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  • Twazzup and App Engine

    Twazzup and App Engine An interview with the developers behind twazzup.com on how App Engine helps them run their application. From: GoogleDevelopers Views: 1298 7 ratings Time: 08:37 More in Science & Technology

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  • Antenna Aligner part 1: In the beginning.

    - by Chris George
    Picture the scene, it's 9pm, I'm in my caravan (yes I know, I've heard all the jokes!) with my family and I'm trying to tune the tv by moving the aerial, retuning, moving the aerial again, retuning... 45 mins and much cursing later I succeed. Surely there must be an easier way than this? Aha, an app; there must be an app for that? So I search in the AppStore for such an app, but curiously drew a blank. Then the seeds of the idea started to grow. I can code, I work in a software house with lots of very clever people, surely I can make an app that points to the nearest digital tv transmitter! Not having looked into app development before, I investigated how one goes about making an iPhone app and was quickly greeted by a now familiar answer "Buy a mac!". That was not an option for many reasons, mostly wife related! My dreams were starting to fade until one of my colleagues pointed out that within Red Gate, the very company I work for, there was on-going development on a piece of software that would allow me to write an app using Visual Studio on a Windows machine, Nomad! Once I signed up for the beta program I got to work learning the Jquery mobile / Phonegap framework. Within a couple of hours I had written (in Visual Studio), built in the cloud (using Nomad) and published (via TestFlight) my first iPhone app onto my iPhone ! It didn't do much, but it was a step in the right direction. To be continued...

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  • TSQL formatting - a sure fire way to start a conversation.

    - by fatherjack
    There are probably as many opinions on ways to format code as there are people writing code and I am not here to say that any one is better than any other. Well, that isn't true. I am here to say that one way is better than another but this isn't a matter of preference or personal taste, this is an example of where sloppy formatting can cause TSQL to weird and whacky things but following some simple methods can make your code more reliable and more robust when . Take these two pieces of code, ready...(read more)

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  • TortoiseSVN and Subversion Cookbook Part 3: In, Out, and Around

    Subversion doesn't have to be difficult, especially if you have Michael Sorens's guide at hand. After dealing in previous articles with checkouts and commits in Subversion, and covering the various file-manipulation operations that are required for Subversion, Michael now deals in this article with file macro-management, the operations such as putting things in, and taking things out, that deal with repositories and projects.

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  • Dartisans Ep. 16: Dart and Web Components Reloaded

    Dartisans Ep. 16: Dart and Web Components Reloaded In this episode of Dartisans, Dimitri Glazkov (one of the godfathers of Web Components) will give a presentation on Web Components. Also, John Messerly and Siggi Cherem (who helped build the dart-lang/dart-web-components library) will give a presentation on using Web Components in Dart. A lot of things have changed since our last episode focused on Web Components, and this is shaping up to be an awesome edition of Dartisans! From: GoogleDevelopers Views: 0 0 ratings Time: 01:00:00 More in Science & Technology

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  • Press a Button and open a URL in another ViewController

    - by Dennis Borup Jakobsen
    I am trying to learn Xcode by making a simple app. But I been looking on the net for hours (days) and I cant figure it out how I make a button that open a UIWebView in another ViewController :S first let me show you some code that I have ready: I have a few Buttons om my main Storyboard that each are title some country codes like UK, CA and DK. When I press one of those Buttons I have an IBAction like this: - (IBAction)ButtonPressed:(UIButton *)sender { // Google button pressed NSURL* allURLS; if([sender.titleLabel.text isEqualToString:@"DK"]) { // Create URL obj allURLS = [NSURL URLWithString:@"http://google.dk"]; }else if([sender.titleLabel.text isEqualToString:@"US"]) { allURLS = [NSURL URLWithString:@"http://google.com"]; }else if([sender.titleLabel.text isEqualToString:@"CA"]) { allURLS = [NSURL URLWithString:@"http://google.ca"]; } NSURLRequest* req = [NSURLRequest requestWithURL:allURLS]; [myWebView loadRequest:req]; } How do I make this open UIWebview on my other Viewcontroller named myWebView? please help a lost man :D

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  • Antenna Aligner Part 3: Kaspersky

    - by Chris George
    Quick one today. Since starting this project, I've been encountering times where Nomad fails to build my app. It would then take repeated attempts at building to then see a build go through successfully. Rob, who works on Nomad at Red Gate, investigated this and it showed that certain parts of the message required to trigger the 'cloud build' were not getting through to the Nomad app, causing the HTTP connection to stall until timeout. After much scratching heads, it turns out that the Kaspersky Internet Security system I have installed on my laptop at home, was being very aggressive and was causing the problem. Perhaps it's trying to protect me from myself? Anyway, we came up with an interim solution why the Nomad guys investigate with Kaspersky by setting Visual Studio to be a trusted application with the Kaspersky settings and setting it to not scan network traffic. Hey presto! This worked and I have not had a single build problem since (other than losing internet connection, or that embarrassing moment when you blame everyone else then realise you've accidentally switched off your wireless on the laptop).

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  • From 0 to MVP in 4 weeks

    - by fatherjack
    You may know from my previous posts that I have just started a local SQL Server User Group. 3 weeks ago there was no such group within 100 miles and then we had a meeting. Now, in eight days time, there is going to be a second meeting and I am very excited to be able to say that we will be having an MVP speaker for one of the sessions. Aaron Nelson (Blog|Twitter) made an incredibly generous offer of speaking for us on using PowerShell with SQL Server and I didn't hang around before I said "Yes...(read more)

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  • Dartisans ep 12 - Dart + Web Components

    Dartisans ep 12 - Dart + Web Components Web Components are ushering in the "declarative renaissance" for modern web development. Watch this episode of Dartisans to learn how you can build Web Components with Dart, and compile them into JavaScript to run across the modern web. Learn more about Dart at www.dartlang.org From: GoogleDevelopers Views: 2 0 ratings Time: 46:17 More in Science & Technology

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  • AsyncBridge? Async on .NET 4.0 using VS11

    - by Alex.Davies
    I've just found something quite cool. It's a code snippet that lets you use the real VS 11 C#5 compiler to write code that uses the async and await keywords, but to target .NET 4.0. It was published by Daniel Grunwald (from SharpDevelop).That means I can stop using the Async CTP for VS2010, which is not at all supported anymore, and a pain to install if you have windows updates turned on. Obviously I couldn't ask all my users to install .NET 4.5 beta, but .NET Demon is a VS 2010 extension, so we already have .NET 4.0. At the time of writing, VS11 is in beta still, but hopefully it's stable enough for my team to use!I would have written the code myself, but I had the wrong impression that the C# 5 beta compiler only looked in mscorlib for the helper classes it needs to implement async methods. Turns out you can provide them yourself. You can get the code here: https://gist.github.com/1961087You just add it to your project, and the compiler will apparently pick it up and use it to implement async/await. I'm at my parents' place for Easter without access to a machine with VS 11 to try it out. Let me know whether you get it to work!This reminds me of LINQBridge, which let us use C# 3 LINQ, but only require .NET 2. We should stick up a webpage to explain, with a nice easy dll, put it in nuget, and call it AsyncBridge.If you were really enthusiastic, you could re-implement the skeleton of the Task Parallel Library against .NET 2 to use async/await without even requiring .NET 4. Our usage stats suggest that practically everyone that uses Red Gate tools already has .NET 4 installed though, so I don't think I'll go to the effort.

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  • Just interviewed, turned down, now got an email asking to chat with recruiter. No response. What should I do? [closed]

    - by Lambert
    I was turned down after two interviews by a prominent company for an internship, and only a couple days later, I was asked when I had 10-15 minutes to chat today. Of course, I loved to, so I emailed within just 10 minutes of their email and let them know what times I was available at, and asked them when the best time should be, and if I should go somewhere or expect a phone call. No reply has come from them since yesterday afternoon, the recruiter wanted to talk to me today. I don't want to lose this opportunity, but I have no way to contact the recruiter other than by email, and the recruiter hasn't responded to my emails from yesterday, even though we were supposed to talk today. What's the best thing I can do (preferably within the next few hours!) to get the job? Is that even probably why she emailed me, or was a different reason likely? Any ideas?

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  • Know your Data Lineage

    - by Simon Elliston Ball
    An academic paper without the footnotes isn’t an academic paper. Journalists wouldn’t base a news article on facts that they can’t verify. So why would anyone publish reports without being able to say where the data has come from and be confident of its quality, in other words, without knowing its lineage. (sometimes referred to as ‘provenance’ or ‘pedigree’) The number and variety of data sources, both traditional and new, increases inexorably. Data comes clean or dirty, processed or raw, unimpeachable or entirely fabricated. On its journey to our report, from its source, the data can travel through a network of interconnected pipes, passing through numerous distinct systems, each managed by different people. At each point along the pipeline, it can be changed, filtered, aggregated and combined. When the data finally emerges, how can we be sure that it is right? How can we be certain that no part of the data collection was based on incorrect assumptions, that key data points haven’t been left out, or that the sources are good? Even when we’re using data science to give us an approximate or probable answer, we cannot have any confidence in the results without confidence in the data from which it came. You need to know what has been done to your data, where it came from, and who is responsible for each stage of the analysis. This information represents your data lineage; it is your stack-trace. If you’re an analyst, suspicious of a number, it tells you why the number is there and how it got there. If you’re a developer, working on a pipeline, it provides the context you need to track down the bug. If you’re a manager, or an auditor, it lets you know the right things are being done. Lineage tracking is part of good data governance. Most audit and lineage systems require you to buy into their whole structure. If you are using Hadoop for your data storage and processing, then tools like Falcon allow you to track lineage, as long as you are using Falcon to write and run the pipeline. It can mean learning a new way of running your jobs (or using some sort of proxy), and even a distinct way of writing your queries. Other Hadoop tools provide a lot of operational and audit information, spread throughout the many logs produced by Hive, Sqoop, MapReduce and all the various moving parts that make up the eco-system. To get a full picture of what’s going on in your Hadoop system you need to capture both Falcon lineage and the data-exhaust of other tools that Falcon can’t orchestrate. However, the problem is bigger even that that. Often, Hadoop is just one piece in a larger processing workflow. The next step of the challenge is how you bind together the lineage metadata describing what happened before and after Hadoop, where ‘after’ could be  a data analysis environment like R, an application, or even directly into an end-user tool such as Tableau or Excel. One possibility is to push as much as you can of your key analytics into Hadoop, but would you give up the power, and familiarity of your existing tools in return for a reliable way of tracking lineage? Lineage and auditing should work consistently, automatically and quietly, allowing users to access their data with any tool they require to use. The real solution, therefore, is to create a consistent method by which to bring lineage data from these data various disparate sources into the data analysis platform that you use, rather than being forced to use the tool that manages the pipeline for the lineage and a different tool for the data analysis. The key is to keep your logs, keep your audit data, from every source, bring them together and use the data analysis tools to trace the paths from raw data to the answer that data analysis provides.

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  • Subterranean IL: The ThreadLocal type

    - by Simon Cooper
    I came across ThreadLocal<T> while I was researching ConcurrentBag. To look at it, it doesn't really make much sense. What's all those extra Cn classes doing in there? Why is there a GenericHolder<T,U,V,W> class? What's going on? However, digging deeper, it's a rather ingenious solution to a tricky problem. Thread statics Declaring that a variable is thread static, that is, values assigned and read from the field is specific to the thread doing the reading, is quite easy in .NET: [ThreadStatic] private static string s_ThreadStaticField; ThreadStaticAttribute is not a pseudo-custom attribute; it is compiled as a normal attribute, but the CLR has in-built magic, activated by that attribute, to redirect accesses to the field based on the executing thread's identity. TheadStaticAttribute provides a simple solution when you want to use a single field as thread-static. What if you want to create an arbitary number of thread static variables at runtime? Thread-static fields can only be declared, and are fixed, at compile time. Prior to .NET 4, you only had one solution - thread local data slots. This is a lesser-known function of Thread that has existed since .NET 1.1: LocalDataStoreSlot threadSlot = Thread.AllocateNamedDataSlot("slot1"); string value = "foo"; Thread.SetData(threadSlot, value); string gettedValue = (string)Thread.GetData(threadSlot); Each instance of LocalStoreDataSlot mediates access to a single slot, and each slot acts like a separate thread-static field. As you can see, using thread data slots is quite cumbersome. You need to keep track of LocalDataStoreSlot objects, it's not obvious how instances of LocalDataStoreSlot correspond to individual thread-static variables, and it's not type safe. It's also relatively slow and complicated; the internal implementation consists of a whole series of classes hanging off a single thread-static field in Thread itself, using various arrays, lists, and locks for synchronization. ThreadLocal<T> is far simpler and easier to use. ThreadLocal ThreadLocal provides an abstraction around thread-static fields that allows it to be used just like any other class; it can be used as a replacement for a thread-static field, it can be used in a List<ThreadLocal<T>>, you can create as many as you need at runtime. So what does it do? It can't just have an instance-specific thread-static field, because thread-static fields have to be declared as static, and so shared between all instances of the declaring type. There's something else going on here. The values stored in instances of ThreadLocal<T> are stored in instantiations of the GenericHolder<T,U,V,W> class, which contains a single ThreadStatic field (s_value) to store the actual value. This class is then instantiated with various combinations of the Cn types for generic arguments. In .NET, each separate instantiation of a generic type has its own static state. For example, GenericHolder<int,C0,C1,C2> has a completely separate s_value field to GenericHolder<int,C1,C14,C1>. This feature is (ab)used by ThreadLocal to emulate instance thread-static fields. Every time an instance of ThreadLocal is constructed, it is assigned a unique number from the static s_currentTypeId field using Interlocked.Increment, in the FindNextTypeIndex method. The hexadecimal representation of that number then defines the specific Cn types that instantiates the GenericHolder class. That instantiation is therefore 'owned' by that instance of ThreadLocal. This gives each instance of ThreadLocal its own ThreadStatic field through a specific unique instantiation of the GenericHolder class. Although GenericHolder has four type variables, the first one is always instantiated to the type stored in the ThreadLocal<T>. This gives three free type variables, each of which can be instantiated to one of 16 types (C0 to C15). This puts an upper limit of 4096 (163) on the number of ThreadLocal<T> instances that can be created for each value of T. That is, there can be a maximum of 4096 instances of ThreadLocal<string>, and separately a maximum of 4096 instances of ThreadLocal<object>, etc. However, there is an upper limit of 16384 enforced on the total number of ThreadLocal instances in the AppDomain. This is to stop too much memory being used by thousands of instantiations of GenericHolder<T,U,V,W>, as once a type is loaded into an AppDomain it cannot be unloaded, and will continue to sit there taking up memory until the AppDomain is unloaded. The total number of ThreadLocal instances created is tracked by the ThreadLocalGlobalCounter class. So what happens when either limit is reached? Firstly, to try and stop this limit being reached, it recycles GenericHolder type indexes of ThreadLocal instances that get disposed using the s_availableIndices concurrent stack. This allows GenericHolder instantiations of disposed ThreadLocal instances to be re-used. But if there aren't any available instantiations, then ThreadLocal falls back on a standard thread local slot using TLSHolder. This makes it very important to dispose of your ThreadLocal instances if you'll be using lots of them, so the type instantiations can be recycled. The previous way of creating arbitary thread-static variables, thread data slots, was slow, clunky, and hard to use. In comparison, ThreadLocal can be used just like any other type, and each instance appears from the outside to be a non-static thread-static variable. It does this by using the CLR type system to assign each instance of ThreadLocal its own instantiated type containing a thread-static field, and so delegating a lot of the bookkeeping that thread data slots had to do to the CLR type system itself! That's a very clever use of the CLR type system.

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  • Cheating on Technical Debt

    - by Tony Davis
    One bad practice guaranteed to cause dismay amongst your colleagues is passing on technical debt without full disclosure. There could only be two reasons for this. Either the developer or DBA didn’t know the difference between good and bad practices, or concealed the debt. Neither reflects well on their professional competence. Technical debt, or code debt, is a convenient term to cover all the compromises between the ideal solution and the actual solution, reflecting the reality of the pressures of commercial coding. The one time you’re guaranteed to hear one developer, or DBA, pass judgment on another is when he or she inherits their project, and is surprised by the amount of technical debt left lying around in the form of inelegant architecture, incomplete tests, confusing interface design, no documentation, and so on. It is often expedient for a Project Manager to ignore the build-up of technical debt, the cut corners, not-quite-finished features and rushed designs that mean progress is satisfyingly rapid in the short term. It’s far less satisfying for the poor person who inherits the code. Nothing sends a colder chill down the spine than the dawning realization that you’ve inherited a system crippled with performance and functional issues that will take months of pain to fix before you can even begin to make progress on any of the planned new features. It’s often hard to justify this ‘debt paying’ time to the project owners and managers. It just looks as if you are making no progress, in marked contrast to your predecessor. There can be many good reasons for allowing technical debt to build up, at least in the short term. Often, rapid prototyping is essential, there is a temporary shortfall in test resources, or the domain knowledge is incomplete. It may be necessary to hit a specific deadline with a prototype, or proof-of-concept, to explore a possible market opportunity, with planned iterations and refactoring to follow later. However, it is a crime for a developer to build up technical debt without making this clear to the project participants. He or she needs to record it explicitly. A design compromise made in to order to hit a deadline, be it an outright hack, or a decision made without time for rigorous investigation and testing, needs to be documented with the same rigor that one tracks a bug. What’s the best way to do this? Ideally, we’d have some kind of objective assessment of the level of technical debt in a software project, although that smacks of Science Fiction even as I write it. I’d be interested of hear of any methods you’ve used, but I’m sure most teams have to rely simply on the integrity of their colleagues and the clear perceptions of the project manager… Cheers, Tony.

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  • Developing Schema Compare for Oracle (Part 2): Dependencies

    - by Simon Cooper
    In developing Schema Compare for Oracle, one of the issues we came across was the size of the databases. As detailed in my last blog post, we had to allow schema pre-filtering due to the number of objects in a standard Oracle database. Unfortunately, this leads to some quite tricky situations regarding object dependencies. This post explains how we deal with these dependencies. 1. Cross-schema dependencies Say, in the following database, you're populating SchemaA, and synchronizing SchemaA.Table1: SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(Col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100) REFERENCES SchemaB.Table1(Col1)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100) PRIMARY KEY); We need to do a rebuild of SchemaA.Table1 to change Col1 from a VARCHAR2(100) to a NUMBER. This consists of: Creating a table with the new schema Inserting data from the old table to the new table, with appropriate conversion functions (in this case, TO_NUMBER) Dropping the old table Rename new table to same name as old table Unfortunately, in this situation, the rebuild will fail at step 1, as we're trying to create a NUMBER column with a foreign key reference to a VARCHAR2(100) column. As we're only populating SchemaA, the naive implementation of the object population prefiltering (sticking a WHERE owner = 'SCHEMAA' on all the data dictionary queries) will generate an incorrect sync script. What we actually have to do is: Drop foreign key constraint on SchemaA.Table1 Rebuild SchemaB.Table1 Rebuild SchemaA.Table1, adding the foreign key constraint to the new table This means that in order to generate a correct synchronization script for SchemaA.Table1 we have to know what SchemaB.Table1 is, and that it also needs to be rebuilt to successfully rebuild SchemaA.Table1. SchemaB isn't the schema that the user wants to synchronize, but we still have to load the table and column information for SchemaB.Table1 the same way as any table in SchemaA. Fortunately, Oracle provides (mostly) complete dependency information in the dictionary views. Before we actually read the information on all the tables and columns in the database, we can get dependency information on all the objects that are either pointed at by objects in the schemas we’re populating, or point to objects in the schemas we’re populating (think about what would happen if SchemaB was being explicitly populated instead), with a suitable query on all_constraints (for foreign key relationships) and all_dependencies (for most other types of dependencies eg a function using another function). The extra objects found can then be included in the actual object population, and the sync wizard then has enough information to figure out the right thing to do when we get to actually synchronize the objects. Unfortunately, this isn’t enough. 2. Dependency chains The solution above will only get the immediate dependencies of objects in populated schemas. What if there’s a chain of dependencies? A.tbl1 -> B.tbl1 -> C.tbl1 -> D.tbl1 If we’re only populating SchemaA, the implementation above will only include B.tbl1 in the dependent objects list, whereas we might need to know about C.tbl1 and D.tbl1 as well, in order to ensure a modification on A.tbl1 can succeed. What we actually need is a graph traversal on the dependency graph that all_dependencies represents. Fortunately, we don’t have to read all the database dependency information from the server and run the graph traversal on the client computer, as Oracle provides a method of doing this in SQL – CONNECT BY. So, we can put all the dependencies we want to include together in big bag with UNION ALL, then run a SELECT ... CONNECT BY on it, starting with objects in the schema we’re populating. We should end up with all the objects that might be affected by modifications in the initial schema we’re populating. Good solution? Well, no. For one thing, it’s sloooooow. all_dependencies, on my test databases, has got over 110,000 rows in it, and the entire query, for which Oracle was creating a temporary table to hold the big bag of graph edges, was often taking upwards of two minutes. This is too long, and would only get worse for large databases. But it had some more fundamental problems than just performance. 3. Comparison dependencies Consider the following schema: SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100)); What will happen if we used the dependency algorithm above on the source & target database? Well, SchemaA.Table1 has a foreign key reference to SchemaB.Table1, so that will be included in the source database population. On the target, SchemaA.Table1 has no such reference. Therefore SchemaB.Table1 will not be included in the target database population. In the resulting comparison of the two objects models, what you will end up with is: SOURCE  TARGET SchemaA.Table1 -> SchemaA.Table1 SchemaB.Table1 -> (no object exists) When this comparison is synchronized, we will see that SchemaB.Table1 does not exist, so we will try the following sequence of actions: Create SchemaB.Table1 Rebuild SchemaA.Table1, with foreign key to SchemaB.Table1 Oops. Because the dependencies are only followed within a single database, we’ve tried to create an object that already exists. To fix this we can include any objects found as dependencies in the source or target databases in the object population of both databases. SchemaB.Table1 will then be included in the target database population, and we won’t try and create objects that already exist. All good? Well, consider the following schema (again, only explicitly populating SchemaA, and synchronizing SchemaA.Table1): SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100) PRIMARY KEY); CREATE TABLE SchemaC.Table1 ( Col1 NUMBER);   CREATE TABLE SchemaC.Table1 ( Col1 VARCHAR2(100) REFERENCES SchemaB.Table1); Although we’re now including SchemaB.Table1 on both sides of the comparison, there’s a third table (SchemaC.Table1) that we don’t know about that will cause the rebuild of SchemaB.Table1 to fail if we try and synchronize SchemaA.Table1. That’s because we’re only running the dependency query on the schemas we’re explicitly populating; to solve this issue, we would have to run the dependency query again, but this time starting the graph traversal from the objects found in the other database. Furthermore, this dependency chain could be arbitrarily extended.This leads us to the following algorithm for finding all the dependencies of a comparison: Find initial dependencies of schemas the user has selected to compare on the source and target Include these objects in both the source and target object populations Run the dependency query on the source, starting with the objects found as dependents on the target, and vice versa Repeat 2 & 3 until no more objects are found For the schema above, this will result in the following sequence of actions: Find initial dependenciesSchemaA.Table1 -> SchemaB.Table1 found on sourceNo objects found on target Include objects in both source and targetSchemaB.Table1 included in source and target Run dependency query, starting with found objectsNo objects to start with on sourceSchemaB.Table1 -> SchemaC.Table1 found on target Include objects in both source and targetSchemaC.Table1 included in source and target Run dependency query on found objectsNo objects found in sourceNo objects to start with in target Stop This will ensure that we include all the necessary objects to make any synchronization work. However, there is still the issue of query performance; the CONNECT BY on the entire database dependency graph is still too slow. After much sitting down and drawing complicated diagrams, we decided to move the graph traversal algorithm from the server onto the client (which turned out to run much faster on the client than on the server); and to ensure we don’t read the entire dependency graph onto the client we also pull the graph across in bits – we start off with dependency edges involving schemas selected for explicit population, and whenever the graph traversal comes across a dependency reference to a schema we don’t yet know about a thunk is hit that pulls in the dependency information for that schema from the database. We continue passing more dependent objects back and forth between the source and target until no more dependency references are found. This gives us the list of all the extra objects to populate in the source and target, and object population can then proceed. 4. Object blacklists and fast dependencies When we tested this solution, we were puzzled in that in some of our databases most of the system schemas (WMSYS, ORDSYS, EXFSYS, XDB, etc) were being pulled in, and this was increasing the database registration and comparison time quite significantly. After debugging, we discovered that the culprits were database tables that used one of the Oracle PL/SQL types (eg the SDO_GEOMETRY spatial type). These were creating a dependency chain from the database tables we were populating to the system schemas, and hence pulling in most of the system objects in that schema. To solve this we introduced blacklists of objects we wouldn’t follow any dependency chain through. As well as the Oracle-supplied PL/SQL types (MDSYS.SDO_GEOMETRY, ORDSYS.SI_COLOR, among others) we also decided to blacklist the entire PUBLIC and SYS schemas, as any references to those would likely lead to a blow up in the dependency graph that would massively increase the database registration time, and could result in the client running out of memory. Even with these improvements, each dependency query was taking upwards of a minute. We discovered from Oracle execution plans that there were some columns, with dependency information we required, that were querying system tables with no indexes on them! To cut a long story short, running the following query: SELECT * FROM all_tab_cols WHERE data_type_owner = ‘XDB’; results in a full table scan of the SYS.COL$ system table! This single clause was responsible for over half the execution time of the dependency query. Hence, the ‘Ignore slow dependencies’ option was born – not querying this and a couple of similar clauses to drastically speed up the dependency query execution time, at the expense of producing incorrect sync scripts in rare edge cases. Needless to say, along with the sync script action ordering, the dependency code in the database registration is one of the most complicated and most rewritten parts of the Schema Compare for Oracle engine. The beta of Schema Compare for Oracle is out now; if you find a bug in it, please do tell us so we can get it fixed!

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  • Chrome Apps Office Hours: Controlling an AR Parrot Drone

    Chrome Apps Office Hours: Controlling an AR Parrot Drone Ask and vote for questions: goo.gl Join us next week as we show you how we used a Chrome App to control an AR Parrot Drone! This is just one of the many cool things that you can do with Chrome Apps. Using the networking APIs, we were able to pilot the AR Parrot Drone, and get data back from its on-board sensors. We'll take the app apart, show you how were were able to get everything to work, and maybe even take it for a live spin on air! From: GoogleDevelopers Views: 0 0 ratings Time: 00:00 More in Science & Technology

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  • Simple Query tuning with STATISTICS IO and Execution plans

    A great deal can be gleaned from the use of the STATISTICS IO and the execution plan, when you are checking that a query is performing properly. Josef Richberg, the current holder of the 'Exceptional DBA' award, explains how an apparently draconian IT policy turns out to be a useful ways of ensuring that Stored Procedures are carefully checked for performance before they are released

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  • Calling all developers building ASP.NET applications

    - by Laila Lotfi
    We know that developers building desktop apps have to contend with memory management issues, and we’d like to learn more about the memory challenges ASP.NET developers are facing. To be more specific, we’re carrying out some exploratory research leading into the next phase of development on ANTS Memory Profiler, and our development team would love to speak to developers building ASP.NET applications. You don’t need to have ever used ANTS profiler – this will be a more general conversation about: - your current site architecture, and how you manage the memory requirements of your applications on your back-end servers and web services. - how you currently diagnose memory leaks and where you do this (production server, or during testing phase, or if you normally manage to get them all during the local development). - what specific memory problems you’ve experienced – if any. Of course, we’ll compensate you for your time with a $50 Amazon voucher (or equivalent in other currencies), and our development team’s undying gratitude. If you’d like to participate, please just drop me a line on [email protected].

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  • Android: Goto HTTP Url on Button Click

    - by George
    Hi all, I want to go to a web page on the click of a button in my android app. So say, I have a button called "Google", when the user clicks on that button I want google.com to open up on the screen. How is this achieved? Also, is there a way I can gain control back to my app once the user is finished with google? Thanks George

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  • Software Tuned to Humanity

    - by Phil Factor
    I learned a great deal from a cynical old programmer who once told me that the ideal length of time for a compiler to do its work was the same time it took to roll a cigarette. For development work, this is oh so true. After intently looking at the editing window for an hour or so, it was a relief to look up, stretch, focus the eyes on something else, and roll the possibly-metaphorical cigarette. This was software tuned to humanity. Likewise, a user’s perception of the “ideal” time that an application will take to move from frame to frame, to retrieve information, or to process their input has remained remarkably static for about thirty years, at around 200 ms. Anything else appears, and always has, to be either fast or slow. This could explain why commercial applications, unlike games, simulations and communications, aren’t noticeably faster now than they were when I started programming in the Seventies. Sure, they do a great deal more, but the SLAs that I negotiated in the 1980s for application performance are very similar to what they are nowadays. To prove to myself that this wasn’t just some rose-tinted misperception on my part, I cranked up a Z80-based Jonos CP/M machine (1985) in the roof-space. Within 20 seconds from cold, it had loaded Wordstar and I was ready to write. OK, I got it wrong: some things were faster 30 years ago. Sure, I’d now have had all sorts of animations, wizzy graphics, and other comforting features, but it seems a pity that we have used all that extra CPU and memory to increase the scope of what we develop, and the graphical prettiness, but not to speed the processes needed to complete a business procedure. Never mind the weight, the response time’s great! To achieve 200 ms response times on a Z80, or similar, performance considerations influenced everything one did as a developer. If it meant writing an entire application in assembly code, applying every smart algorithm, and shortcut imaginable to get the application to perform to spec, then so be it. As a result, I’m a dyed-in-the-wool performance freak and find it difficult to change my habits. Conversely, many developers now seem to feel quite differently. While all will acknowledge that performance is important, it’s no longer the virtue is once was, and other factors such as user-experience now take precedence. Am I wrong? If not, then perhaps we need a new school of development technique to rival Agile, dedicated once again to producing applications that smoke the rear wheels rather than pootle elegantly to the shops; that forgo skeuomorphism, cute animation, or architectural elegance in favor of the smell of hot rubber. I struggle to name an application I use that is truly notable for its blistering performance, and would dearly love one to do my everyday work – just as long as it doesn’t go faster than my brain.

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  • ASP.NET 4.0 Features

    ASP.NET v4 is released with Visual studio 2010. Web developers are presented with a bewildering range of new features and so Ludmal De Silva has described what he considers to be the most important new features in ASP.NET V4

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  • DBA in Space

    - by Neil Davidson
    Every now and then, you come across an idea that makes your heart jump and your skin tingle. That happened to me a few months ago, when Richard and Anthony pitched a small group of us an idea. "It's called DBA in Space", Richard said. I don't remember the rest of the pitch. "DBA in Space" is one of those phrases that's so simple, remarkable and clear that it sticks and it sticks hard. Sure, lots of people have done much hard, gritty work over the past few months to make it happen. Sure, there's...(read more)

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