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• iPhone , core data, whether NSManagedObject use lazy load mechanism when it was create ?

  - by Robin

  Hi, all, I have use core data in app, I have definite a class that most like as follows: @interface Master : NSManagedObject { } @property (nonatomic, retain) NSSet* Details; .... the entity Master contains a property 'Details' that is relate to another table, this is typical Master-Details relationship, I trace the app , but I find a issue that the property 'Details' value was construct even it never be invoked ..... but I consider that the core data 'should' use some lazy mechanism to improve performance, or maybe I miss some configure step ? because the Master entity contains at least five 'Child' table properties , I have to consider this problem before use the core data .... any help ? thanks for your time!

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• Entity Framework projections

  - by David McClelland

  We are investigating the Entity Framework to see if it will meet our particular needs. Here is the scenario I am interested in: I have a large table (let's call it VeryWideRecord) which has many columns, and it has a corresponding business object (it's also called VeryWideRecord). I would like to be able to query my database for a VeryWideRecord business object, but only have values for certain columns returned by the underlying SQL. Can I do this with the Entity Framework? I am uncertain as to whether this could be done with the Entity Framework's table splitting feature, because the application needs to be able (at runtime) to change the columns that are requested. The reason for this is that we are trying to minimize the amount of information that is going across the wire. I see how this could be done using NHibernate (example), but how can I do this with the Entity Framework?

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• ModelName(django.contrib.auth.models.User) vs ModelName(models.Model)

  - by amr.negm

  I am developing a django project. I created some apps, some of those are related to User model, for instance, I have a feeds app that handles user feeds, and another app that deals with extra user data like age, contacts, and friends. for each of these, I created a table that should be connected to the User model, which I using for storing and authenticating users. I found two ways to deal with this issue. One, is through extending User model to be like this: ModelName(User): friends = models.ManyToMany('self') ..... Two, is through adding a foreign key to the new table like this: ModelName(models.Model): user = models.ForeignKey(User, unique=True) friends = friends = models.ManyToMany('self') ...... I can't decide which to use in which case. in other words, what are the core differences between both?

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• How to change the image by click keyboard arrows?

  - by Nitz

  Hey Guys, I have made one project in java. Now in this particular module, i am showing the user , so i am showing them a stock inventory. Now for doing this. As you will see in the screen shot [ i have put screenshot so you can understand well ]. To show the images , i have made one table and i have put labels in that and then i am setting the icon at the label. Now as soon as user click on the any image, then that image i put on big label. But this works perfect on mouse click but client want that , if user navigate the by keyboard arrow keys then in same should be happen. Means : User navigate by key board then it should reflect on that table [user should know that which is currently seleted ] and then as soon as the user navigate by key board arrow events and then click enter then that image should reflect on big label. Here is the Link for that screenshot.

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• How can i rewrite this query for faster execution

  - by sam

  SELECT s1.ID FROM binventory_ostemp s1 JOIN ( SELECT Cust_FkId, ProcessID, MAX(Service_Duration) AS duration FROM binventory_ostemp WHERE ProcessID='4d2d6068678bc' AND Overall_Rank IN ( SELECT MIN(Overall_Rank) FROM binventory_ostemp WHERE ProcessID='4d2d6068678bc' GROUP BY Cust_FkId ) GROUP BY Cust_FkId ) AS s2 ON s1.Cust_FkId = s2.Cust_FkId AND s1.ProcessID=s2.ProcessID AND s1.Service_Duration=s2.duration AND s1.ProcessID='4d2d6068678bc' GROUP BY s1.Cust_FkId It just goes away if there are more than 10K rows in that table. What it does is find rows for each customer who has min. of overall rank and in those max. of service duration for a given processid Table Data ID Cust_FkId Overall_Rank Service_Duration ProcessID 1 23 2 30 4d2d6068678bc 2 23 1 45 4d2d6068678bc 3 23 1 60 4d2d6068678bc 4 56 3 90 4d2d6068678bc 5 56 2 50 4d2d6068678bc 6 56 2 85 4d2d6068678bc

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• Design question - loading info from DB

  - by eriks

  I need to build a class that will represent a row in some table in DB (lets say the table is 'Subscriber' and so is the class). I can have the class Subscriber which constructor receives the Objectkey of subscriber, retrieves info from DB and initializes its members. I add another class - SubscriberLoader which have a static method 'LoadSubscriber'. This method will receive the subscriber objectkey, retrieve info from DB, crate a Subscriber object and initialize its members. Subscriber constructor will be private and SubscirberLoader will be friend class of Subscriber - this way, client could build a Subscriber only using the loader. which of the two in better? any other suggestions?

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• pitfalls with mixing storage engines in mysql with django?

  - by Dave Orr

  I'm running a django system over mysql in amazon's cloud, and the database default is innodb. But now I want to put a fulltext index on a couple of tables for searching, which evidently requires myisam. The obvious solution is to just tell mysql to ALTER TABLE to myisam, but are there going to be any issues with that? One that comes to mind is that I'll have to remember to do that any time I build a new version of the database, which should theoretically be rare, but there doesn't seem to be a way to tell django to please set the storage engine at the table level. I guess I could write a migration (we use south). Any other things I might be missing? What could possibly go wrong?

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• Two Different Types of Associatons on the Same Two Tables in Rails

  - by tmo256

  I have two models, users and themes, that I'm currently joining in a HABTM association in a themes_users table. Basically, after a user creates a new theme, it becomes available to other users to select for their own use. However, only the original creator of the theme should have the ability to edit it. So, I need to have some other kind of association to handle that relationship, something like an created_by_id field in the theme. In this way, the user model acts as two different roles: they can be an implementer of a theme AND/OR the owner of the theme. The implementer relationship is handled by the themes_users join table; the question is: What is the right way to handle this secondary association? Do I need to make users polymorphic and then make the created_by_id reference an "owner"? Or is there something easier? Thanks so much for your help!

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• Java long task - Did it stop writing to file?

  - by rockit

  I am writing a lot of data to a file, and while keeping my eye on the file it eventually stopped growing in size. Essentially my task is getting information from a database, and printing out all non-unique values in column A. Since there are many rows to the database table, and the database table is across my network, this is taking days to complete. Thus I'm concerned that since the file isn't growing, that it isn't actually writing to the file anymore. Which is odd, I have no "catch"'s in my code, so if there was a problem writing to file, wouldn't it have thrown an error?! Should I let the task complete (estimate 2-3 days from today), or is there something else that I don't know going on here making my application not write to the file?! my algorithm goes something like this Declare file Create new file Open file for writing get database connection get resultset from database for each row in the resultset - write column "A" to file - if row# % 100000 then write to screen "completed " + row# + " rows" when no more rows exist close file write to screen - "completed"

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• Customizing Bugzilla 4.0.2 Bug ID numbers

  - by Marcus Polk

  Is it possible to customize Bugzilla bug numbers and add a letter designator, to immediately know it came from Bugzilla? My company is evaluating Bugzilla and has now added many new bugs. We also use 2 other bug databases. This wasn't my decision and I believe they were trying to incorporate better reporting, etc. I read an answer here about "seeding" Bugzilla bug numbers, by setting the "AUTO_INCREMENT" field in the "bugs" table to a different value. I wish I would've thought about this sooner and found this board. Setting that value to start at 9000 or some extraordinary value would have ensured that we knew exactly which bugs came from Bugzilla. However, would it be possible to change the field in the "bugs" table to accept letters, as well? Of course that would probably just mess up the whole auto incrementing of the numbers. Any help or advice is greatly appreciated. Thank you.

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• How do I calculate a good hash code for a list of strings?

  - by Ian Ringrose

  Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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• postgresql count

  - by dars

  Can this be done in PGSQL? I have a view which I created where hostname,ip, and datacenter are from one table, and ifdesc and if stats from another table. the view output looks like this: hostname | ip | datacenter | ifdesc | ifadminstat | ifoperstat| ---------- ------------------------------------------------------------------ r1 1.1.1.1 dc GigabitEthernet1/1 2 1 r1 1.1.1.1 dc GigabitEthernet1/2 2 2 r1 1.1.1.1 dc GigabitEthernet1/3 2 2 r1 1.1.1.1 dc GigabitEthernet1/4 2 1 r1 1.1.1.1 dc GigabitEthernet2/1 2 2 r1 1.1.1.1 dc GigabitEthernet2/2 2 2 r2 2.2.2.2 dc GigabitEthernet1/1 2 2 r2 2.2.2.2 dc GigabitEthernet1/2 2 2 I need to get a count of "ifadminstat = 2" and "ifoperstat = 2" for all interfaces on each blade, for each router (for example... for r1, how many interfaces on blade 1 (GigabitEthernet1/1-48) have "ifadminstat = 2" and "ifoperstat = 2". I am trying to do the counting in Postgresql then present the results on a website using PHP.

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• mysql database design: thread and reply of a reply?

  - by ajsie

  in my forum i have threads and replies. one thread has multiple replies. but then, a reply can be a reply of an reply (like google wave). because of that a reply has to have a column "reply_id" so it can point to the parent reply. but then, the "top-level" replies (the replies directly under the thread) will have no parent reply. so how can i fix this? how should the columns be in the reply table (and thread table). at the moment it looks like this: threads: id title body replies: id thread_id (all replies will belong to a thread) reply_id (here lies the problem. the top-level replies wont have a parent reply) body what could a smart design look like to enable reply a reply?

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• Can you modify SQL DB schema in a transaction to know if all changes were applied?

  - by Chris F

  As part of my (new) database version control methodology, I'm writing a "change script" and want the change script to insert a new row into the SchemaChangeLog table if the script is executed successfully, or to reverse changes if any single change in the script fails. Is it possible to do schema changes in a transaction and only if it gets committed to then do the INSERT? For example (psuedo-code, I'm not too good with SQL): SET XACT_ABORT ON BEGIN TRANSACTION PRINT 'Add Col2 to Table1' IF NOT EXIST (SELECT * FROM sys.columns WHERE NAME='Col2' AND object_id=OBJECT_ID('Table1')) BEGIN ALTER TABLE [dbo].[Table1] ADD Col2 int NULL END -- maybe COMMIT here? INSERT INTO SchemaChangeLog VALUES(...) COMMIT TRANSACTION

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• Getting counts of 0 from a query with a double group by

  - by Maltiriel

  I'm trying to write a query that gets the counts for a table (call it item) categorized by two different things, call them type and code. What I'm hoping for as output is the following: Type Code Count 1 A 3 1 B 0 1 C 10 2 A 0 2 B 13 2 C 2 And so forth. Both type and code are found in lookup tables, and each item can have just one type but more than one code, so there's also a pivot (aka junction or join) table for the codes. I have a query that can get this result: Type Code Count 1 A 3 1 C 10 2 B 13 2 C 2 and it looks like (with join conditions omitted): SELECT typelookup.name, codelookup.name, COUNT(item.id) FROM typelookup LEFT OUTER JOIN item JOIN itemcodepivot RIGHT OUTER JOIN codelookup GROUP BY typelookup.name, codelookup.name Is there any way to alter this query to get the results I'm looking for? This is in MySQL, if that matters. I'm not actually sure this is possible all in one query, but if it is I'd really like to know how. Thanks for any ideas.

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• Log Shipped but Won't Update

  - by MooCow

  I'm currently taking the MS SQL 2K5 Admin course at a local college and ran into a problem with the Log Shipping part. My setup is the following: Windows 7 x64 SQL 2005 SP3 2 SQL server instances on the same machine Log Shipping settings: Performed full then log back up of Primary Manually restore on Secondary in STANDBY MODE Insert a new record into the table Set up Log Shipping on Primary using SQL Authenication login to connect to the Secondary Set up timers and copy destination on Secondary Monitoring instance not being used I set up a shared folder for WORKGROUP so both instances on the machine can read & write to it. I can see transaction logs generated and copied as defined by the Transaction Shipping wizard. However, the specified table on the Secondary instance is not updating.

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• I need to simplify a MySQL sub query for performance - please help

  - by Richard

  I have the following query which is takin 3 seconds on a table of 1500 rows, does someone know how to simplify it? SELECT dealers.name, dealers.companyName, dealer_accounts.balance FROM dealers INNER JOIN dealer_accounts ON dealers.id = dealer_accounts.dealer_id WHERE dealer_accounts.id = ( SELECT id FROM dealer_accounts WHERE dealer_accounts.dealer_id = dealers.id AND dealer_accounts.date < '2010-03-30' ORDER BY dealer_accounts.date DESC, dealer_accounts.id DESC LIMIT 1 ) ORDER BY dealers.name I need the latest dealer_accounts record for each dealer by a certain date with the join on the dealer_id field on the dealer_accounts table. This really should be simple, I don't know why I am struggling to find something.

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• Grouping records by subsets SQL

  - by Stacy

  I have a database with PermitHolders (PermitNum = PK) and DetailedFacilities of each Permit Holder. In the tblPermitDetails table there are 2 columns PermitNum (foreign Key) FacilityID (integer Foreign Key Lookup to Facility table). A permitee can have 1 - 29 items on their permit, e.i. Permit 50 can have a Boat Dock (FacID 4), a Paved walkway (FacID 17) a Retaining Wall (FacID 20) etc. I need an SQL filter/display whatever, ALL PERMIT #s that have ONLY FacIDs 19, 20, or 28, NOT ones that have those plus "x" others,....just that subset. I've worked on this for 4 days, would someone PLEASE help me? I HAVE posted to other BB but have not received any helpful suggestions.

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• sql server procedure optimization

  - by stackoverflow

  SQl Server 2005: Option: 1 CREATE TABLE #test (customerid, orderdate, field1 INT, field2 INT, field3 INT) CREATE UNIQUE CLUSTERED INDEX Idx1 ON #test(customerid) CREATE INDEX Idx2 ON #test(field1 DESC) CREATE INDEX Idx3 ON #test(field2 DESC) CREATE INDEX Idx4 ON #test(field3 DESC) INSERT INTO #test (customerid, orderdate, field1 INT, field2 INT, field3 INT) SELECT customerid, orderdate, field1, field2, field3 FROM ATABLERETURNING4000000ROWS compared to Option: 2 CREATE TABLE #test (customerid, orderdate, field1 INT, field2 INT, field3 INT) INSERT INTO #test (customerid, orderdate, field1 INT, field2 INT, field3 INT) SELECT customerid, orderdate, field1, field2, field3 FROM ATABLERETURNING4000000ROWS CREATE UNIQUE CLUSTERED INDEX Idx1 ON #test(customerid) CREATE INDEX Idx2 ON #test(field1 DESC) CREATE INDEX Idx3 ON #test(field2 DESC) CREATE INDEX Idx4 ON #test(field3 DESC) When we use the second option it runs close to 50% faster. Why is this?

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• CodeIgniter Question: How to delete records using ActiveRecord with mySQL function as WHERE conditio

  - by Jhourlad Estrella

  I have a table named ChatSessions where I keep track of active users in the chatroom. I need to prune expired user sessions from the table every 10 minutes. Using pure php-mysql is plain simple but I'm totally clueless how to convert this into ActiveRecord in CodeIgniter. The plain SQL query is below: SELECT * FROM `ChatSessions` WHERE `SessionExpires` < DATE_SUB( NOW( ) , INTERVAL 10 MINUTE ) Can anybody tell me what is the equivalent code in CodeIgniter using ActiveRecord? Thanks in advanced.

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• Database design efficiency with 1 to many relationships limited 1 to 3

  - by Joe

  This is in mysql, but its a database design issue. If you have a one to many relationship, like a bank customer to bank-accounts, typically you would have the table that records the bank-account information have a foreign key that keeps track of the relationship between account and customer. Now this follows the 3rd normal form thing and is a widely accepted way of doing it. Now lets say that you are going to limit a user to only having 3 accounts. The current database implementation will support this and nothing would need to change. But another way to do this would have 3 coloms in the account table that have the id of the 3 respective accounts in them. By the way this violates 1st normal form of db design. The question is what would be the advantage and disadvantages of having the user account relationship recored in this way over the traditional?

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• How taxing would a game map grid be to a web browser?

  - by Vilx-

  Suppose we're making a strategy game (think Civilization) in a web browser. The game has a visible map portion - say 30x30 squares. Each square is 30x30px and has several overlaid images - the terrain, resources, units, roads, etc. The classical way of drawing this would be with a huge <table> where each cell would contain absolutely positioned images. It would probably be rendered in Javascript to reduce traffic. But it's still several thousand images and a huge table. Can the browser take it? Will the performance not drop below any acceptable limits? Alternatively I could keep a pre-rendered map image with as many overlays as possible, but that would be more work, I think.

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• Class in TR without one TD

  - by Roy Grendester

  <table> <tr class="here"><td><input type="text" readonly=readonly></td></tr> <tr class="here"><td><input type="text" readonly=readonly></td></tr> <tr class="here"><td><input type="text" ></td></tr> </table> td { padding: 15px; margin: 10px; } .here { background-color: red; } http://jsfiddle.net/dZYEM/ How can i modify class .here that this working where child input has attribute readonly? I dont want modify html. EDIT: now i have: jsfiddle.net/dZYEM/2/ i would like receive: http://jsfiddle.net/dZYEM/3/ but without use style. I want receive this only with css.

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• Getting highest results in a JOIN

  - by Keithamus

  I've got three tables; Auctions, Auction Bids and Users. The table structure looks something like this: Auctions: id title -- ----- 1 Auction 1 2 Auction 2 Auction Bids: id user_id auction_id bid_amt -- ------- ---------- ------- 1 1 1 200.00 2 2 1 202.00 3 1 2 100.00 Users is just a standard table, with id and user name. My aim is to join these tables so I can get the highest values of these bids, as well as get the usernames related to those bids; so I have a result set like so: auction_id auction_title auctionbid_amt user_username ---------- ------------- -------------- ------------- 1 Auction 1 202.00 Bidder2 2 Auction 2 100.00 Bidder1 So far my query is as follows: SELECT a.id, a.title, ab.bid_points, u.display_name FROM auction a LEFT JOIN auctionbid ab ON a.id = ab.auction_id LEFT JOIN users u ON u.id = ab.user_id GROUP BY a.id This gets the single rows I am after, but it seems to display the lowest bid_amt, not the highest.

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• Why is Postgres doing a Hash in this query?

  - by Claudiu

  I have two tables: A and P. I want to get information out of all rows in A whose id is in a temporary table I created, tmp_ids. However, there is additional information about A in the P table, foo, and I want to get this info as well. I have the following query: SELECT A.H_id AS hid, A.id AS aid, P.foo, A.pos, A.size FROM tmp_ids, P, A WHERE tmp_ids.id = A.H_id AND P.id = A.P_id I noticed it going slowly, and when I asked Postgres to explain, I noticed that it combines tmp_ids with an index on A I created for H_id with a nested loop. However, it hashes all of P before doing a Hash join with the result of the first merge. P is quite large and I think this is what's taking all the time. Why would it create a hash there? P.id is P's primary key, and A.P_id has an index of its own.

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