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• How can I build something like Amazon S3 in Perl?

  - by Joel G

  I am looking to code a file storage application in perl similar to amazon s3. I already have a amazon s3 clone that I found online called parkplace but its in ruby and is old also isn't built for high loads. I am not really sure what modules and programs I should use so id like some help picking them out. My requirements are listed below (yes I know there are lots but I could start simple then add more once I get it going): Easy API implementation for client side apps. (maybe REST (?) Centralized database server for the USERDB (maybe PostgreSQL (?). Logging of all connections, bandwidth used, well pretty much everything to a centralized server (maybe PostgreSQL again (?). Easy server side configuration (config file(s) stored on the servers). Web based control panel for admin(s) and user(s) to show logs. (could work just running queries from the databases) Fast High Uptime Low memory usage Some sort of load distribution/load balancer (maybe a dns based or pound or perlbal or something else (?). Maybe a cache of some sort (memcached or parlbal or something else (?). Thanks in advance

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• refactor LINQ TO SQL custom properties that instantiate datacontext

  - by Thiago Silva

  I am working on an existing ASP.NET MVC app that started small and has grown with time to require a good re-architecture and refactoring. One thing that I am struggling with is that we've got partial classes of the L2S entities so we could add some extra properties, but these props create a new data context and query the DB for a subset of data. This would be the equivalent to doing the following in SQL, which is not a very good way to write this query as oppsed to joins: SELECT tbl1.stuff, (SELECT nestedValue FROM tbl2 WHERE tbl2.Foo = tbl1.Bar), tbl1.moreStuff FROM tbl1 so in short here's what we've got in some of our partial entity classes: public partial class Ticket { public StatusUpdate LastStatusUpdate { get { //this static method call returns a new DataContext but needs to be refactored var ctx = OurDataContext.GetContext(); var su = Compiled_Query_GetLastUpdate(ctx, this.TicketId); return su; } } } We've got some functions that create a compiled query, but the issue is that we also have some DataLoadOptions defined in the DataContext, and because we instantiate a new datacontext for getting these nested property, we get an exception "Compiled Queries across DataContexts with different LoadOptions not supported" . The first DataContext is coming from a DataContextFactory that we implemented with the refactorings, but this second one is just hanging off the entity property getter. We're implementing the Repository pattern in the refactoring process, so we must stop doing stuff like the above. Does anyone know of a good way to address this issue?

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• Database warehoue design: fact tables and dimension tables

  - by morpheous

  I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to see some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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• Defining jUnit Test cases Correctly

  - by Epitaph

  I am new to Unit Testing and therefore wanted to do some practical exercise to get familiar with the jUnit framework. I created a program that implements a String multiplier public String multiply(String number1, String number2) In order to test the multiplier method, I created a test suite consisting of the following test cases (with all the needed integer parsing, etc) @Test public class MultiplierTest { Multiplier multiplier = new Multiplier(); // Test for 2 positive integers assertEquals("Result", 5, multiplier.multiply("5", "1")); // Test for 1 positive integer and 0 assertEquals("Result", 0, multiplier.multiply("5", "0")); // Test for 1 positive and 1 negative integer assertEquals("Result", -1, multiplier.multiply("-1", "1")); // Test for 2 negative integers assertEquals("Result", 10, multiplier.multiply("-5", "-2")); // Test for 1 positive integer and 1 non number assertEquals("Result", , multiplier.multiply("x", "1")); // Test for 1 positive integer and 1 empty field assertEquals("Result", , multiplier.multiply("5", "")); // Test for 2 empty fields assertEquals("Result", , multiplier.multiply("", "")); In a similar fashion, I can create test cases involving boundary cases (considering numbers are int values) or even imaginary values. 1) But, what should be the expected value for the last 3 test cases above? (a special number indicating error?) 2) What additional test cases did I miss? 3) Is assertEquals() method enough for testing the multiplier method or do I need other methods like assertTrue(), assertFalse(), assertSame() etc 4) Is this the RIGHT way to go about developing test cases? How am I "exactly" benefiting from this exercise? 5)What should be the ideal way to test the multiplier method? I am pretty clueless here. If anyone can help answer these queries I'd greatly appreciate it. Thank you.

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• ColdFusion 8: Database Connection Reset Error

  - by Gavin

  I have been getting these intermittent ColdFusion Database connection reset errors and was wondering if anyone had experience with this and had a particular solution that worked? Here is the error: Error Executing Database Query.[Macromedia][SQLServer JDBC Driver]A problem occurred when attempting to contact the server (Server returned: Connection reset). Please ensure that the server parameters passed to the driver are correct and that the server is running. Also ensure that the maximum number of connections have not been exceeded for this server. This doesn't happen with any particular query, the code breaks in different queries every time, returning a SQLState error 08s01. These query's logic are fine, no logic errors etc. I checked the network logs and there were no database server connection refusals at the time of the error. Once the first error occurs, it keeps happening for no more than a minute or so at random times of the day, every few days. I've googled this thing and so far anyone that has had this issue was only on CF6 or 7, which the fixes coldFusion put out are only for CF6 or 7. Server configuration wise: The ColdFusion server is version 8 The database server is SQL Server 2005 Standard The database connections allowed setting is set to unlimited on both SQL Server and ColdFusion Any help would be greatly appreciated, Thanks!

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• Taking the data mapper approach in Zend Framework

  - by Seeker

  Let's assume the following tables setup for a Zend Framework app. user (id) groups (id) groups_users (id, user_id, group_id, join_date) I took the Data Mapper approach to models which basically gives me: Model_User, Model_UsersMapper, Model_DbTable_Users Model_Group, Model_GroupsMapper, Model_DbTable_Groups Model_GroupUser, Model_GroupsUsersMapper, Model_DbTable_GroupsUsers (for holding the relationships which can be seen as aentities; notice the "join_date" property) I'm defining the _referenceMap in Model_DbTable_GroupsUsers: protected $_referenceMap = array ( 'User' => array ( 'columns' => array('user_id'), 'refTableClass' => 'Model_DbTable_Users', 'refColumns' => array('id') ), 'App' => array ( 'columns' => array('group_id'), 'refTableClass' => 'Model_DbTable_Groups', 'refColumns' => array('id') ) ); I'm having these design problems in mind: 1) The Model_Group only mirrors the fields in the groups table. How can I return a collection of groups a user is a member of and also the date the user joined that group for every group? If I just added the property to the domain object, then I'd have to let the group mapper know about it, wouldn't I? 2) Let's say I need to fetch the groups a user belongs to. Where should I put this logic? Model_UsersMapper or Model_GroupsUsersMapper? I also want to make use of the referencing map (dependent tables) mechanism and probably use findManyToManyRowset or findDependentRowset, something like: $result = $this->getDbTable()->find($userId); $row = $result->current(); $groups = $row->findManyToManyRowset( 'Model_DbTable_Groups', 'Model_DbTable_GroupsUsers' ); This would produce two queries when I could have just written it in a single query. I will place this in the Model_GroupsUsersMapper class. An enhancement would be to add a getGroups method to the Model_User domain object which lazily loads the groups when needed by calling the appropriate method in the data mapper, which begs for the second question. Should I allow the domain object know about the data mapper?

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• Kohana 3 ORM: How to get data from pivot table? and all other tables for that matter

  - by zenna

  I am trying to use ORM to access data stored, in three mysql tables 'users', 'items', and a pivot table for the many-many relationship: 'user_item' I followed the guidance from http://stackoverflow.com/questions/1946357/kohana-3-orm-read-additional-columns-in-pivot-tables and tried $user = ORM::factory('user',1); $user->items->find_all(); $user_item = ORM::factory('user_item', array('user_id' => $user, 'item_id' => $user->items)); if ($user_item->loaded()) { foreach ($user_item as $pivot) { print_r($pivot); } } But I get the SQL error: "Unknown column 'user_item.id' in 'order clause' [ SELECT user_item.* FROM user_item WHERE user_id = '1' AND item_id = '' ORDER BY user_item.id ASC LIMIT 1 ]" Which is clearly erroneous because Kohana is trying to order the elements by a column which doesn't exist: user_item.id. This id doesnt exist because the primary keys of this pivot table are the foreign keys of the two other tables, 'users' and 'items'. Trying to use: $user_item = ORM::factory('user_item', array('user_id' => $user, 'item_id' => $user->items)) ->order_by('item_id', 'ASC'); Makes no difference, as it seems the order_by() or any sql queries are ignored if the second argument of the factory is given. Another obvious error with that query is that the item_id = '', when it should contain all the elements. So my question is how can I get access to the data stored in the pivot table, and actually how can I get access to the all items held by a particular user as I even had problems with that? Thanks

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• Hibernate ScrollableResults Do Not Return The Whole Set of Results

  - by mlaverd

  Some of the queries we run have 100'000+ results and it takes forever to load them and then send them to the client. So I'm using ScrollableResults to have a paged results feature. But we're topping at roughly 50k results (never exactly the same amount of results). I'm on an Oracle9i database, using the Oracle 10 drivers and Hibernate is configured to use the Oracle9 dialect. I tried with the latest JDBC driver (ojdbc6.jar) and the problem was reproduced. We also followed some advice and added an ordering clause, but the problem was reproduced. Here is a code snippet that illustrates what we do: Criteria crit = sess.createCriteria(ABC.class); crit.add(Restrictions.eq("property", value)); crit.setFetchSize(pageSize); crit.addOrder(Order.asc("property")); ScrollableResults sr = crit.scroll(); ... ... do{ for (Object entry : page) sess.evict(entry); //to avoid having our memory just explode out of proportion page.clear(); for (int i =0 ; i < pageSize && ! metLastRow; i++){ if (resultSet.next()) page.add(sr.get(0)); else metLastRow = true; } metLastRow = metLastRow?metLastRow:sr.isLast(); sendToClient(page); }while(!metLastRow); So, why is it that I get the result set to tell me its at the end when it should be having so much more results?

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• Cakephp Function in mode not executing

  - by Rixius

  I have a function in my Comic Model as such: <?php class Comic extends AppModel { var $name = "Comic"; // Methods for retriving information. function testFunc(){ $mr = $this->find('all'); return $mr; } } ?> And I am calling it in my controller as such: <?php class ComicController extends AppController { var $name = "Comic"; var $uses = array('Comic'); function index() { } function view($q) { $this->set('array',$this->Comic->testFunc()); } } ?> When I try to load up the page; I get the following error: Warning (512): SQL Error: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'testFunc' at line 1 [CORE/cake/libs/model/datasources/dbo_source.php, line 525] Query: testFunc And the SQL dump looks like this: (default) 2 queries took 1 ms Nr Query Error Affected Num. rows Took (ms) 1 DESCRIBE comics 10 10 1 2 testFunc 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'testFunc' at line 1 0 So it looks like, instead of running the testFunc() function, it is trying to run a query of "testFunc" and failing...

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• Is it possible to disable user sessions for guest in Joomla 1.5

  - by WebolizeR

  Hi; Is it possible to disable session handling in Joomla 1.5 for guests. I donot use user system in the frontend, i assumed that it's not needed to run queries like below: Site will use APC or Memcache as caching system under heavy load, so it's important for me tHanks for your comments # DELETE FROM jos_session WHERE ( time < '1274709357' ) # SELECT * FROM jos_session WHERE session_id = '70c247cde8dcc4dad1ce111991772475' # UPDATE jos_session SET time='1274710257',userid='0',usertype='',username='',gid='0',guest='1',client_id='0',data='__default|a:8:{s:15:\"session.counter\";i:5;s:19:\"session.timer.start\";i:1274709740;s:18:\"session.timer.last\";i:1274709749;s:17:\"session.timer.now\";i:1274709754;s:22:\"session.client.browser\";s:88:\"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3\";s:8:\"registry\";O:9:\"JRegistry\":3:{s:17:\"_defaultNameSpace\";s:7:\"session\";s:9:\"_registry\";a:1:{s:7:\"session\";a:1:{s:4:\"data\";O:8:\"stdClass\":0:{}}}s:7:\"_errors\";a:0:{}}s:4:\"user\";O:5:\"JUser\":19:{s:2:\"id\";i:0;s:4:\"name\";N;s:8:\"username\";N;s:5:\"email\";N;s:8:\"password\";N;s:14:\"password_clear\";s:0:\"\";s:8:\"usertype\";N;s:5:\"block\";N;s:9:\"sendEmail\";i:0;s:3:\"gid\";i:0;s:12:\"registerDate\";N;s:13:\"lastvisitDate\";N;s:10:\"activation\";N;s:6:\"params\";N;s:3:\"aid\";i:0;s:5:\"guest\";i:1;s:7:\"_params\";O:10:\"JParameter\":7:{s:4:\"_raw\";s:0:\"\";s:4:\"_xml\";N;s:9:\"_elements\";a:0:{}s:12:\"_elementPath\";a:1:{i:0;s:74:\"C:\xampp\htdocs\sites\iv.mynet.com\libraries\joomla\html\parameter\element\";}s:17:\"_defaultNameSpace\";s:8:\"_default\";s:9:\"_registry\";a:1:{s:8:\"_default\";a:1:{s:4:\"data\";O:8:\"stdClass\":0:{}}}s:7:\"_errors\";a:0:{}}s:9:\"_errorMsg\";N;s:7:\"_errors\";a:0:{}}s:13:\"session.token\";s:32:\"a2b19c7baf223ad5fd2d5503e18ed323\";}' WHERE session_id='70c247cde8dcc4dad1ce111991772475'

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• Fulltext search on many tables

  - by Rob

  I have three tables, all of which have a column with a fulltext index. The user will enter search terms into a single text box, and then all three tables will be searched. This is better explained with an example: documents doc_id name FULLTEXT table2 id doc_id a_field FULLTEXT table3 id doc_id another_field FULLTEXT (I realise this looks stupid but that's because I've removed all the other fields and tables to simplify it). So basically I want to do a fulltext search on name, a_field and another_field, and then show the results as a list of documents, preferably with what caused that document to be found, e.g. if another_field matched, I would display what another_field is. I began working on a system whereby three fulltext search queries are performed and the results inserted into a table with a structure like: search_results table_name row_id score (This could later be made to cache results for a few days with e.g. a hash of the search terms). This idea has two problems. The first is that the same document can be in the search results up to three times with different scores. Instead of that, if the search term is matched in two tables, it should have one result, but a higher score. The second is that parsing the results is difficult. I want to display a list of documents, but I don't immediately know the doc_id without a join of some kind; however the table to join to is dependant on the table_name column, and I'm not sure how to accomplish that. Wanting to search multiple related tables like this must be a common thing, so I guess what I'm asking is am I approaching this in the right way? Can someone tell me the best way of doing it please.

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• System.AccessViolationException when using TPT inheritance in Entity Framework CTP5

  - by Ben

  Hi, I'm using TPT inheritance in EF CTP5 with SQL CE 4. I have an abstract base class "Widget" with common properties like "Title". I can successfully save concrete Widget implementations e.g. "TwitterWidget". However, I have a problem retrieving all widgets (or rather ALL widget implementations). My repository exposes the following: public IQueryable<Widget> GetAll(); This effectively returns the IDbSet from the DbContext. The following queries work fine: repo.GetAll().ToList(); repo.GetAll().Where(w => w.Title == "Test").ToList(); repo.GetAll().SingleOrDefault(w => w.Title == "Test"); repo.GetAll().Where(w => w.Title == "Test").OrderBy(x => x.Title).ToList(); However, if I write the following query: repo.GetAll().OrderBy(w => w.Title); I get the following error: Test 'PlanetCloud.Portfolio.Tests.Data.PersistenceTestFixture.Can_get_widgets' failed: System.AccessViolationException : Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at System.Data.SqlServerCe.NativeMethodsHelper.GetValues(IntPtr pSeCursor, Int32 seGetColumn, IntPtr prgBinding, Int32 cDbBinding, IntPtr pData, IntPtr pError) at System.Data.SqlServerCe.NativeMethods.GetValues(IntPtr pSeCursor, Int32 seGetColumn, IntPtr prgBinding, Int32 cDbBinding, IntPtr pData, IntPtr pError) at System.Data.SqlServerCe.SqlCeDataReader.FetchValue(Int32 index) at System.Data.SqlServerCe.SqlCeDataReader.IsDBNull(Int32 ordinal) at lambda_method(Closure , Shaper ) at System.Data.Common.Internal.Materialization.Shaper.HandleEntityAppendOnly[TEntity](Func`2 constructEntityDelegate, EntityKey entityKey, EntitySet entitySet) at lambda_method(Closure , Shaper ) at System.Data.Common.Internal.Materialization.Coordinator`1.ReadNextElement(Shaper shaper) at System.Data.Common.Internal.Materialization.Shaper`1.SimpleEnumerator.MoveNext() at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source) However, I can execute the following query without problems: var widgets = repo.GetAll().OfType<Widget>().OrderBy(w => w.Title).ToList(); So if I specify the type as the base class prior to my orderby clause it works. The question is why?

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• Hibernate: Dirty Checking and Only Update of Dirty Attributes?

  - by jens

  Hello Experts, in "good old JDBC days" I wrote a lot of SQL Queries that did very targeted updates of only the "attributes/members" that were actually changed: For Example having an object with the following members: public String name; public String address; public Date date; If only date was changed in some Business Method I would only issue an SQL UPDATE for the date member. ==It seems however (thats my "impression" of hibernate) that when working with a standard Hibernate mapping (mapping the full class), even updates of only one single member lead to a full update of the object in SQL Statements generated by Hibernate. My Questions are: 1.) Is this observation correct, that hibernate DOES NOT intelligently check (in a fully mapped class), what member(s) where changed and then only issue updates for the specific changed members, but rather always will update (in the generated SQL Update Statement) all mapped members (of a class), even if they were not changed (in case the object is dirty due to one member being dirty...) 2.) What can I do to make Hibernate only update those members, that have been changed? I am searching for a solution to have hibernate only update the member that actually changed. (I know hibernate does some big work on doing dirty-checking, but as far as I know this dirtychecking is only relevant to identify if the object as whole is dirty, not what single member is dirty.) Thank you very much! Jens

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• Can someone describe the nested set model from a C#/LINQ perspective?

  - by Chad

  I know the nested set model doesn't pertain to the C# language or LINQ directly... it's what I'm using to develop my web app. For hierarchical data (categories with sub-categories in my case), I'm currently using something similar to the Adjacency List model. At the moment, I've only got 2 levels of categories, but I'd like to take it further and allow for n levels of categories using the nested set model. I'm not quite clear on how to use it in a C# context. Here's the article I'm reading on the nested set model. Though this article cleared up my confusion some, I still have a big ?? in my head: - Is inserting, updating or deleting categories tedious? It looks like the left and right numbers would require re-numbering... what would the LINQ queries look like for the following scenarios? Delete a child node (re-number all node's left/right values) Delete a parent node (what do you do with the orphans?) Move a child node to a different parent node (renumber again) If my understanding is correct, at all times the child node's left/right values will always be between the parent node's left/right values, am I correct? Seems easy enough, if only the categories were static... most likely I need to spend more time to get my head around the concept. Any help is greatly appreciated!

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• Huge mysql table with Zend Framework

  - by Uffo

  I have a mysql table with over 4 million of data; well the problem is that SOME queries WORK and SOME DON'T it depends on the search term, if the search term has a big volume of data in the table than I get the following error: Fatal error: Allowed memory size of 1048576000 bytes exhausted (tried to allocate 75 bytes) in /home/****/public_html/Zend/Db/Statement/Pdo.php on line 290 I currently have Zend Framework cache for metadata enabled, I have index on all the fields from that table.The site is running on a dedicated server with 2gb of ram. I've also set memory limit to: ini_set("memory_limit","1000M"); Any other things that I can optimize? Those are the types of query that I'm currently using: $do = $this->select() ->where('branche LIKE ?','%'.mysql_escape_string($branche).'%') ->order('premium DESC'); } //For name if(empty($branche) && empty($plz)) { $do = $this->select("MATCH(`name`) AGAINST ('{$theString}') AS score") ->where('MATCH(`name`) AGAINST( ? IN BOOLEAN MODE)', $theString) ->order('premium DESC, score'); } And a few other, but they are pretty much the same. Best Regards

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• Using prepared statements with JDBCTemplate

  - by Bernhard V

  Hi. I'm using the Jdbc template and want to read from the database using prepared statements. I iterate over many lines in a csv file and on every line I execute some sql select queries with it's values. Now I want to speed up my reading from the database but I just can't get the Jdbc template to work with prepared statements. Actually I even don't know how to do it. There is the PreparedStatementCreator and the PreparedStatementCreator. As in this example both of them are created with anonymous inner classes. But inside the PreparedStatementCreator class I don't have access to the values I want to set in the prepared statement. Since I'm iterating through a csv file I can't hard code them as a String because I don't know them. I also can't pass them to the PreparedStatementCreator because there are no arguments for the constructor. I was used to the creation of prepared statements being fairly simple. Something like PreparedStatement updateSales = con.prepareStatement( "UPDATE COFFEES SET SALES = ? WHERE COF_NAME LIKE ? "); updateSales.setInt(1, 75); updateSales.setString(2, "Colombian"); updateSales.executeUpdate(): as in the Java tutorial. Your help would be very appreciated.

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• Nhibernate/Hibernate, lookup tables and object design

  - by Simon G

  Hi, I've got two tables. Invoice with columns CustomerID, InvoiceDate, Value, InvoiceTypeID (CustomerID and InvoiceDate make up a composite key) and InvoiceType with InvoiceTypeID and InvoiceTypeName columns. I know I can create my objects like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceType InvoiceType { get; set; } } public class InvoiceType { public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } So the generated sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice WHERE CustomerID = x AND InvoiceDate = y SELECT InvoiceTypeID, InvoiceTypeName FROM InvoiceType WHERE InvoiceTypeID = z But rather that having two select queries executed to retrieve the data I would rather have one. I would also like to avoid using child object for simple lookup lists. So my object would look something like: public class Invoice { public virtual int CustomerID { get; set; } public virtual DateTime InvoiceDate { get; set; } public virtual decimal Value { get; set; } public virtual InvoiceTypeID { get; set; } public virtual InvoiceTypeName { get; set; } } And my sql would look something like: SELECT CustomerID, InvoiceDate, Value, InvoiceTypeID FROM Invoice INNER JOIN InvoiceType ON Invoice.InvoiceTypeID = InvoiceType.InvoiceTypeID WHERE CustomerID = x AND InvoiceDate = y My question is how do I create the mapping for this? I've tried using join but this tried to join using CustomerID and InvoiceDate, am I missing something obvious? Thanks

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• Why I am not able to update the column based on a condition which is not the primary key

  - by Gaurav Sharma

  Why I am not able to update the column based on a condition which is not the primary key. I am trying to update the constituencies table where name matches a specific criterial as shown below but the below queries shows an error Error code 1064, SQL state 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table constituencies set city_id = '1' where constituencies.name = "East Delhi"' at line 1 update table constituencies set city_id = '1' where constituencies.name = "East Delhi"; update table constituencies set city_id = '1' where constituencies.name = "South Delhi"; update table constituencies set city_id = '1' where constituencies.name = "Delhi Sadar"; update table constituencies set city_id = '1' where constituencies.name = "Karol Bagh"; update table constituencies set city_id = '1' where constituencies.name = "New Delhi"; update table constituencies set city_id = '1' where constituencies.name = "Outer Delhi"; update table constituencies set city_id = '1' where constituencies.name = "North East Delhi"; update table constituencies set city_id = '1' where constituencies.name = "North West Delhi"; update table constituencies set city_id = '1' where constituencies.name = "West Delhi"; Is it necessary that the condition should be checked with a primary key only ? Please throw some light on the above.

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• Subsonic 3 ActiveRecord nested select for NotIn bug?

  - by Junto

  I have the following Subsonic 3.0 query, which contains a nested NotIn query: public List<Order> GetRandomOrdersForNoReason(int shopId, int typeId) { // build query var q = new SubSonic.Query.Select().Top("1") .From("Order") .Where("ShopId") .IsEqualTo(shopId) .And(OrderTable.CustomerId).NotIn( new Subsonic.Query.Select("CustomerId") .From("Customer") .Where("TypeId") .IsNotEqualTo(typeId)) .OrderDesc("NewId()"); // Output query Debug.WriteLine(q.ToString()); // returned typed list return q.ExecuteTypedList<Order>(); } The internal query appears to be incorrect: SELECT TOP 1 * FROM [Order] WHERE ShopId = @0 AND CustomerId NOT IN (SELECT CustomerId FROM [Customer] WHERE TypeId = @0) ORDER BY NewId() ASC You'll notice that both parameters are @0. I'm assuming that the parameters are enumerated (starting at zero), for each "new" Select query. However, in this case where the two Select queries are nested, I would have expected the output to have two parameters named @0 and @1. My query is based on one that Rob Conery gave on his blog as a preview of the "Pakala" query tool that became Subsonic 3. His example was: int records = new Select(Northwind.Product.Schema) .Where("productid") .In( new Select("productid").From(Northwind.Product.Schema) .Where("categoryid").IsEqualTo(5) ) .GetRecordCount(); Has anyone else seen this behavior? Is it a bug, or is this an error or my part? Since I'm new to Subsonic I'm guessing that this probably programmer error on my part but I'd like confirmation if possible.

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• Programmatically talking to a Serial Port in OS X or Linux

  - by deadprogrammer

  I have a Prolite LED sign that I like to set up to show scrolling search queries from a apache logs and other fun statistics. The problem is, my G5 does not have a serial port, so I have to use a usb to serial dongle. It shows up as /dev/cu.usbserial and /dev/tty.usbserial . When i do this everything seems to be hunky-dory: stty -f /dev/cu.usbserial speed 9600 baud; lflags: -icanon -isig -iexten -echo iflags: -icrnl -ixon -ixany -imaxbel -brkint oflags: -opost -onlcr -oxtabs cflags: cs8 -parenb Everything also works when I use the serial port tool to talk to it. If I run this piece of code while the above mentioned serial port tool, everthing also works. But as soon as I disconnect the tool the connection gets lost. #!/usr/bin/python import serial ser = serial.Serial('/dev/cu.usbserial', 9600, timeout=10) ser.write("<ID01><PA> \r\n") read_chars = ser.read(20) print read_chars ser.close() So the question is, what magicks do I need to perform to start talking to the serial port without the serial port tool? Is that a permissions problem? Also, what's the difference between /dev/cu.usbserial and /dev/tty.usbserial?

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• Beginner SQL question: querying gold and silver tag badges in Stack Exchange Data Explorer

  - by polygenelubricants

  I'm using the Stack Exchange Data Explorer to learn SQL, but I think the fundamentals of the question is applicable to other databases. I'm trying to query the Badges table, which according to Stexdex (that's what I'm going to call it from now on) has the following schema: Badges Id UserId Name Date This works well for badges like [Epic] and [Legendary] which have unique names, but the silver and gold tag-specific badges seems to be mixed in together by having the same exact name. Here's an example query I wrote for [mysql] tag: SELECT UserId as [User Link], Date FROM Badges Where Name = 'mysql' Order By Date ASC The (slightly annotated) output is: as seen on stexdex: User Link Date --------------- ------------------- // all for silver except where noted Bill Karwin 2009-02-20 11:00:25 Quassnoi 2009-06-01 10:00:16 Greg 2009-10-22 10:00:25 Quassnoi 2009-10-31 10:00:24 // for gold Bill Karwin 2009-11-23 11:00:30 // for gold cletus 2010-01-01 11:00:23 OMG Ponies 2010-01-03 11:00:48 Pascal MARTIN 2010-02-17 11:00:29 Mark Byers 2010-04-07 10:00:35 Daniel Vassallo 2010-05-14 10:00:38 This is consistent with the current list of silver and gold earners at the moment of this writing, but to speak in more timeless terms, as of the end of May 2010 only 2 users have earned the gold [mysql] tag: Quassnoi and Bill Karwin, as evidenced in the above result by their names being the only ones that appear twice. So this is the way I understand it: The first time an Id appears (in chronological order) is for the silver badge The second time is for the gold Now, the above result mixes the silver and gold entries together. My questions are: Is this a typical design, or are there much friendlier schema/normalization/whatever you call it? In the current design, how would you query the silver and gold badges separately? GROUP BY Id and picking the min/max or first/second by the Date somehow? How can you write a query that lists all the silver badges first then all the gold badges next? Imagine also that the "real" query may be more complicated, i.e. not just listing by date. How would you write it so that it doesn't have too many repetition between the silver and gold subqueries? Is it perhaps more typical to do two totally separate queries instead? What is this idiom called? A row "partitioning" query to put them into "buckets" or something?

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• Optimizing PHP require_once's for low disk i/o?

  - by buggedcom

  Q1) I'm designing a CMS (-who isn't!) but priority is being given to caching. Literally everything is cached. DB rows, DB id queries, Configuration data, processed data, compiled templates. Currently it has two layers of caching. The first is a opcode cache or memory cache such as apc, eaccelerator, xcache or memcached. If an entry is not found in there it is then searched for in the secondary slow cache, ie php includes. Are the opcode caches actually faster than doing a require_once to a php file with a var_export'd array of data in it? My tests are inconclusive as my development box (5.3 of XAMPP) keeps throwing errors installing any of the aforementioned programs. Q2) The CMS has numerous helper classes that are autoloaded on demand instead of loading all files. Mostly each has a require before it so no autoloading needs to take place, however this is not the question. Because a page script can have up to 50/60 helper files included I have a feeling that if the site was under pressure it would buckle because of all the i/o that this incurs. Ignore for the moment that there is output cache in place that would remove the need for what I am about to suggest, and also that opcode caches would render this moot. What I have tried to do is join all the helper files required for the scripts execution in one single file. This is achievable and works well, however it has a side effect of greatly increasing the memory usage dramatically even though technically the same code is being used. What are your thoughts and opinions on this?

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• How to make comment reply query in MYSQL?

  - by Prashant

  I am having comment reply (only till one level) functionality. All comments can have as many as replies but no replies can have their further replies. So my database table structure is like below Id ParentId Comment 1 0 this is come sample comment text 2 0 this is come sample comment text 3 0 this is come sample comment text 4 1 this is come sample comment text 5 0 this is come sample comment text 6 3 this is come sample comment text 7 1 this is come sample comment text In the above structures, commentid, 1 (has 2 replies) and 3 (1 reply) has replies. So to fetch the comments and their replies, one simple method is first I fetch all the comments having ParentId as 0 and then by running a while loop fetch all the replies of that particular commentId. But that seems to be running hundreds of queries if I'll have around 200 comments on a particular record. So I want to make a query which will fetch Comments with their replies sequentially as following; Id ParentId Comment 1 0 this is come sample comment text 4 1 this is come sample comment text 7 1 this is come sample comment text 2 0 this is come sample comment text 3 0 this is come sample comment text 6 3 this is come sample comment text 5 0 this is come sample comment text I also have a comment date column in my comment table, if anyone wants to use this with comment query. So finally I want to fetch all the comments and their replies by using one single mysql query. Please tell me how I can do that? Thanks

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• Need Help with SQL Subquery

  - by Pete Augello

  Hey: I am trying to write a query that will return all orders that only have a Subscription included. It is easy enough to write a query that includes all Orders with Subscriptions, another that includes all orders without a Subscription and then compare them with an unmatched query. But I don't want to have to store Queries in my Access database, I prefer to have it all in my ASP code, and I can't get this to work with just one complex query. Here are samples of what works if I store them: Query1 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((Not ((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query2 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query3 SELECT Query2.OrderID, Query2.ProductID FROM Query2 LEFT JOIN Query1 ON Query2.OrderID = Query1.OrderID WHERE (((Query1.OrderID) Is Null)); So, my question is 'how do I write Query3 so that it doesn't refer to Query1 or Query2?' or, am I missing some other way do do this? Thanks, Pete [email protected]

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• Load Ruby on Rails models without loading the entire framework

  - by epochwolf

  I'm looking to create a custom daemon that will run various database tasks such as delaying mailings and user notifications (each notice is a separate row in the notifications table). I don't want to use script/runner or rake to do these tasks because it is possible that some of the tasks only require the create of one or two database rows or thousands of rows depending on the task. I don't want the overhead of launching a ruby process or loading the entire rails framework for each operation. I plan to keep this daemon in memory full time. To create this daemon I would like to use my models from my ruby on rails application. I have a number of rails plugins such as acts_as_tree and AASM that I will need loaded if I where to use the models. Some of the plugins I need to load are custom hacks on ActiveRecord::Base that I've created. (I am willing to accept removing or recoding some of the plugins if they need components from other parts of rails.) My questions are Is this a good idea? And - Is this possible to do in a way that doesn't have me manually including each file in my models and plugins? If not a good idea What is a good alternative? (I am not apposed to doing writing my own SQL queries but I would have to add database constraints and a separate user for the daemon to prevent any stupid accidents. Given my lack of familiarity with configuring a database, I would like to use active record as a crutch.)

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