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• .Net Remote Log Querying

  - by jlafay

  I have a Win Service that I'm working on that consists of the service, WF Service (using WorkflowServiceHost), a Workflow (WorkflowApplication) that queries/processes data from a SQL Server DB, and a Comm Marshall class that handles data flow between the service and the WF. The WF does a lot of heavy data processing and the original app (early VB6) logged all the processing and displayed the results on the screen of the host machine. Critical events will be committed to eventlog because I strongly believe that should be common practice because admins naturally will look there and because it already has support for remote viewing. The workflow will also need to write logging events as it processes and iterates according to our business logic. Such as: records queried, records returned, processed records, etc. The data is very critical and we need to log actions as they occur. The logs are currently kept as text files on disk and I think that is ok. Ideally I would like to record log events in XML so it's easier to query and because it is less costly than a DB, especially since our DB servers do a lot of heavy processing anyways. Since we are replacing essentially a VB6 application with a robust windows service (taking advantage of WF 4.0), it has been requested that a remote client also be created. It receives callbacks from the service after subscribing to it and being added to a collection of subscribers. Basic statistics and summaries are updated client side after receiving basic monitoring data of what is going on with the service. We would like to also provide a way to provide details when we need to examine what is going on further because this is a long running data processing service and issues need to be addressed immediately. What is the best way to implement some type of query from the client that is sent to the service and returned to the client? Would it be efficient to implement another method to expose on the service and then have that pass that off to some querying class/object to examine the XML files by whichever specification and then return it to the client? That's the main concern. I don't want the service to processing to bottleneck much while this occurs. It seems that WF already auto-magically threads well for the most part but I want to make sure this is the right way to go about it. Any suggestions/recommendations on how to architect and implement a small log querying framework for a remote service would be awesome.

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• DB Design Pattern - Many to many classification / categorised tagging.

  - by Robin Day

  I have an existing database design that stores Job Vacancies. The "Vacancy" table has a number of fixed fields across all clients, such as "Title", "Description", "Salary range". There is an EAV design for "Custom" fields that the Clients can setup themselves, such as, "Manager Name", "Working Hours". The field names are stored in a "ClientText" table and the data stored in a "VacancyClientText" table with VacancyId, ClientTextId and Value. Lastly there is a many to many EAV design for custom tagging / categorising the vacancies with things such as Locations/Offices the vacancy is in, a list of skills required. This is stored as a "ClientCategory" table listing the types of tag, "Locations, Skills", a "ClientCategoryItem" table listing the valid values for each Category, e.g., "London,Paris,New York,Rome", "C#,VB,PHP,Python". Finally there is a "VacancyClientCategoryItem" table with VacancyId and ClientCategoryItemId for each of the selected items for the vacancy. There are no limits to the number of custom fields or custom categories that the client can add. I am now designing a new system that is very similar to the existing system, however, I have the ability to restrict the number of custom fields a Client can have and it's being built from scratch so I have no legacy issues to deal with. For the Custom Fields my solution is simple, I have 5 additional columns on the Vacancy Table called CustomField1-5. This removes one of the EAV designs. It is with the tagging / categorising design that I am struggling. If I limit a client to having 5 categories / types of tag. Should I create 5 tables listing the possible values "CustomCategoryItems1-5" and then an additional 5 many to many tables "VacancyCustomCategoryItem1-5" This would result in 10 tables performing the same storage as the three tables in the existing system. Also, should (heaven forbid) the requirements change in that I need 6 custom categories rather than 5 then this will result in a lot of code change. Therefore, can anyone suggest any DB Design Patterns that would be more suitable to storing such data. I'm happy to stick with the EAV approach, however, the existing system has come across all the usual performance issues and complex queries associated with such a design. Any advice / suggestions are much appreciated. The DBMS system used is SQL Server 2005, however, 2008 is an option if required for any particular pattern.

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• How to combine a list of choices to determine which select statement

  - by Larry

  I have a mysql db and am using php 5.2 What I am trying to do is offer a list of options for a person to select (only 1). The chosen option will cause a select, update, or delete statement to be ran. The results of the statement do not need to be shown, although, showing the old and then the new would be nice (no problems with that part tho'.). Pseudo-Code: Assign $choice = 0 Check the value of $choice // This way, if it = 100, we do a break Select a Choice:<br> 1. Adjust Status Value (+60) // $choice = 1<br> 2. Show all Ships <br> // $choice = 2 3. Show Ships in Port <br> // $choice = 3 ... 0. $choice="100" // if the value =100, quit this part Use either case (switch) or if/else statements to run the users choice1 If the choice is 1, then run the "Select" statement with the variable of $sql1 -- "SELECT .... If the choice is 2, then run the "Select" statement with the variable of $sql2 --- SELECT * FROM Ships If the choice is 3, then run the "Select" statement with the variable of $sql3 <br> .... If the choice is 0, then we are done. I figured the (3) statements would be assigned in php as: $sql1="...". $sql2="SELECT * FROM Ships" $sql3="SELECT * FROM Ships WHERE nPort="1" My idea was to use the switch statement, but got lost on it. :( I would like the options to be available over and over again, until a variable ($choice) is selected. In which case, this particular page is done and goes back to the "Main Menu"? The coding and display, if I use it, I can do. Just not sure how to write the way to select which one I want. It is possible that I would run all of the queries, and other times, only one, so that is why I would like the choice. An area I get confused in is the proper forms to use such as -- ' ' " " and ...?? Not sure the # of options I will end up with, but it will be more than 5 but less than 20 / page. So if I get the system down for 2-3 choices, I can replicate it for as many as I may need. And, as always, if a better way exists, I am willing to try it. Thanks again... Larry

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• How do I add a filter button to this pagination?

  - by ClarkSKent

  Hey, I want to add a button(link), that when clicked will filter the pagination results. I'm new to php (and programming in general) and would like to add a button like 'Automotive' and when clicked it updates the 2 mysql queries in my pagination script, seen here: As you can see, the category automotive is hardcoded in, I want it to be dynamic, so when a link is clicked it places whatever the id or class is in the category part of the query. 1: $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); 2: $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); This is the entire current php pagination script that I am using: <?php //connecting to the database $error = "Could not connect to the database"; mysql_connect('localhost','root','root') or die($error); mysql_select_db('ajax_demo') or die($error); //max displayed per page $per_page = 2; //get start variable $start = $_GET['start']; //count records $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); //count max pages $max_pages = $record_count / $per_page; //may come out as decimal if (!$start) $start = 0; //display data $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); while ($row = mysql_fetch_assoc($get)) { // get data $name = $row['id']; $age = $row['site_name']; echo $name." (".$age.")<br />"; } //setup prev and next variables $prev = $start - $per_page; $next = $start + $per_page; //show prev button if (!($start<=0)) echo "<a href='pagi_test.php?start=$prev'>Prev</a> "; //show page numbers //set variable for first page $i=1; for ($x=0;$x<$record_count;$x=$x+$per_page) { if ($start!=$x) echo " <a href='pagi_test.php?start=$x'>$i</a> "; else echo " <a href='pagi_test.php?start=$x'><b>$i</b></a> "; $i++; } //show next button if (!($start>=$record_count-$per_page)) echo " <a href='pagi_test.php?start=$next'>Next</a>"; ?>

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• Hibernate Communications Link Failure in Restlet-Hibernate Based Java 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?)

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• Java code optimization leads to numerical inaccuracies and errors

  - by rano

  I'm trying to implement a version of the Fuzzy C-Means algorithm in Java and I'm trying to do some optimization by computing just once everything that can be computed just once. This is an iterative algorithm and regarding the updating of a matrix, the clusters x pixels membership matrix U, this is the update rule I want to optimize: where the x are the element of a matrix X (pixels x features) and v belongs to the matrix V (clusters x features). And m is a parameter that ranges from 1.1 to infinity. The distance used is the euclidean norm. If I had to implement this formula in a banal way I'd do: for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < V.length; j++) { double num = D[i][j]; double sumTerms = 0; for(int k = 0; k < V.length; k++) { double thisDistance = D[i][k]; sumTerms += Math.pow(num / thisDistance, (1.0 / (m - 1.0))); } U[i][j] = (float) (1f / sumTerms); } } In this way some optimization is already done, I precomputed all the possible squared distances between X and V and stored them in a matrix D but that is not enough, since I'm cycling througn the elements of V two times resulting in two nested loops. Looking at the formula the numerator of the fraction is independent of the sum so I can compute numerator and denominator independently and the denominator can be computed just once for each pixel. So I came to a solution like this: int nClusters = V.length; double exp = (1.0 / (m - 1.0)); for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < nClusters; j++) { double distance = D[i][j]; double denominator = D[i][nClusters]; double numerator = Math.pow(distance, exp); U[i][j] = (float) (1f / (numerator * denominator)); } } Where I precomputed the denominator into an additional column of the matrix D while I was computing the distances: for (int i = 0; i < X.length; i++) { for (int j = 0; j < V.length; j++) { double sum = 0; for (int k = 0; k < nDims; k++) { final double d = X[i][k] - V[j][k]; sum += d * d; } D[i][j] = sum; D[i][B.length] += Math.pow(1 / D[i][j], exp); } } By doing so I encounter numerical differences between the 'banal' computation and the second one that leads to different numerical value in U (not in the first iterates but soon enough). I guess that the problem is that exponentiate very small numbers to high values (the elements of U can range from 0.0 to 1.0 and exp , for m = 1.1, is 10) leads to ver y small values, whereas by dividing the numerator and the denominator and THEN exponentiating the result seems to be better numerically. The problem is it involves much more operations. Am I doing something wrong? Is there a possible solution to get both the code optimized and numerically stable? Any suggestion or criticism will be appreciated.

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• SQL Native Client 10 Performance miserable (due to server-side cursors)

  - by namezero

  we have an application that uses ODBC via CDatabase/CRecordset in MFC (VS2010). We have two backends implemented. MSSQL and MySQL. Now, when we use MSSQL (with the Native Client 10.0), retrieving records with SELECT is dramatically slow via slow links (VPN, for example). The MySQL ODBC driver does not exhibit this nasty behavior. For example: CRecordset r(&m_db); r.Open(CRecordset::snapshot, L"SELECT a.something, b.sthelse FROM TableA AS a LEFT JOIN TableB AS b ON a.ID=b.Ref"); r.MoveFirst(); while(!r.IsEOF()) { // Retrieve CString strData; crs.GetFieldValue(L"a.something", strData); crs.MoveNext(); } Now, with the MySQL driver, everything runs as it should. The query is returned, and everything is lightning fast. However, with the MSSQL Native Client, things slow down, because on every MoveNext(), the driver communicates with the server. I think it is due to server-side cursors, but I didn't find a way to disable them. I have tried using: ::SQLSetConnectAttr(m_db.m_hdbc, SQL_ATTR_ODBC_CURSORS, SQL_CUR_USE_ODBC, SQL_IS_INTEGER); But this didn't help either. There are still long-running exec's to sp_cursorfetch() et al in SQL Profiler. I have also tried a small reference project with SQLAPI and bulk fetch, but that hangs in FetchNext() for a long time, too (even if there is only one record in the resultset). This however only happens on queries with LEFT JOINS, table-valued functions, etc. Note that the query doesn't take that long - executing the same SQL via SQL Studio over the same connection returns in a reasonable time. Question1: Is is possible to somehow get the native client to "cache" all results locally use local cursors in a similar fashion as the MySQL driver seems to do it? Maybe this is the wrong approach altogether, but I'm not sure how else to do this. All we want is to retrieve all data at once from a SELECT, then never talk the server again until the next query. We don't care about recordset updates, deletes, etc or any of that nonsense. We only want to retrieve data. We take that recordset, get all the data, and delete it. Question2: Is there a more efficient way to just retrieve data in MFC with ODBC?

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• Please help fix and optimize this query

  - by user607217

  I am working on a system to find potential duplicates in our customers table (SQL 2005). I am using the built-in SOUNDEX value that our software computes when customers are added/updated, but I also implemented the double metaphone algorithm for better matching. This is the most-nested query I have created, and I can't help but think there is a better way to do it and I'd like to learn. In the inner-most query I am joining the customer table to the metaphone table I created, then finding customers that have identical pKey (primary phonetic key). I take that, union that with customers that have matching soundex values, and then proceed to score those matches with various text similarity functions. This is currently working, but I would also like to add a union of customers whose aKey (alternate phonetic key) match. This would be identical to "QUERY A" except to substitute on (c1Akey = c2Akey) for the join. However, when I attempt to include that, I get errors when I try to execute my query. Here is the code: --Create aggregate ranking select c1Name, c2Name, nDiff, c1Addr, c2Addr, aDiff, c1SSN, c2SSN, sDiff, c1DOB, c2DOB, dDiff, nDiff+aDiff+dDiff+sDiff as Score ,(sDiff+dDiff)*1.5 + (nDiff+dDiff)*1.5 + (nDiff+sDiff)*1.5 + aDiff *.5 + nDiff *.5 as [Rank] FROM ( --Create match scores for different fields SELECT c1Name, c2Name, c1Addr, c2Addr, c1SSN, c2SSN, c1LTD, c2LTD, c1DOB, c2DOB, dbo.Jaro(c1name, c2name) AS nDiff, dbo.JaroWinkler(c1addr, c2addr) AS aDiff, CASE WHEN c1dob = '1901-01-01' OR c2dob = '1901-01-01' OR c1dob = '1800-01-01' OR c2dob = '1800-01-01' THEN .5 ELSE dbo.SmithWaterman(c1dob, c2dob) END AS dDiff, CASE WHEN c1ssn = '000-00-0000' OR c2ssn = '000-00-0000' THEN .5 ELSE dbo.Jaro(c1ssn, c2ssn) END AS sDiff FROM -- Generate list of possible matches based on multiple phonetic matching fields ( select * from -- List of similar names from pKey field of ##Metaphone table --QUERY A BEGIN (select customers.custno as c1Custno, name as c1Name, haddr as c1Addr, ssn as c1SSN, lasttripdate as c1LTD, dob as c1DOB, soundex as c1Soundex, pkey as c1Pkey, akey as c1Akey from Customers WITH (nolock) join ##Metaphone on customers.custno = ##Metaphone.custno) as c1 JOIN (select customers.custno as c2Custno, name as c2Name, haddr as c2Addr, ssn as c2SSN, lasttripdate as c2LTD, dob as c2DOB, soundex as c2Soundex, pkey as c2Pkey, akey as c2Akey from Customers with (nolock) join ##Metaphone on customers.custno = ##Metaphone.custno) as c2 on (c1Pkey = c2Pkey) and (c1Custno < c2Custno) WHERE (c1Name <> 'PARENT, GUARDIAN') and c1soundex != c2soundex --QUERY A END union --List of similar names from pregenerated SOUNDEX field (select t1.custno, t1.name, t1.haddr, t1.ssn, t1.lasttripdate, t1.dob, t1.[soundex], 0, 0, t2.custno, t2.name, t2.haddr, t2.ssn, t2.lasttripdate, t2.dob, t2.[soundex], 0, 0 from Customers t1 WITH (nolock) join customers t2 with (nolock) on t1.[soundex] = t2.[soundex] and t1.custno < t2.custno where (t1.name <> 'PARENT, GUARDIAN')) ) as a ) as b where (sDiff+dDiff)*1.5 + (nDiff+dDiff)*1.5 + (nDiff+sDiff)*1.5 + aDiff *.5 + nDiff *.5 >= 7.5 order by [rank] desc, score desc Previously, I was using joins such as on c1.pkey = c2.pkey or c1.akey = c2.akey or c1.soundex = c2.soundex but the performance was horrendous, and using unions seems to be working a lot better. Out of 103K customers, tt is currently generating a list of 8.5M potential matches (based on the phonetic codes) in 2.25 minutes, and then taking another 2 to score, rank and filter those down to about 3000. So I am happy with the performance, I just can't help but think there is a better way to structure this, and I need help adding the extra union condition. Thanks!

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• T-SQL generated from LINQ to SQL is missing a where clause

  - by Jimmy W

  I have extended some functionality to a DataContext object (called "CodeLookupAccessDataContext") such that the object exposes some methods to return results of LINQ to SQL queries. Here are the methods I have defined: public List<CompositeSIDMap> lookupCompositeSIDMap(int regionId, int marketId) { var sidGroupId = CompositeSIDGroupMaps.Where(x => x.RegionID.Equals(regionId) && x.MarketID.Equals(marketId)) .Select(x => x.CompositeSIDGroup); IEnumerator<int> sidGroupIdEnum = sidGroupId.GetEnumerator(); if (sidGroupIdEnum.MoveNext()) return lookupCodeInfo<CompositeSIDMap, CompositeSIDMap>(x => x.CompositeSIDGroup.Equals(sidGroupIdEnum.Current), x => x); else return null; } private List<TResult> lookupCodeInfo<T, TResult>(Func<T, bool> compLambda, Func<T, TResult> selectLambda) where T : class { System.Data.Linq.Table<T> dataTable = this.GetTable<T>(); var codeQueryResult = dataTable.Where(compLambda) .Select(selectLambda); List<TResult> codeList = new List<TResult>(); foreach (TResult row in codeQueryResult) codeList.Add(row); return codeList; } CompositeSIDGroupMap and CompositeSIDMap are both tables in our database that are represented as objects in my DataContext object. I wrote the following code to call these methods and display the T-SQL generated after calling these methods: using (CodeLookupAccessDataContext codeLookup = new CodeLookupAccessDataContext()) { codeLookup.Log = Console.Out; List<CompositeSIDMap> compList = codeLookup.lookupCompositeSIDMap(5, 3); } I got the following results in my log after invoking this code: SELECT [t0].[CompositeSIDGroup] FROM [dbo].[CompositeSIDGroupMap] AS [t0] WHERE ([t0].[RegionID] = @p0) AND ([t0].[MarketID] = @p1) -- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [5] -- @p1: Input Int (Size = 0; Prec = 0; Scale = 0) [3] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.1 SELECT [t0].[PK_CSM], [t0].[CompositeSIDGroup], [t0].[InputSID], [t0].[TargetSID], [t0].[StartOffset], [t0].[EndOffset], [t0].[Scale] FROM [dbo].[CompositeSIDMap] AS [t0] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.1 The first T-SQL statement contains a where clause as specified and returns one column as expected. However, the second statement is missing a where clause and returns all columns, even though I did specify which rows I wanted to view and which columns were of interest. Why is the second T-SQL statement generated the way it is, and what should I do to ensure that I filter out the data according to specifications via the T-SQL? Also note that I would prefer to keep lookupCodeInfo() and especially am interested in keeping it enabled to accept lambda functions for specifying which rows/columns to return.

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• How to handle very frequent updates to a Lucene index

  - by fsm

  I am trying to prototype an indexing/search application which uses very volatile indexing data sources (forums, social networks etc), here are some of the performance requirements, Very fast turn-around time (by this I mean that any new data (such as a new message on a forum) should be available in the search results very soon (less than a minute)) I need to discard old documents on a fairly regular basis to ensure that the search results are not dated. Last but not least, the search application needs to be responsive. (latency on the order of 100 milliseconds, and should support at least 10 qps) All of the requirements I have currently can be met w/o using Lucene (and that would let me satisfy all 1,2 and 3), but I am anticipating other requirements in the future (like search relevance etc) which Lucene makes easier to implement. However, since Lucene is designed for use cases far more complex than the one I'm currently working on, I'm having a hard time satisfying my performance requirements. Here are some questions, a. I read that the optimize() method in the IndexWriter class is expensive, and should not be used by applications that do frequent updates, what are the alternatives? b. In order to do incremental updates, I need to keep committing new data, and also keep refreshing the index reader to make sure it has the new data available. These are going to affect 1 and 3 above. Should I try duplicate indices? What are some common approaches to solving this problem? c. I know that Lucene provides a delete method, which lets you delete all documents that match a certain query, in my case, I need to delete all documents which are older than a certain age, now one option is to add a date field to every document and use that to delete documents later. Is it possible to do range queries on document ids (I can create my own id field since I think that the one created by lucene keeps changing) to delete documents? Is it any faster than comparing dates represented as strings? I know these are very open questions, so I am not looking for a detailed answer, I will try to treat all of your answers as suggestions and use them to inform my design. Thanks! Please let me know if you need any other information.

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• App losing db connection

  - by DaveKub

  I'm having a weird issue with an old Delphi app losing it's database connection. Actually, I think it's losing something else that then makes the connection either drop or be unusable. The app is written in Delphi 6 and uses the Direct Oracle Access component (v4.0.7.1) to connect to an Oracle 9i database. The app runs as a service and periodically queries the db using a TOracleQuery object (qryAlarmList). The method that is called to do this looks like this: procedure TdmMain.RefreshAlarmList; begin try qryAlarmList.Execute; except on E: Exception do begin FStatus := ssError; EventLog.LogError(-1, 'TdmMain.RefreshAlarmList', 'Message: ' + E.Message); end; end; end; It had been running fine for years, until a couple of Perl scripts were added to this machine. These scripts run every 15 minutes and look for datafiles to import into the db, and then they do a some calculations and a bunch of reads/writes to/from the db. For some reason, when they are processing large amounts of data, and then the Delphi app tries to query the db, the Delphi app throws an exception at the "qryAlarmList.Execute" line in the above code listing. The exception is always: Access violation at address 00000000. read of address 00000000 HOW can something that the Perl scripts are doing cause this?? There are other Perl scripts on this machine that load data using the same modules and method calls and we didn't have problems. To make it even weirder, there are two other apps that will also suddenly lose their ability to talk to the database at the same time as the Perl stuff is running. Neither of those apps run on this machine, but both are Delphi 6 apps that use the same DOA component to connect to the same database. We have other apps that connect to the same db, written in Java or C# and they don't seem to have any problems. I've tried adding code before the '.Execute' method is called to: check the session's connection (session.CheckConnection(true); always comes back as 'ccOK'). see whether I can access a field of the qryAlarmList object to see if maybe it's become null; can access it fine. check the state of the qryAlarmList; always says it's qsIdle. Does anyone have any suggestions of something to try? This is driving me nuts! Dave

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• Is order of parameters for database Command object really important?

  - by nawfal

  I was debugging a database operation code and I found that proper UPDATE was never happening though the code never failed as such. This is the code: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); But after some tweaking this worked: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); Why is it so important that the parameters in WHERE clause has to be given the last in case of OleDb connection? Having worked with MySQL previously, I could (and usually do) write parameters of WHERE clause first because that's more logical to me. Is parameter order important when querying database in general? Some performance concern or something? Is there a specific order to be maintained in case of other databases like DB2, Sqlite etc? Update: I got rid of ? and included proper names with and without @. The order is really important. In both cases only when WHERE clause parameters was mentioned last, actual update happened. To make matter worse, in complex queries, its hard to know ourselves which order is Access expecting, and in all situations where order is changed, the query doesnt do its intended duty with no warning/error!!

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• Printing a variable only when it changes?

  - by user1781639

  First off, my question was a little vague or confusing since I'm not really sure how to phrase my question to be specific. I'm trying to query a database of stockists for a Knitting company (school project using PHP) but I'm looking to print the city as a heading instead of with each stockists information. Here is what I have at the moment: $sql = "SELECT * FROM mc16korustockists where locale = 'south'"; $result = pg_exec($sql); $nrows = pg_numrows($result); print $nrows; $items = pg_fetch_all($result); print_r($items); for ($i=0; $i<$nrows2; $i++) { print "<h2>"; print $items[$i]['city']; print "</h2>"; print $items[$i]['name']; print $items[$i]['address']; print $items[$i]['city']; print $items[$i]['phone']; print "<br />"; print "<br />"; } I'm querying the database for all of the data in it, the rows being ref, name, address, city and phone, and executing it. Querying the number of rows then using that to determine how many iterations for the loop to run is all fine but what I'd like to have is for the h2 heading to appear above the for ($i=0;) line. Trying just breaks my page so that might be out of the question. I figure I'd have to count the number of entries in 'city' until it detects a change then change the heading to that name I think? That or make a heap of queries and set a variable for each name but at point, I might as well do it manually (and I highly doubt it would be best practice). Oh, and I'd welcome any critiques to my PHP since I'm just starting out. Thanks and if you need any more information, just ask! P.S. Our class is learning with PostgreSQL instead of MySQL as you can see in the tags.

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• Function returning MYSQL_ROW

  - by Gabe

  I'm working on a system using lots of MySQL queries and I'm running into some memory problems I'm pretty sure have to do with me not handling pointers right... Basically, I've got something like this: MYSQL_ROW function1() { string query="SELECT * FROM table limit 1;"; MYSQL_ROW return_row; mysql_init(&connection); // "connection" is a global variable if (mysql_real_connect(&connection,HOST,USER,PASS,DB,0,NULL,0)){ if (mysql_query(&connection,query.c_str())) cout << "Error: " << mysql_error(&connection); else{ resp = mysql_store_result(&connection); //"resp" is also global if (resp) return_row = mysql_fetch_row(resp); mysql_free_result(resp); } mysql_close(&connection); }else{ cout << "connection failed\n"; if (mysql_errno(&connection)) cout << "Error: " << mysql_errno(&connection) << " " << mysql_error(&connection); } return return_row; } And function2(): MYSQL_ROW function2(MYSQL_ROW row) { string query = "select * from table2 where code = '" + string(row[2]) + "'"; MYSQL_ROW retorno; mysql_init(&connection); if (mysql_real_connect(&connection,HOST,USER,PASS,DB,0,NULL,0)){ if (mysql_query(&connection,query.c_str())) cout << "Error: " << mysql_error(&conexao); else{ // My "debugging" shows me at this point `row[2]` is already fubar resp = mysql_store_result(&connection); if (resp) return_row = mysql_fetch_row(resp); mysql_free_result(resp); } mysql_close(&connection); }else{ cout << "connection failed\n"; if (mysql_errno(&connection)) cout << "Error : " << mysql_errno(&connection) << " " << mysql_error(&connection); } return return_row; } And main() is an infinite loop basically like this: int main( int argc, char* args[] ){ MYSQL_ROW row = NULL; while (1) { row = function1(); if(row != NULL) function2(row); } } (variable and function names have been generalized to protect the innocent) But after the 3rd or 4th call to function2, that only uses row for reading, row starts losing its value coming to a segfault error... Anyone's got any ideas why? I'm not sure the amount of global variables in this code is any good, but I didn't design it and only got until tomorrow to fix and finish it, so workarounds are welcome! Thanks!

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• What classes should I map against with NHibernate?

  - by apollodude217

  Currently, we use NHibernate to map business objects to database tables. Said business objects enforce business rules: The set accessors will throw an exception on the spot if the contract for that property is violated. Also, the properties enforce relationships with other objects (sometimes bidirectional!). Well, whenever NHibernate loads an object from the database (e.g. when ISession.Get(id) is called), the set accessors of the mapped properties are used to put the data into the object. What's good is that the middle tier of the application enforces business logic. What's bad is that the database does not. Sometimes crap finds its way into the database. If crap is loaded into the application, it bails (throws an exception). Sometimes it clearly should bail because it cannot do anything, but what if it can continue working? E.g., an admin tool that gathers real-time reports runs a high risk of failing unnecessarily instead of allowing an admin to even fix a (potential) problem. I don't have an example on me right now, but in some instances, letting NHibernate use the "front door" properties that also enforce relationships (especially bidi) leads to bugs. What are the best solutions? Currently, I will, on a per-property basis, create a "back door" just for NHibernate: public virtual int Blah {get {return _Blah;} set {/*enforces BR's*/}} protected virtual int _Blah {get {return blah;} set {blah = value;}} private int blah; I showed the above in C# 2 (no default properties) to demonstrate how this gets us basically 3 layers of, or views, to blah!!! While this certainly works, it does not seem ideal as it requires the BL to provide one (public) interface for the app-at-large, and another (protected) interface for the data access layer. There is an additional problem: To my knowledge, NHibernate does not give you a way to distinguish between the name of the property in the BL and the name of the property in the entity model (i.e. the name you use when you query, e.g. via HQL--whenever you give NHibernate the name (string) of a property). This becomes a problem when, at first, the BR's for some property Blah are no problem, so you refer to it in your O/R mapping... but then later, you have to add some BR's that do become a problem, so then you have to change your O/R mapping to use a new _Blah property, which breaks all existing queries using "Blah" (common problem with programming against strings). Has anyone solved these problems?!

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• remove data layer and put into it's own domain

  - by user334768

  I have a SL4 application that uses EF4 & RIA Services. DB is SQL 2008. All is working well. Now I want to put the Database and web services on one domain (A.com) with the web service exposing the same methods available in my working project. (one listed at top of message) Then put a Silverlight application (same one as above) on domain(B.com) and call the web services on A.com. I thought I had a fair understanding of RIA Services. Enough to get the above application working. Now when I say "working" I do mean on my local dev machine. I have yet to deployed as SL4 & .NET 4 application to my hosting site. But I don't think I understand it well enough. I normally create a new business app, add EF then create the RIA DomainService. Add any [Includes] I need, modify my linq queries and run application. And it works. Now I need to break off my data layer and put it on another hosting site (A.com) And put my UI and business logic on another hosting site (B.com) I think I need to do the following : On the Database & web service site: domain(A.com) create application, create EF4, create RIA Services and deploy. At this time, are the methods exposed available as a "WEB SERVICE" to other applications calling by http:// a.com/serviceName.svc address? I think I need to do the following : On the application site : domain(B.com) create a business application (later will need authentication and navigation). How can I create an EF when I don't have access to the database? (I know I do have access but I want know what happens here when I do not have access to the database, but only data provided by a web service) If I can not create an EF how do I create my RIA Service? I hope any one who takes time to help me understands what I'm asking. Sorry so long.

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• C# slowdown while creating a bitmap - calculating distances from a large List of places for each pixel

  - by user576849

  I'm creating a graphic of the glow of lights above a geographic location based upon Walkers Law: Skyglow=0.01*Population*DistanceFromCenter^-2.5 I have a CSV file of places with 66,000 records using 5 fields (id,name,population,latitude,longitude), parsed on the FormLoad event and stored it in: List<string[]> placeDataList Then I set up nested loops to fill in a bitmap using SetPixel. For each pixel on the bitmap, which represents a coordinate on a map (latitude and longitude), the program loops through placeDataList – calculating the distance from that coordinate (pixel) to each place record. The distance (along with population) is used in a calculation to find how much cumulative sky glow is contributed to the coordinate from each place record. So, for every pixel, 66,000 distance calculations must be made. The problem is, this is predictably EXTREMELY slow – on the order of one line of pixels per 30 seconds or so on a 320 pixel wide image. This is unrelated to SetPixel, which I know is also slow, because the speed is similarly slow when adding the distance calculation results to an array. I don’t actually need to test all 66,000 records for every pixel, only the records within 150 miles (i.e. no skyglow is contributed to a coordinate from a small town 3000 miles away). But to find which records are within 150 miles of my coordinate I would still need to loop through all the records for each pixel. I can't use a smaller number of records because all 66,000 places contribute to skyglow for SOME coordinate in my map as it loops. This seems like a Catch-22, so I know there must be a better method out there. Like I mentioned, the slowdown is related to how many calculations I’m making per pixel, not anything to do with the bitmap. Any suggestions? private void fillPixels(int width) { Color pixelColor; int pixel_w = width; int pixel_h = (int)Math.Floor((width * 0.424088664)); Bitmap bmp = new Bitmap(pixel_w, pixel_h); for (int i = 0; i < pixel_h; i++) for (int j = 0; j < pixel_w; j++) { pixelColor = getPixelColor(i, j); bmp.SetPixel(j, i, pixelColor); } bmp.Save("Nightfall", System.Drawing.Imaging.ImageFormat.Jpeg); pictureBox1.Image = bmp; MessageBox.Show("Done"); } private Color getPixelColor(int height, int width) { int c; double glow,d,cityLat,cityLon,cityPop; double testLat, testLon; int size_h = (int)Math.Floor((size_w * 0.424088664)); ; testLat = (height * (24.443136 / size_h)) + 24.548874; testLon = (width * (57.636853 / size_w)) -124.640767; glow = 0; for (int i = 0; i < placeDataList.Count; i++) { cityPop=Convert.ToDouble(placeDataList[i][2]); cityLat=Convert.ToDouble(placeDataList[i][3]); cityLon=Convert.ToDouble(placeDataList[i][4]); d = distance(testLat, testLon, cityLat, cityLon,"M"); if(d<150) glow = glow+(0.01 * cityPop * Math.Pow(d, -2.5)); } if (glow >= 1) glow=1; c = (int)Math.Ceiling(glow * 255); return Color.FromArgb(c, c, c); }

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• What does Apache need to support both mysqli and PDO?

  - by Nathan Long

  I'm considering changing some PHP code to use PDO for database access instead of mysqli (because the PDO syntax makes more sense to me and is database-agnostic). To do that, I'd need both methods to work while I'm making the changeover. My problem is this: so far, either one or the other method will crash Apache. Right now I'm using XAMPP in Windows XP, and PHP Version 5.2.8. Mysqli works fine, and so does this: $dbc = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password); echo 'Connected to database'; $sql = "SELECT * FROM `employee`"; But this line makes Apache crash: $dbc->query($sql); I don't want to redo my entire Apache or XAMPP installation, but I'd like for PDO to work. So I tried updating libmysql.dll from here, as oddvibes recommended here. That made my simple PDO query work, but then mysqli queries crashed Apache. (I also tried the suggestion after that one, to update php_pdo_mysql.dll and php_pdo.dll, to no effect.) Test Case I created this test script to compare PDO vs mysqli. With the old copy of libmysql.dll, it crashes if $use_pdo is true and doesn't if it's false. With the new copy of libmysql.dll, it's the opposite. if ($use_pdo){ $dbc = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password); echo 'Connected to database<br />'; $sql = "SELECT * FROM `employee`"; $dbc->query($sql); foreach ($dbc->query($sql) as $row){ echo $row['firstname'] . ' ' . $row['lastname'] . "<br>\n"; } } else { $dbc = @mysqli_connect($hostname, $username, $password, $dbname) OR die('Could not connect to MySQL: ' . mysqli_connect_error()); $sql = "SELECT * FROM `employee`"; $result = @mysqli_query($dbc, $sql) or die(mysqli_error($dbc)); while ($row = mysqli_fetch_array($result,MYSQLI_ASSOC)) { echo $row['firstname'] . ' ' . $row['lastname'] . "<br>\n"; } } What does Apache need in order to support both methods of database query?

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• Insert a transformed integer_sequence into a variadic template argument?

  - by coderforlife

  How do you insert a transformed integer_sequence (or similar since I am targeting C++11) into a variadic template argument? For example I have a class that represents a set of bit-wise flags (shown below). It is made using a nested-class because you cannot have two variadic template arguments for the same class. It would be used like typedef Flags<unsigned char, FLAG_A, FLAG_B, FLAG_C>::WithValues<0x01, 0x02, 0x04> MyFlags. Typically, they will be used with the values that are powers of two (although not always, in some cases certain combinations would be made, for example one could imagine a set of flags like Read=0x1, Write=0x2, and ReadWrite=0x3=0x1|0x2). I would like to provide a way to do typedef Flags<unsigned char, FLAG_A, FLAG_B, FLAG_C>::WithDefaultValues MyFlags. template<class _B, template <class,class,_B> class... _Fs> class Flags { public: template<_B... _Vs> class WithValues : public _Fs<_B, Flags<_B,_Fs...>::WithValues<_Vs...>, _Vs>... { // ... }; }; I have tried the following without success (placed inside the Flags class, outside the WithValues class): private: struct _F { // dummy class which can be given to a flag-name template template <_B _V> inline constexpr explicit _F(std::integral_constant<_B, _V>) { } }; // we count the flags, but only in a dummy way static constexpr unsigned _count = sizeof...(_Fs<_B, _F, 1>); static inline constexpr _B pow2(unsigned exp, _B base = 2, _B result = 1) { return exp < 1 ? result : pow2(exp/2, base*base, (exp % 2) ? result*base : result); } template <_B... _Is> struct indices { using next = indices<_Is..., sizeof...(_Is)>; using WithPow2Values = WithValues<pow2(_Is)...>; }; template <unsigned N> struct build_indices { using type = typename build_indices<N-1>::type::next; }; template <> struct build_indices<0> { using type = indices<>; }; //// Another attempt //template < _B... _Is> struct indices { // using WithPow2Values = WithValues<pow2(_Is)...>; //}; //template <unsigned N, _B... _Is> struct build_indices // : build_indices<N-1, N-1, _Is...> { }; //template < _B... _Is> struct build_indices<0, _Is...> // : indices<_Is...> { }; public: using WithDefaultValues = typename build_indices<_count>::type::WithPow2Values; Of course, I would be willing to have any other alternatives to the whole situation (supporting both flag names and values in the same template set, etc). I have included a "working" example at ideone: http://ideone.com/NYtUrg - by "working" I mean compiles fine without using default values but fails with default values (there is a #define to switch between them). Thanks!

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• Perl - Calling subclass constructor from superclass (OO)

  - by Emmel

  This may turn out to be an embarrassingly stupid question, but better than potentially creating embarrassingly stupid code. :-) This is an OO design question, really. Let's say I have an object class 'Foos' that represents a set of dynamic configuration elements, which are obtained by querying a command on disk, 'mycrazyfoos -getconfig'. Let's say that there are two categories of behavior that I want 'Foos' objects to have: Existing ones: one is, query ones that exist in the command output I just mentioned (/usr/bin/mycrazyfoos -getconfig`. Make modifications to existing ones via shelling out commands. Create new ones that don't exist; new 'crazyfoos', using a complex set of /usr/bin/mycrazyfoos commands and parameters. Here I'm not really just querying, but actually running a bunch of system() commands. Affecting changes. Here's my class structure: Foos.pm package Foos, which has a new($hashref-{name = 'myfooname',) constructor that takes a 'crazyfoo NAME' and then queries the existence of that NAME to see if it already exists (by shelling out and running the mycrazyfoos command above). If that crazyfoo already exists, return a Foos::Existing object. Any changes to this object requires shelling out, running commands and getting confirmation that everything ran okay. If this is the way to go, then the new() constructor needs to have a test to see which subclass constructor to use (if that even makes sense in this context). Here are the subclasses: Foos/Existing.pm As mentioned above, this is for when a Foos object already exists. Foos/Pending.pm This is an object that will be created if, in the above, the 'crazyfoo NAME' doesn't actually exist. In this case, the new() constructor above will be checked for additional parameters, and it will go ahead and, when called using -create() shell out using system() and create a new object... possibly returning an 'Existing' one... OR As I type this out, I am realizing it is perhaps it's better to have a single: (an alternative arrangement) Foos class, that has a -new() that takes just a name -create() that takes additional creation parameters -delete(), -change() and other params that affect ones that exist; that will have to just be checked dynamically. So here we are, two main directions to go with this. I'm curious which would be the more intelligent way to go.

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• Execution plan issue requires reset on SQL Server 2005, how to determine cause?

  - by Tony Brandner

  We have a web application that delivers training to thousands of corporate students running on top of SQL Server 2005. Recently, we started seeing that a single specific query in the application went from 1 second to about 30 seconds in terms of execution time. The application started throwing timeouts in that area. Our first thought was that we may have incorrect indexes, so we reviewed the tables and indexes. However, similar queries elsewhere in the application also run quickly. Reviewing the indexes showed us that they were configured as expected. We were able to narrow it down to a single query, not a stored procedure. Running this query in SQL Studio also runs quickly. We tried running the application in a different server environment. So a different web server with the same query, parameters and database. The query still ran slow. The query is a fairly large one related to determining a student's current list of training. It includes joins and left joins on a dozen tables and subqueries. A few of the tables are fairly large (hundreds of thousands of rows) and some of the other tables are small lookup tables. The query uses a grouping clause and a few where conditions. A few of the tables are quite active and the contents change often but the volume of added rows doesn't seem extreme. These symptoms led us to consider the execution plan. First off, as soon as we reset the execution plan cache with the SQL command 'DBCC FREEPROCCACHE', the problem went away. Unfortunately, the problem started to reoccur within a few days. The problem has continued to plague us for awhile now. It's usually the same query, but we did appear to see the problem occur in another single query recently. It happens enough to be a nuisance. We're having a heck of a time trying to fix it since we can't reproduce it in any other environment other than production. I have downloaded the High Availability guide from Red Gate and I read up more on execution plans. I hope to run the profiler on the live server, but I'm a bit concerned about impact. I would like to ask - what is the best way to figure out what is triggering this problem? Has anyone else seen this same issue?

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• Why is FubuMVC new()ing up my view model in PartialForEach?

  - by Jon M

  I'm getting started with FubuMVC and I have a simple Customer - Order relationship I'm trying to display using nested partials. My domain objects are as follows: public class Customer { private readonly IList<Order> orders = new List<Order>(); public string Name { get; set; } public IEnumerable<Order> Orders { get { return orders; } } public void AddOrder(Order order) { orders.Add(order); } } public class Order { public string Reference { get; set; } } I have the following controller classes: public class CustomersController { public IndexViewModel Index(IndexInputModel inputModel) { var customer1 = new Customer { Name = "John Smith" }; customer1.AddOrder(new Order { Reference = "ABC123" }); return new IndexViewModel { Customers = new[] { customer1 } }; } } public class IndexInputModel { } public class IndexViewModel { public IEnumerable<Customer> Customers { get; set; } } public class IndexView : FubuPage<IndexViewModel> { } public class CustomerPartial : FubuControl<Customer> { } public class OrderPartial : FubuControl<Order> { } IndexView.aspx: (standard html stuff trimmed) <div> <%= this.PartialForEach(x => x.Customers).Using<CustomerPartial>() %> </div> CustomerPartial.ascx: <%@ Control Language="C#" Inherits="FubuDemo.Controllers.Customers.CustomerPartial" %> <div> Customer Name: <%= this.DisplayFor(x => x.Name) %> <br /> Orders: (<%= Model.Orders.Count() %>) <br /> <%= this.PartialForEach(x => x.Orders) %> </div> OrderPartial.ascx: <%@ Control Language="C#" Inherits="FubuDemo.Controllers.Customers.OrderPartial" %> <div> Order <br /> Ref: <%= this.DisplayFor(x => x.Reference) %> </div> When I view Customers/Index, I see the following: Customers Customer Name: John Smith Orders: (1) It seems that in CustomerPartial.ascx, doing Model.Orders.Count() correctly picks up that 1 order exists. However PartialForEach(x = x.Orders) does not, as nothing is rendered for the order. If I set a breakpoint on the Order constructor, I see that it initially gets called by the Index method on CustomersController, but then it gets called by FubuMVC.Core.Models.StandardModelBinder.Bind, so it is getting re-instantiated by FubuMVC and losing the content of the Orders collection. This isn't quite what I'd expect, I would think that PartialForEach would just pass the domain object directly into the partial. Am I missing the point somewhere? What is the 'correct' way to achieve this kind of result in Fubu?

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• How to setup Lucene/Solr for a B2B web app?

  - by Bill Paetzke

  Given: 1 database per client (business customer) 5000 clients Clients have between 2 to 2000 users (avg is ~100 users/client) 100k to 10 million records per database Users need to search those records often (it's the best way to navigate their data) Possibly relevant info: Several new clients each week (any time during business hours) Multiple web servers and database servers (users can login via any web server) Let's stay agnostic of language or sql brand, since Lucene (and Solr) have a breadth of support For Example: Joel Spolsky said in Podcast #11 that his hosted web app product, FogBugz On-Demand, uses Lucene. He has thousands of on-demand clients. And each client gets their own database. They use an index per client and store it in the client's database. I'm not sure on the details. And I'm not sure if this is a serious mod to Lucene. The Question: How would you setup Lucene search so that each client can only search within its database? How would you setup the index(es)? Where do you store the index(es)? Would you need to add a filter to all search queries? If a client cancelled, how would you delete their (part of the) index? (this may be trivial--not sure yet) Possible Solutions: Make an index for each client (database) Pro: Search is faster (than one-index-for-all method). Indices are relative to the size of the client's data. Con: I'm not sure what this entails, nor do I know if this is beyond Lucene's scope. Have a single, gigantic index with a database_name field. Always include database_name as a filter. Pro: Not sure. Maybe good for tech support or billing dept to search all databases for info. Con: Search is slower (than index-per-client method). Flawed security if query filter removed. One last thing: I would also accept an answer that uses Solr (the extension of Lucene). Perhaps it's better suited for this problem. Not sure.

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• MS Access 07 - Q re lookup column vs many-to-many; Q re checkboxes in many-to-many forms

  - by TBinLondon

  Hello, I'm creating a database with Access. This is just a test database, similar to my requirements, so I can get my skills up before creating one for work. I've created a database for a fictional school as this is a good playground and rich data (many students have many subjects have many teachers, etc). Question 1 What is the difference, if any, between using a Lookup column and a many-to-many associate table? Example: I have Tables 'Teacher' and 'Subject'. Many teachers have many subjects. I can, and have, created a table 'Teacher_Subject' and run queries with this. I have then created a lookup column in teachers table with data from subjects. The lookup column seems to take the place of the teacher_subject table. (though the data on relationships is obviously duplicated between lookup table and teacher_subject and may vary). Which one is the 'better' option? Is there a snag with using lookup tables? (I realize that this is a very 'general' question. Links to other resources and answers saying 'that depends...' are appreciated) Question 2 What attracts me to lookup tables is the following: When creating a form for entering subjects for teachers, with lookup I can simply create checkboxes and click a subject for a teacher 'on' or 'off'. Each click on/off creates/removes a record in the lookup column (which replaces teacher_subject). If I use a form from a query from teacher subject with teacher as main form and subject as subform I run into this problem: In the subform I can either select each subject that teacher has in a bombo box, i.e. click, scroll down, select, go to next row, click, scroll down, etc. (takes too long) OR I can create a list box listing all available subjects in each row but allowing me to select only one. (takes up too much space). Is it possible to have a click on/off list box for teacher_subject, creating/removing a record there with each click? Note - I know zero SQL or VB. If the correct answer is "you need to know SQL for this" then that's cool. I just need to know. Thanks!

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• Can't iterate over nestled dict in django

  - by fredrik

  Hi, Im trying to iterate over a nestled dict list. The first level works fine. But the second level is treated like a string not dict. In my template I have this: {% for product in Products %} <li> <p>{{ product }}</p> {% for partType in product.parts %} <p>{{ partType }}</p> {% for part in partType %} <p>{{ part }}</p> {% endfor %} {% endfor %} </li> {% endfor %} It's the {{ part }} that just list 1 char at the time based on partType. And it seams that it's treated like a string. I can however via dot notation reach all dict but not with a for loop. The current output looks like this: Color C o l o r Style S ..... The Products object looks like this in the log: [{'product': <models.Products.Product object at 0x1076ac9d0>, 'parts': {u'Color': {'default': u'Red', 'optional': [u'Red', u'Blue']}, u'Style': {'default': u'Nice', 'optional': [u'Nice']}, u'Size': {'default': u'8', 'optional': [u'8', u'8.5']}}}] What I trying to do is to pair together a dict/list for a product from a number of different SQL queries. The web handler looks like this: typeData = Products.ProductPartTypes.all() productData = Products.Product.all() langCode = 'en' productList = [] for product in productData: typeDict = {} productDict = {} for type in typeData: typeDict[type.typeId] = { 'default' : '', 'optional' : [] } productDict['product'] = product productDict['parts'] = typeDict defaultPartsData = Products.ProductParts.gql('WHERE __key__ IN :key', key = product.defaultParts) optionalPartsData = Products.ProductParts.gql('WHERE __key__ IN :key', key = product.optionalParts) for defaultPart in defaultPartsData: label = Products.ProductPartLabels.gql('WHERE __key__ IN :key AND partLangCode = :langCode', key = defaultPart.partLabelList, langCode = langCode).get() productDict['parts'][defaultPart.type.typeId]['default'] = label.partLangLabel for optionalPart in optionalPartsData: label = Products.ProductPartLabels.gql('WHERE __key__ IN :key AND partLangCode = :langCode', key = optionalPart.partLabelList, langCode = langCode).get() productDict['parts'][optionalPart.type.typeId]['optional'].append(label.partLangLabel) productList.append(productDict) logging.info(productList) templateData = { 'Languages' : Settings.Languges.all().order('langCode'), 'ProductPartTypes' : typeData, 'Products' : productList } I've tried making the dict in a number of different ways. Like first making a list, then a dict, used tulpes anything I could think of. Any help is welcome! Bouns: If someone have an other approach to the SQL quires, that is more then welcome. I feel that it kinda stupid to run that amount of quires. What is happening that each product part has a different label base on langCode. ..fredrik

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