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  • How can I optimize the SELECT statement running on an Oracle database?

    - by Elvis Lou
    I have a SELECT statement in ORACLE: SELECT COUNT(DISTINCT ds1.endpoint_msisdn) multiple30, dss1.service, dss1.endpoint_provisioning_id, dss1.company_scope, Nvl(x.subscription_status, dss1.subscription_status) subscription_status FROM daily_summary ds1 join daily_summary ds2 ON ds1.endpoint_msisdn = ds2.endpoint_msisdn, daily_summary_static dss1, daily_summary_static dss2, (SELECT NULL subscription_status FROM dual UNION ALL SELECT -2 subscription_status FROM dual) x WHERE ds1.summary_ts >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND ds1.summary_ts <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss1.last_active >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND dss1.last_active <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss2.last_active >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND dss2.last_active <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss1.service <> dss2.service AND ( dss1.company_scope = 2 OR dss1.company_scope = 5 ) AND ( dss2.company_scope = 2 OR dss2.company_scope = 5 ) AND dss1.company_scope = dss2.company_scope AND ds1.endpoint_noc_id = dss1.endpoint_noc_id AND ds1.endpoint_host_id = dss1.endpoint_host_id AND ds1.endpoint_instance_id = dss1.endpoint_instance_id AND ds2.endpoint_noc_id = dss2.endpoint_noc_id AND ds2.endpoint_host_id = dss2.endpoint_host_id AND ds2.endpoint_instance_id = dss2.endpoint_instance_id AND dss1.endpoint_provisioning_id = dss2.endpoint_provisioning_id AND Least(1, ds1.total_actions) = 1 AND Least(1, ds2.total_actions) = 1 GROUP BY dss1.service, dss1.endpoint_provisioning_id, dss1.company_scope, Nvl(x.subscription_status, dss1.subscription_status); This query took about 26 minutes to return in my environment, but if I remove the section: dss1.last_active >= to_date('10-04-2012','dd-mm-yyyy') - 30 AND dss1.last_active <= to_date('10-04-2012','dd-mm-yyyy') AND dss2.last_active >= to_date('10-04-2012','dd-mm-yyyy') - 30 AND dss2.last_active <= to_date('10-04-2012','dd-mm-yyyy') AND it only took 20 seconds to run. We have index on the column last_active, I don't know why the section slow down the performance so much? any ideas?

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  • comma separated values in oracle function body

    - by dmitry
    I've got following oracle function but it does not work and errors out. I used Ask Tom's way to convert comma separated values to be used in select * from table1 where col1 in <> declared in package header: TYPE myTableType IS table of varchar2 (255); Part of package body: l_string long default iv_value_with_comma_separated|| ','; l_data myTableType := myTableType(); n NUMBER; begin begin LOOP EXIT when l_string is null; n := instr( l_string, ',' ); l_data.extend; l_data(l_data.count) := ltrim( rtrim( substr( l_string, 1, n-1 ) ) ); l_string := substr( l_string, n+1 ); END LOOP; end; OPEN my_cursor FOR select * from table_a where column_a in (select * from table (l_data)); CLOSE my_cursor END; above fails but it works fine when I remove select * from table (l_data) Can someone please tell me what I might be doing wrong here??

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  • Java Generics Class Parameter Type Inference

    - by Pindatjuh
    Given the interface: public interface BasedOnOther<T, U extends BasedList<T>> { public T getOther(); public void staticStatisfied(final U list); } The BasedOnOther<T, U extends BasedList<T>> looks very ugly in my use-cases. It is because the T type parameter is already defined in the BasedList<T> part, so the "uglyness" comes from that T needs to be typed twice. Problem: is it possible to let the Java compiler infer the generic T type from BasedList<T> in a generic class/interface definition? Ultimately, I'd like to use the interface like: class X implements BasedOnOther<BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } } // Does not compile, due to invalid parameter count. Instead: class X implements BasedOnOther<SomeType, BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } }

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  • fix a columns width when a list is bound to a datagridview

    - by Andy
    I have a list that I have bound to a datagridview. I want the first column to be a fixed size. The data is bound to the dataGridView and I can't seem to find a way to access an individual colums properties. if I try myDatagridview.colums[0] I get an index out of bounds, since it says the columns count is 0. private DataGridView setUpDataGrid(List<NVRlineVal> _NVRData) { //setup dataGridView DataGridView NVRDataGridView = new System.Windows.Forms.DataGridView(); NVRDataGridView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize; NVRDataGridView.Dock = System.Windows.Forms.DockStyle.Fill; NVRDataGridView.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill; NVRDataGridView.Location = new System.Drawing.Point(3, 3); NVRDataGridView.Name = "NVRDataGridView" + nvrIndex; NVRDataGridView.RowHeadersWidthSizeMode = System.Windows.Forms.DataGridViewRowHeadersWidthSizeMode.AutoSizeToDisplayedHeaders; NVRDataGridView.Size = new System.Drawing.Size(380, 401); NVRDataGridView.TabIndex = 0; NVRDataGridView.DataSource = _NVRData; var test = NVRDataGridView.Columns; NVRDataGridView.DataMember = "devState"; DataGridViewAutoSizeColumnMode.None; } Any ideas on how to have a fixed column width for only one of these columns, the rest will autosize?

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  • JAVA Procedure Error

    - by Sam....
    java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]Procedure 'STP_Insert_tblReceipt' expects parameter '@CPVFlag', which was not supplied. I m getting error at This Point when trying to call procedure... Everything is perfect ,,,Count of Question marks are similar to parameter provided cs = conn.prepareCall("{call STP_Insert_tblReceipt(?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?)}"); // cs = conn.prepareCall("{call STP_Receipt_Form_Insertion_Trial(?,?,?, ?,?,?, ?,?,?, ?,?,?, ?)}"); cs.setLong(1, Long.parseLong(txtMobileNo.getText())); cs.setString(2, String.valueOf(cboDistributor.getSelectedItem())); cs.setLong(3, Long.parseLong(txtBoxNo.getText())); cs.setInt(4, Integer.parseInt(txtFileNo.getText())); cs.setString(5, pickUp_date); cs.setString(6, rec_date); cs.setString(7, String.valueOf(cmbCtrlNo.getSelectedItem())); cs.setString(8, UserName); cs.setString(9, rec_date); cs.setString(10, RegionLocation); cs.setString(11, txtRemark.getText().trim()); cs.setString(12, txtSimNo.getText().trim()); cs.setInt(13, 2); cs.setString(14, String.valueOf(cmbAryanRegion.getSelectedItem())); cs.setString(15, String.valueOf(cboPickUpType.getSelectedItem())); cs.setString(16, String.valueOf(txtCafNo.getText())); cs.setString(17, distributorId); //cs.setString(18, circleName); cs.setString(18, cboCircle.getSelectedItem().toString()); cs.registerOutParameter(19, java.sql.Types.INTEGER); cs.setString(20, auditorName); cs.setString(21, retailerName); cs.setString(22, retailerCode); cs.setInt(23, mappedFlag); //cs.setString(24, distCode); cs.setString(24, cboDistCode.getSelectedItem().toString()); //cs.setString(25, zoneName); cs.setString(25, cboZone.getSelectedItem().toString()); cs.setString(26, comment); **cs.setInt(27, 1);** **this is for CPV Flag** After this cs.execute();

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  • CSS overflow detection in JavaScript

    - by ring0
    In order to display a line of text (like in a forum), and end that line with "..." if the text would overflow the line (not truncating using the CSS overflow property), there are a number of ways. I'm still seeking the best solution. For instance, Adding in CSS a "..." as a background-image is a possibility, but it would appear all the time, and this is not a good solution. Some sites just count the characters and if over - say - 100, truncates the string to keep only 100 (or 97) chars and add a "..." at the end. But fonts are usually not proportional, so the result is not pretty. For instance the space - in pixels - taken by "AAA" and "iii" is clearly different "AAA" and "iii" via a proportional font have the same width There is another idea to get the exact size in pixels of the string: create in Javascript a DIV insert the text in it (via innerHTML for instance) measure the width (via .offsetWidth) which is not implemented yet. However, I wonder if there could be any browser compatibility problem? Did any one tried this solution? Other recommendations would be welcome.

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  • SQL Server stored procedure + set error message from the records of a table

    - by lucky
    Hello, My question is I have a table with the set of records. I am calling a stored procedure for some other purpose. But when ever it finds some duplicate records. It need to return as error message back to php. C1 C2 c3 abc 32 21.03.2010 def 35 04.04.2010 pqr 45 30.03.2010 abc 12 04.05.2010 xyz 56 01.03.2010 ghi 21 06.05.2010 def 47 17.02.2010 klm 93 04.03.2010 xyz 11 01.03.2010 For the above set it need to check for the records that has the same c1. The stored procedure should return as abc,def,xyz are duplicate. I tried something like this. This will not work it has more than 1 set of duplicate records. Please help me to enhance this to solve the purpose. SET @duplicate = (SELECT c1 FROM temp GROUP BY c1 HAVING count(c1) > 1) --Check for duplicate concession Nr. IF(len(@duplicate) > '1') BEGIN SET @error = @error + ' Duplicate C1 Number:- ' + @duplicate SET @errorcount = @errorcount + 1 END As this one type error I am checking for errorcount. IF @errorcount <> '0' BEGIN GOTO E_General_Error END -- If an error occurs, rollback and exit E_General_Error: PRINT 'Error' SET @error = @error IF @@error <> 0 SET @error = 'Database update failed' ROLLBACK TRANSACTION update_database RETURN END Now it is able to return Duplicate c1 number abc. If there are more than 1 problem comes. Thanks in advance!

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  • Emptying the datastore in GAE

    - by colwilson
    I know what you're thinking, 'O not that again!', but here we are since Google have not yet provided a simpler method. I have been using a queue based solution which worked fine: import datetime from models import * DELETABLE_MODELS = [Alpha, Beta, AlphaBeta] def initiate_purge(): for e in config.DELETABLE_MODELS: deferred.defer(delete_entities, e, 'purging', _queue = 'purging') class NotEmptyException(Exception): pass def delete_entities(e, queue): try: q = e.all(keys_only=True) db.delete(q.fetch(200)) ct = q.count(1) if ct > 0: raise NotEmptyException('there are still entities to be deleted') else: logging.info('processing %s completed' % queue) except Exception, err: deferred.defer(delete_entities, e, then, queue, _queue = queue) logging.info('processing %s deferred: %s' % (queue, err)) All this does is queue a request to delete some data (once for each class) and then if the queued process either fails or knows there is still some stuff to delete, it re-queues itself. This beats the heck out of hitting the refresh on a browser for 10 minutes. However, I'm having trouble deleting AlphaBeta entities, there are always a few left at the end. I think because it contains Reference Properties: class AlphaBeta(db.Model): alpha = db.ReferenceProperty(Alpha, required=True, collection_name='betas') beta = db.ReferenceProperty(Beta, required=True, collection_name='alphas') I have tried deleting the indexes relating to these entity types, but that did not make any difference. Any advice would be appreciated please.

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  • how to rotate around each record in linq and show that in view

    - by Sadegh
    Hi, I have four tables in my database and i want to join that's and return record's and show that into searchController! My query is this: public IQueryable PerformSearch(string query) { if (!string.IsNullOrEmpty(query)) { var results = from tbl1 in context.Table1 join tbl2 in context.Table2 on tbl1.Id equals tbl2.Id join tbl3 in context.Table3 on tbl2.Id equals tbl3.Id join tbl4 in context.Table4 on tbl3.Id equals tbl4.Id where tbl1.col2.Contains(query) orderby tbl1.Count descending select new { col1 = tbl1.Col1, col1 = tbl1.Col1, col1 = tbl1.Col1, . . . }; return results.AsQueryable(); } else return null; } And this method called in SearchController as below: public class SearchController : System.Web.Mvc.Controller { public System.Web.Mvc.ActionResult Search(System.String query) { var search = new Search(); ViewData["result"] = search.PerformSearch(query); return View("Search"); } } I don't know how i can rotate around each record (plus vs intellisense feature) returned by PeformSeach method and show that in view! Also is this a good way? thanks in advance

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  • Gridview Paging via ObjectDataSource: Why is maximumRows being set to -1?

    - by Bryan
    So before I tried custom gridview paging via ObjectDataSource... I think I read every tutorial known to man just to be sure I got it. It didn't look like rocket science. I've set the AllowPaging = True on my gridview. I've specified PageSize="10" on my gridview. I've set EnablePaging="True" on the ObjectDataSource. I've added the 2 paging parms (maximumRows & startRowIndex) to my business object's select method. I've created an analogous "count" method with the same signature as the select method. The only problem I seem to have is during execution... the ObjectDataSource is supplying my business object with a maximumRows value of -1 and I can't for the life of me figure out why. I've searched to the end of the web for anyone else having this problem and apparently I'm the only one. The StartRowIndex parameter seems to be working just fine. Any ideas?

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  • Is there a better way to write this LINQ query?

    - by Raj Aththanayake
    Hi Is there a better simplified way to write this query. My logic is if collection contains customer ids and countrycodes, do the query ordey by customer id ascending. If there are no contain id in CustIDs then do the order by customer name. Is there a better way to write this query? I'm not really familiar with complex lambdas. var custIdResult = (from Customer c in CustomerCollection where (c.CustomerID.ToLower().Contains(param.ToLower()) && (countryCodeFilters.Any(item => item.Equals(c.CountryCode))) ) select c).ToList(); if (custIdResult.Count > 0) { return from Customer c in custIdResult where ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode))) orderby c.CustomerID ascending select c; } else { return from Customer c in CustomerCollection where (c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode))) orderby c.CustomerName descending select c; }

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  • Cursor returns zero rows from query to table

    - by brockoli
    I've created an SQLiteDatabase in my app and populated it with some data. I can connect to my AVD with a terminal and when I issue select * from articles; I get a list of all the rows in my table and everything looks fine. However, in my code when I query my table, I get a cursor back that has my tables columns, but zero rows of data. Here is my code.. mDbHelper.open(); Cursor articles = mDbHelper.fetchAllArticles(); startManagingCursor(articles); Cursor feeds = mDbHelper.fetchAllFeeds(); startManagingCursor(feeds); mDbHelper.close(); int titleColumn = articles.getColumnIndex("title"); int feedIdColumn = articles.getColumnIndex("feed_id"); int feedTitleColumn = feeds.getColumnIndex("title"); /* Check if our result was valid. */ if (articles != null) { int count = articles.getCount(); /* Check if at least one Result was returned. */ if (articles.moveToFirst()) { In the above code, my Cursor articles returns with my 4 columns, but when I call getCount() it returns zero, even though I can see hundreds of rows of data in that table from command line. Any idea what I might be doing wrong here? Also.. here is my code for fetchAllArticles.. public Cursor fetchAllArticles() { return mDb.query(ARTICLES_TABLE, new String[] {ARTICLE_KEY_ROWID, ARTICLE_KEY_FEED_ID, ARTICLE_KEY_TITLE, ARTICLE_KEY_URL}, null, null, null, null, null); } Rob W.

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  • Parse a CSV file using python (to make a decision tree later)

    - by Margaret
    First off, full disclosure: This is going towards a uni assignment, so I don't want to receive code. :). I'm more looking for approaches; I'm very new to python, having read a book but not yet written any code. The entire task is to import the contents of a CSV file, create a decision tree from the contents of the CSV file (using the ID3 algorithm), and then parse a second CSV file to run against the tree. There's a big (understandable) preference to have it capable of dealing with different CSV files (I asked if we were allowed to hard code the column names, mostly to eliminate it as a possibility, and the answer was no). The CSV files are in a fairly standard format; the header row is marked with a # then the column names are displayed, and every row after that is a simple series of values. Example: # Column1, Column2, Column3, Column4 Value01, Value02, Value03, Value04 Value11, Value12, Value13, Value14 At the moment, I'm trying to work out the first part: parsing the CSV. To make the decisions for the decision tree, a dictionary structure seems like it's going to be the most logical; so I was thinking of doing something along these lines: Read in each line, character by character If the character is not a comma or a space Append character to temporary string If the character is a comma Append the temporary string to a list Empty string Once a line has been read Create a dictionary using the header row as the key (somehow!) Append that dictionary to a list However, if I do things that way, I'm not sure how to make a mapping between the keys and the values. I'm also wondering whether there is some way to perform an action on every dictionary in a list, since I'll need to be doing things to the effect of "Everyone return their values for columns Column1 and Column4, so I can count up who has what!" - I assume that there is some mechanism, but I don't think I know how to do it. Is a dictionary the best way to do it? Would I be better off doing things using some other data structure? If so, what?

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  • How to show ModelState.AddModelError when the Model is Empty in MVC4

    - by kk1076
    I am displaying a shopping cart. I need to check for empty values in Shopping cart and display a message like "The Shopping Cart is empty". When I use ModelState.AddModelError in myAction, it throws an exception as there is null reference in Model. How to display the ErrorMessage. My Action public ActionResult Index() { string id = Request.QueryString["UserID"]; IList<CartModel> objshop = new List<CartModel>(); objshop = GetCartDetails(id); if (objshop.Count > 0) { return View(objshop.ToList()); } else { ModelState.AddModelError("", "Your Shopping Cart is empty!"); } return View(); } My View @{ @Html.ValidationSummary(true) } <th > @Html.DisplayNameFor(model => model.ProductName) </th> <th > @Html.DisplayNameFor(model => model.Quantity) </th> <th > @Html.DisplayNameFor(model => model.Rate) </th> <th > @Html.DisplayNameFor(model => model.Price) </th> @foreach (var item in Model) { <td> @Html.DisplayFor(modelItem => item.ProductName)</td> <td> @Html.DisplayFor(modelItem => item.Quantity)</td> <td> @Html.DisplayFor(modelItem => item.Rate) </td> <td> @Html.DisplayFor(modelItem => item.Price) </td> } Any suggestions.

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  • most efficient method of turning multiple 1D arrays into columns of a 2D array

    - by Ty W
    As I was writing a for loop earlier today, I thought that there must be a neater way of doing this... so I figured I'd ask. I looked briefly for a duplicate question but didn't see anything obvious. The Problem: Given N arrays of length M, turn them into a M-row by N-column 2D array Example: $id = [1,5,2,8,6] $name = [a,b,c,d,e] $result = [[1,a], [5,b], [2,c], [8,d], [6,e]] My Solution: Pretty straight forward and probably not optimal, but it does work: <?php // $row is returned from a DB query // $row['<var>'] is a comma separated string of values $categories = array(); $ids = explode(",", $row['ids']); $names = explode(",", $row['names']); $titles = explode(",", $row['titles']); for($i = 0; $i < count($ids); $i++) { $categories[] = array("id" => $ids[$i], "name" => $names[$i], "title" => $titles[$i]); } ?> note: I didn't put the name = value bit in the spec, but it'd be awesome if there was some way to keep that as well.

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  • How to get a list of all Subversion commit author usernames?

    - by Quinn Taylor
    I'm looking for an efficient way to get the list of unique commit authors for an SVN repository as a whole, or for a given resource path. I haven't been able to find an SVN command specifically for this (and don't expect one) but I'm hoping there may be a better way that what I've tried so far in Terminal (on OS X): svn log --quiet | grep "^r" | awk '{print $3}' svn log --quiet --xml | grep author | sed -E "s:</?author>::g" Either of these will give me one author name per line, but they both require filtering out a fair amount of extra information. They also don't handle duplicates of the same author name, so for lots of commits by few authors, there's tons of redundancy flowing over the wire. More often than not I just want to see the unique author usernames. (It actually might be handy to infer the commit count for each author on occasion, but even in these cases it would be better if the aggregated data were sent across instead.) I'm generally working with client-only access, so svnadmin commands are less useful, but if necessary, I might be able to ask a special favor of the repository admin if strictly necessary or much more efficient. The repositories I'm working with have tens of thousands of commits and many active users, and I don't want to inconvenience anyone.

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  • Display Yearly Report When Data Not Available (CI, PHP, MySQL)

    - by tegaralaga
    First of all, i do apologize for my bad english, cos english isn't my native language. I want to display yearly report based on month, let say i got order on January, August, December, but the rest there's no order. So in MySQL database only have 3 order (Jan,Aug,Dec). When i query use CI ( select month(order_date) as month_name , count(order_id) as amount from order where year(order_date)=2011 group by month(order_date) ) there's only 3 data let say the 3 data is (use $query-result_array()) Array ( [0] => Array ( [month_num] => 1 [amount] => 4 ) [1] => Array ( [month_num] => 8 [amount] => 1 ) [2] => Array ( [month_num] => 12 [amount] => 19 ) ) how to make it to 12 data (12 Month) the array become like this (when data not available the amount is 0) Array ( [0] => Array ( [month_num] => 1 [amount] => 4 ) [1] => Array ( [month_num] => 2 [amount] => 0 ) [2] => Array ( [month_num] => 3 [amount] => 0 ) etc ) Thanks in advance :)

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  • Oracle - UPSERT with update not executed for unmodified values

    - by Buthrakaur
    I'm using following update or insert Oracle statement at the moment: BEGIN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM; IF (SQL%ROWCOUNT = 0) THEN INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END; This runs fine except that the update statement performs dummy update if the data is same as the parameter values provided. I would not mind the dummy update in normal situation, but there's a replication/synchronization system build over this table using triggers on tables to capture updated records and executing this statement frequently for many records simply means that I'd cause huge traffic in triggers and the sync system. Is there any simple method how to reformulate this code that the update statement wouldn't update record if not necessary without using following IF-EXISTS check code which I find not sleek enough and maybe also not most efficient for this task? DECLARE CNT NUMBER; BEGIN SELECT COUNT(1) INTO CNT FROM DSMS WHERE DSM = :DSM; IF SQL%FOUND THEN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM AND (SURNAME != :SURNAME OR FIRSTNAME != :FIRSTNAME OR VALID != :VALID); ELSE INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END;

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  • C++ - passing references to boost::shared_ptr

    - by abigagli
    If I have a function that needs to work with a shared_ptr, wouldn't it be more efficient to pass it a reference to it (so to avoid copying the shared_ptr object)? What are the possible bad side effects? I envision two possible cases: 1) inside the function a copy is made of the argument, like in ClassA::take_copy_of_sp(boost::shared_ptr<foo> &sp) { ... m_sp_member=sp; //This will copy the object, incrementing refcount ... } 2) inside the function the argument is only used, like in Class::only_work_with_sp(boost::shared_ptr<foo> &sp) //Again, no copy here { ... sp->do_something(); ... } I can't see in both cases a good reason to pass the boost::shared_ptr by value instead of by reference. Passing by value would only "temporarily" increment the reference count due to the copying, and then decrement it when exiting the function scope. Am I overlooking something? Andrea. EDIT: Just to clarify, after reading several answers : I perfectly agree on the premature-optimization concerns, and I alwasy try to first-profile-then-work-on-the-hotspots. My question was more from a purely technical code-point-of-view, if you know what I mean.

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  • ReaderWriterLockSlim and Pulse/Wait

    - by Jono
    Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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  • Which database I can used and relationship in it ??

    - by mimo-hamad
    My projece make me confused which I didn't find clear things that make me understand the required database and the relationships in it So, would a super one help me to solve it ?!! ;D this is required: 1) Model the data stored in the database (Identify the entities, roles, relationships, constraints, etc.) 2) Write the Oracle commands to create the database, find appropriate data, and populate the database 3) Write five different queries on your database, using the SELECT/FROM/WHERE construct provided in SQL. Your five queries should illustrate several different aspects of database querying, such as: a. Queries over more than one relation (by listing more than one relation in the FROM clause) b. Queries involving aggregate functions, such as SUM, COUNT, and AVG c. Queries involving complicated selects and joins d. Queries involving GROUP BY, HAVING or other similar functions. e. Queries that require the use of the DISTINCT keyword. And this the condition that we need to determine it to solve the required Q's above : 5) It is desired to develop an Internet membership club to buy products at special prices online. To join, new members must be referred by another existing member of the club. The system will keep the following information for each member: The member ID, referring member, birth date, member name, address, phone, mobile, credit card type, number and expiration date. The items are always shipped to the member's address noted in the membership application. The shipping fees will differ for each order.For each item to be requested, the member will select an item from a long list of possible items. For each item in the database, we store an item ID, an item name, description, and list price. The list price will be different from the actual sale price. The available quantity and the back-ordered quantity (the back-ordered quantity is the quantity on-order by the club from its suppliers) is also noted

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  • ASP.NET MVC URL Routing problem

    - by Sadegh
    hi, i have defined a route as below: context.MapRoute("SearchEngineWebSearch", "search/web/{query}/{index}/{size}", new { controller = "search", action = "web", query = "", index = 0, size = 5 }); and action method to handle request match with that: public System.Web.Mvc.ActionResult Web(string query = "", int index = 0, int size = 5) { if (string.IsNullOrEmpty(query)) return RedirectToRoute("SearchEngineBasicSearch"); var search = new Search(); var results = search.PerformSearch(query, index, size); ViewData["Query"] = query; if (results != null && results.Count() > 0) { ViewData["Results"]= results; return View("Web"); } else return View("Not-Found"); } and form to sent parameter to action method: <% using (Html.BeginForm("Web", "Search", FormMethod.Post)) { %> <input name="query" type="text" value="<%: ViewData["Query"]%>" class="search-field" /> <input type="submit" value="Search" class="search-button" /> <input type="hidden" name="index" value="2" /> <input type="hidden" name="size" value="2" /> <%} %> now after click on submit and sending value to action method all route values updated but url values still is equals to first time of sending parameter. for example if i sent for first time request such as http://localhost/search/web/google and for next time http://localhost/search/web/yahoo, query parameter which passed to action method is yahoo but url after postback is http://localhost/search/web/google still! can anybody help me plz? ;)

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  • Basic question on retain/release semantics from Apple's reference library

    - by davetron5000
    I have done Objective-C way back when, and have recently (i.e. just now) read the documentation on Apple's site regarding the use of retain and release. However, there is a bit of code in their Creating an iPhone Application page that has me a bit confused: - (void)setUpPlacardView { // Create the placard view -- it calculates its own frame based on its image. PlacardView *aPlacardView = [[PlacardView alloc] init]; self.placardView = aPlacardView; [aPlacardView release]; // What effect does this have on self.placardView?! placardView.center = self.center; [self addSubview:placardView]; } Not seeing the entire class, it seems that self.placardView is also a PlacardView * and the assignment of it to aPlacardView doesn't seem to indicate it will retain a reference to it. So, it appears to me that the line I've commented ([aPlacardView release];) could result in aPlacardView having a retain count of 0 and thus being deallocated. Since self.placardView points to it, wouldn't that now point at deallocated memory and cause a problem?

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  • iphone table view check mark accessory problem

    - by Pankaj Kainthla
    I have a table with 50 rows. I want to select particular rows with checkmark accessory but when i select some rows and scroll down the table then i see pre checked rows. I know that table cell are reused but i want to emit this problem what can i do about this? - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // return [array count]; return 50; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; TableViewCell *cell = (TableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[TableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text=[NSString stringWithFormat:@"%i",[indexPath row]]; return cell; } // Override to support row selection in the table view. - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath]; if (cell.accessoryType == UITableViewCellAccessoryNone) { cell.accessoryType = UITableViewCellAccessoryCheckmark; } else { cell.accessoryType = UITableViewCellAccessoryNone; }

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  • How does Amazon's Statistically Improbable Phrases work?

    - by ??iu
    How does something like Statistically Improbable Phrases work? According to amazon: Amazon.com's Statistically Improbable Phrases, or "SIPs", are the most distinctive phrases in the text of books in the Search Inside!™ program. To identify SIPs, our computers scan the text of all books in the Search Inside! program. If they find a phrase that occurs a large number of times in a particular book relative to all Search Inside! books, that phrase is a SIP in that book. SIPs are not necessarily improbable within a particular book, but they are improbable relative to all books in Search Inside!. For example, most SIPs for a book on taxes are tax related. But because we display SIPs in order of their improbability score, the first SIPs will be on tax topics that this book mentions more often than other tax books. For works of fiction, SIPs tend to be distinctive word combinations that often hint at important plot elements. For instance, for Joel's first book, the SIPs are: leaky abstractions, antialiased text, own dog food, bug count, daily builds, bug database, software schedules One interesting complication is that these are phrases of either 2 or 3 words. This makes things a little more interesting because these phrases can overlap with or contain each other.

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