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• Dynamic data-entry value store

  - by simendsjo

  I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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• Closure Tables - Is this enough data to display a tree view?

  - by James Pitt

  Here is the table I have created by testing the closure table method. | id | parentId | childId | hops | | | | | 270 | 6 | 6 | 0 | 271 | 7 | 7 | 0 | 272 | 8 | 8 | 0 | 273 | 9 | 9 | 0 | 276 | 10 | 10 | 0 | 281 | 9 | 10 | 1 | 282 | 7 | 9 | 1 | 283 | 7 | 10 | 2 | 285 | 7 | 8 | 1 | 286 | 6 | 7 | 1 | 287 | 6 | 9 | 2 | 288 | 6 | 10 | 3 | 289 | 6 | 8 | 2 | 293 | 6 | 9 | 1 | 294 | 6 | 10 | 2 I am trying to create a simple tree of this using PHP. There does not seem to be enough data to create the table. For example, when I look purely at parentId = 6: -Part 6 -Part 7 - ? - ? -Part 9 - ? - ? We know that parts 8 and 10 exists below Part 7 or 9, but not which. We know that part 10 exists at both 3 and 4 nodes deep but where? If I look at other data in the table it is possible to tell it should be: - Part 6 - Part 7 - Part 9 - Part 10 - Part 9 - Part 10 I thought one of the benefits of closure tables was there was no need for recursive queries? Could you help explain what I am doing wrong? EDIT: For clarification, this is a mapping table. There is another table called "parts" which has a column called part_id that correlates to both the parentId and childId columns in the "closure" table. The "id" column in the table above (closure) is just for the purposes of maintaining a primary key. It is not really necessary. The methods I have used to create this closure table is described in the following article: http://dirtsimple.org/2010/11/simplest-way-to-do-tree-based-queries.html EDIT2: It can have two and three hops. I will explain easier by assigning names to the items. Part 6 = Bicycle Part 7 = Gears Part 8 = Chain Part 9 = Bolt Part 10 = Nut Nut is part of Bolt. The Bolt and Nut combo exists directly within Bicycle and within Gears which is part of Bicycle. In relation to what method to use I have looked at Adjacency, Edges, Enum Paths, Closures, DAGS(networks) and the Nested Set Model. I am still trying to work out what is what, but this is an extremely complex component database where there are multiple parents and any modification to a sub-tree must propogate through the other trees. More importantly there will be insertions, deletions and tree views that I wish to avoid recursion during general use, even at the cost of database space and query time during entry.

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• Variable lenght arguments in log4cxx LOG4CXX_ macros

  - by Horacio

  I am using log4cxx in a big C++ project but I really don't like how log4cxx handles multiple variables when logging: LOG4CXX_DEBUG(logger, "test " << var1 << " and " << var3 " and .....) I prefer using printf like variable length arguments: LOG4CXX_DEBUG(logger, "test %d and %d", var1, var3) So I implemented this small wrapper on top of log4cxx #include <string.h> #include <stdio.h> #include <stdarg.h> #include <log4cxx/logger.h> #include "log4cxx/basicconfigurator.h" const char * log_format(const char *fmt, ...); #define MYLOG_TRACE(logger, fmt, ...) LOG4CXX_TRACE(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_DEBUG(logger, fmt, ...) LOG4CXX_DEBUG(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_INFO(logger, fmt, ...) LOG4CXX_INFO(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_WARN(logger, fmt, ...) LOG4CXX_WARN(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_ERROR(logger, fmt, ...) LOG4CXX_ERROR(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_FATAL(logger, fmt, ...) LOG4CXX_FATAL(logger, log_format(fmt, ## __VA_ARGS__)) static log4cxx::LoggerPtr logger(log4cxx::Logger::getRootLogger()); int main(int argc, char **argv) { log4cxx::BasicConfigurator::configure(); MYLOG_INFO(logger, "Start "); MYLOG_WARN(logger, log_format("In running this in %d threads safe?", 1000)); MYLOG_INFO(logger, "End "); return 0; } const char *log_format(const char *fmt, ...) { va_list va; static char formatted[1024]; va_start(va, fmt); vsprintf(formatted, 1024, fmt, va); va_end(va); return formatted; } And this works perfectly but I know using that static variable (formatted) can become problematic if I start using threads and each thread logging to the same place. I am no expert in log4cxx so I was wondering if the LOG4CXX macros are handling concurrent thread access automatically? or do I have to implement some sort of locking around the log_format method? something that I wan't to avoid due to performance implications. Also I would like to ask why if I replace the vsprintf inside the log_format method with vsnprintf (that is more secure) then I get nothing printed? To compile and test this program (in Ubuntu) use : g++ -o loggertest loggertest.cpp -llog4cxx

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• Want to set 'src' of script to my IP-Won't load in Safari or Chrome. Relative link asp.netmvc

  - by Ozaki

  I have a script that links to the server I am hosting (IP can change) usually I would just use for links: var url ='http://' + window.location.hostname + 'end of url'; But in this case it isnt appearing to be so easy. I have tried: (1) $('#scriptid').attr('src', url); as well as: (2) var script = document.createElement( 'script' ); script.type = 'text/javascript'; script.src = url; $("#insert").append( script ); Now case (2) works loads the script runs the script. But when at the end of my script it hits the 'write data' it decides to replace the entire page with just the data. Any idea on how I can do this? Note: I am using plain html not ASP. With ASP backend that is just the way it has to be. Ok it now is <script src="myscript.js"></script> C# router.AddAsyncRoute("myscript.js"...... It workes in IE & FF. But I get blank pages in Chrome & Safari. I am using document.write to write a script onto my page. Any ideas why Chrome & Safari don't like this? I am so far assuming that in Crhome & Safari it takes longer to run the script therefore launching the document.write after the DOM has loaded therefore replacing the page with a blank one. edit the script im trying to run is a modification of: d = new dTree('d'); d.add(0,-1,'My example tree'); d.add(1,0,'Node 1','default.html'); d.add(2,0,'Node 2','default.html'); d.add(3,1,'Node 1.1','default.html'); d.add(4,0,'Node 3','default.html'); d.add(5,3,'Node 1.1.1','default.html') document.write(d); Any ideas how I can get around this? I am not to sure how to implement an appenChild in this case as the script is changing constantly with live data. So every refresh it will generally have changed some...

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• java concurrency: many writers, one reader

  - by Janning

  I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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• question about book example - Java Concurrency in Practice, Listing 4.12

  - by mike

  Hi, I am working through an example in Java Concurrency in Practice and am not understanding why a concurrent-safe container is necessary in the following code. I'm not seeing how the container "locations" 's state could be modified after construction; so since it is published through an 'unmodifiableMap' wrapper, it appears to me that an ordinary HashMap would suffice. EG, it is accessed concurrently, but the state of the map is only accessed by readers, no writers. The value fields in the map are syncronized via delegation to the 'SafePoint' class, so while the points are mutable, the keys for the hash, and their associated values (references to SafePoint instances) in the map never change. I think my confusion is based on what precisely the state of the collection is in the problem. Thanks!! -Mike Listing 4.12, Java Concurrency in Practice, (this listing available as .java here, and also in chapter form via google) /////////////begin code @ThreadSafe public class PublishingVehicleTracker { private final Map<String, SafePoint> locations; private final Map<String, SafePoint> unmodifiableMap; public PublishingVehicleTracker( Map<String, SafePoint> locations) { this.locations = new ConcurrentHashMap<String, SafePoint>(locations); this.unmodifiableMap = Collections.unmodifiableMap(this.locations); } public Map<String, SafePoint> getLocations() { return unmodifiableMap; } public SafePoint getLocation(String id) { return locations.get(id); } public void setLocation(String id, int x, int y) { if (!locations.containsKey(id)) throw new IllegalArgumentException( "invalid vehicle name: " + id); locations.get(id).set(x, y); } } // monitor protected helper-class @ThreadSafe public class SafePoint { @GuardedBy("this") private int x, y; private SafePoint(int[] a) { this(a[0], a[1]); } public SafePoint(SafePoint p) { this(p.get()); } public SafePoint(int x, int y) { this.x = x; this.y = y; } public synchronized int[] get() { return new int[] { x, y }; } public synchronized void set(int x, int y) { this.x = x; this.y = y; } } ///////////end code

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• many-to-many performance concerns with fluent nhibernate.

  - by Ciel

  I have a situation where I have several many-to-many associations. In the upwards of 12 to 15. Reading around I've seen that it's generally believed that many-to-many associations are not 'typical', yet they are the only way I have been able to create the associations appropriate for my case, so I'm not sure how to optimize any further. Here is my basic scenario. class Page { IList<Tag> Tags { get; set; } IList<Modification> Modifications { get; set; } IList<Aspect> Aspects { get; set; } } This is one of my 'core' classes, and coincidentally one of my core tables. Virtually half of the objects in my code can have an IList<Page>, and some of them have IList<T> where T has its own IList<Page>. As you can see, from an object oriented standpoint, this is not really a problem. But from a database standpoint this begins to introduce a lot of junction tables. So far it has worked fine for me, but I am wondering if anyone has any ideas on how I could improve on this structure. I've spent a long time thinking and in order to achieve the appropriate level of association required, I cannot think of any way to improve it. The only thing I have come up with is to make intermediate classes for each object that has an IList<Page>, but that doesn't really do anything that the HasManyToMany does not already do except introduce another class. It does not extend the functionality and, from what I can tell, it does not improve performance. Any thoughts? I am also concerned about Primary Key limits in this scenario. Most everything needs to be able to have these properties, but the Pages cannot be unique to each object, because they are going to be frequently shared and joined between multiple objects. All relationships are one-sided. (That is, a Page has no knowledge of what owns it). Because of this, I also have no Inverse() mapped HasManyToMany collections. Also, I have read the similar question : Usage of ORMs like NHibernate when there are many associations - performance concerns But it really did not answer my concerns.

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• how to filter data from xml file for displaying only selected as nodes in treeview

  - by michale

  I have an xml file named "books.xml" provided in the link "http://msdn.microsoft.com/en-us/library/windows/desktop/ms762271(v=vs.85).aspx". What my requirement was to disaplay only the <title> from xml information as nodes in tree view. But when i did the following coding its displaying all the values as nodes like "catalog" as rootnode, book as parent node for all then author,title,genre etc as nodes but i want only root node catalogue and title as nodes not even book. Can any body guide me what modification i need to do in the exisitng logic for displaying title as nodes OpenFileDialog dlg = new OpenFileDialog(); dlg.Title = "Open XML document"; dlg.Filter = "XML Files (*.xml)|*.xml"; dlg.FileName = Application.StartupPath + "\\..\\..\\Sample.xml"; if (dlg.ShowDialog() == DialogResult.OK) { try { //Just a good practice -- change the cursor to a //wait cursor while the nodes populate this.Cursor = Cursors.WaitCursor; //First, we'll load the Xml document XmlDocument xDoc = new XmlDocument(); xDoc.Load(dlg.FileName); //Now, clear out the treeview, //and add the first (root) node treeView1.Nodes.Clear(); treeView1.Nodes.Add(new TreeNode(xDoc.DocumentElement.Name)); TreeNode tNode = new TreeNode(); tNode = (TreeNode)treeView1.Nodes[0]; //We make a call to addTreeNode, //where we'll add all of our nodes addTreeNode(xDoc.DocumentElement, tNode); //Expand the treeview to show all nodes treeView1.ExpandAll(); } catch (XmlException xExc) //Exception is thrown is there is an error in the Xml { MessageBox.Show(xExc.Message); } catch (Exception ex) //General exception { MessageBox.Show(ex.Message); } finally { this.Cursor = Cursors.Default; //Change the cursor back } }} //This function is called recursively until all nodes are loaded private void addTreeNode(XmlNode xmlNode, TreeNode treeNode) { XmlNode xNode; TreeNode tNode; XmlNodeList xNodeList; if (xmlNode.HasChildNodes) //The current node has children { xNodeList = xmlNode.ChildNodes; for (int x = 0; x <= xNodeList.Count - 1; x++) //Loop through the child nodes { xNode = xmlNode.ChildNodes[x]; treeNode.Nodes.Add(new TreeNode(xNode.Name)); tNode = treeNode.Nodes[x]; addTreeNode(xNode, tNode); } } else //No children, so add the outer xml (trimming off whitespace) treeNode.Text = xmlNode.OuterXml.Trim(); }

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• Coroutines in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7?

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• Move options between multiple lists

  - by Martha

  We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. EDIT: Having now actually sat down to try to code the non-javascripty bits, I need to revise my question, because I realized that multiple select lists won't really work from the "how do I inform the server about all this lovely new information" standpoint. So the html code is now a pseudo-listbox, i.e. an unordered list (ul) displayed in a box with a scrollbar, and each list item (<li>) has a set of five radio buttons (unselected/own/read/like/heard). My task is still roughly the same: how to take this one list and make it easy to categorize the items, in such a way that the user can tell at a glance what is in what category. (The pseudo-listbox has some of the same disadvantages as a multi-select listbox, namely it's hard to tell what's selected if the list is long enough to scroll.) The dream solution would be a drag-and-drop type thing, but at this point even buttons would be OK. Another modification (a good one) is that the client has revised the lists, so the longest is now "only" 62 items long (instead of the many hundreds they had before). The categories will still mostly contain zero, one, or two selected items, possibly a couple more if the user was overzealous. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :) [existing code deleted because it's largely irrelevant.]

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• JPA Inheritance and Relations - Clarification question

  - by Michael

  Here the scenario: I have a unidirectional 1:N Relation from Person Entity to Address Entity. And a bidirectional 1:N Relation from User Entity to Vehicle Entity. Here is the Address class: @Entity public class Address implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) privat Long int ... The Vehicles Class: @Entity public class Vehicle implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne private User owner; ... @PreRemove protected void preRemove() { //this.owner.removeVehicle(this); } public Vehicle(User owner) { this.owner = owner; ... The Person Class: @Entity @Inheritance(strategy = InheritanceType.JOINED) @DiscriminatorColumn(name="PERSON_TYP") public class Person implements Serializable { @Id protected String username; @OneToMany(cascade = CascadeType.ALL, orphanRemoval=true) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME"), inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) protected List<Address> addresses; ... @PreRemove protected void prePersonRemove(){ this.addresses = null; } ... The User Class which is inherited from the Person class: @Entity @Table(name = "Users") @DiscriminatorValue("USER") public class User extends Person { @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; ... When I try to delete a User who has an address I have to use orphanremoval=true on the corresponding relation (see above) and the preRemove function where the address List is set to null. Otherwise (no orphanremoval and adress list not set to null) a foreign key contraint fails. When i try to delete a user who has an vehicle a concurrent Acces Exception is thrown when do not uncomment the "this.owner.removeVehicle(this);" in the preRemove Function of the vehicle. The thing i do not understand is that before i used this inheritance there was only a User class which had all relations: @Entity @Table(name = "Users") public class User implements Serializable { @Id protected String username; @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; @OneToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME") inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) ptivate List<Address> addresses; ... No orphanremoval, and the vehicle class has used the uncommented statement above in its preRemove function. And - I could delte a user who has an address and i could delte a user who has a vehicle. So why doesn't everything work without changes when i use inheritance? I use JPA 2.0, EclipseLink 2.0.2, MySQL 5.1.x and Netbeans 6.8

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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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• Neo4j 1.9.4 (REST Server,CYPHER) performance issue

  - by user2968943

  I have Neo4j 1.9.4 installed on 24 core 24Gb ram (centos) machine and for most queries CPU usage spikes goes to 200% with only few concurrent requests. Domain: some sort of social application where few types of nodes(profiles) with 3-30 text/array properties and 36 relationship types with at least 3 properties. Most of nodes currently has ~300-500 relationships. Current data set footprint(from console): LogicalLogSize=4294907 (32MB) ArrayStoreSize=1675520 (12MB) NodeStoreSize=1342170 (10MB) PropertyStoreSize=1739548 (13MB) RelationshipStoreSize=6395202 (48MB) StringStoreSize=1478400 (11MB) which is IMHO really small. most queries looks like this one(with more or less WITH .. MATCH .. statements and few queries with variable length relations but the often fast): START targetUser=node({id}), currentUser=node({current}) MATCH targetUser-[contact:InContactsRelation]->n, n-[:InLocationRelation]->l, n-[:InCategoryRelation]->c WITH currentUser, targetUser,n, l,c, contact.fav is not null as inFavorites MATCH n<-[followers?:InContactsRelation]-() WITH currentUser, targetUser,n, l,c,inFavorites, COUNT(followers) as numFollowers RETURN id(n) as id, n.name? as name, n.title? as title, n._class as _class, n.avatar? as avatar, n.avatar_type? as avatar_type, l.name as location__name, c.name as category__name, true as isInContacts, inFavorites as isInFavorites, numFollowers it runs in ~1s-3s(for first run) and ~1s-70ms (for consecutive and it depends on query) and there is about 5-10 queries runs for each impression. Another interesting behavior is when i try run query from console(neo4j) on my local machine many consecutive times(just press ctrl+enter for few seconds) it has almost constant execution time but when i do it on server it goes slower exponentially and i guess it somehow related with my problem. Problem: So my problem is that neo4j is very CPU greedy(for 24 core machine its may be not an issue but its obviously overkill for small project). First time i used AWS EC2 m1.large instance but over all performance was bad, during testing, CPU always was over 100%. Some relevant parts of configuration: neostore.nodestore.db.mapped_memory=1280M wrapper.java.maxmemory=8192 note: I already tried configuration where all memory related parameters where HIGH and it didn't worked(no change at all). Question: Where to digg? configuration? scheme? queries? what i'm doing wrong? if need more info(logs, configs) just ask ;)

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• Connection hangs after time of inactivity

  - by Sinuhe

  In my application, Spring manages connection pool for database access. Hibernate uses these connections for its queries. At first glance, I have no problems with the pool: it works correctly with concurrent clients and a pool with only one connection. I can execute a lot of queries, so I think that I (or Spring) don't leave open connections. My problem appears after some time of inactivity (sometimes 30 minutes, sometimes more than 2 hours). Then, when Hibernate does some search, it lasts too much. Setting log4j level to TRACE, I get this logs: ... 18:27:01 DEBUG nsactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate3.SessionHolder@99abd7] for key [org.hibernate.impl.SessionFactoryImpl@7d2897] bound to thread [http-8080-Processor24] 18:27:01 DEBUG HibernateTransactionManager - Found thread-bound Session [org.hibernate.impl.SessionImpl@8878cd] for Hibernate transaction 18:27:01 DEBUG HibernateTransactionManager - Using transaction object [org.springframework.orm.hibernate3.HibernateTransactionManager$HibernateTransactionObject@1b2ffee] 18:27:01 DEBUG HibernateTransactionManager - Creating new transaction with name [com.acjoventut.service.GenericManager.findByExample]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT 18:27:01 DEBUG HibernateTransactionManager - Preparing JDBC Connection of Hibernate Session [org.hibernate.impl.SessionImpl@8878cd] 18:27:01 TRACE SessionImpl - setting flush mode to: AUTO 18:27:01 DEBUG JDBCTransaction - begin 18:27:01 DEBUG ConnectionManager - opening JDBC connection Here it gets frozen for about 2 - 10 minutes. But then continues: 18:30:11 DEBUG JDBCTransaction - current autocommit status: true 18:30:11 DEBUG JDBCTransaction - disabling autocommit 18:30:11 TRACE JDBCContext - after transaction begin 18:30:11 DEBUG HibernateTransactionManager - Exposing Hibernate transaction as JDBC transaction [jdbc:oracle:thin:@212.31.39.50:30998:orcl, UserName=DEVELOP, Oracle JDBC driver] 18:30:11 DEBUG nsactionSynchronizationManager - Bound value [org.springframework.jdbc.datasource.ConnectionHolder@843a9d] for key [org.apache.commons.dbcp.BasicDataSource@7745fd] to thread [http-8080-Processor24] 18:30:11 DEBUG nsactionSynchronizationManager - Initializing transaction synchronization ... After that, it works with no problems, until another period of inactivity. IMHO, it seems like connection pool returns an invalid/closed connection, and when Hibernate realizes that, ask another connection to the pool. I don't know how can I solve this problem or things I can do for delimiting it. Any help achieving this will be appreciate. Thanks. EDIT: Well, it finally was due a firewall rule. Database detects the connection is lost, but pool (dbcp or c3p0) not. So, it tries to query the database with no success. What is still strange for me is that timeout period is very variable. Maybe the rule is specially strange or firewall doesn't work correctly. Anyway, I have no access to that machine and I can only wait for an explanation. :(

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• SOAP WCF Webservice behaves differently when called locally or remotely

  - by Idriss

  I have a WCF SOAP 1.1 Webservice with the configuration specified below. A concurrent call to any method of this endpoint hangs until the other returns when called remotely (from another computer on the network). I cannot replicate this when these methods are called locally (with a client located on the same machine). I tried to increase the maxConcurrentCalls with no luck ... the service behavior seems to be different according to the client local/remote location. Any guess? Thanks, <?xml version="1.0" encoding="utf-8"?> <configuration> <system.serviceModel> <services> <service behaviorConfiguration="MyCustomBehavior" name="CONTOSO.CONTOSOServerApi.IContosoServiceApiImplV1"> <endpoint address="" binding="customBinding" bindingConfiguration="WebBinding" bindingNamespace="http://contoso.com" contract="CONTOSO.CONTOSOServerApiInterfaceV1.IContosoServiceApiV1" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="MyCustomBehavior"> <serviceMetadata httpGetEnabled="true" httpGetUrl="http://localhost:8080/MyEndPointV1" /> <serviceDebug httpHelpPageEnabled="false" includeExceptionDetailInFaults="true" /> <serviceThrottling maxConcurrentSessions="10000" maxConcurrentCalls="1000"/> <dataContractSerializer maxItemsInObjectGraph="2147483647" /> </behavior> </serviceBehaviors> </behaviors> <bindings> <customBinding> <binding name="WebBinding"> <textMessageEncoding messageVersion="Soap11" maxReadPoolSize="2147483647" maxWritePoolSize="2147483647"> <readerQuotas maxDepth="2147483647" maxStringContentLength="2147483647" maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647" /> </textMessageEncoding> <httpsTransport /> </binding> </customBinding> </bindings> </system.serviceModel> </configuration>

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• Why the parent page get refreshed when I click the link to open thickbox-styled form?

  - by user333205

  Hi, all: I'm using Thickbox 3.1 to show signup form. The form content comes from jquery ajax post. The jquery lib is of version 1.4.2. I placed a "signup" link into a div area, which is a part of my other large pages, and the whole content of that div area is ajax+posted from my server. To make thickbox can work in my above arangement, I have modified the thickbox code a little like that: //add thickbox to href & area elements that have a class of .thickbox function tb_init(domChunk){ $(domChunk).live('click', function(){ var t = this.title || this.name || null; var a = this.href || this.alt; var g = this.rel || false; tb_show(t,a,g); this.blur(); return false; });} This modification is the only change against the original version. Beacause the "signup" link is placed in ajaxed content, so I Use live instead of binding the click event directly. When I tested on my pc, the thickbox works well. I can see the signup form quickly, without feeling the content of the parent page(here, is the other large pages) get refreshed. But after transmiting my site files into VHost, when I click the "signup" link, the signup form get presented very slowly. The large pages get refreshed evidently, because the borwser(ie6) are reloading images from server incessantly. These images are set as background images in CSS files. I think that's because the slow connection of network. But why the parent pages get refreshed? and why the browser reloads those images one more time? Havn't those images been placed in local computer's disk? Is there one way to stop that reloadding? Because the signup form can't get displayed sometimes due to slow connection of network. To verified the question, you can access http://www.juliantec.info/track-the-source.html and click the second link in left grey area, that is the "signup" link mentioned above. Thinks!

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• GHC.Generics and Type Families

  - by jberryman

  This is a question related to my module here, and is simplified a bit. It's also related to this previous question, in which I oversimplified my problem and didn't get the answer I was looking for. I hope this isn't too specific, and please change the title if you can think if a better one. Background My module uses a concurrent chan, split into a read side and write side. I use a special class with an associated type synonym to support polymorphic channel "joins": {-# LANGUAGE TypeFamilies #-} class Sources s where type Joined s newJoinedChan :: IO (s, Messages (Joined s)) -- NOT EXPORTED --output and input sides of channel: data Messages a -- NOT EXPORTED data Mailbox a instance Sources (Mailbox a) where type Joined (Mailbox a) = a newJoinedChan = undefined instance (Sources a, Sources b)=> Sources (a,b) where type Joined (a,b) = (Joined a, Joined b) newJoinedChan = undefined -- and so on for tuples of 3,4,5... The code above allows us to do this kind of thing: example = do (mb , msgsA) <- newJoinedChan ((mb1, mb2), msgsB) <- newJoinedChan --say that: msgsA, msgsB :: Messages (Int,Int) --and: mb :: Mailbox (Int,Int) -- mb1,mb2 :: Mailbox Int We have a recursive action called a Behavior that we can run on the messages we pull out of the "read" end of the channel: newtype Behavior a = Behavior (a -> IO (Behavior a)) runBehaviorOn :: Behavior a -> Messages a -> IO () -- NOT EXPORTED This would allow us to run a Behavior (Int,Int) on either of msgsA or msgsB, where in the second case both Ints in the tuple it receives actually came through separate Mailboxes. This is all tied together for the user in the exposed spawn function spawn :: (Sources s) => Behavior (Joined s) -> IO s ...which calls newJoinedChan and runBehaviorOn, and returns the input Sources. What I'd like to do I'd like users to be able to create a Behavior of arbitrary product type (not just tuples) , so for instance we could run a Behavior (Pair Int Int) on the example Messages above. I'd like to do this with GHC.Generics while still having a polymorphic Sources, but can't manage to make it work. spawn :: (Sources s, Generic (Joined s), Rep (Joined s) ~ ??) => Behavior (Joined s) -> IO s The parts of the above example that are actually exposed in the API are the fst of the newJoinedChan action, and Behaviors, so an acceptable solution can modify one or all of runBehaviorOn or the snd of newJoinedChan. I'll also be extending the API above to support sums (not implemented yet) like Behavior (Either a b) so I hoped GHC.Generics would work for me. Questions Is there a way I can extend the API above to support arbitrary Generic a=> Behavior a? If not using GHC's Generics, are there other ways I can get the API I want with minimal end-user pain (i.e. they just have to add a deriving clause to their type)?

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• Creating multiple heads in remote repository

  - by Jab

  We are looking to move our team (~10 developers) from SVN to mercurial. We are trying to figure out how to manage our workflow. In particular, we are trying to see if creating remote heads is the right solution. We currently have a very large repository with multiple, related projects. They share a lot of code, but pieces of the project are deployed by different teams (3 teams) independent of other portions of the code-base. So each team is working on concurrent large features. The way we currently handles this in SVN are branches. Team1 has a branch for Feature1, same deal for the other teams. When Team1 finishes their change, it gets merged into the trunk and deployed out. The other teams follow suite when their project is complete, merging of course. So my initial thought are using Named Branches for these situations. Team1 makes a Feature1 branch off of the default branch in Hg. Now, here is the question. Should the team PUSH that branch, in it's current/half-state to the repository. This will create a second head in the core repo. My initial reaction was "NO!" as it seems like a bad idea. Handling multiple heads on our repository just sounds awful, but there are some advantages... First, the teams want to setup Continuous Integration to build this branch during their development cycle(months long). This will only work if the CI can pull this branch from the repo. This is something we do now with SVN, copy a CI build and change the branch. Easy. Second, it makes it easier for any team member to jump onto the branch and start working. Without pushing to the core repo, they would have to receive a push from a developer on that team with the changeset information. It is also possible to lose local commits to hardware failure. The chances increase a lot if it's a branch by a single developer who has followed the "don't push until finished" approach. And lastly is just for ease of use. The developers can easily just commit and push on their branch at any time without consequence(as they do today, in their SVN branches). Is there a better way to handle this scenario that I may be missing? I just want a veteran's opinion before moving forward with the strategy. For bug fixes we like the general workflow of mecurial, anonymous branches that only consist of 1-2 commits. The simplicity is great for those cases. By the way, I've read this , great article which seems to favor Named branches.

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• Does my TPL partitioner cause a deadlock?

  - by Scott Chamberlain

  I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the .Net example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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• How to dynamically change the content of a facet in a custom component?

  - by romaintaz

  Hello, Let's consider that I want to extend an existing JSF component, such as the <rich:datatable/>. My main requirement is to dynamically modify the content of a <f:facet>, to change its content. What is the best way to achieve that? Or where is the best place in the code to achieve that? In my faces-config.xml, I have the following declaration: <faces-config> ... <component> <component-type>my.component.dataTable</component-type> <component-class>my.project.component.table.MyHtmlDataTable</component-class> </component> ... <render-kit> <render-kit-id>HTML_BASIC</render-kit-id> <renderer> <component-family>org.richfaces.DataTable</component-family> <renderer-type>my.renderkit.dataTable</renderer-type> <renderer-class>my.project.component.table.MyDataTableRenderer</renderer-class> </renderer> ... Also, my my-project.taglib.xml file (as I use Facelets) looks like: <facelet-taglib> <namespace>http://my.project/jsf</namespace> <tag> <tag-name>dataTable</tag-name> <component> <component-type>my.component.dataTable</component-type> <renderer-type>my.renderkit.dataTable</renderer-type> </component> </tag> So as you can see, I have two classes in my project for my custom datatable: MyHtmlDataTable and MyDataTableRenderer. One of my idea is to modify the content of the <f:facet> directly in the doEncodeBegin() method of my renderer. This is working (in fact almost working), but I don't really think that's the better place to achieve my modification. What do you think? Technical information: JSF 1.2, Facelets, Richfaces 3.3.2, Java 1.6

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• SQL Server architecture guidance

  - by Liam

  Hi, We are designing a new version of our existing product on a new schema. Its an internal web application with possibly 100 concurrent users (max)This will run on a SQL Server 2008 database. On of the discussion items recently is whether we should have a single database of split the database for performance reasons across 2 separate databases. The database could grow anywhere from 50-100GB over 5 years. We are Developers and not DBAs so it would be nice to get some general guidance. [I know the answer is not simple as it depends on the schema, archiving policy, amount of data etc. ] Option 1 Single Main Database [This is my preferred option]. The plan would be to have all the tables in a single database and possibly to use file groups and partitioning to separate the data if required across multiple disks. [Use schema if appropriate]. This should deal with the performance concerns One of the comments wrt this was that the a single server instance would still be processing this data so there would still be a processing bottle neck. For reporting we could have a separate reporting DB but this is still being discussed. Option 2 Split the database into 2 separate databases DB1 - Customers, Accounts, Customer resources etc DB2 - This would contain the bulk of the data [i.e. Vehicle tracking data, financial transaction tables etc]. These tables would typically contain a lot of data. [It could reside on a separate server if required] This plan would involve keeping the main data in a smaller database [DB1] and retaining the [mainly] read only transaction type data in a separate DB [DB2]. The UI would mainly read from DB1 and thus be more responsive. [I'm aware that this option makes it harder for Referential Integrity to be enforced.] Points for consideration As we are at the design stage we can at least make proper use of indexes to deal performance issues so thats why option 1 to me is attractive and its more of a standard approach. For both options we are considering implementing an archiving database. Apologies for the long Question. In summary the question is 1 DB or 2? Thanks in advance, Liam

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• Extend argparse to write set names in the help text for optional argument choices and define those sets once at the end

  - by Kent

  Example of the problem If I have a list of valid option strings which is shared between several arguments, the list is written in multiple places in the help string. Making it harder to read: def main(): elements = ['a', 'b', 'c', 'd', 'e', 'f'] parser = argparse.ArgumentParser() parser.add_argument( '-i', nargs='*', choices=elements, default=elements, help='Space separated list of case sensitive element names.') parser.add_argument( '-e', nargs='*', choices=elements, default=[], help='Space separated list of case sensitive element names to ' 'exclude from processing') parser.parse_args() When running the above function with the command line argument --help it shows: usage: arguments.py [-h] [-i [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]]] [-e [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]]] optional arguments: -h, --help show this help message and exit -i [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]] Space separated list of case sensitive element names. -e [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]] Space separated list of case sensitive element names to exclude from processing What would be nice It would be nice if one could define an option list name, and in the help output write the option list name in multiple places and define it last of all. In theory it would work like this: def main_optionlist(): elements = ['a', 'b', 'c', 'd', 'e', 'f'] # Two instances of OptionList are equal if and only if they # have the same name (ALFA in this case) ol = OptionList('ALFA', elements) parser = argparse.ArgumentParser() parser.add_argument( '-i', nargs='*', choices=ol, default=ol, help='Space separated list of case sensitive element names.') parser.add_argument( '-e', nargs='*', choices=ol, default=[], help='Space separated list of case sensitive element names to ' 'exclude from processing') parser.parse_args() And when running the above function with the command line argument --help it would show something similar to: usage: arguments.py [-h] [-i [ALFA [ALFA ...]]] [-e [ALFA [ALFA ...]]] optional arguments: -h, --help show this help message and exit -i [ALFA [ALFA ...]] Space separated list of case sensitive element names. -e [ALFA [ALFA ...]] Space separated list of case sensitive element names to exclude from processing sets in optional arguments: ALFA {a,b,c,d,e,f} Question I need to: Replace the {'l', 'i', 's', 't', 's'} shown with the option name, in the optional arguments. At the end of the help text show a section explaining which elements each option name consists of. So I ask: Is this possible using argparse? Which classes would I have to inherit from and which methods would I need to override? I have tried looking at the source for argparse, but as this modification feels pretty advanced I don´t know how to get going.

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• SQL Server - Get Inserted Record Identity Value when Using a View's Instead Of Trigger

  - by CuppM

  For several tables that have identity fields, we are implementing a Row Level Security scheme using Views and Instead Of triggers on those views. Here is a simplified example structure: -- Table CREATE TABLE tblItem ( ItemId int identity(1,1) primary key, Name varchar(20) ) go -- View CREATE VIEW vwItem AS SELECT * FROM tblItem -- RLS Filtering Condition go -- Instead Of Insert Trigger CREATE TRIGGER IO_vwItem_Insert ON vwItem INSTEAD OF INSERT AS BEGIN -- RLS Security Checks on inserted Table -- Insert Records Into Table INSERT INTO tblItem (Name) SELECT Name FROM inserted; END go If I want to insert a record and get its identity, before implementing the RLS Instead Of trigger, I used: DECLARE @ItemId int; INSERT INTO tblItem (Name) VALUES ('MyName'); SELECT @ItemId = SCOPE_IDENTITY(); With the trigger, SCOPE_IDENTITY() no longer works - it returns NULL. I've seen suggestions for using the OUTPUT clause to get the identity back, but I can't seem to get it to work the way I need it to. If I put the OUTPUT clause on the view insert, nothing is ever entered into it. -- Nothing is added to @ItemIds DECLARE @ItemIds TABLE (ItemId int); INSERT INTO vwItem (Name) OUTPUT INSERTED.ItemId INTO @ItemIds VALUES ('MyName'); If I put the OUTPUT clause in the trigger on the INSERT statement, the trigger returns the table (I can view it from SQL Management Studio). I can't seem to capture it in the calling code; either by using an OUTPUT clause on that call or using a SELECT * FROM (). -- Modified Instead Of Insert Trigger w/ Output CREATE TRIGGER IO_vwItem_Insert ON vwItem INSTEAD OF INSERT AS BEGIN -- RLS Security Checks on inserted Table -- Insert Records Into Table INSERT INTO tblItem (Name) OUTPUT INSERTED.ItemId SELECT Name FROM inserted; END go -- Calling Code INSERT INTO vwItem (Name) VALUES ('MyName'); The only thing I can think of is to use the IDENT_CURRENT() function. Since that doesn't operate in the current scope, there's an issue of concurrent users inserting at the same time and messing it up. If the entire operation is wrapped in a transaction, would that prevent the concurrency issue? BEGIN TRANSACTION DECLARE @ItemId int; INSERT INTO tblItem (Name) VALUES ('MyName'); SELECT @ItemId = IDENT_CURRENT('tblItem'); COMMIT TRANSACTION Does anyone have any suggestions on how to do this better? I know people out there who will read this and say "Triggers are EVIL, don't use them!" While I appreciate your convictions, please don't offer that "suggestion".

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• MySQL Split Time Ranges into Smaller Chunks

  - by Neren

  Hello all, I've recently been tasked with finishing a PHP/MySQL web app when the developer quit last week. I'm no MySQL expert, so I apologize if this is an intensely simple question. I've searched SO for the better part of two days trying to find a relatively easy solution to my problem, which is as follows. Problem in a Nutshell: I have a MySQL table full of start and end datetime (GMT -5) & UNIX Timestamp values covering durations of irregular length and need to break/split/divide them into more-regular time chunks (5 minutes). I'm not after a count of row entries per time chunk/bucket/period, if that makes any sense. Data Example: started, ended, started_UNIX, ended_UNIX 2010-10-25 15:12:33, 2010-10-25 15:47:09, 1288033953, 1288036029 What I'm hoping to get: 2010-10-25 15:12:33, 2010-10-25 15:15:00, 1288033953, 1288037700 2010-10-25 15:15:00, 2010-10-25 15:20:00, 1288037700, 1288038000 2010-10-25 15:20:00, 2010-10-25 15:25:00, 1288038000, 1288038300 2010-10-25 15:25:00, 2010-10-25 15:30:00, 1288038300, 1288038600 2010-10-25 15:30:00, 2010-10-25 15:35:00, 1288038600, 1288038900 2010-10-25 15:35:00, 2010-10-25 15:40:00, 1288038900, 1288039200 2010-10-25 15:40:00, 2010-10-25 15:45:00, 1288039200, 1288039500 2010-10-25 15:45:00, 2010-10-25 15:47:09, 1288039500, 1288039629 If you're interested, here's the quick & dirty on the app and why I need the data: App overview: The application receives very simple POST requests generated by a basic sensor device when its input pins go to ground, which submits an INSERT query to the database where MySQL records a timestamp (as started). When the input pins return from a grounded state, the device submits a different POST request, which causes the PHP app to submit an UPDATE query, where a modification time timestamp is inserted (as ended). My employer recently changed the periodic reporting unit of measure from Seconds "On" Per Day to Seconds "On" Per 5 Minute Interval. I had formulated what I thought would be a workable solution, but when I looked at it on paper, it looked like Rube Goldberg's nightmare constructed in MySQL, so that was out. Any suggestions as to how to break these spans into 5 minute blocks? Keeping it all in MySQL would be my preference, though I'll take any suggestions. Thank you for any suggestions you may have. Again, I apologize if this is a no-brainer. If I ask any additional questions of the SO collective consciousness in the future, I'll try to word them a bit better. Any help will be happily welcomed. Thanks, Neren

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• How to create a database deadlock using jdbc and JUNIT

  - by Isawpalmetto

  I am trying to create a database deadlock and I am using JUnit. I have two concurrent tests running which are both updating the same row in a table over and over again in a loop. My idea is that you update say row A in Table A and then row B in Table B over and over again in one test. Then at the same time you update row B table B and then row A Table A over and over again. From my understanding this should eventually result in a deadlock. Here is the code For the first test. public static void testEditCC() { try{ int rows = 0; int counter = 0; int large=10000000; Connection c=DataBase.getConnection(); while(counter<large) { int pid = 87855; int cCode = 655; String newCountry="Egypt"; int bpl = 0; stmt = c.createStatement(); rows = stmt.executeUpdate("UPDATE main " + //create lock on main table "SET BPL="+cCode+ "WHERE ID="+pid); rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table counter++; } assertTrue(rows == 1); //rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')"); } catch(SQLException ex) { ex.printStackTrace(); //ex.getMessage(); } } And here is the code for the second test. public static void testEditCC() { try{ int rows = 0; int counter = 0; int large=10000000; Connection c=DataBase.getConnection(); while(counter<large) { int pid = 87855; int cCode = 655; String newCountry="Jordan"; int bpl = 0; stmt = c.createStatement(); //stmt.close(); rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table rows = stmt.executeUpdate("UPDATE main " + //create lock on main table "SET BPL="+cCode+ "WHERE ID="+pid); counter++; } assertTrue(rows == 1); //rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')"); } catch(SQLException ex) { ex.printStackTrace(); } } I am running these two separate JUnit tests at the same time and am connecting to an apache Derby database that I am running in network mode within Eclipse. Can anyone help me figure out why a deadlock is not occurring? Perhaps I am using JUnit wrong.

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