's end. I have been given a new project to create a supplemental web interface for displaying some of the same reports as the Windows Forms application so certain users can obtain reports without installing the Windows app. What I've done so far is create a new Web Project and added it to my current Solution. I have split both the reports (.rdlc) and DataSets out of the Windows Forms project into their own projects so they can be accessed by both the Windows and Web applications. So far, this is working fine. Here's my dilemma: As I said before, the DataSets are currently set up to connect to a local Sql Ce database file. This is correct for the Windows app, but for the Web application I would like to use these same TableAdapters and queries to connect to the Sql Server 2005 database. I have found that the designer generated, strongly-typed TableAdapter classes have a ConnectionModifier property that allows you to make the TableAdapter's Connection public. This exposes the Connection property and allows me to set it, however it is strongly-typed as a SqlCeConnection, whereas I would like to set it to a SqlConnection for my Web project. I'm assuming the DataSet Designer strongly-types the Connection, Command, and DataAdapter objects based on the Provider of the ConnectionString as indicated in the app.config file. Is there any way I can use some generic provider so that the DataSet Designer will use object types that can connect to both a Sql Ce database file AND the actual Sql Server 2005 database? I know that SqlCeConnection and SqlConnection both inherit from DbConnection, which implements IDbConnection. Relatively, the same goes for SqlCeCommand/SqlCommand:DbCommand:IDbCommand. It would be nice if I could just figure out a way for the designer to use the Interface types rather than the strong types, but I'm hesitant that that is possible. I hope my problem and question are clear. Any help is much appreciated. Let me know if there's anything I can clarify.

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• Hibernate Communications Link Failure in Hibernate Based Java Servlet application powered by MySQL

  - by Vatsala

  Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?) edit - Here are the c3p0 parameters I tried out - select 1; 2

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• Using multiple aggregate functions in an algebraic expression in (ANSI) SQL statement

  - by morpheous

  I have the following aggregate functions (AGG FUNCs): foo(), foobar(), fredstats(), barneystats(). I want to know if I can use multiple AGG FUNCs in an algebraic expression. This may seem a strange/simplistic question for seasoned SQL developers - however, the but the reason I ask is that so far, all AGG FUNCs examples I have seen are of the simplistic variety e.g. max(salary) < 100, rather than using the AGG FUNCs in an expression which involves using multiple AGG FUNCs in an expression (like agg_func1() agg_func2()). The information below should help clarify further. Given tables with the following schemas: CREATE TABLE item (id int, length float, weight float); CREATE TABLE item_info (item_id, name varchar(32)); # Is it legal (ANSI) SQL to write queries of this format ? SELECT id, name, foo, foobar, fredstats FROM A, B (SELECT id, foo(123) as foo, foobar('red') as foobar, fredstats('weight') as fredstats FROM item GROUP BY id HAVING [ALGEBRAIC EXPRESSION] ORDER BY id AS A), item_info AS B WHERE item.id = B.id Where: ALGEBRAIC EXPRESSION is the type of expression that can be used in a WHERE clause - for example: ((foo(x) < foobar(y)) AND foobar(y) IN (1,2,3)) OR (fredstats(x) <> 0)) I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible. Assuming it is legal to include AGG FUNCS in the way I have done above, I'd like to know: Is there a more efficient way to write the above query ? Is there any way I can speed up the query in terms of a judicious choice of indexes on the tables item and item_info ? Is there a performance hit of using AGG FUNCs in an algebraic expression like I am (i.e. an expression involving the output of aggregate functions rather than constants? Can the expression also include 'scaled' AGG FUNC? (for example: 2*foo(123) < -3*foobar(456) ) - will scaling (i.e. multiplying an AGG FUNC by a number have an effect on performance?) How can I write the query above using INNER JOINS instead?

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• PostgreSQL - fetch the row which has the Max value for a column

  - by Joshua Berry

  I'm dealing with a Postgres table (called "lives") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that will give me the most recent lives_remaining total for each usr_id There are multiple users (distinct usr_id's) time_stamp is not a unique identifier: sometimes user events (one by row in the table) will occur with the same time_stamp. trans_id is unique only for very small time ranges: over time it repeats remaining_lives (for a given user) can both increase and decrease over time example: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 07:00 | 1 | 1 | 1 09:00 | 4 | 2 | 2 10:00 | 2 | 3 | 3 10:00 | 1 | 2 | 4 11:00 | 4 | 1 | 5 11:00 | 3 | 1 | 6 13:00 | 3 | 3 | 1 As I will need to access other columns of the row with the latest data for each given usr_id, I need a query that gives a result like this: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 11:00 | 3 | 1 | 6 10:00 | 1 | 2 | 4 13:00 | 3 | 3 | 1 As mentioned, each usr_id can gain or lose lives, and sometimes these timestamped events occur so close together that they have the same timestamp! Therefore this query won't work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp) AS max_timestamp FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp = b.time_stamp Instead, I need to use both time_stamp (first) and trans_id (second) to identify the correct row. I also then need to pass that information from the subquery to the main query that will provide the data for the other columns of the appropriate rows. This is the hacked up query that I've gotten to work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp || '*' || trans_id) AS max_timestamp_transid FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp_transid = b.time_stamp || '*' || b.trans_id ORDER BY b.usr_id Okay, so this works, but I don't like it. It requires a query within a query, a self join, and it seems to me that it could be much simpler by grabbing the row that MAX found to have the largest timestamp and trans_id. The table "lives" has tens of millions of rows to parse, so I'd like this query to be as fast and efficient as possible. I'm new to RDBM and Postgres in particular, so I know that I need to make effective use of the proper indexes. I'm a bit lost on how to optimize. I found a similar discussion here. Can I perform some type of Postgres equivalent to an Oracle analytic function? Any advice on accessing related column information used by an aggregate function (like MAX), creating indexes, and creating better queries would be much appreciated! P.S. You can use the following to create my example case: create TABLE lives (time_stamp timestamp, lives_remaining integer, usr_id integer, trans_id integer); insert into lives values ('2000-01-01 07:00', 1, 1, 1); insert into lives values ('2000-01-01 09:00', 4, 2, 2); insert into lives values ('2000-01-01 10:00', 2, 3, 3); insert into lives values ('2000-01-01 10:00', 1, 2, 4); insert into lives values ('2000-01-01 11:00', 4, 1, 5); insert into lives values ('2000-01-01 11:00', 3, 1, 6); insert into lives values ('2000-01-01 13:00', 3, 3, 1);

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• Prevent SQL Injection in Dynamic column names

  - by Mr Shoubs

  I can't get away without writing some dynamic sql conditions in a part of my system (using Postgres). My question is how best to avoid SQL Injection with the method I am currently using. EDIT (Reasoning): There are many of columns in a number of tables (a number which grows (only) and is maintained elsewhere). I need a method of allowing the user to decide which (predefined) column they want to query (and if necessary apply string functions to). The query itself is far too complex for the user to write themselves, nor do they have access to the db. There are 1000's of users with varying requirements and I need to remain as flexible as possible - I shouldn't have to revisit the code unless the main query needs to change - Also, there is no way of knowing what conditions the user will need to use. I have objects (received via web service) that generates a condition (the generation method is below - it isn't perfect yet) for some large sql queries. The _FieldName is user editable (parameter name was, but it didn't need to be) and I am worried it could be an attack vector. I put double quotes (see quoted identifier) around the field name in an attempt to sanitize the string, this way it can never be a key word. I could also look up the field name against a list of fields, but it would be difficult to maintain on a timely basis. Unfortunately the user must enter the condition criteria, I am sure there must be more I can add to the sanatize method? and does quoting the column name make it safe? (my limited testing seems to think so). an example built condition would be "AND upper(brandloaded.make) like 'O%' and upper(brandloaded.make) not like 'OTHERBRAND'" ... Any help or suggestions are appreciated. Public Function GetCondition() As String Dim sb As New Text.StringBuilder 'put quote around the table name in an attempt to prevent some sql injection 'http://www.postgresql.org/docs/8.2/static/sql-syntax-lexical.html sb.AppendFormat(" {0} ""{1}"" ", _LogicOperator.ToString, _FieldName) Select Case _ConditionOperator Case ConditionOperatorOptions.Equals sb.Append(" = ") ... End Select sb.AppendFormat(" {0} ", Me.UniqueParameterName) 'for parameter Return Me.Sanitize(sb) End Function Private Function Sanitize(ByVal sb As Text.StringBuilder) As String 'compare against a similar blacklist mentioned here: http://forums.asp.net/t/1254125.aspx sb.Replace(";", "") sb.Replace("'", "") sb.Replace("\", "") sb.Replace(Chr(8), "") Return sb.ToString End Function Public ReadOnly Property UniqueParameterName() As String Get Return String.Concat(":" _UniqueIdentifier) End Get End Property

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• PHP 5.2 Function needed for GENERIC sorting of a recordset array

  - by donbriggs

  Somebody must have come up with a solution for this by now. We are using PHP 5.2. (Don't ask me why.) I wrote a PHP class to display a recordset as an HTML table/datagrid, and I wish to expand it so that we can sort the datagrid by whichever column the user selects. In the below example data, we may need to sort the recordset array by Name, Shirt, Assign, or Age fields. I will take care of the display part, I just need help with sorting the data array. As usual, I query a database to get a result, iterate throught he result, and put the records into an assciateiave array. So, we end up with an array of arrays. (See below.) I need to be able to sort by any column in the dataset. However, I will not know the column names at design time, nor will I know if the colums will be string or numeric values. I have seen a ton of solutions to this, but I have not seen a GOOD and GENERIC solution Can somebody please suggest a way that I can sort the recordset array that is GENERIC, and will work on any recordset? Again, I will not know the fields names or datatypes at design time. The array presented below is ONLY an example. UPDATE: Yes, I would love to have the database do the sorting, but that is just not going to happen. The queries that we are running are very complex. (I am not really querying a table of Star Trek characters.) They include joins, limits, and complex WHERE clauses. Writing a function to pick apart the SQL statement to add an ORDER BY is really not an option. Besides, sometimes we already have the array that is a result of the query, rather than the ability to run a new query. Array ( [0] => Array ( [name] => Kirk [shrit] => Gold [assign] => Bridge ) [1] => Array ( [name] => Spock [shrit] => Blue [assign] => Bridge ) [2] => Array ( [name] => Uhura [shrit] => Red [assign] => Bridge ) [3] => Array ( [name] => Scotty [shrit] => Red [assign] => Engineering ) [4] => Array ( [name] => McCoy [shrit] => Blue [assign] => Sick Bay ) )

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• Flex AS3: ProgressBar doesn't move

  - by jolierouge

  Hey All, I am a little stuck and need some advice/help. I have a progress bar: <mx:ProgressBar id="appProgress" mode="manual" width="300" label="{appProgressMsg}" minimum="0" maximum="100"/> I have two listener functions, one sets the progress, and one sets the appProgressMsg: public function incProgress(e:TEvent):void { var p:uint = Math.floor(e.data.number / e.data.total * 100); trace("Setting Perc." + p); appProgress.setProgress(p, 100); } public function setApplicationProgressStep(e:TEvent):void { trace("Setting step:" + e.data); appProgressMsg = e.data; } I want to reuse this progress bar alot. And not necessarily for ProgressEvents, but when going through steps. For instance, I loop over a bunch of database inserts, and want to undate the progress etc. Here is a sample: public function updateDatabase(result:Object):void { var total:int = 0; var i:int = 0; var r:SQLResult; trace("updateDatabase called."); for each (var table:XML in this.queries.elements("table")) { var key:String = table.attribute("name"); if (result[key]) { send(TEvent.UpdateApplicationProgressStep, "Updating " + key); i = 1; total = result[key].length; for each (var row:Object in result[key]) { //now, we need to see if we already have this record. send(TEvent.UpdateApplicationProgress, { number:i, total: total } ); r = this.query("select * from " + key + " where server_id = '" + row.id + "'"); if (r.data == null) { //there is no entry with this id, make one. this.query(table.insert, row); } else { //it exists, so let's update. this.update(key, row); } i++; } } } } Everything works fine. That is, the listener functions are called and I get trace output like: updateDatabase called. Setting step:Updating project Setting Perc 25 Setting Perc 50 Setting Perc 75 Setting Perc 100 The issue is, only the very last percent and step is shown. that is, when it's all done, the progress bar jumps to 100% and shows the last step label. Does anyone know why this is? Thanks in advance for any help, Jason

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• Expression Too Complex In Access 2007

  - by Jazzepi

  When I try to run this query in Access through the ODBC interface into a MySQL database I get an "Expression too complex in query expression" error. The essential thing I'm trying to do is translate abbreviated names of languages into their full body English counterparts. I was curious if there was some way to "trick" access into thinking the expression is smaller with sub queries, or if someone else had a better idea of how to solve this problem. I thought about making a temporary table and doing a join on it, but that's not supported in Access SQL. Just as an FYI, the query worked fine until I added the big long IFF chain. I tested the query on a smaller IFF chain for three languages, and that wasn't an issue, so the problem definitely stems from the huge IFF chain (It's 26 deep). Also, I might be able to drop some of the options (like combining the different forms of Chinese or Portuguese) As a test, I was able to get the SQL query to work after paring it down to 14 IFF() statements, but that's a far cry from the 26 languages I'd like to represent. SELECT TOP 5 Count( * ) AS [Number of visits by language], IIf(login.lang="ar","Arabic",IIf(login.lang="bg","Bulgarian",IIf(login.lang="zh_CN","Chinese (Simplified Han)",IIf(login.lang="zh_TW","Chinese (Traditional Han)",IIf(login.lang="cs","Czech",IIf(login.lang="da","Danish",IIf(login.lang="de","German",IIf(login.lang="en_US","United States English",IIf(login.lang="en_GB","British English",IIf(login.lang="es","Spanish",IIf(login.lang="fr","French",IIf(login.lang="el","Greek",IIf(login.lang="it","Italian",IIf(login.lang="ko","Korean",IIf(login.lang="hu","Hungarian",IIf(login.lang="nl","Dutch",IIf(login.lang="pl","Polish",IIf(login.lang="pt_PT","European Portuguese",IIf(login.lang="pt_BR","Brazilian Portuguese",IIf(login.lang="ru","Russian",IIf(login.lang="sk","Slovak",IIf(login.lang="sl","Slovenian","IIf(login.lang="fi","Finnish",IIf(login.lang="sv","Swedish",IIf(login.lang="tr","Turkish","Unknown")))))))))))))))))))))))))) AS [Language] FROM login, reservations, reservation_users, schedules WHERE (reservations.start_date Between DATEDIFF('s','1970-01-01 00:00:00',[Starting Date in the Following Format YYYY/MM/DD]) And DATEDIFF('s','1970-01-01 00:00:00',[Ending Date in the Following Format YYYY/MM/DD])) And reservations.is_blackout=0 And reservation_users.memberid=login.memberid And reservation_users.resid=reservations.resid And reservation_users.invited=0 And reservations.scheduleid=schedules.scheduleid And scheduletitle=[Schedule Title] GROUP BY login.lang ORDER BY Count( * ) DESC; @ Michael Todd I completely agree. The list of languages should have been a table in the database and the login.lang should have been a FK into that table. Unfortunately this isn't how the database was written, and it's not really mine to modify. The languages are placed into the login.lang field by the PHP running on top of the database.

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