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• Approach for authentication and storing user details.

  - by cappuccino

  Hey folks, I am using the Zend Framework but my question is broadly about sessions / databases / auth (PHP MySQL). Currently this is my approach to authentication: 1) User signs in, the details are checked in database. - Standard stuff really. 2) If the details are correct only the user's unique ID is stored in the session and a security token (user unique ID + IP + Browser info + salt). The session in written to the filesystem. I've been reading around and many are saying that storing stuff in sessions is not a good idea, and that you should really only write a unique ID which refers back to the user's details and a security token to prevent session hijacking. So this is the approach i've taken, i use to write the user's details in session, but i've moved that out. Wanted to know your opinions on this. I'm keeping sessions in the filesystem since i don't run on multiple servers, and since i'm only writting a tiny tiny bit of data to sessions, i thought that performance would be greater keeping sessions in the filesystem to reduce load on the database. Once the session is written on authentication, it really is only read-only from then on. 3) The rest of the user's details (like subscription details, permissions, account info etc) are cached in the filesystem (this can always be easily moved to memory if i wanted even more performance). So rather than keeping the user's details in session, the user's details are cached in the file system. I'm using Zend_Cache and the unique cache id is something like md5(/cache/auth/2892), the number is the unique id of the user. I guess the benefit of this method is that once the user is logged in, there is essentially not database queries being run to get the user's details. Just wonder if this approach is better than keeping the whole lot in session... 4) As the user moves throughout the site the only thing that is checked is the ID in the session and the security token. So, overall the first question is 1) is the filesystem more efficient than a database for this purpose 2) have i taken enough security precautions 3) is separating user detail's from the session into a cached file a pointless task? Thanks.

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• How to design a high-level application protocol for metadata syncing between devices and server?

  - by Jaanus

  I am looking for guidance on how to best think about designing a high-level application protocol to sync metadata between end-user devices and a server. My goal: the user can interact with the application data on any device, or on the web. The purpose of this protocol is to communicate changes made on one endpoint to other endpoints through the server, and ensure all devices maintain a consistent picture of the application data. If user makes changes on one device or on the web, the protocol will push data to the central repository, from where other devices can pull it. Some other design thoughts: I call it "metadata syncing" because the payloads will be quite small, in the form of object IDs and small metadata about those ID-s. When client endpoints retrieve new metadata over this protocol, they will fetch actual object data from an external source based on this metadata. Fetching the "real" object data is out of scope, I'm only talking about metadata syncing here. Using HTTP for transport and JSON for payload container. The question is basically about how to best design the JSON payload schema. I want this to be easy to implement and maintain on the web and across desktop and mobile devices. The best approach feels to be simple timer- or event-based HTTP request/response without any persistent channels. Also, you should not have a PhD to read it, and I want my spec to fit on 2 pages, not 200. Authentication and security are out of scope for this question: assume that the requests are secure and authenticated. The goal is eventual consistency of data on devices, it is not entirely realtime. For example, user can make changes on one device while being offline. When going online again, user would perform "sync" operation to push local changes and retrieve remote changes. Having said that, the protocol should support both of these modes of operation: Starting from scratch on a device, should be able to pull the whole metadata picture "sync as you go". When looking at the data on two devices side by side and making changes, should be easy to push those changes as short individual messages which the other device can receive near-realtime (subject to when it decides to contact server for sync). As a concrete example, you can think of Dropbox (it is not what I'm working on, but it helps to understand the model): on a range of devices, the user can manage a files and folders—move them around, create new ones, remove old ones etc. And in my context the "metadata" would be the file and folder structure, but not the actual file contents. And metadata fields would be something like file/folder name and time of modification (all devices should see the same time of modification). Another example is IMAP. I have not read the protocol, but my goals (minus actual message bodies) are the same. Feels like there are two grand approaches how this is done: transactional messages. Each change in the system is expressed as delta and endpoints communicate with those deltas. Example: DVCS changesets. REST: communicating the object graph as a whole or in part, without worrying so much about the individual atomic changes. What I would like in the answers: Is there anything important I left out above? Constraints, goals? What is some good background reading on this? (I realize this is what many computer science courses talk about at great length and detail... I am hoping to short-circuit it by looking at some crash course or nuggets.) What are some good examples of such protocols that I could model after, or even use out of box? (I mention Dropbox and IMAP above... I should probably read the IMAP RFC.)

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• save the transient instance before flushing

  - by eugenn

  Exception: object references an unsaved transient instance - save the transient instance before flushing: Child How to reproduce issue: 1. Hibernate is load the entity "Parent". The property "child" is null 2. The "Parent" is rendered on the screen and after that the "child" property is auto instantiated. So I have the following graph: Parent.child != null Parent.child.childId = null Parent.child.childKey = "" Parent.child.childName = "" Question: How I could to force the Hibernate to ignore updating or inserting Child entity WHEN childId = null? If childId != null I would like just create relation. <hibernate-mapping> <class name="com.test.Parent" entity-name="ParentObject" table="parent" dynamic-insert="false" dynamic-update="true" optimistic-lock="version"> <id name="rowId" type="long"> <column name="RowID" /> <generator class="native" /> </id> <version name="versionSequence" type="integer" unsaved-value="null" generated="never" insert="false"> <column name="VersionSequence" /> </version> <many-to-one name="child" entity-name="Child" fetch="select" optimistic-lock="true" embed-xml="false" update="true" insert="false"> <column name="ChildID" /> </many-to-one> <property name="dateCreated" type="timestamp"> <column name="DateCreated" length="0" /> </property> <property name="dateUpdated" type="timestamp" update="false"> <column name="DateUpdated" length="0" /> </property> </class> </hibernate-mapping> <hibernate-mapping> <class name="com.Child" entity-name="Child" table="Child" dynamic-insert="false" dynamic-update="true" optimistic-lock="version"> <id name="childId" type="long" > <column name="ChildID" /> <generator class="native" /> </id> <version name="versionSequence" type="integer" insert="false" generated="never" > <column name="VersionSequence" /> </version> <property name="childKey" type="string" > <column name="ChildKey" length="20" /> </property> <property name="childName" type="string" > <column name="ChildName" length="30" /> </property> <property name="childNumber" type="string" > <column name="ChildNumber" /> </property> <property name="dateCreated" type="timestamp"> <column name="DateCreated" /> </property> <property name="dateUpdated" type="timestamp" update="false"> <column name="DateUpdated" /> </property> </class> </hibernate-mapping>

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• What are the Options for Storing Hierarchical Data in a Relational Database?

  - by orangepips

  Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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• Implementing a logging library in .NET with a database as the storage medium

  - by Dave

  I'm just starting to work on a logging library that everyone can use to keep track of any sort of system information while the user is running our application. The simplest example so far is to track Info, Warnings, and Errors. I want all plugins to be able to use this feature, but since each developer might have a different idea of what's important to report, I want to keep this as generic as possible. In the C++ world, I would normally use something like a stl::pair<string,string> to act as a key value pair structure, and have a stl::list of these to act as a "row" in the log. The log cache would then be a list<list<pair<string,string>>> (ugh!). This way, the developers can use a const string key like INFO, WARNING, ERROR to have a consistent naming for a column in the database (for SELECTing specific types of information). I'd like the database to be able to deal with any number of distinct column names. For example, John might have an INFO row with a column called USER, and Bill might have an INFO row with a column called FILENAME. I want the log viewer to be able to display all information, and if one report doesn't have a value for INFO / FILENAME, those fields should just appear blank. So one option is to use List<List<KeyValuePair<String,String>>, and the another is to have the log library consumer somehow "register" its schema, and then have the database do an ALTER TABLE to handle this situation. Yet another idea is to have a table that's just for key value pairs, with a foreign key that maps the key value pairs back to the original log entry. I obviously don't want logging to bog down the system, so I only lock the log cache to make a copy of the data (and remove the already-copied data), then a background thread will dump the information to the database. My specific questions regarding this are: Do you see any performance issues? In other words, have you ever tried something like this and found that certain things just don't work well in practice? Is there a more .NETish way to implement the key value pairs, other than List<List<KeyValuePair<String,String>>>? Even if there is a way to do #2 better, is the ALTER TABLE idea I proposed above a Bad Thing? Would you recommend multiple databases over a single one? I don't yet have an idea of how frequently the log would get written to, but we ideally would like to have lots of low level information. Perhaps there should be a DB with a fixed schema only for the low level stuff, and then another DB that's more flexible for reporting information back to users.

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• Persistent (purely functional) Red-Black trees on disk performance

  - by Waneck

  I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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• C++ using cdb_read returns extra characters on some reads

  - by Moe Be

  Hi All, I am using the following function to loop through a couple of open CDB hash tables. Sometimes the value for a given key is returned along with an additional character (specifically a CTRL-P (a DLE character/0x16/0o020)). I have checked the cdb key/value pairs with a couple of different utilities and none of them show any additional characters appended to the values. I get the character if I use cdb_read() or cdb_getdata() (the commented out code below). If I had to guess I would say I am doing something wrong with the buffer I create to get the result from the cdb functions. Any advice or assistance is greatly appreciated. char* HashReducer::getValueFromDb(const string &id, vector <struct cdb *> &myHashFiles) { unsigned char hex_value[BUFSIZ]; size_t hex_len; //construct a real hex (not ascii-hex) value to use for database lookups atoh(id,hex_value,&hex_len); char *value = NULL; vector <struct cdb *>::iterator my_iter = myHashFiles.begin(); vector <struct cdb *>::iterator my_end = myHashFiles.end(); try { //while there are more databases to search and we have not found a match for(; my_iter != my_end && !value ; my_iter++) { //cerr << "\n looking for this MD5:" << id << " hex(" << hex_value << ") \n"; if (cdb_find(*my_iter, hex_value, hex_len)){ //cerr << "\n\nI found the key " << id << " and it is " << cdb_datalen(*my_iter) << " long\n\n"; value = (char *)malloc(cdb_datalen(*my_iter)); cdb_read(*my_iter,value,cdb_datalen(*my_iter),cdb_datapos(*my_iter)); //value = (char *)cdb_getdata(*my_iter); //cerr << "\n\nThe value is:" << value << " len is:" << strlen(value)<< "\n\n"; }; } } catch (...){} return value; }

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• JPA2 adding referential contraint to table complicates criteria query with lazy fetch, need advice

  - by Quaternion

  Following is a lot of writing for what I feel is a pretty simple issue. Root of issue is my ignorance, not looking so much for code but advice. Table: Ininvhst (Inventory-schema inventory history) column ihtran (inventory history transfer code) using an old entity mapping I have: @Basic(optional = false) @Column(name = "IHTRAN") private String ihtran; ihtran is really a foreign key to table Intrnmst ("Inventory Transfer Master" which contains a list of "transfer codes"). This was not expressed in the database so placed a referential constraint on Ininvhst re-generating JPA2 entity classes produced: @JoinColumn(name = "IHTRAN", referencedColumnName = "TMCODE", nullable = false) @ManyToOne(optional = false) private Intrnmst intrnmst; Now previously I was using JPA2 to select the records/(Ininvhst entities) from the Ininvhst table where "ihtran" was one of a set of values. I used in.value() to do this... here is a snippet: cq = cb.createQuery(Ininvhst.class); ... In in = cb.in(transactionType); //Get in expression for transacton types for (String s : transactionTypes) { //has a value in = in.value(s);//check if the strings we are looking for exist in the transfer master } predicateList.add(in); My issue is that the Ininvhst used to contain a string called ihtran but now it contains Ininvhst... So I now need a path expression: this.predicateList = new ArrayList<Predicate>(); if (transactionTypes != null && transactionTypes.size() > 0) { //list of strings has some values Path<Intrnmst> intrnmst = root.get(Ininvhst_.intrnmst); //get transfermaster from Ininvhst Path<String> transactionType = intrnmst.get(Intrnmst_.tmcode); //get transaction types from transfer master In<String> in = cb.in(transactionType); //Get in expression for transacton types for (String s : transactionTypes) { //has a value in = in.value(s);//check if the strings we are looking for exist in the transfer master } predicateList.add(in); } Can I add ihtran back into the entity along with a join column that is both references "IHTRAN"? Or should I use a projection to somehow return Ininvhst along with the ihtran string which is now part of the Intrnmst entity. Or should I use a projection to return Ininvhst and somehow limit Intrnmst just just the ihtran string. Further information: I am using the resulting list of selected Ininvhst objects in a web application, the class which contains the list of Ininvhst objects is transformed into a json object. There are probably quite a few serialization methods that would navigate the object graph the problem is that my current fetch strategy is lazy so it hits the join entity (Intrnmst intrnmst) and there is no Entity Manager available at that point. At this point I have prevented the object from serializing the join column but now I am missing a critical piece of data. I think I've said too much but not knowing enough I don't know what you JPA experts need. What I would like is my original object to have both a string object and be able to join on the same column (ihtran) and have it as a string too, but if this isn't possible or advisable I want to hear what I should do and why. Pseudo code/English is more than fine.

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• uninitialized constant Encoding rake db:migrate

  - by Denis

  Hi, My RoR App use rails 2.1.2 When I run rake db:migrate --trace I get the following error, Any idea? ** Invoke db:migrate (first_time) ** Invoke environment (first_time) ** Execute environment ** Execute db:migrate rake aborted! uninitialized constant Encoding /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activesupport/lib/active_support/dependencies.rb:278:in `load_missing_constant' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activesupport/lib/active_support/dependencies.rb:467:in `const_missing' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activesupport/lib/active_support/dependencies.rb:479:in `const_missing' /Library/Ruby/Gems/1.8/gems/sqlite3-0.0.8/lib/sqlite3/encoding.rb:9:in `find' /Library/Ruby/Gems/1.8/gems/sqlite3-0.0.8/lib/sqlite3/database.rb:66:in `initialize' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb:13:in `new' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb:13:in `sqlite3_connection' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb:292:in `send' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb:292:in `connection=' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb:260:in `retrieve_connection' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb:78:in `connection' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/migration.rb:408:in `initialize' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/migration.rb:373:in `new' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/migration.rb:373:in `up' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/activerecord/lib/active_record/migration.rb:356:in `migrate' /Users/denisjacquemin/Documents/code/projects/BmfOnRails/vendor/rails/railties/lib/tasks/databases.rake:99 /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run' /Users/denisjacquemin/.gem/ruby/1.8/gems/rake-0.8.7/bin/rake:31 /usr/bin/rake:19:in `load' /usr/bin/rake:19 My database.yml development: adapter: sqlite3 database: db/development.sqlite3 pool: 5 timeout: 5000 thanks

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• Retrieving information from DOM elements returned using ajax

  - by niczoom

  I am new(ish) to jQuery and am testing out the extraction of DOM element data using jQuery. Below, detailed on the firebug console I tried to extract data 10 different ways (from 1- to 10-) using data returned directly from the ajax request (rtnData). And then to compare, I wrapped (rtnData) in a div to make it a jQuery object, and stored it in $test, (var $test= $('<div/>').html(rtnData);) Displayed below in Firebug Console Output, I cant figure out is why 5- return's nothing and e- returns the center tag contents. Same with 8- and e-, they both look for #ticker div id but 8- returns nothing and e- returns the correct html?? Also when searching for h1 tag .text(), why does 10- return blank and j- return the correct data? Thanks, Nic. Use the following page to run the ajax request below in Firebug Console: http://www.liamharding.com/pgi/pgi.php jQuery code ran using Firebug Console: $.ajax({ url: 'pgiproxy.php', type: 'POST', dataType: 'html', data: ({ data : $("#formdata").serialize(), mode : "graph"}), success: function(rtnData){ console.log("0- ", rtnData); console.log("1- ", $('img', rtnData)); console.log("2- ", $('a', rtnData)); console.log("3- ", $('span.cr', rtnData)); console.log("4- ", $('span.cr', rtnData).html()); console.log("5- ", $('center', rtnData)); console.log("6- ", $('table', rtnData)); console.log("7- ", $('#ticker_data', rtnData)); console.log("8- ", $('#ticker', rtnData)); console.log("9- ", $('#last', rtnData)); console.log("10- ", $('h1', rtnData).text()); var $test= $('<div/>').html(rtnData); console.log("z- ", $test); console.log("a- ", $('img', $test)); console.log("b- ", $('a', $test)); console.log("c- ", $('span.cr', $test)); console.log("d- ", $('span.cr', $test).html()); console.log("e- ", $('center', $test)); console.log("f- ", $('table', $test)); console.log("g- ", $('#ticker_data', $test)); console.log("h- ", $('#ticker', $test)); console.log("i- ", $('#last', $test)); console.log("j- ", $('h1', $test).text()); }, error: function(){ alert('ERROR'); } }); Firebug Console Output: 1- jQuery(img#GnuPlotChart 624e4629...8946.gif) 2- jQuery(a.button javascri...eload();, a.button javascri...close();) 3- jQuery(span.cr) 4- <span class="tl"></span><span class="tr"></span><span class="bl"></span><span class="br"></span> 5- jQuery() 6- jQuery(table.rbox-table) 7- jQuery(div#ticker_data.rbox) 8- jQuery() 9- jQuery(th#last, td#last.num) 10- z- jQuery(div) a- jQuery(img#GnuPlotChart 624e4629...8946.gif) b- jQuery(a.button javascri...eload();, a.button javascri...close();) c- jQuery(span.cr) d- <span class="tl"></span><span class="tr"></span><span class="bl"></span><span class="br"></span> e- jQuery(center) f- jQuery(table.rbox-table, table) g- jQuery(div#ticker_data.rbox) h- jQuery(div#ticker) i- jQuery(th#last, td#last.num) j- Legacy Charts

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• Android database closed exception

  - by Bombastic

  I'm working on a project where I'm downloading and saving data from web to sqlite database. A few minutes ago I receive a strange exception to our server from a user which is saying that the sqlite database is already closed..and I just checked the whole file where the exception happened and I'm not calling dbHelper.close();. Here is the function where the app crashes and LogCat message : public void insertCollectionCountries(JSONObject obj, Context context) { //Insert in collection_countries if(RPCCommunicator.isServiceRunning){ Log.w("","JsonCollection - insertCollectionCountries"); ContentValues valuesCountries = new ContentValues(); try { collectionId = Integer.parseInt(obj.getString("collection_id")); dbHelper.deleteSQL("collection_countries", "collection_id=?", new String[] {Integer.toString(collectionId)}); JSONArray arrayCountries = obj.getJSONArray("country_availability"); for (int i=0; i<arrayCountries.length(); i++) { valuesCountries.put("collection_id", collectionId); String countryCode = arrayCountries.getString(i); valuesCountries.put("country_code", countryCode); dbHelper.executeQuery("collection_countries", valuesCountries); } } catch (JSONException e){ e.printStackTrace(); } } } and the error is on that line : dbHelper.executeQuery("collection_countries", valuesCountries); here is the LogCat message : java.lang.IllegalStateException: database /data/data/com.stampii.stampii/databases/stampii_sys_tpl.sqlite (conn# 0) already closed at android.database.sqlite.SQLiteDatabase.verifyDbIsOpen(SQLiteDatabase.java:2123) at android.database.sqlite.SQLiteDatabase.setTransactionSuccessful(SQLiteDatabase.java:734) at com.stampii.stampii.comm.rpc.SystemDatabaseHelper.execQuery(SystemDatabaseHelper.java:298) at com.stampii.stampii.comm.rpc.SystemDatabaseHelper.executeQuery(SystemDatabaseHelper.java:291) at com.stampii.stampii.jsonAPI.JsonCollection.insertCollectionCounries(JsonCollection.java:548) at com.stampii.stampii.jsonAPI.JsonCollection.executeInsert(JsonCollection.java:181) at com.stampii.stampii.collections.MyService.downloadCollections(MyService.java:122) at com.stampii.stampii.collections.MyService$2.run(MyService.java:74) at java.lang.Thread.run(Thread.java:1020) and function in my dbHelperClass which I'm using to insert data : public boolean executeQuery(String tableName,ContentValues values){ return execQuery(tableName,values); } private boolean execQuery(String tableName,ContentValues values){ sqliteDb = instance.getWritableDatabase(); sqliteDb.beginTransaction(); sqliteDb.insert(tableName, null, values); sqliteDb.setTransactionSuccessful(); sqliteDb.endTransaction(); return true; } Any ideas which can close my sqlite database or what can cause that exception, because I've tested this code on a few emulators with different Android versions, different devices (HTC EVO 3D, Samsung Galaxy Nexus,HTC Desire, LG OPTIMUS PAD, Samsung Galaxy S2, Samsung Galaxy Note) and it's working fine. Thanks in advance!

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• Java DriverManager Always Assigns My Driver

  - by JGB146

  I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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• Can sorting Japanese kanji words be done programatically?

  - by Mason

  I've recently discovered, to my astonishment (having never really thought about it before), machine-sorting Japanese proper nouns is apparently not possible. I work on an application that must allow the user to select a hospital from a 3-menu interface. The first menu is Prefecture, the second is City Name, and the third is Hospital. Each menu should be sorted, as you might expect, so the user can find what they want in the menu. Let me outline what I have found, as preamble to my question: The expected sort order for Japanese words is based on their pronunciation. Kanji do not have an inherent order (there are tens of thousands of Kanji in use), but the Japanese phonetic syllabaries do have an order: ???????????????????... and on for the fifty traditional distinct sounds (a few of which are obsolete in modern Japanese). This sort order is called ???? (gojuu on jun , or '50-sound order'). Therefore, Kanji words should be sorted in the same order as they would be if they were written in hiragana. (You can represent any kanji word in phonetic hiragana in Japanese.) The kicker: there is no canonical way to determine the pronunciation of a given word written in kanji. You never know. Some kanji have ten or more different pronunciations, depending on the word. Many common words are in the dictionary, and I could probably hack together a way to look them up from one of the free dictionary databases, but proper nouns (e.g. hospital names) are not in the dictionary. So, in my application, I have a list of every prefecture, city, and hospital in Japan. In order to sort these lists, which is a requirement, I need a matching list of each of these names in phonetic form (kana). I can't come up with anything other than paying somebody fluent in Japanese (I'm only so-so) to manually transcribe them. Before I do so though: Is it possible that I am totally high on fire, and there actually is some way to do this sorting without creating my own mappings of kanji words to phonetic readings, that I have somehow overlooked? Is there a publicly available mapping of prefecture/city names, from the government or something? That would reduce the manual mapping I'd need to do to only hospital names. Does anybody have any other advice on how to approach this problem? Any programming language is fine--I'm working with Ruby on Rails but I would be delighted if I could just write a program that would take the kanji input (say 40,000 proper nouns) and then output the phonetic representations as data that I could import into my Rails app. ??????????

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• SQL query - choosing 'last updated' record in a group, better db design?

  - by Jimmy

  Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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• Can highlight the current menu item, but can't add the class= to style unhighleted menu items

  - by bradpotts

  <?php $activesidebar[$currentsidebar]="id=isactive";?> <div class="span3"> <div class="well sidebar-nav hidden-phone"> <ul class="nav nav-list"> <li class="nav-header" <?php echo $activesidebar[1] ?>>Marketing Services</li> <li><a href="#">Marketing Technology</a></li> <li><a href="#">Generate More Sales</a></li> <li><a href="#">Direct Email Marketing</a></li> <li class="nav-header" <?php echo $activesidebar[2] ?>>Advertising Services</li> <li><a href="../services-advertising-mass-media-network.php">Traditional Medias</a></li> <li><a href="#">Online & Social Medias</a></li> <li><a href="#">Media Planing & Purchasing</a></li> <li class="nav-header" <?php echo $activesidebar[3] ?>>Technology Services</li> <li><a href="#">Managed Websites</a></li> <li><a href="#">Managed Web Servers</a></li> <li><a href="#">Managed Databases</a></li> <li class="nav-header" <?php echo $activesidebar[4] ?>>About Us</li> <li><a href="../aboutus-contactus.php">Contact Us</a></li> </ul> </div> This is added to the current page I want to add this on. <?php $currentsidebar =2; include('module-sidebar-navigation.php');?> I had programmed this menu individually on each page, but to make my website dynamic I used one file and use php includes to load the file. I can get the menu to highlight on the current page assigning an id="isactive", how can I assign id="notactive" to the other 3 menu items that are not active on that page. Is there an else or elseif I have to include?

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• Which is the "best" data access framework/approach for C# and .NET?

  - by Frans

  (EDIT: I made it a community wiki as it is more suited to a collaborative format.) There are a plethora of ways to access SQL Server and other databases from .NET. All have their pros and cons and it will never be a simple question of which is "best" - the answer will always be "it depends". However, I am looking for a comparison at a high level of the different approaches and frameworks in the context of different levels of systems. For example, I would imagine that for a quick-and-dirty Web 2.0 application the answer would be very different from an in-house Enterprise-level CRUD application. I am aware that there are numerous questions on Stack Overflow dealing with subsets of this question, but I think it would be useful to try to build a summary comparison. I will endeavour to update the question with corrections and clarifications as we go. So far, this is my understanding at a high level - but I am sure it is wrong... I am primarily focusing on the Microsoft approaches to keep this focused. ADO.NET Entity Framework Database agnostic Good because it allows swapping backends in and out Bad because it can hit performance and database vendors are not too happy about it Seems to be MS's preferred route for the future Complicated to learn (though, see 267357) It is accessed through LINQ to Entities so provides ORM, thus allowing abstraction in your code LINQ to SQL Uncertain future (see Is LINQ to SQL truly dead?) Easy to learn (?) Only works with MS SQL Server See also Pros and cons of LINQ "Standard" ADO.NET No ORM No abstraction so you are back to "roll your own" and play with dynamically generated SQL Direct access, allows potentially better performance This ties in to the age-old debate of whether to focus on objects or relational data, to which the answer of course is "it depends on where the bulk of the work is" and since that is an unanswerable question hopefully we don't have to go in to that too much. IMHO, if your application is primarily manipulating large amounts of data, it does not make sense to abstract it too much into objects in the front-end code, you are better off using stored procedures and dynamic SQL to do as much of the work as possible on the back-end. Whereas, if you primarily have user interaction which causes database interaction at the level of tens or hundreds of rows then ORM makes complete sense. So, I guess my argument for good old-fashioned ADO.NET would be in the case where you manipulate and modify large datasets, in which case you will benefit from the direct access to the backend. Another case, of course, is where you have to access a legacy database that is already guarded by stored procedures. ASP.NET Data Source Controls Are these something altogether different or just a layer over standard ADO.NET? - Would you really use these if you had a DAL or if you implemented LINQ or Entities? NHibernate Seems to be a very powerful and powerful ORM? Open source Some other relevant links; NHibernate or LINQ to SQL Entity Framework vs LINQ to SQL

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• ANSI C as core of a C# project? Is this possible?

  - by Nektarios

  I'm writing a NON-GUI app which I want to be cross platform between OS X and Windows. I'm looking at the following architecture, but I don't know if it will work on the windows side: (Platform specific entry point) - ANSI C main loop = ANSI C model code doing data processing / logic = (Platform specific helpers) So the core stuff I'm planning to write in regular ANSI C, because A) it should be platform independent, B) I'm extremely comfortable with C, C) It can do the job and do it well (Platform specific entry point) can be written in whatever necessary to get the job done, this is a small amount of code, doesn't matter to me. (Platform specific helpers) is the sticky thing. This is stuff like parsing XML, accessing databases, graphics toolkit stuff, whatever. Things that aren't easy in C. Things that modern languages/frameworks will give for free. On OS X this code will be written in Objective-C interfacing with Cocoa. On Windows I'm thinking my best bet is to use C# So on Windows my architecture (simplified) looks like (C# or C?) - ANSI C - C# Is this possible? Some thoughts/suggestions so far.. 1) Compile my C core as a .dll -- this is fine, but seems there's no way to call my C# helpers unless I can somehow get function pointers and pass them to my core, but that seems unlikely 2) Compile a C .exe and a C# .exe and have them talk via shared memory or some kind of IPC. I'm not entirely opposed to this but it obviously introduces a lot of complexity so it doesn't seem ideal 3) Instead of C# use C++, it gets me some nice data management stuff and nice helper code. And I can mix it pretty easily. And the work I do could probably easily port to Linux. But I really don't like C++, and I don't want this to turn in to a 3rd-party-library-fest. Not that it's a huge deal, but it's 2010.. anything for basic data management should be built in. And targetting Linux is really not a priority. Note that no "total" alternatives are OK as suggested in other similar questions on SO I've seen; java, RealBasic, mono.. this is an extremely performance intensive application doing soft realtime for game/simulation purposes, I need C & friends here to do it right (maybe you don't, but I do)

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

  - by Bill Paetzke

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

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

  - by nawfal

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

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• Suggest an alternative way to organize/build a database solution.

  - by Hamish Grubijan

  We are using Visual Studio 2010, but this was first conceived with VS2003. I will forward the best suggestions to my team. The current setup almost makes me vomit. It is a C# solution with most projects containing .sql files. Because we support Microsoft, Oracle, and Sybase, and so home-brewed a pre-processor, much like C preprocessor, except that substitutions are performed by a home-brewed C# program without using yacc and tools like that. #ifdefs are used for conditional macro definitions, and yeah - macros are the way this is done. A macro can expand to another macro or two, but this should eventually terminate. Only macros have #ifdef in them - the rest of the SQL-like code just uses these macros. Now, the various configurations: Debug, MNDebug, MNRelease, Release, SQL_APPLY_ALL, SQL_APPLY_MSFT, SQL_APPLY_ORACLE, SQL_APPLY_SYBASE, SQL_BUILD_OUTPUT_ALL, SQL_COMPILE, as well as 2 more. Also: Any CPU, Mixed Platforms, Win32. What drives me nuts is having to configure it correctly as well as choosing the right one out of 12 x 3 = 36 configurations as well as having to substitute database name depending on the type of database: config, main, or gateway. I am thinking that configuration should be reduced to just Debug, Release, and SQL_APPLY. Also, using 0, 1, and 2 seems so 80s ... Finally, I think my intention to build or not to build 3 types of databases for 3 types of vendors should be configured with just a tic tac toe board like: XOX OOX XXX In this case it would mean build MSFT+CONFIG, all SYBASE, and all GATEWAY. Still, the overall thing which uses a text file and a pre-processor and many configurations seems incredibly clunky. It is year 2010 now and someone out there is bound to have a very clean and/or creative tool/solution. The only pro would be that the existing collection of macros has been well tested. Have you ever had to write SQL that would work for several vendors? How did you do it? SqlVars.txt (Every one of 30 users makes a copy of a template and modifies this to suit their needs): // This is the default parameters file and should not be changed. // You can overwrite any of these parameters by copying the appropriate // section to override into SqlVars.txt and providing your own information. //Build types are 0-Config, 1-Main, 2-Gateway BUILD_TYPE=1 REMOVE_COMMENTS=1 // Login information used when applying to a Microsoft SQL server database SQL_APPLY_MSFT_version=SQL2005 SQL_APPLY_MSFT_database=msftdb SQL_APPLY_MSFT_server=ABC SQL_APPLY_MSFT_user=msftusr SQL_APPLY_MSFT_password=msftpwd // Login information used when applying to an Oracle database SQL_APPLY_ORACLE_version=ORACLE10g SQL_APPLY_ORACLE_server=oradb SQL_APPLY_ORACLE_user=orausr SQL_APPLY_ORACLE_password=orapwd // Login information used when applying to a Sybase database SQL_APPLY_SYBASE_version=SYBASE125 SQL_APPLY_SYBASE_database=sybdb SQL_APPLY_SYBASE_server=sybdb SQL_APPLY_SYBASE_user=sybusr SQL_APPLY_SYBASE_password=sybpwd ... (THIS GOES ON)

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• JAVA: Can't get context parameters in Filter

  - by DaTval

  Hello, I have a filter and parameters in web.xml web.xml is like this: <filter> <description> </description> <display-name>AllClassFilter</display-name> <filter-name>AllClassFilter</filter-name> <filter-class>com.datval.homework.AllClassFilter</filter-class> <init-param> <param-name>DB_URL</param-name> <param-value>jdbc:derby:C:/Users/admin/workspace/homework03/homework/databases/StudentsDB;create=true</param-value> </init-param> <init-param> <param-name>DB_DIALECT</param-name> <param-value>org.hibernate.dialect.DerbyDialect</param-value> </init-param> <init-param> <param-name>DB_DRIVER</param-name> <param-value>org.apache.derby.jdbc.EmbeddedDriver</param-value> </init-param> </filter> mapping is working well. But I can't get this parameters in my filter. public void init(FilterConfig config) throws ServletException { // TODO Auto-generated method stub debugMessage = config.getInitParameter("debugMessage"); ctx = config.getServletContext(); } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // TODO Auto-generated method stub // place your code here ctx.log("Start - " + debugMessage); String myDbUrl = ctx.getInitParameter("DB_URL"); String DB_DIALECT = ctx.getInitParameter("DB_DIALECT"); String DB_DRIVER = ctx.getInitParameter("DB_DRIVER"); Map<String,String> pr = new HashMap<String,String>(); pr.put("hibernate.connection.url", myDbUrl); pr.put("hibernate.dialect", DB_DIALECT); pr.put("hibernate.connection.driver_class", DB_DRIVER); EntityManagerFactory emf = Persistence.createEntityManagerFactory("students",pr); EntityManager em = emf.createEntityManager(); request.setAttribute("em", em); chain.doFilter(request, response); em.close(); ctx.log("end - " + debugMessage); } I have checked and myDbUrl is null. What I'm doing wrong? Any idea? Sorry about code, I will change it later :)

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• Performance - FunctionCall vs Event vs Action vs Delegate

  - by hwcverwe

  Currently I am using Microsoft Sync Framework to synchronize databases. I need to gather information per record which is inserted/updated/deleted by Microsoft Sync Framework and do something with this information. The sync speed can go over 50.000 records per minute. So that means my additional code need to be very lightweight otherwise it will be a huge performance penalty. Microsoft Sync Framework raises an SyncProgress event for each record. I am subscribed to that code like this: // Assembly1 SyncProvider.SyncProgress += OnSyncProgress; // .... private void OnSyncProgress(object sender, DbSyncProgressEventArgs e) { switch (args.Stage) { case DbSyncStage.ApplyingInserts: // MethodCall/Delegate/Action<>/EventHandler<> => HandleInsertedRecordInformation // Do something with inserted record info break; case DbSyncStage.ApplyingUpdates: // MethodCall/Delegate/Action<>/EventHandler<> => HandleUpdatedRecordInformation // Do something with updated record info break; case DbSyncStage.ApplyingDeletes: // MethodCall/Delegate/Action<>/EventHandler<> => HandleDeletedRecordInformation // Do something with deleted record info break; } } Somewhere else in another assembly I have three methods: // Assembly2 public class SyncInformation { public void HandleInsertedRecordInformation(...) {...} public void HandleUpdatedRecordInformation(...) {...} public void HandleInsertedRecordInformation(...) {...} } Assembly2 has a reference to Assembly1. So Assembly1 does not know anything about the existence of the SyncInformation class which need to handle the gathered information. So I have the following options to trigger this code: use events and subscribe on it in Assembly2 1.1. EventHandler< 1.2. Action< 1.3. Delegates using dependency injection: public class Assembly2.SyncInformation : Assembly1.ISyncInformation Other? I know the performance depends on: OnSyncProgress switch using a method call, delegate, Action< or EventHandler< Implementation of SyncInformation class I currently don't care about the implementation of the SyncInformation class. I am mainly focused on the OnSyncProgress method and how to call the SyncInformation methods. So my questions are: What is the most efficient approach? What is the most in-efficient approach? Is there a better way than using a switch in OnSyncProgress?

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• Rails Active Record find(:all, :order => ) issue.

  - by CodingWithoutComments

  I seem to be unable to use :order_by for more than one column at a time. For example, I have a "Show" model with date and attending columns. If I run the following code: @shows = Show.find(:all, :order => "date") I get the following results: [#<Show id: 7, date: "2009-04-18", attending: 2>, #<Show id: 1, date: "2009-04-18", attending: 78>, #<Show id: 2, date: "2009-04-19", attending: 91>, #<Show id: 3, date: "2009-04-20", attending: 16>, #<Show id: 4, date: "2009-04-21", attending: 136>] If I run the following code: @shows = Show.find(:all, :order => "attending DESC") [#<Show id: 4, date: "2009-04-21", attending: 136>, #<Show id: 2, date: "2009-04-19", attending: 91>, #<Show id: 1, date: "2009-04-18", attending: 78>, #<Show id: 3, date: "2009-04-20", attending: 16>, #<Show id: 7, date: "2009-04-18", attending: 2>] But, if I run: @shows = Show.find(:all, :order => "date, attending DESC") OR @shows = Show.find(:all, :order => "date, attending ASC") OR @shows = Show.find(:all, :order => "date ASC, attending DESC") I get the same results as only sorting by date: [#<Show id: 7, date: "2009-04-18", attending: 2>, #<Show id: 1, date: "2009-04-18", attending: 78>, #<Show id: 2, date: "2009-04-19", attending: 91>, #<Show id: 3, date: "2009-04-20", attending: 16>, #<Show id: 4, date: "2009-04-21", attending: 136>] Where as, I want to get these results: [#<Show id: 1, date: "2009-04-18", attending: 78>, #<Show id: 7, date: "2009-04-18", attending: 2>, #<Show id: 2, date: "2009-04-19", attending: 91>, #<Show id: 3, date: "2009-04-20", attending: 16>, #<Show id: 4, date: "2009-04-21", attending: 136>] This is the query being generated from the logs: [4;35;1mUser Load (0.6ms)[0m [0mSELECT * FROM "users" WHERE ("users"."id" = 1) LIMIT 1[0m [4;36;1mShow Load (3.0ms)[0m [0;1mSELECT * FROM "shows" ORDER BY date ASC, attending DESC[0m [4;35;1mUser Load (0.6ms)[0m [0mSELECT * FROM "users" WHERE ("users"."id" = 1) [0m Finally, here is my model: create_table "shows", :force => true do |t| t.string "headliner" t.string "openers" t.string "venue" t.date "date" t.text "description" t.datetime "created_at" t.datetime "updated_at" t.decimal "price" t.time "showtime" t.integer "attending", :default => 0 t.string "time" end What am I missing? What am I doing wrong? UPDATE: Thanks for all your help, but it seems that all of you were stumped as much as I was. What solved the problem was actually switching databases. I switched from the default sqlite3 to mysql.

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• ODBC: when is the best time to create my database?

  - by mawg

  I have a windows program which generates PGP forms which will be filled in later. Those PHP forms will populate a database. It looks very much like MySql, but I can't be certain, so let's call it ODBC. And, yes, it does have to be a windows program. There will also be PHP forms which query the database - examine which tables and fields it contains and then generates forms which can be used to search the database (e.g, it finds a table with fields "employee_name", etc and generates a form which lets you search based on employee name. Let's call that design time and run time. At design time, some manager or IT guy or similar gets to define the nature of the database and at runtime 1) a worker fills in the form daily and 2) management can extract reports. Here's my question: given that the database is defined at "design time" (and populated at run time), where and how is best to do so? 1 I could use an ODBC interface from the windows program, but I am having difficulty finding something good to work with Delphi. Things like ADO and firebird tend to expect you to already have a database and allow you to manipulate it, but I can find no code example of how to create a database and some tables, so ... 2 I could used DOS commands from Delphi in my windows program. I just tried and got a response to MySql --version, but am not sure if MySql etc are more interactive. That is, can I use a script file or a very long stacked command with semicolons and returns separating? e.g 'CREATE DATABASE db; CREATE TABLE t1;' 3) Since the best way to work with databases seems to be PHP, perhaps my windows program could spit out a PHP page which would, when run in a browser, create the database. I have tried to make this as uncomplicated as I can, but please feel free to ask questions. It may be that there are several valid ways, but there is probably one 'better' solution in terms of ease of implementation or maintenance. Better scratch option 3. What if the user later wants to come back and have the windows program change the input form? It needs to update the database too.

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• What is the best approach in SQL to store multi-level descriptions?

  - by gime

  I need a new perspective on how to design a reliable and efficient SQL database to store multi-level arrays of data. This problem applies to many situations but I came up with this example: There are hundreds of products. Each product has an undefined number of parts. Each part is built from several elements. All products are described in the same way. All parts would require the same fields to describe them (let's say: price, weight, part name), all elements of all parts also have uniform design (for example: element code, manufacturer). Plain and simple. One element may be related to only part, and each part is related to one product only. I came up with idea of three tables: Products: -------------------------------------------- prod_id prod_name prod_price prod_desc 1 hoover 120 unused next Parts: ---------------------------------------------------- part_id part_name part_price part_weight prod_id 3 engine 10 20 1 and finally Elements: --------------------------------------- el_id el_code el_manufacturer part_id 1 BFG12 GE 3 Now, select a desired product, select all from PARTS where prod_id is the same, and then select all from ELEMENTS where part_id matches - after multiple queries you've got all data. I'm just not sure if this is the right approach. I've got also another idea, without ELEMENTS table. That would decrease queries but I'm a bit afraid it might be lame and bad practice. Instead of ELEMENTS table there are two more fields in the PARTS table, so it looks like this: part_id, part_name, part_price, part_weight, prod_id, part_el_code, part_el_manufacturer they would be text type, and for each part, information about elements would be stored as strings, this way: part_el_code | code_of_element1; code_of_element2; code_of_element3 part_el_manufacturer | manuf_of_element1; manuf_of_element2; manuf_of_element3 Then all we need is to explode() data from those fields, and we get arrays, easy to display. Of course this is not perfect and has some limitations, but is this idea ok? Or should I just go with the first idea? Or maybe there is a better approach to this problem? It's really hard to describe it in few words, and that means it's hard to search for answer. Also, understanding the principles of designing databases is not that easy as it seems.

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