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  • What are your thoughts on Raven DB?

    - by Ronnie Overby
    What are your thoughts on Raven DB? I see this below my title: The question you're asking appears subjective and is likely to be closed. Please don't do that. I think the question is legit because: Raven DB is brand-spanking-new. RDBMS's are probably the de facto for data persistence for .net developers, which Raven DB is not. Given these points, I would like to know your general opinions. Admittedly, the question is sort of broad. That is intentional, because I am trying to learn as much about it as possible, however here are some of my initial concerns and questions: What about using Raven DB for data storage in a shared web hosting environment, since Raven DB is interacted with through HTTP? Are there any areas that Raven DB is particularly well or not well suited for? How does it rank among alternatives, from a .net developer's perspective?

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  • Managing data charts

    - by Tom Gullen
    My dbml file is just getting bigger and bigger and more unwieldy: I favoured an all-in-one approach as supposed to multiple data contexts because when I tried that it was near impossible to manage in code. I was advised it was better to have them all in one chart and the difficulty will be simply in managing this chart and not in code. The chart I've got is becoming a pain to manage, if I want to even remove a table and re-add it it sometimes takes a little while to manually find it! There isn't even a list I can find in VS2010 of the objects you have in that chart! Is there a better way of doing this?

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  • South migration error: NoMigrations exception for django.contrib.auth

    - by danpalmer
    I have been using South on my project for a while, but I recently did a huge amount of development and changed development machine and I think something messed up in the process. The project works fine, but I can't apply migrations. Whenever I try to apply a migration I get the following traceback: danpalmer:pest Dan$ python manage.py migrate frontend Traceback (most recent call last): File "manage.py", line 11, in <module> execute_manager(settings) File "/Library/Python/2.6/site-packages/django/core/management/__init__.py", line 362, in execute_manager utility.execute() File "/Library/Python/2.6/site-packages/django/core/management/__init__.py", line 303, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/Library/Python/2.6/site-packages/django/core/management/base.py", line 195, in run_from_argv self.execute(*args, **options.__dict__) File "/Library/Python/2.6/site-packages/django/core/management/base.py", line 222, in execute output = self.handle(*args, **options) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/management/commands/migrate.py", line 102, in handle delete_ghosts = delete_ghosts, File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/migration/__init__.py", line 182, in migrate_app applied = check_migration_histories(applied, delete_ghosts) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/migration/__init__.py", line 85, in check_migration_histories m = h.get_migration() File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/models.py", line 34, in get_migration return self.get_migrations().migration(self.migration) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/models.py", line 31, in get_migrations return Migrations(self.app_name) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/migration/base.py", line 60, in __call__ self.instances[app_label] = super(MigrationsMetaclass, self).__call__(app_label_to_app_module(app_label), **kwds) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/migration/base.py", line 88, in __init__ self.set_application(application, force_creation, verbose_creation) File "/Library/Python/2.6/site-packages/South-0.7-py2.6.egg/south/migration/base.py", line 159, in set_application raise exceptions.NoMigrations(application) south.exceptions.NoMigrations: Application '<module 'django.contrib.auth' from '/Library/Python/2.6/site-packages/django/contrib/auth/__init__.pyc'>' has no migrations. I am not that experienced with South and I haven't met this error before. The only helpful mention I can find online about this error is for pre-0.7 I think and I am on South 0.7. I ran 'easy_install -U South' just to make sure. Thanks for any help that you can provide. I really appreciate it.

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  • Can a Compound key be set as a primary key to another table?

    - by Nikos
    Can a compound key be set as a primary key to another table? For instance i have the tables: Books -with Primary Key:Product_ID Client -with Primary key: Client_ID Clients_Books -with Compound Primary Key:Product_Id and Client_ID I want to set this compound Primary key from Clients_Books as a Primary Key to another table named: Order_Details. But I don't want to use the Product_ID and the Client_ID from the Books, Clients tables. Does this make sense? All opinions more than welcome.

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  • Entity Relationship Diagram - Relationship Strength?

    - by 01010011
    Hi, I am trying to figure out under what circumstances I should use weak (non-identifying) relationships (where the primary key of the related entity does not contain a primary key component of the parent entity), verses when I should use strong (identifying) relationships (primary key of the related entity contains a primary key component of the parent entity). For example, when designing an Entity Relationship Diagram , if I have two entities, (e.g. book and purchaser), how do I know when to choose the solid Crows Foot or the dashed Crows Foot to connect the two entities? Any assistance will be appreciated. Thanks in advance.

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  • Another rookie question; How to implement Count() here?

    - by Camran
    I have this query: SELECT mt.*, fordon.*, boende.*, elektronik.*, business.*, hem_inredning.*, hobby.* FROM classified mt LEFT JOIN fordon ON fordon.classified_id = mt.classified_id LEFT JOIN boende ON boende.classified_id = mt.classified_id LEFT JOIN elektronik ON elektronik.classified_id = mt.classified_id LEFT JOIN business ON business.classified_id = mt.classified_id LEFT JOIN hem_inredning ON hem_inredning.classified_id = mt.classified_id LEFT JOIN hobby ON hobby.classified_id = mt.classified_id ORDER BY modify_date DESC I need to implement a count here, to just count all rows in combination with the JOINS you see. How should I do this? SELECT COUNT(mt.*, fordon.* etc) FROM ? // This method wont work Thanks

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  • Getting the record ID just added with mysql prepared statements

    - by dmontain
    I'm inserting a record using PDO (very similar to mysqli). $addRecord->execute(); To know if the operation worked, I've learned that I can save it to a variable $result that can be used as true false $result = $addRecord->execute(); if ($result){ //add successful } else { //add unsuccessful } What I'd like to do is also get the record id just added. In the table, each record has an auto_incremented field called id. I tried doing this $new_id = $result['id']; but it seems that $result is purely boolean and doesn't actually hold the actual record that was added. Can someone confirm this and how would I then access the record just added? Note that several people may be adding to the same table at the same time, so I think getting just the last one would not be very accurate.

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  • What is the proper query to get all the children in a tree?

    - by Nathan Adams
    Lets say I have the following MySQL structure: CREATE TABLE `domains` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `domain` CHAR(50) NOT NULL, `parent` INT(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=MYISAM AUTO_INCREMENT=10 DEFAULT CHARSET=latin1 insert into `domains`(`id`,`domain`,`parent`) values (1,'.com',0); insert into `domains`(`id`,`domain`,`parent`) values (2,'example.com',1); insert into `domains`(`id`,`domain`,`parent`) values (3,'sub1.example.com',2); insert into `domains`(`id`,`domain`,`parent`) values (4,'sub2.example.com',2); insert into `domains`(`id`,`domain`,`parent`) values (5,'s1.sub1.example.com',3); insert into `domains`(`id`,`domain`,`parent`) values (6,'s2.sub1.example.com',3); insert into `domains`(`id`,`domain`,`parent`) values (7,'sx1.s1.sub1.example.com',5); insert into `domains`(`id`,`domain`,`parent`) values (8,'sx2.s2.sub1.example.com',6); insert into `domains`(`id`,`domain`,`parent`) values (9,'x.sub2.example.com',4); In my mind that is enough to emulate a simple tree structure: .com | example / \ sub1 sub2 ect My problem is that give sub1.example.com I want to know all the children of sub1.example.com without using multiple queries in my code. I have tried joining the table to itself and tried to use subqueries, I can't think of anything that will reveal all the children. At work we are using MPTT to keep in hierarchal order a list of domains/subdomains however, I feel that there is an easier way to do it. I did some digging and someone did something similar but they required the use of a function in MySQL. I don't think for something simple like this we would need a whole function. Maybe I am just dumb and not seeing some sort of obvious solution. Also, feel free to alter the structure.

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  • Querying a Cassandra column family for rows that have not been updated in X days

    - by knorv
    I'm moving an existing MySQL based application over to Cassandra. So far finding the equivalent Cassandra data model has been quite easy, but I've stumbled on the following problem for which I'd appreciate some input: Consider a MySQL table holding millions of entities: CREATE TABLE entities ( id INT AUTO_INCREMENT NOT NULL, entity_information VARCHAR(...), entity_last_updated DATETIME, PRIMARY KEY (id), KEY (entity_last_updated) ); The table is regularly queried for entities that need to be updated: SELECT id FROM entities WHERE entity_last_updated IS NULL OR entity_last_updated < DATE_ADD(NOW(), INTERVAL -7*24 HOUR) ORDER BY entity_last_updated ASC; The entities returned by this queries are then updated using the following query: UPDATE entities SET entity_information = ?, entity_last_updated = NOW() WHERE id = ?; What would be the corresponding Cassandra data model that would allow me to store the given information and effectively query the entities table for entities that need to be updated (that is: entities that have not been updated in the last seven days)?

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  • SQL Query problem: How to merge two lists.

    - by ProfK
    I have a base table of Participants and Answers, with the following structure: ParticipantId, BusUnitId, QuestionNum, Answer. In this table, QuestionNum ranges, say, from 1 to 6. I also have two other tables that sort of link QuestionNum to the actual question table, BusUnitQuestions, and ParticipantQuestions. For each QuestionNum, I must get the actual question text, based on QuestionId. BusUnitId, QuestionId ParticipantId, QuestionId Now assuming records with QuestionNum from 1 to 6. BusUnitQuestions has 3 records, so QuestionNum 1 to 3 must join to Question on the QuestionId's from BusUnitQuestions, and QuestionNum 4 to 6 must join to Question on the QuestionId's from ParticipantQuestions. I assume I need to use ROW_NUMBER() in the subquery from BusUnitQuestions to join to my answer table, but I'm lost after that. If anyone at all understands me, do you have any suggestions?

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  • Any PICK programmers on stack?

    - by Coov
    I work in a shop that is divided into two types of programmers. Programmers that code in .net & sql and programmers that code in pick. Actually, a few of the programmers are writing code in both pick and .net. I was curious if there are any pick programmers out there using StackOverflow? I'd like to get the pick programmers involved in the stack community.

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  • Is there an "embedded DBMS" to support multiple writer applications (processes) on the same db files

    - by Amir Moghimi
    I need to know if there is any embedded DBMS (preferably in Java and not necessarily relational) which supports multiple writer applications (processes) on the same set of db files. BerkeleyDB supports multiple readers but just one writer. I need multiple writers and multiple readers. UPDATE: It is not a multiple connection issue. I mean I do not need multiple connections to a running DBMS application (process) to write data. I need multiple DBMS applications (processes) to commit on the same storage files. HSQLDB, H2, JavaDB (Derby) and MongoDB do not support this feature. I think that there may be some File System limitations that prohibit this. If so, is there a File System that allows multiple writers on a single file? Use Case: The use case is a high-throughput clustered system that intends to store its high-volume business log entries into a SAN storage. Storing business logs in separate files for each server does not fit because query and indexing capabilities are needed on the whole biz logs. Because "a SAN typically is its own network of storage devices that are generally not accessible through the regular network by regular devices", I want to use SAN network bandwidth for logging while cluster LAN bandwidth is being used for other server to server and client to server communications.

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  • Synchronising tables across remote Access databases

    - by Paul H
    Hi folks, I'm helping out a business by providing an Access DB to manage requests of various types. As they are a construction company, they have one machine in an 'office' on the building site, plus 3 based in their main office. The machine on site has no internet connectivity. Is there any (reasonably simple) way to synchronise these databases every so often? I realise the tables could be merged, but each has an autoincrement field which must be synced between instances (i.e. when merging two tables the autoincrement should be reassigned based on the combination of records). Cheers in advance, Paul

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  • One check constraint or multiple check constraints?

    - by RenderIn
    Any suggestions on whether fewer check constraints are better, or more? How should they be grouped if at all? Suppose I have 3 columns which are VARCHAR2(1 BYTE), each of which is a 'T'/'F' flag. I want to add a check constraint to each column specifying that only characters IN ('T', 'F') are allowed. Should I have 3 separate check constraints, one for each column: COL_1 IN ('T', 'F') COL_2 IN ('T', 'F') COL_3 IN ('T', 'F') Or a single check constraint: COL_1 IN ('T', 'F') AND COL_2 IN ('T', 'F') AND COL_3 IN ('T', 'F') My thoughts are it is best to keep these three separate, as the columns are logically unrelated to each other. The only case I would have a check constraint that examines more than one column is if there was some relationship between the value in one and the value in another, e.g.: (PARENT_CNT > 0 AND PRIMARY_PARENT IS NOT NULL) OR (PARENT_CNT = 0 AND PRIMARY_PARENT IS NULL)

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  • Tokyo Tyrant indexes

    - by viraptor
    I was wondering about size requirements for Tokyo Tyrant indexes. If I have an index on field x and insert a record with fields y and z only, does the x index grow? Also: does the insert time grow in that case?

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  • moving to NoSql

    - by radi
    hi , i recently read this article nosql-vs-rdbms and i dont know too much about nosql and i didnt use it in my projects , so i have some questions : what is the main feature that nosql has over Rdbms ? if you think that it is best than rdbms : where and how i can learn about it (books - tutorials)? i want to be a DBA , what this career will be after moving to nosql ? thanks

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  • moving to NoSql

    - by radi
    hi , i recently read this article nosql-vs-rdbms and i dont know too much about nosql and i didnt use it in my projects , so i have some questions : what is the main feature that nosql has over Rdbms ? if you think that it is best than rdbms : where and how i can learn about it (books - tutorials)? i want to be a DBA , what this career will be after moving to nosql ? thanks

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  • Starting out NLP - Python + large data set

    - by pencilNero
    Hi, I've been wanting to learn python and do some NLP, so have finally gotten round to starting. Downloaded the english wikipedia mirror for a nice chunky dataset to start on, and have been playing around a bit, at this stage just getting some of it into a sqlite db (havent worked with dbs in the past unfort). But I'm guessing sqlite is not the way to go for a full blown nlp project(/experiment :) - what would be the sort of things I should look at ? HBase (.. and hadoop) seem interesting, i guess i could run then im java, prototype in python and maybe migrate the really slow bits to java... alternatively just run Mysql.. but the dataset is 12gb, i wonder if that will be a problem? Also looked at lucene, but not sure how (other than breaking the wiki articles into chunks) i'd get that to work.. What comes to mind for a really flexible NLP platform (i dont really know at this stage WHAT i want to do.. just want to learn large scale lang analysis tbh) ? Many thanks.

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  • Database Schema for survey polling application with a default choice.

    - by user156814
    I have a survey application, where users can create surveys and give choices for every survey. Other users can choose their answers for the aurvey and then polls are taken to get the results of the survey. I already have the database schema for this Questions id, user_id, category_id, question_text, date_started Answers id, user_id, question_id, choice_id, explanation, date_added Choices id, question_id, choice_text As for now, users can choose their own choice answers to their surveys... but I want to be able to add a default "I dont care" or "I dont know" choice to every survey for people who simply dont care about the topic to take sides or who cant choose. So lets say theres a survey that asks who was a better president, George W. Bush, Bill Clinton, Ronald Reagon, or Richard Nixon... I want to be able to add a default "I dont care" option. I was thinking to just add that extra choice EVERY TIME a user creates a survey, but then I wouldn't have much control over the text for that choice after that survey has been created, and I want to know if theres a better way to do this, like create another table or something Thanks

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  • Speed Difference between native OLE DB and ADO.NET

    - by weijiajun
    I'm looking for suggestions as well as any benchmarks or observations people have. We are looking to rewrite our data access layer and are trying to decide between native C++ OLEDB or ADO.NET for connecting with databases. Currently we are specifically targeting Oracle which would mean we would use the Oracle OLE DB provider and the ODP.NET. Requirements: 1. All applications will be in managed code so using native C++ OLEDB would require C++/CLI to work (no PInvoke way to slow). 2. Application must work with multiple databases in the future, currently just targeting Oracle specifically. Question: 1. Would it be more performant to use ADO.NET to accomplish this or use native C++ OLE DB wrapped in a Managed C++ interface for managed code to access? Any ideas, or help or places to look on the web would be greatly appreciated.

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  • Stringtemplate: is it ok to Apply Templates, in which HashMap uses, To Multi-Valued Attributes

    - by user1071830
    There is two template in my .stg file, and both of them apply on multi-value a HashMap. The HashMap is employed as an injected object. And I need those instance of HashMap can be injected for many times. My trouble is, when I switch to another template, ANTLR seems to consider the second HashMap as a List -- multipul objects and null value. Part of my .stg file shows as follows: tpl_hash(BAR, FOO) ::= << <FOO:foo(); separator="\n"> <BAR:bar(); separator="\n"> >> foo(nn) ::= << foo: <nn.name; null="NULL"> . <nn.national; null="NULL"> >> bar(mm) ::= << bar: <mm.name> @ <mm.national> >> Part of my .g file shows: HashMap hm = new HashMap(); hm.put("name", $name.text); hm.put("national", "German"); tpl_hash.add("FOO",new HashMap(hm)); HashMap hm2 = new HashMap(); hm2.put("name", $name.text); hm2.put("national", "German"); tpl_hash.add("BAR",new HashMap(hm2)); The result I expect is : bar: Kant @ German foo: Russell @ England But, I got: foo: NULL . NULL foo: NULL . NULL bar: @ bar: @ If we replace BAR with FOO, as is, keeping FOO and BAR with identical template, the output is right, like the following. bar: Russell @ German bar: Russell @ German In docs, "synchronized ST add (String name, Object value) in org.stringtemplate.v4.ST" said: "If you send in a List and then inject a single value element, add() copies original list and adds the new value." What about a HashMap? Does ANTLR consider the HashMap, key/value pair access, an object purposely, as a List and as multi-value injected by mistake? Thanks a lot in advance.

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