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• MongoDB query to return only embedded document

  - by Matt

  assume that i have a BlogPost model with zero-to-many embedded Comment documents. can i query for and have MongoDB return only Comment objects matching my query spec? eg, db.blog_posts.find({"comment.submitter": "some_name"}) returns only a list of comments. edit: an example: import pymongo connection = pymongo.Connection() db = connection['dvds'] db['dvds'].insert({'title': "The Hitchhikers Guide to the Galaxy", 'episodes': [{'title': "Episode 1", 'desc': "..."}, {'title': "Episode 2", 'desc': "..."}, {'title': "Episode 3", 'desc': "..."}, {'title': "Episode 4", 'desc': "..."}, {'title': "Episode 5", 'desc': "..."}, {'title': "Episode 6", 'desc': "..."}]}) episode = db['dvds'].find_one({'episodes.title': "Episode 1"}, fields=['episodes']) in this example, episode is: {u'_id': ObjectId('...'), u'episodes': [{u'desc': u'...', u'title': u'Episode 1'}, {u'desc': u'...', u'title': u'Episode 2'}, {u'desc': u'...', u'title': u'Episode 3'}, {u'desc': u'...', u'title': u'Episode 4'}, {u'desc': u'...', u'title': u'Episode 5'}, {u'desc': u'...', u'title': u'Episode 6'}]} but i just want: {u'desc': u'...', u'title': u'Episode 1'}

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• Rails: Auto-Detecting Database Adapter

  - by Dex

  The new version of the ar-extensions gem requires that you load the appropriate adapter yourself. On my development side I use mysql, however Heroku uses PostgreSQL. For example, on my development side I need to do this: require 'ar-extensions/adapters/mysql' require 'ar-extensions/import/mysql' How can I audo-detect which adapter to use?

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• Google app engine: query that return entity ID using python

  - by Peter

  hi how do I return the entity ID using python in GAE? Assuming I have following class Names(db.Model): name = db.StringProperty()

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• How many users are sufficient to make a heavy load for web application

  - by galymzhan

  I have a web application, which has been suffering high load recent days. The application runs on single server which has 8-core Intel CPU and 4gb of RAM. Software: Drupal 5 (Apache 2, PHP5, MySQL5) running on Debian. After reaching 500 authenticated and 200 anonymous users (simultaneous), the application drastically decreases its performance up to total failure. The biggest load comes from authenticated users, who perform activities, causing insert/update/deletes on db. I think mysql is a bottleneck. Is it normal to slow down on such number of users? EDIT: I forgot to mention that I did some kind of profiling. I runned commands top, htop and they showed me that all memory was being used by MySQL! After some time MySQL starts to perform terribly slow, site goes down, and we have to restart/stop apache to reduce load. Administrators said that there was about 200 active mysql connections at that moment. The worst point is that we need to solve this ASAP, I can't do deep profiling analysis/code refactoring, so I'm considering 2 ways: my tables are MyIsam, I heard they use table-level locking which is very slow, is it right? could I change it to Innodb without worry? what if I take MySQL, and move it to dedicated machine with a lot of RAM?

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• How to use AJAX to populate state list depending on Country list?

  - by jasondavis

  I have the code below that will change a state dropdown list when you change the country list. How can I make it change the state list ONLY when country ID number 2234 and 224 are selected? If another country is selected is should change into this text input box <input type="text" name="othstate" value="" class="textBox"> The form <form method="post" name="form1"> <select style="background-color: #ffffa0" name="country" onchange="getState(this.value)"> <option>Select Country</option> <option value="223">USA</option> <option value="224">Canada</option> <option value="225">England</option> <option value="226">Ireland</option> </select> <select style="background-color: #ffffa0" name="state"> <option>Select Country First</option> </select> The javascript <script> function getState(countryId) { var strURL="findState.php?country="+countryId; var req = getXMLHTTP(); if (req) { req.onreadystatechange = function() { if (req.readyState == 4) { // only if "OK" if (req.status == 200) { document.getElementById('statediv').innerHTML=req.responseText; } else { alert("There was a problem while using XMLHTTP:\n" + req.statusText); } } } req.open("GET", strURL, true); req.send(null); } } </script>

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• Whats a good API for generating reports for a java web application?

  - by Ahmad

  I have a J2EE application that has a lot of reports, the situation now is the following: Report filters' values are sent to the application over DWR mainly, the data are retrieved from Oracle DB throw DB procedures and returned back to the client. However, some customization is required every now and then (new data filters, columns, ordering, ...), and these changes are painful to implement since we need to modify the JSPs, DB Procedures, the application itself, ... What API do you recommend to use for such reports?

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• Fix a 404: missing parameters error from a GET request to CherryPy

  - by norabora

  I'm making a webpage using CherryPy for the server-side, HTML, CSS and jQuery on the client-side. I'm also using a mySQL database. I have a working form for users to sign up to the site - create a username and password. I use jQuery to send an AJAX POST request to the CherryPy which queries the database to see if that username exists. If the username exists, alert the user, if it doesn't, add it to the database and alert success. $.post('submit', postdata, function(data) { alert(data); }); Successful jQuery POST. I want to change the form so that instead of checking that the username exists on submit, a GET request is made as on the blur event from the username input. The function gets called, and it goes to the CherryPy, but then I get an error that says: HTTPError: (404, 'Missing parameters: username'). $.get('checkUsername', getdata, function(data) { alert(data); }); Unsuccessful jQuery GET. The CherryPy: @cherrypy.expose def submit(self, **params): cherrypy.response.headers['Content-Type'] = 'application/json' e = sqlalchemy.create_engine('mysql://mysql:pw@localhost/6470') c = e.connect() com1 = "SELECT * FROM `users` WHERE `username` = '" + params["username"] + "'" b = c.execute(com1).fetchall() if not len(b) > 0: com2 = "INSERT INTO `6470`.`users` (`username` ,`password` ,`website` ,`key`) VALUES ('" com2 += params["username"] + "', MD5( '" + params["password"] + "'), '', NULL);" a = c.execute(com2) c.close() return simplejson.dumps("Success!") #login user and send them to home page c.close() return simplejson.dumps("This username is not available.") @cherrypy.expose def checkUsername(self, username): cherrypy.response.headers['Content-Type'] = 'application/json' e = sqlalchemy.create_engine('mysql://mysql:pw@localhost/6470') c = e.connect() command = "SELECT * FROM `users` WHERE `username` = '" + username + "'" a = c.execute(command).fetchall(); c.close() sys.stdout.write(str(a)) return simplejson.dumps("") I can't see any differences between the two so I don't know why the GET request is giving me a problem. Any insight into what I might be doing wrong would be helpful. If you have ideas about the jQuery, CherryPy, config files, anything, I'd really appreciate it.

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• How can I make this LinqToSQL query work? (SqlExecption)

  - by kversch

  The following code gives me an SqlException: OO theCourse = subject.Course; var students = dc.studentsCourses.Where(x = x.course == theCourse).Select(x = x.student); "Invalid object name 'dbo.studentsCourses'." I tried the following code instead but I also get an Exception. My original question was asked on Aardvark and can be read bellow: var allStudents = from s in dc.students select s; List thestudents = new List(); foreach (student s in allStudents) { if (s.courses.Contains(theCourse)) { thestudents.Add(s); } } I did a right click, "run custom tool" on my dbml and checked my names of my tables and entities. The project compiles but I get an Exception at runtime on this line: "if (s.courses.Contains(theCourse))" Any ideas? Original question on Aardvark: How do I do a LinqToSQL query that gives me this: I want to select all students that attended a certain lesson. The lesson is from a certain course. So select the course the lesson is from. Now select all the students that are following that course. There is a many-to-many relationship between the students and the courses table in my DB. I already extended my LINQ entities to be able to select student.Courses and course.Students using this method: http://www.codeproject.com/KB/linq/linq-to-sql-many-to-many.aspx

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• SQL Server: Mitigating schema changes/upgrades

  - by bradhe

  I haven't spent a ton of time researching this yet, mostly looking for best practices on upgrading/changing DB schemas. We're actively developing a new product and as such we often have additions or changes to our DB schema. We also have many copies of the DB -- one for the test environment, one for the prod environment, dev environments, you name it. We don't really want to have to blow away test data every time we want to make a change to the DB. Are there good ways of automating this or handling this? None of us have really ever had to deal with this so...

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• convert xml document to comma delimited (CSV) file using xslt stylesheet.

  - by Brad H

  I need some assistance converting an xml document to a CSV file using an xslt stylesheet. I am trying to use the following xsl and I can't seem to get it right. I want my comma delimited file to include column headings, followed by the data. My biggest issues are removing the final comma after the last item and inserting a carriage return so each group of data appears on a separate line. I have been using XML Notepad. <xsl:template match="/"> <xsl:element name="table"> <xsl:apply-templates select="/*/*[1]" mode="header" /> <xsl:apply-templates select="/*/*" mode="row" /> </xsl:element> </xsl:template> <xsl:template match="*" mode="header"> <xsl:element name="tr"> <xsl:apply-templates select="./*" mode="column" /> </xsl:element> </xsl:template> <xsl:template match="*" mode="row"> <xsl:element name="tr"> <xsl:apply-templates select="./*" mode="node" /> </xsl:element> </xsl:template> <xsl:template match="*" mode="column"> <xsl:element name="th"> <xsl:value-of select="translate(name(.),'qwertyuiopasdfghjklzxcvbnm_','QWERTYUIOPASDFGHJKLZXCVBNM ')" /> </xsl:element>, </xsl:template> <xsl:template match="*" mode="node"> <xsl:element name="td"> <xsl:value-of select="." /> </xsl:element>, </xsl:template>

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• JDBC CLASSPATH Not Working

  - by AeroDroid

  I'm setting up a simple JDBC connection to my working MySQL database on my server. I'm using the Connector-J provided by MySQL. According to their documentation, I'm suppose to create the CLASSPATH variable to point to the directory where the mysql-connector-java-5.0.8-bin.jar is located. I used export set CLASSPATH=/path/mysql-connector-java-5.0.8-bin.jar:$CLASSPATH. When I type echo $CLASSPATH to see if it exists, everything seems fine. But then when I open a new terminal and type echo $CLASSPATH it's no longer there. I think this is the main reason why my Java server won't connect to the JDBC, because it isn't saving the CLASSPATH variable I set. Anyone got suggestions or fixes on how to set up JDBC in the first place?

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• how can i pass parameter to linq query

  - by girish

  i want to pass parameter to linq query... public IEnumerable GetPhotos() { PhotoDBDataContext db = new PhotoDBDataContext(); var tProduct = db.Photos; var query = from p in db.Photos orderby p.PhotoId descending select new { p.Album, p.AlbumId, p.Description, p.Photographer, p.PhotographerId, p.PhotoId, p.Tags, p.Thumbnail, p.Url }; return query; } in above example "orderby p.PhotoId descending" is used, i want to use parameter in place of p.PhotoId is it possible...

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• SQL Server problems reading columns with a foreign key

  - by illdev

  I have a weird situation, where simple queries seem to never finish for instance SELECT top 100 ArticleID FROM Article WHERE ProductGroupID=379114 returns immediately SELECT top 1000 ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT top 1000 ArticleID FROM Article returns immediately By 'returning' I mean 'in query analyzer the green check mark appears and it says "Query executed successfully"'. I sometimes get the rows painted to the grid in qa, but still the query goes on waiting for my client to time out - 'sometimes': SELECT ProductGroupID AS Product23_1_, ArticleID AS ArticleID1_, ArticleID AS ArticleID18_0_, Inventory_Name AS Inventory3_18_0_, Inventory_UnitOfMeasure AS Inventory4_18_0_, BusinessKey AS Business5_18_0_, Name AS Name18_0_, ServesPeople AS ServesPe7_18_0_, InStock AS InStock18_0_, Description AS Descript9_18_0_, Description2 AS Descrip10_18_0_, TechnicalData AS Technic11_18_0_, IsDiscontinued AS IsDisco12_18_0_, Release AS Release18_0_, Classifications AS Classif14_18_0_, DistributorName AS Distrib15_18_0_, DistributorProductCode AS Distrib16_18_0_, Options AS Options18_0_, IsPromoted AS IsPromoted18_0_, IsBulkyFreight AS IsBulky19_18_0_, IsBackOrderOnly AS IsBackO20_18_0_, Price AS Price18_0_, Weight AS Weight18_0_, ProductGroupID AS Product23_18_0_, ConversationID AS Convers24_18_0_, DistributorID AS Distrib25_18_0_, type AS Type18_0_ FROM Article AS articles0_ WHERE (IsDiscontinued = '0') AND (ProductGroupID = 379121) shows this behavior. I have no idea what is going on. Probably select is broken ;) I got a foreign key on ProductGroups ALTER TABLE [dbo].[Article] WITH CHECK ADD CONSTRAINT [FK_ProductGroup_Articles] FOREIGN KEY([ProductGroupID]) REFERENCES [dbo].[ProductGroup] ([ProductGroupID]) GO ALTER TABLE [dbo].[Article] CHECK CONSTRAINT [FK_ProductGroup_Articles] there are some 6000 rows and IsDiscontinued is a bit, not null, but leaving this condition out does not change the outcome. Anyone can tell me how to handle such a situation? More info, anyone? Additional Info: this does not seem to be restricted to this Foreign Key, but all/some referencing this entity.

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• should i advocate migrating from access to (my)sql

  - by HotOil

  Hi: We have a windows MFC app that is written against an access database on a company server. The db is not that big: 19 MB. There are at most 2-3 users accessing it at any one time. It is used in a factory environment where access speed (or lack thereof) over the intranet becomes noticeable as it is part of the manufacturing time for our widgets. The scenario is this: as each widget is completed, it gets a record in the db.. by the end of the year, the db is larger and searching for a record takes longer and longer. The solution so far has been to manually move older records to an archival table about once a year. We are reworking other portions of this app right now, and it would be a good time to move to another db if we are going to do it. It is my understanding that if we were using sql, the search time would not go up as the table gets bigger because the entire .mdb does not have to be sent over the network each time. Is this correct? Does anyone have any insight about whether it could be worth it to go to the trouble (time and money) of migrating to a new db, or should I just add more functionality to the application we have now, and maybe automatically purge the older records from time to time, and add additional facilities to the app to get at the older records when needed? Thanks for any wisdom you can share..

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• getJSON for dropbox data

  - by gheil.apl

  Although i used getJSON in http://jsbin.com/dbJSON/edit i have not been able to connect with any of my own made up data. i tried 4, and the example at Flickr for "cats". Only the latter worked... this is the output: {assoc: null,assoc.js: null,stub: null,stub.js: null,cat: [object Object]} i am at that "base", as i did get the image there, but db.tgu.ca/repsychal/poems/10/0512-g2g/assoc.json db.tgu.ca/repsychal/poems/10/0512-g2g/assoc.js db.tgu.ca/repsychal/poems/10/0512-g2g/stub.json db.tgu.ca/repsychal/poems/10/0512-g2g/stub.js were all invisible==null! (they are all URL, just put h t t p //: in front ... a restriction on the # of URL in a post) How do i get "my" data into the page?

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• Why don't copy this dokument attributes from the source xml file??

  - by siegfried storr

  Hi anyone, i'm working the first time with xslt and i really don't understand why this xsl don't copy attributes from the source xml. Perhaps someone can give me a hint?? <xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output omit-xml-declaration="yes" indent="yes"/> <xsl:variable name="rpl" select="document('ParamInvoice.xml')"/> <xsl:template match="/"> <xsl:copy> <xsl:apply-templates select="* | @*"/> </xsl:copy> </xsl:template> <xsl:template match="*"> <xsl:variable name="vInvoiceElement" select="$rpl/StoraInvoice/*[name()=name(current())]"/> <xsl:copy> <xsl:if test="$vInvoiceElement/Attribute"> <xsl:call-template name="AttributeErzeugen"> <xsl:with-param name="pAttr" select="$vInvoiceElement/Attribute"/> </xsl:call-template> </xsl:if> <xsl:apply-templates/> </xsl:copy> </xsl:template> <xsl:template name="AttributeErzeugen"> <xsl:param name="pAttr"/> <xsl:for-each select="$pAttr"> <xsl:attribute name="{@name}"><xsl:value-of select="."/></xsl:attribute> </xsl:for-each> </xsl:template> </xsl:stylesheet>

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• get another sequence elements'value in one sequence.

  - by lxusharp

  I have an XML file as below, and I want to transform it with xslt. I want to achieve is: when do the for-each of "s1" elements, I want to get the corresponding "r1"'s "value" attbute value. the xslt I wrote as below, but it does not work, can anyone give a help? thanks. <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl"> <xsl:output method="html" indent="yes"/> <xsl:template mode="getr1" match="summary" > <xsl:param name="index"/> <xsl:value-of select="r1[$index][@value]"/> </xsl:template> <xsl:template match="/"> <html> <body> <ul> <xsl:for-each select="root/s1"> <xsl:variable name="i" select="position()"/> <li> <xsl:value-of select ="@name"/> : <!--<xsl:apply-templates mode="getr1" select="/root/summary"> <xsl:with-param name="index" select="$i" /> </xsl:apply-templates>--> <!--I want to get the corresponding r1's value according to the index --> <!-- but above code is not work.--> </li> </xsl:for-each> </ul> </body> </html> </xsl:template> </xsl:stylesheet>

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• Set database based on how the application was started

  - by AaronThomson

  I have two Rails applications (lets call them APP-1 and APP-2), each of them has a dependancy on a third Rails application (APP-3). I would like to be able to run the tests for APP-1 and APP-2 in parallel on my CI server. The problem is, both need to start up APP-3 and write to a DB via the APP-3. This causes conflicts and failures if the tests are run in parallel. My idea for a solution is for APP-1 and APP-2 to each start their own instance of APP-3 and to have each instance point to a different DB. Is there a way to dynamically set the DB in the database.yml of APP-3 so that it connects to a different DB depending on which APP starts it up? FYI. APP-1 and APP-2 currently start APP-3 via rake tasks.

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• active record relations – who needs it?

  - by M2_

  Well, I`m confused about rails queries. For example: Affiche belongs_to :place Place has_many :affiches We can do this now: @affiches = Affiche.all( :joins => :place ) or @affiches = Affiche.all( :include => :place ) and we will get a lot of extra SELECTs, if there are many affiches: Place Load (0.2ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.3ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.8ms) SELECT "places".* FROM "places" WHERE "places"."id" = 444 LIMIT 1 Place Load (1.0ms) SELECT "places".* FROM "places" WHERE "places"."id" = 222 LIMIT 1 ...and so on... And (sic!) with :joins used every SELECT is doubled! Technically we cloud just write like this: @affiches = Affiche.all( ) and the result is totally the same! (Because we have relations declared). The wayout of keeping all data in one query is removing the relations and writing a big string with "LEFT OUTER JOIN", but still there is a problem of grouping data in multy-dimentional array and a problem of similar column names, such as id. What is done wrong? Or what am I doing wrong? UPDATE: Well, i have that string Place Load (2.5ms) SELECT "places".* FROM "places" WHERE ("places"."id" IN (3,444,222,57,663,32,154,20)) and a list of selects one by one id. Strange, but I get these separate selects when I`m doing this in each scope: <%= link_to a.place.name, **a.place**( :id => a.place.friendly_id ) %> the marked a.place is the spot, that produces these extra queries.

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• Queries within queries: Is there a better way?

  - by mririgo

  As I build bigger, more advanced web applications, I'm finding myself writing extremely long and complex queries. I tend to write queries within queries a lot because I feel making one call to the database from PHP is better than making several and correlating the data. However, anyone who knows anything about SQL knows about JOINs. Personally, I've used a JOIN or two before, but quickly stopped when I discovered using subqueries because it felt easier and quicker for me to write and maintain. Commonly, I'll do subqueries that may contain one or more subqueries from relative tables. Consider this example: SELECT (SELECT username FROM users WHERE records.user_id = user_id) AS username, (SELECT last_name||', '||first_name FROM users WHERE records.user_id = user_id) AS name, in_timestamp, out_timestamp FROM records ORDER BY in_timestamp Rarely, I'll do subqueries after the WHERE clause. Consider this example: SELECT user_id, (SELECT name FROM organizations WHERE (SELECT organization FROM locations WHERE records.location = location_id) = organization_id) AS organization_name FROM records ORDER BY in_timestamp In these two cases, would I see any sort of improvement if I decided to rewrite the queries using a JOIN? As more of a blanket question, what are the advantages/disadvantages of using subqueries or a JOIN? Is one way more correct or accepted than the other?

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• Trouble using South with Django and Heroku

  - by Dan

  I had an existing Django project that I've just added South to. I ran syncdb locally. I ran manage.py schemamigration app_name locally I ran manage.py migrate app_name --fake locally I commit and pushed to heroku master I ran syncdb on heroku I ran manage.py schemamigration app_name on heroku I ran manage.py migrate app_name on heroku I then receive this: $ heroku run python notecard/manage.py migrate notecards Running python notecard/manage.py migrate notecards attached to terminal... up, run.1 Running migrations for notecards: - Migrating forwards to 0005_initial. > notecards:0003_initial Traceback (most recent call last): File "notecard/manage.py", line 14, in <module> execute_manager(settings) File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager utility.execute() File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 379, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv self.execute(*args, **options.__dict__) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 220, in execute output = self.handle(*args, **options) File "/app/lib/python2.7/site-packages/south/management/commands/migrate.py", line 105, in handle ignore_ghosts = ignore_ghosts, File "/app/lib/python2.7/site-packages/south/migration/__init__.py", line 191, in migrate_app success = migrator.migrate_many(target, workplan, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 221, in migrate_many result = migrator.__class__.migrate_many(migrator, target, migrations, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 292, in migrate_many result = self.migrate(migration, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 125, in migrate result = self.run(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 99, in run return self.run_migration(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 81, in run_migration migration_function() File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 57, in <lambda> return (lambda: direction(orm)) File "/app/notecard/notecards/migrations/0003_initial.py", line 15, in forwards ('user', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['auth.User'])), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 226, in create_table ', '.join([col for col in columns if col]), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 150, in execute cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/util.py", line 34, in execute return self.cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute return self.cursor.execute(query, args) django.db.utils.DatabaseError: relation "notecards_semester" already exists I have 3 models. Section, Semester, and Notecards. I've added one field to the Notecards model and I cannot get it added on Heroku. Thank you.

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• Delete query in Linq

  - by Ani

  I have this simple code but it shows error. I dont know where I am going wrong. I shows error in last line.."DeleteOnSubmit" linq_testDataContext db = new linq_testDataContext(); var remove = from aremove in db.logins where aremove.username == userNameString && aremove.Password == pwdString select aremove; db.logins.DeleteOnSubmit(remove); Thanks, Ani

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• Spring + iBatis + Hessian caching

  - by ILya

  Hi. I have a Hessian service on Spring + iBatis working on Tomcat. I'm wondering how to cache results... I've made the following config in my sqlmap file: <sqlMap namespace="Account"> <cacheModel id="accountCache" type="MEMORY" readOnly="true" serialize="false"> <flushInterval hours="24"/> <flushOnExecute statement="Account.addAccount"/> <flushOnExecute statement="Account.deleteAccount"/> <property name="reference-type" value="STRONG" /> </cacheModel> <typeAlias alias="Account" type="domain.Account" /> <select id="getAccounts" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts; </select> <select id="getAccount" parameterClass="Long" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts where id=#id#; </select> <insert id="addAccount" parameterClass="Account"> fix all; insert into accounts (id, name, pin) values (#id#, #name#, #pin#); </insert> <delete id="deleteAccount" parameterClass="Long"> fix all; delete from accounts where id = #id#; </delete> </sqlMap> Then i've done some tests... I have a hessian client application. I'm calling getAccounts several times and after each call it's a query to DBMS. How to make my service to query DBMS only a first time (after server restart) getAccounts called and for the following calls to use a cache?

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• (Oracle) How get total number of results when using a pagination query?

  - by BestPractices

  I am using Oracle 10g and the following paradigm to get a page of 15 results as a time (so that when the user is looking at page 2 of a search result, they see records 16-30). select * from ( select rownum rnum, a.* from (my_query) a where rownum <= 30 ) where rnum > 15; Right now I'm having to run a separate SQL statement to do a "select count" on "my_query" in order to get the total number of results for my_query (so that I can show it to the user and use it to figure out total number of pages, etc). Is there any way to get the total number of results without doing this via a second query, i.e. by getting it from above query? I've tried adding "max(rownum)", but it doesn't seem to work (I get an error [ORA-01747] that seems to indicate it doesnt like me having the keyword rownum in the group by). My rationale for wanting to get this from the original query rather than doing it in a separate SQL statement is that "my_query" is an expensive query so I'd rather not run it twice (once to get the count, and once to get the page of data) if I dont have to; but whatever solution I can come up with to get the number of results from within a single query (and at the same time get the page of data I need) should not add much if any additional overhead, if possible. Please advise. Here is exactly what I'm trying to do for which I receive an ORA-01747 error because I believe it doesnt like me having ROWNUM in the group by. Note, If there is another solution that doesnt use max(ROWNUM), but something else, that is perfectly fine too. This solution was my first thought as to what might work. SELECT * FROM (SELECT r.*, ROWNUM RNUM, max(ROWNUM) FROM (SELECT t0.ABC_SEQ_ID AS c0, t0.FIRST_NAME, t0.LAST_NAME, t1.SCORE FROM ABC t0, XYZ t1 WHERE (t0.XYZ_ID = 751) AND t0.XYZ_ID = t1.XYZ_ID ORDER BY t0.RANK ASC) r WHERE ROWNUM <= 30 GROUP BY r.*, ROWNUM) WHERE RNUM > 15

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• Helping linqtosql datacontext use implicit conversion between varchar column in the database and tab

  - by user213256

  I am creating an mssql database table, "Orders", that will contain a varchar(50) field, "Value" containing a string that represents a slightly complex data type, "OrderValue". I am using a linqtosql datacontext class, which automatically types the "Value" column as a string. I gave the "OrderValue" class implicit conversion operators to and from a string, so I can easily use implicit conversion with the linqtosql classes like this: // get an order from the orders table MyDataContext db = new MyDataContext(); Order order = db.Orders(o => o.id == 1); // use implicit converstion to turn the string representation of the order // value into the complex data type. OrderValue value = order.Value; // adjust one of the fields in the complex data type value.Shipping += 10; // use implicit conversion to store the string representation of the complex // data type back in the linqtosql order object order.Value = value; // save changes db.SubmitChanges(); However, I would really like to be able to tell the linqtosql class to type this field as "OrderValue" rather than as "string". Then I would be able to avoid complex code and re-write the above as: // get an order from the orders table MyDataContext db = new MyDataContext(); Order order = db.Orders(o => o.id == 1); // The Value field is already typed as the "OrderValue" type rather than as string. // When a string value was read from the database table, it was implicity converted // to "OrderValue" type. order.Value.Shipping += 10; // save changes db.SubmitChanges(); In order to achieve this desired goal, I looked at the datacontext designer and selected the "Value" field of the "Order" table. Then, in properties, I changed "Type" to "global::MyApplication.OrderValue". The "Server Data Type" property was left as "VarChar(50) NOT NULL" The project built without errors. However, when reading from the database table, I was presented with the following error message: Could not convert from type 'System.String' to type 'MyApplication.OrderValue'. at System.Data.Linq.DBConvert.ChangeType(Object value, Type type) at Read_Order(ObjectMaterializer1 ) at System.Data.Linq.SqlClient.ObjectReaderCompiler.ObjectReader2.MoveNext() at System.Linq.Buffer1..ctor(IEnumerable1 source) at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source) at Example.OrdersProvider.GetOrders() at ... etc From the stack trace, I believe this error is happening while reading the data from the table. When presented with converting a string to my custom data type, even though the implicit conversion operators are present, the DBConvert class gets confused and throws an error. Is there anything I can do to help it not get confused and do the implicit conversion? Thanks in advance, and apologies if I have posted in the wrong forum. cheers / Ben

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