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• HBase as web app backend

  - by NathanD

  Can anyone advise if it is a good idea to have HBase as primary data source for web-based application? My primary concern is HBase's response time to queries. Is it possible to have sub-second response? edit: more details about the app itself. Amount of data: ~500GB of text data, expect to reach 1TB soon Number of concurrent users using the app: up to 50 The app will be used to present reports about data stored in HBase, like how many times keyword "X" occured in last 24h. For ~80% of requests from that app I will know the exact key, 20% will be scans (I'm looking into HBase schema design related topics to make it run fast)

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• Top x rows and group by (again)

  - by Tibor Szasz

  Hello, I know it's a frequent question but I just can't figure it out and the examples I found didn't helped. What I learned, the best strategy is to try to find the top and bottom values of the top range and then select the rest, but implementing is a bit tricky. Example table: id | title | group_id | votes I'd like to get the top 3 voted rows from the table, for each group. I'm expecting this result: 91 | hello1 | 1 | 10 28 | hello2 | 1 | 9 73 | hello3 | 1 | 8 84 | hello4 | 2 | 456 58 | hello5 | 2 | 11 56 | hello6 | 2 | 0 17 | hello7 | 3 | 50 78 | hello8 | 3 | 9 99 | hello9 | 3 | 1 I've fond complex queries and examples, but they didn't really helped.

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• "lock request time out period exceeded" Error When Trying to See DB Hierarchies

  - by Lloyd Banks

  I have a DB that I can run basic queries (albeit much slower than normal) off of. When I try to see the hierarchy trees for tables, views, or procedures in SSMS Object Explorer, I get the "lock request time out period exceeded". My Report Server reports that run off of objects in this DB are no longer completing. Jobs associated with procedures stored on this DB also do not run. I tried using sp_who2 to find and kill all connections on the DB. This has not solved the problem. What is going on here? How can I resolve this?

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• how do i use MySql ENUM type? (and is it right for a news feed)

  - by Haroldo

  I'm creating a table called news_feed, this will log all the actions a user performs. Lets say I want to store user1234 deleted article412 at midday I then need a table like so timestamp | user_id | subject_type | subject_id | method . there would be 5 potential methods to log, methods = add/edit/delete/update/report and lets say 2 possible subject_type subjects = article/comment I know i could make my own key where 0=add, 1=delete etc etc but this would make my queries cumbersome to use/write as i'd need to keep consulting the key. Is there a MySql type which can read lots of identially values quickly? is this ENUM? how do i use it?!!

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• In MongoDB, how can I replicate this simple query using map/reduce in ruby?

  - by Matthew Rathbone

  Hi, So using the regular MongoDB library in Ruby I have the following query to find average filesize across a set of 5001 documents: avg = 0 total = collection.count() Rails.logger.info "#{total} asset creation stats in the system" collection.find().each {|row| avg += (row["filesize"] * (1/total.to_f)) if row["filesize"]} Its pretty simple, so I'm trying to do the same using map/reduce as a learning exercise. This is what I came up with: map = 'function(){emit("filesizes", {size: this.filesize, num: 1});}' reduce = 'function(k, vals){ var result = {size: 0, num: 0}; for(var x in vals) { var new_total = result.num + vals[x].num; result.num = new_total result.size = result.size + (vals[x].size * (vals[x].num / new_total)); } return result; }' @results = collection.map_reduce(map, reduce) However the two queries come back with two different results! What am I doing wrong?

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• Replace repeating character with array elements in PHP

  - by Will Croft

  I hope this is blindingly obvious: I'm looking for the fastest way to replace a repeating element in a string with the elements in a given array, e.g. for SQL queries and parameter replacement. $query = "SELECT * FROM a WHERE b = ? AND c = ?"; $params = array('bee', 'see'); Here I would like to replace the instances of ? with the corresponding ordered array elements, as so: SELECT * FROM a WHERE b = 'bee' and c = 'see' I see that this might be done using preg_replace_callback, but is this the fastest way or am I missing something obvious?

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• java jdbc connection to mysql problem

  - by fatnjazzy

  Hi, I am trying to connect to mysql from java web application in eclipse. Connection con = null; try { //DriverManager.registerDriver(new com.mysql.jdbc.Driver()); Class.forName("com.mysql.jdbc.Driver"); con = DriverManager.getConnection("jdbc:mysql://localhost/db_name","root" ,""); if(!con.isClosed()) System.out.println("Successfully connected to " + "MySQL server using TCP/IP..."); } catch(Exception e) { System.err.println("Exception: " + e.getMessage()); } finally { try { if(con != null) con.close(); } catch(SQLException e) { System.out.println(e.toString()); } } I am always getting the Exception: com.mysql.jdbc.Driver I have downloaded this jar http://forums.mysql.com/read.php?39,218287,220327 import it to the "java build path/lib" the mysql version is 5.1.3 under. running: mysql 5.1.3 (db is up and running queries form PHP) windows XP java jee Thanks

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• Python - Using "Google AJAX Search" API's Local Search Objects

  - by user330739

  Hi! I've just started using Google's search API to find addresses and the distances between those addresses. I used geopy for this, but, I often had the problem of not getting the correct addresses for my queries. I decided to experiment, therefore, with Google's "Local Search" (http://code.google.com/apis/ajaxsearch/local.html). Anyway, I wanted to ask if I could use the "Local Search" objects provided by the API within python. Something tells me that I can't and that I have to use json. Does anyone know if there is a work around? PS: Im trying to make something like this: http://www.google.com/uds/samples/random/lead.html ... except a matrix type deal where the insides will be filled with distances between the addresses. Thanks for reading!

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• Oracle (Old?) Joins

  - by Grasper

  I have been porting oracle selects, and I have been running across a lot of queries like so: SELECT e.last_name, d.department_name FROM employees e, departments d WHERE e.department_id(+) = d.department_id; ...and: SELECT last_name, d.department_id FROM employees e, departments d WHERE e.department_id = d.department_id(+); Are there any guides/tutorials for converting all of the variants of the (+) syntax? What is that syntax even called (so I can scour google)? When was this standard phased out? Any info is appreciated.

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• lambda expression for a query on two tables that returns records from one table

  - by peetee

  I have two tables TableA (articles) int id int Type string name and TableB (compatibles) int linked_ID int tableA_ID TableA records: id=1, Type=0, name="ArticleA" id=2, Type=1, name="ArticleB" id=3, Type=2, name="ArticleC" id=4, Type=1, name="ArticleD" TableB records: linked_ID= 1, tableA_ID=2 linked_ID= 1, tableA_ID=3 linked_ID= 1, tableA_ID=4 TableB has a list of arcicels that are compatible to a certain article. I am quite new to queries (didn't need them in my projects yet). But as C# and WPF allow some pretty cool automation with Binding I would like to add a binding that returns the following: Give me all articles that are of Type 1 and compatible to my selected article (id=1). The simple part of it works well (articles has a list of all articles): private ObservableCollection<Article> _articles = new ObservableCollection<Article>(); [fill it with the available articles] and then: comboBoxArticles.ItemsSource = _articles.AsBindable().Where( c => c.Typ == 0 ); How can I extend the Where clause to query another table? Thanks a lot in advance.

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• nHibernate query by example with multiple associated objects

  - by BurnWithLife

  I'm trying to use nhibernate's query by example to build dynamic queries. I'm stuck on how to code for an example object with multiple associations. Here's an example from NHibernate in Action. Its a User object with Items. Example exampleUser = Example.Create(u).IgnoreCase().EnableLike(MatchMode.Anywhere); Example exampleItem = Example.Create(i).IgnoreCase().EnableLike(MatchMode.Anywhere); return GetSession().CreateCriteria(typeof(User)) .Add( exampleUser ) .CreateCriteria("Items") .Add( exampleItem ) .List<User>(); If the User object has let's say a Category object as a property, how could I add that in to the above example? If i put another CreateCriteria at the end it refers to the Items, not the User.

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• HQL updates and domain objects

  - by CaptainAwesomePants

  I have what may be a pretty elementary Hibernate question. Do HQL (and/or Criteria) update queries cause updates to live domain objects? And do they automatically flush now-invalid domain objects from the first-level cache? Example: Player playerReference1 = session.get(Player.class,1); session.createQuery("update players set gold = 100").executeUpdate(); //Question #1 -- does playerReference1.getGold() now return 100? Player playerReference2 = session.get(Player.class,1); //Question #2 -- does playerReference2.getGold() return 100, or is it the same exact object? Should I make a practice of evicting all objects that are affected by an HQL update if there's a chance some code will need it later?

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• Complicated conditional SQL query

  - by DevAno1

  I'm not even sure if it's possible but I need it for my Access database. So I have following db structure : Now I need to perform a query that takes category_id from my product and do the magic : - let's say product belongs to console (category_id is in table Console) - from console_types take type_id, where category_id == category_id - but if product belongs to console_game (category_id is in table console_game) - from console_game take game_cat_id, where category_id == category_id I'm not sure if mysql is capable of such thing. If not I'm really f&%ranked up. Maybe there is a way to split this into 2,3 separate queries ?

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• Duplicate an AppEngine Query object to create variations of a filter without affecting the base quer

  - by Steve Mayne

  In my AppEngine project I have a need to use a certain filter as a base then apply various different extra filters to the end, retrieving the different result sets separately. e.g.: base_query = MyModel.all().filter('mainfilter', 123) Then I need to use the results of various sub queries separately: subquery1 = basequery.filter('subfilter1', 'xyz') #Do something with subquery1 results here subquery2 = basequery.filter('subfilter2', 'abc') #Do something with subquery2 results here Unfortunately 'filter()' affects the state of the basequery Query instance, rather than just returning a modified version. Is there any way to duplicate the Query object and use it as a base? Is there perhaps a standard Python way of duping an object that could be used? The extra filters are actually applied by the results of different forms dynamically within a wizard, and they use the 'running total' of the query in their branch to assess whether to ask further questions. Obviously I could pass around a rudimentary stack of filter criteria, but I'd rather use the Query itself if possible, as it adds simplicity and elegance to the solution.

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• PHP - Frameworks, ORM, Encapsulation.

  - by Ian

  Programming languages/environments aside, are there many developers who are using a framework in PHP, ORM and still abide by encapsulation for the DAL/BLL? I'm managing a team of a few developers and am finding that most of the frameworks require me to do daily code inspection because my developers are using the built in ORM. Right now, I've been using a tool to generate the classes and CRUD myself, with an area for them to write additional queries/functions. What's been happening though, is they are creating vulnerabilities by not doing proper checks on data permission, or allowing the key fields to be manipulated in the form. Any suggestions, other than get a new team and a new language (I've seen Python/Ruby frameworks have the same issues).

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• Can I expect a performance gain from removing this JOIN?

  - by makeee

  I have a "items" table with 1 million rows and a "users" table with 20,000 rows. When I select from the "items" table I do a join on the "users" table (items.user_id = user.id), so that I can grab the "username" from the users table. I'm considering adding a username column to the items table and removing the join. Can I expect a decent performance increase from this? It's already quite fast, but it would be nice to decrease my load (which is pretty high). The downside is that if the user changes their username, items will still reflect their old username, but this is okay with me if I can expect a decent performance increase. I'm asking stackoverflow because benchmarks aren't telling me too much. Both queries finish very quickly. Regardless, I'm wondering if removing the join would lighten load on the database to any significant degree.

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• Compiled query using list of class objects in C#

  - by Sukan

  Hello , Can somebody help me out in creating compiled queries where input is to be a list of class objects? I have seen examples where Func<DataContext, somematchobject, IQueryable<T>> is created and compiled. But can I do something like Func<List<T>, matchObject, T>, and compile it? Basically I want an object(T) meeting certain conditions (as in matchObject) to be returned from a list of objects(List<T>). Will CompiledQuery.Compile help me in this? Please help me experts!!

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• count(*) is it really expensive ?

  - by Anil Namde

  I have a page where i have 4 tabs displaying 4 different reports based of different tables. Now i get row count of each tabled using select count() from table query and display number of rows available in each table on the tabs. Now with each page post back 5 count() queries are executed (4 to get counts and 1 for pagination) and 1 query for getting report. Now my question is should is count(*) query really expensive that i should keep the row counts (at least which are displayed on tab) in view state of page instead of queering each time? How much expensive it is ?

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• Valid Email Addresses - XSS and SQL Injection

  - by PAAMAYIM_NEKUDOTAYIM

  Since there are so many valid characters for email addresses, are there any valid email addresses that can in themselves be XSS attacks or SQL injections? I couldn't find any information on this on the web. The local-part of the e-mail address may use any of these ASCII characters: Uppercase and lowercase English letters (a–z, A–Z) Digits 0 to 9 Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~ Character . (dot, period, full stop) provided that it is not the last character, and provided also that it does not appear two or more times consecutively (e.g. [email protected]). http://en.wikipedia.org/wiki/E-mail_address#RFC_specification I'm not asking how to prevent these attacks (I'm already using parametrized queries and HTML purifier), this is more a proof-of-concept. The first thing that came to mind was 'OR [email protected], except that spaces are not allowed. Do all SQL injections require spaces?

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• What to read as a good intro and quickstart to aspect-oriented programming and metaprogramming?

  - by Ivan

  As I've found myself repeating myself a lot, writing very similar queries and classes for different entities (despite of doing strong object and relational normalisation), etc, I've came to an Idea that I could and should automate the most of this and write an engine which will compile simple declarative models I specify into all the code limiting my job to describe the task and and finally just customise the result as needed. As far as I know this is about metaprogramming and aspect-oriented programming. How do I get acquainted with modern tools available quickly so that I don't invent one more bicycle developing my own?

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• Understanding Plesk Watchdog statistics

  - by weotch

  We have Plesk 8.3 installed. I've started using their Watchdog module to track server useage. Our server routinely has trouble with the amount of traffic we have and I think our MySQL queries need to be smarter. Anyway, looking at the stats from Watchdog, it seems like MySQL usage is low compared to so something else making up the "overall" usage. See this: I was hoping someone with a lot of Plesk exeprience could help me understand what I'm seeing here. Can I not trust Watchdog's reports or am I missing something?

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• OOP App Architecture: Which layer does a lazy loader sit in?

  - by JW

  I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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• Favoriting system on Appengine

  - by Mateusz Cieslak

  Hi, I have the following model structure class Authors(db.Model) : nickname = db.StringProperty(required=True) fullname = db.StringProperty(required=True) class Articles(db.Model) : title = db.StringProperty(required=True) body = db.StringProperty(required=True) author = db.ReferenceProperty(Authors, required=True) class Favorites(db.Model) : who = db.ReferenceProperty(Authors, required=True) what = db.ReferenceProperty(Articles, required=True) I'd like to display 10 last articles according to this pattern: article.title, article.body, article.author(nickname), info if this article has been already favorited by the signed in user. I have added a function which I use to get the authors of these articles using only one query (it is described here) But I don't know what to do with the favorites (I'd like to know which of the displayed articles have been favorited by me using less than 10 queries (I want to display 10 articles)). Is it possible?

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• Accessing database problem

  - by anarche

  Ok, so I've got an SQLiteOpenHelper that prepares and returns a SQLiteDatabase object; this is written singleton-pattern, so the database is opened once and only closed when the Activity closes. From there I have three database wrappers encapsulating the queries (some returning cursors to datasets, some inserting data) used by the Activity. I want to insert data from one View, then have that automatically update in another View on the same Dialogue. I'm writing this on a notepad and testing on the phone (since the emulator crashes the notepad...), so I can't pull up stacktraces atm. So questions: 1) are there limitations to writing to a database, when there are cursors open on the database? 2) Does a Cursor.requery()? call update the ListView with the cursor as a data connector?

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• is there a tool to see the difference between two database tables in mssql?

  - by reinier

  What is a good tool to see the differences between 2 tables (or even better, the datasets returned by 2 queries). EDIT: I'm not interested in the schema changes. Just assume that the schemas are the same. background as to why: I'm porting some legacy code which can fill a database with some pre-calced data. The easiest way to see if I got everything right, is to check the output of the old program, with the new one. I was thinking that if there is some kind of 'diff' tool for databases, this might be great.

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