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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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• 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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• two where conditions in a mysql query

  - by Kaartz

  I have a table like below |date|dom|guid|pid|errors|QA|comm| |2010-03-22|xxxx.com|jsd3j234j|ab|Yes|xxxxxx|bad| |2010-03-22|xxxx.com|jsd3j234j|ab|No|xxxxxx|| |2010-03-22|xxxx.com|jsd3j234j|if|Yes|xxxxxx|bad| |2010-03-22|xxxx.com|jsd3j234j|if|No|xxxxxx|| |2010-03-22|xxxx.com|jsd3j234j|he|Yes|xxxxxx|bad| |2010-03-22|xxxx.com|jsd3j234j|he|No|xxxxxx|| I want to retrieve the total count of "dom" referred to each "QA" and also I need the count of "errors" detected by the "QA" SELECT date, count(dom), QA FROM reports WHERE date="2010-03-22" GROUP BY QA |2010-03-22|2|ab| |2010-03-22|2|if| |2010-03-22|2|he| SELECT date, count(dom), count(errors), QA FROM reports WHERE errors="Yes" GROUP BY QA |2010-03-22|1|ab| |2010-03-22|1|if| |2010-03-22|1|he| I want to combine the above two queries, is it possible. If I use the below query, I am not getting the desired result. SELECT date, count(dom), QA, count(errors) FROM reports WHERE date="2010-03-22" AND errors="Yes" GROUP BY QA I want the below output |2010-03-22|2|ab|1| |2010-03-22|2|if|1| |2010-03-22|2|he|1| Please help me.

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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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• 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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• 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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• 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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• Servicestack CorsFeature Global Options Handler Not Firing on Certain Routes;

  - by gizmoboy

  I've got a service setup using the CorsFeature, and am using the approach that mythz suggested in other answers, collected in a function used in the appHost file: private void ConfigureCors(Funq.Container container) { Plugins.Add(new CorsFeature(allowedOrigins: "*", allowedMethods: "GET, POST, PUT, DELETE, OPTIONS", allowedHeaders: "Content-Type, Authorization, Accept", allowCredentials: true)); PreRequestFilters.Add((httpReq, httpRes) => { //Handles Request and closes Responses after emitting global HTTP Headers if (httpReq.HttpMethod == "OPTIONS") { httpRes.EndRequest(); } }); } However, the pre-request filter is only firing on some of the service requests. One of the base entities we have in the service is a question entity, and there are custom routes defined as follows: [Route("/question")] [Route("/question/{ReviewQuestionId}", "GET,DELETE")] [Route("/question/{ReviewQuestionId}/{ReviewSectionId}", "GET")] Using POSTMAN to fire test queries (all using the OPTIONS verb), we can see that this will fire the pre-request filter: http://localhost/myservice/api/question/ But this will not: http://localhost/myservice/api/question/66 Presumably, this is because the second and third routes explicitly defined the verbs they accept, and OPTIONS isn't one of them. Is it really necessary to spell out OPTIONS in every defined route that restricts the verbs supported?

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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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• Mysql - multiple values and between

  - by realshadow

  Hey, I need to select 10 products and display them. Each product has 3 different prices. The select to get the prices looks like this: SELECT * FROM products_loans WHERE CODE IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND 550 BETWEEN PRICE_FROM AND PRICE_TO; Where 550 is the base price. Now this select returns 3 rows, but I want to modify it so it will return 30 results. I dont like the idea to execute 10 queries at once. I know I can easily achieve that with "OR", but I would like to ask if there is some other more elegant way to this. The select "should" look like this: SELECT * FROM products_loans WHERE KOD IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND (550, 325, 780) BETWEEN CENA_OD AND CENA_DO; Note that there is no "price" column or anything in the table which I could use to do a JOIN and I cant modify the table.

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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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• 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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• 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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• Storing search result for paging and sorting

  - by Mattias

  I've been implementing MS Search Server 2010 and so far its really good. Im doing the search queries via their web service, but due to the inconsistent results, im thinking about caching the result instead. The site is a small intranet (500 employees), so it shouldnt be any problems, but im curious what approach you would take if it was a bigger site. I've googled abit, but havent really come over anything specific. So, a few questions: What other approaches are there? And why are they better? How much does it cost to store a dataview of 400-500 rows? What sizes are feasible? Other points you should take into consideration. Any input is welcome :)

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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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• Is it OK to allow users to query an OLTP SQL Server database with excel?

  - by user169867

  I have a SQL Server 2005 database used by several applications. Some users wish to query the database directly from excel. I can understand this, because it is a useful tool for adhoc queries and then getting the data in a format that's easily transmitted and manipulated by other users. My question is: Does Excel (say 2003/2007) do its querying in a way that won't cause concurency issues? Or is it done in such a way that a seperate datawarehouse database needs to be made to handle this scenario? Thanks for any advise.

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• Help Forming An SQL Query That Selects The Max Difference Of Two Fields

  - by Frank

  I'm trying to select a record with the most effective votes. Each record has an id, the number of upvotes (int) and the number of downvotes (int) in a MySQL database. I know basic update, select, insert queries but I'm unsure of how to form a query that looks something like: SELECT * FROM topics WHERE MAX(topic.upvotes - topic.downvotes). Please excuse my made up SQL. The tutorials on SQL I find on the internet cover very basic stuff. Does anyone recommend a good book on this subject?

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• Regex for finding valid sphinx fields

  - by mlissner

  I'm trying to validate that the fields given to sphinx are valid, but I'm having difficulty. Imagine that valid fields are cat, mouse, dog, puppy. Valid searches would then be: @cat search terms @(cat) search terms @(cat, dog) search term @cat searchterm1 @dog searchterm2 @(cat, dog) searchterm1 @mouse searchterm2 So, I want to use a regular expression to find terms such as cat, dog, mouse in the above examples, and check them against a list of valid terms. Thus, a query such as: @(goat) Would produce an error because goat is not a valid term. I've gotten so that I can find simple queries such as @cat with this regex: (?:@)([^( ]*) But I can't figure out how to find the rest. I'm using python & django, for what that's worth.

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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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• Custom SQL Server driver

  - by hoodoos

  I had a crazy thought about writing my own SQL Server driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing SQL Server client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# language. :)

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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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• Database Design Question

  - by deniz

  Hi, I am designing a database for a project. I have a table that has 10 columns, most of them are used whenever the table is accessed, and I need to add 3 more rows; View Count Thumbs Up (count) Thumbs Down (Count) which will be used on %90 of the queries when the table is accessed. So, my question is that whether it is better to break the table up and create new table which will have these 3 columns + Foreign ID, or just make it 13 columns and use no joins? Since these columns will be used frequently, I guess adding 3 more columns is better, but if I need to create 10 more columns which will be used %90 of the time, should I add them as well, or create a new table and use joins? I am not sure when to break the table if the columns are used very frequently. Do you have any suggestions? Thanks in advance,

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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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• 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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• 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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