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  • How to map combinations of things to a relational database?

    - by Space_C0wb0y
    I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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  • Hibernate database connection configuration

    - by Alvin
    We have 2 different server environments using the same Hibernate configuration. One server has JNDI support for datasource, but the other does not. Currently the Hibernate configuration is configured to use JNDI, which is causing problem on the server that does not support JNDI. I have also tried to put the direct JDBC configuration together with JNDI configuration into the configuration file, but it looks like hibernate always favors JNDI over direct JDBC configuration if both exist. My question is, will it be the same if both JNDI and connection_provider configuration both exists? Will Hibernate still use JNDI over connection_provider? Or is there any way to change the precedence of the database connection property? I do not have access to the server all the time, so I thought I do ask the question before my window of the sever time. Thanks in advance.

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  • When to use Hibernate?

    - by Ramo
    Hi All, I was asked in an interview this question so I answered with the following: -Better Performance: - Efficient queries. - 1st and 2nd level caching. - Good caching gives better scalability. - Good Database Portability: - Changing the DB is as easy as changing the dialect configuration. - Increased Developer Productivity: - Think only in object terms not in query language terms. But I also feel that systems fall in one of the below categories, and Hibernate may not be suited for all these cases, I'm interested in your thoughts about this, do you agree with me? please let me know when would use HB in the following case and why. Write Only Systems: Read Only Systems: Write Mostly Systems: Read Mostly Systems: Regards Ramo

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  • JPA returning null for deleted items from a set

    - by Jon
    This may be related to my question from a few days ago, but I'm not even sure how to explain this part. (It's an entirely different parent-child relationship.) In my interface, I have a set of attributes (Attribute) and valid values (ValidValue) for each one in a one-to-many relationship. In the Spring MVC frontend, I have a page for an administrator to edit these values. Once it's submitted, if any of these fields (as <input> tags) are blank, I remove the ValidValue object like so: Set<ValidValue> existingValues = new HashSet<ValidValue>(attribute.getValidValues()); Set<ValidValue> finalValues = new HashSet<ValidValue>(); for(ValidValue validValue : attribute.getValidValues()) { if(!validValue.getValue().isEmpty()) { finalValues.add(validValue); } } existingValues.removeAll(finalValues); for(ValidValue removedValue : existingValues) { getApplicationDataService().removeValidValue(removedValue); } attribute.setValidValues(finalValues); getApplicationDataService().modifyAttribute(attribute); The problem is that while the database is updated appropriately, the next time I query for the Attribute objects, they're returned with an extra entry in their ValidValue set -- a null, and thus, the next time I iterate through the values to display, it shows an extra blank value in the middle. I've confirmed that this happens at the point of a merge or find, at the point of "Execute query ReadObjectQuery(entity.Attribute). Here's the code I'm using to modify the database (in the ApplicationDataService): public void modifyAttribute(Attribute attribute) { getJpaTemplate().merge(attribute); } public void removeValidValue(ValidValue removedValue) { ValidValue merged = getJpaTemplate().merge(removedValue); getJpaTemplate().remove(merged); } Here are the relevant parts of the entity classes: Entity @Table(name = "attribute") public class Attribute { @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "attribute") private Set<ValidValue> validValues = new HashSet<ValidValue>(0); } @Entity @Table(name = "valid_value") public class ValidValue { @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "attr_id", nullable = false) private Attribute attribute; }

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  • Doctrine 1.2 Column Naming Conventions for Many To Many Relationships

    - by Alan Storm
    I'm working with an existing database schema, and trying to setup two Doctrine models with a Many to Many relationship, as described in this document When creating tables from scratch, I have no trouble getting this working. However, the existing join tables use a different naming convention that what's described in the Doctrine document. Specifically Table 1 -------------------------------------------------- table_1_id ....other columns.... Table 2 -------------------------------------------------- table_2_id ....other columns.... Join Table -------------------------------------------------- fktable1_id fktable_2_id Basically, the previous developers prefaced all forign keys with an fk. From the examples I've seen and some brief experimenting with code, it appears that Doctrine 1.2 requires that the join table use the same column names as the tables it's joining in Is my assumption correct? If so, has the situation changed in Doctrine 2? If the answers to either of the above are true, how do you configure the models so that all the columns "line up"

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  • How to implement automatic reflection of direct SQL Updates of the underlying database, in an ActiveRecord in Ruby on Rails ?

    - by Vadim Eisenberg
    Hello ! I am new to Ruby on Rails and I have a (maybe naive) question: I want to implement reflection of direct SQL Updates of the underlying database in an ActiveRecord (and finally in the generated html). By "direct updates" I mean updating the database bypassing the ActiveRecord methods, for example by MySQL console. I guess here MySQL triggers could be used that would call some stored procedure that would cause the appropriate ActiveRecord to be reloaded. Is there some automatic handling of this scenario in ActiveRecord/Ruby on Rails ? Did somebody implement this scenario ? Can somebody recommend using other MVC frameworks to reflect direct changes in mapped databases ?

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  • Hibernate and Child Objects (add versus clear)

    - by tyndall
    Lets say I have domain model with Automobile and Wheels. Wheels is a List of Wheels Wheels has a many-to-one relationship to Automobile. If I get an object back from Hibernate and it has 4 wheels. I take that object remove the 4 wheels and add 4. And then Save. If I ask Hibernate for the object again and it returns an auto with 8 wheels... what are we doing wrong? I don't have access to the source for a few days but want to give our Java devs a push in the right direction. Thanks.

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  • JPA CascadeType.ALL does not delete orphans.

    - by Paul Whelan
    I am having trouble deleting orphan nodes using JPA with the following mapping @OneToMany (cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "owner") private List<Bikes> bikes; I am having the issue of the orphaned roles hanging around the database. I can use the @org.hibernate.annotations.Cascade Hibernate specific tag but obviously I don't want to tie my solution into a hibernate implementation. Any pointers greatly appreciated.

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  • help with generating models from database for many to many in doctrine

    - by ajsie
    im using doctrine and i have set up some test tables to be generated into models: I want a many-to-many relationship models (3 tables converted into 3 models) (things are simplified to make the point clear) mysql tables: user: id INT // primary key name VARCHAR group: id INT // primary key name VARCHAR user_group: user_id INT // primary and foreign key to user.id group_id INT // primary and foreign key to group.id i thought that it would generate these models (from the documentation): // User.php class User extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name); } public function setUp() { $this->hasMany('Group as Groups', array( 'refClass' => 'UserGroup', 'local' => 'user_id', 'foreign' => 'group_id' ) ); } } // Group.php class Group extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name); } public function setUp() { $this->hasMany('User as Users', array( 'refClass' => 'UserGroup', 'local' => 'group_id', 'foreign' => 'user_id' ) ); } } // UserGroup.php class UserGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('user_id') ); $this->hasColumn('group_id') ); } } but it generated this: // User.php abstract class BaseUser extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name'); } public function setUp() { $this->hasMany('UserGroup', array( 'local' => 'id', 'foreign' => 'user_id')); } } // Group.php abstract class BaseGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name'); } public function setUp() { $this->hasMany('UserGroup', array( 'local' => 'id', 'foreign' => 'group_id')); } } // UserGroup.php abstract class BaseUserGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('user_id'); $this->hasColumn('group_id'); } public function setUp() { $this->hasOne('User', array( 'local' => 'user_id', 'foreign' => 'id')); $this->hasOne('Group', array( 'local' => 'group_id', 'foreign' => 'id')); } } as you can see, there is no 'refClass' in the 'User' and 'Group' models pointing to the 'UserGroup'. the 'UserGroup' table in this case is just another table from Doctrine's perspective not a reference table. I've checked my table definitions in mysql. They are correct. user_group has 2 columns (primary keys and foreign keys), each one pointing to the primary key in either User or Group. But i want the standard many-to-many relationship models in Doctrine models. I'd appreciate some help. I have struggled to figure it out for a half day now. What is wrong? Thanks!

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  • Best way to model Customer <--> Address

    - by Jen
    Every Customer has a physical address and an optional mailing address. What is your preferred way to model this? Option 1. Customer has foreign key to Address Customer (id, phys_address_id, mail_address_id) Address (id, street, city, etc.) Option 2. Customer has one-to-many relationship to Address, which contains a field to describe the address type Customer (id) Address (id, customer_id, address_type, street, city, etc.) Option 3. Address information is de-normalized and stored in Customer Customer (id, phys_street, phys_city, etc. mail_street, mail_city, etc.) One of my overriding goals is to simplify the object-relational mappings, so I'm leaning towards the first approach. What are your thoughts?

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  • Changing the Hibernate 3 settings

    - by Bogdanel
    I use Hibernate3 and Hibernate Tools 3.2.4 to generate hbm.xml and java files and I want to use List instead of HashSet(...). I've tried to modify the hbm.xml files, putting list instead of set. Is there any way to specify to hibernate tools that I want to generate automatically a list not a HashSet? This is an exemple: Java class public class Test implements java.io.Serializable { private Long testId; private Course course; private String testName; private Set<Question> questions = new HashSet<Question>( 0 ); } Test.hbm.xml: <set name="questions" inverse="true" lazy="true" table="questions" fetch="select"> <key> <column name="test_id" not-null="true" /> </key> <one-to-many class="com.app.objects.Question" /> ... </set> I thought that I could find a clue in the "reveng.xml" file, but I failed.

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  • Hibernate / MySQL Bulk insert problem

    - by Marty Pitt
    I'm having trouble getting Hibernate to perform a bulk insert on MySQL. I'm using Hibernate 3.3 and MySQL 5.1 At a high level, this is what's happening: @Transactional public Set<Long> doUpdate(Project project, IRepository externalSource) { List<IEntity> entities = externalSource.loadEntites(); buildEntities(entities, project); persistEntities(project); } public void persistEntities(Project project) { projectDAO.update(project); } This results in n log entries (1 for every row) as follows: Hibernate: insert into ProjectEntity (name, parent_id, path, project_id, state, type) values (?, ?, ?, ?, ?, ?) I'd like to see this get batched, so the update is more performant. It's possible that this routine could result in tens-of-thousands of rows generated, and a db trip per row is a killer. Why isn't this getting batched? (It's my understanding that batch inserts are supposed to be default where appropriate by hibernate).

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  • Another Spring + Hibernate + JPA question

    - by Albinoswordfish
    I'm still struggling with changing my Spring Application to use Hibernate with JPA to do database activities. Well apparently from a previous post I need an persistence.xml file. However do I need to make changes to my current DAO class? public class JdbcProductDao extends Dao implements ProductDao { /** Logger for this class and subclasses */ protected final Log logger = LogFactory.getLog(getClass()); public List<Product> getProductList() { logger.info("Getting products!"); List<Product> products = getSimpleJdbcTemplate().query( "select id, description, price from products", new ProductMapper()); return products; } public void saveProduct(Product prod) { logger.info("Saving product: " + prod.getDescription()); int count = getSimpleJdbcTemplate().update( "update products set description = :description, price = :price where id = :id", new MapSqlParameterSource().addValue("description", prod.getDescription()) .addValue("price", prod.getPrice()) .addValue("id", prod.getId())); logger.info("Rows affected: " + count); } private static class ProductMapper implements ParameterizedRowMapper<Product> { public Product mapRow(ResultSet rs, int rowNum) throws SQLException { Product prod = new Product(); prod.setId(rs.getInt("id")); prod.setDescription(rs.getString("description")); prod.setPrice(new Double(rs.getDouble("price"))); return prod; } } } Also my Product.Java is below public class Product implements Serializable { private int id; private String description; private Double price; public void setId(int i) { id = i; } public int getId() { return id; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public String toString() { StringBuffer buffer = new StringBuffer(); buffer.append("Description: " + description + ";"); buffer.append("Price: " + price); return buffer.toString(); } } I guess my question would be, How would my current classes change after using Hibernate + JPA with an Entity Manager

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  • ReflectionTypeLoadException when I try to run Enable-Migrations with Entity Framework 5.0

    - by Eric Anastas
    I'm trying to use Entity Framework for the first time on one of my projects. I'm using the code first workflow to automatically create my database. Intitaly setting up the database worked fine. Now I'm trying to migrate changes in my classes into the database. The tutorial I'm reading says I need to run "Enable-Migrations" in the package manager console. Yet when I do this I get the following error PM> Enable-Migrations System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module) at System.Reflection.RuntimeModule.GetTypes() at System.Reflection.Assembly.GetTypes() at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.FindType[TBase](String typeName, Func`2 filter, Func`2 noType, Func`3 multipleTypes, Func`3 noTypeWithName, Func`3 multipleTypesWithName) at System.Data.Entity.Migrations.Design.ToolingFacade.GetContextTypeRunner.RunCore() at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run() Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. What am I doing wrong? How do I retrieve the loader exceptions property? Also NuGet says I have EF 5.0, but Version property of the EntityFramework item in my project references says 4.4.0.0. I'm not sure if this is related.

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  • SQL-wrappers (activerecord) to recommened for python?

    - by Horace Ho
    is there an activerecord (any similar SQL-wrapper) for python? which is good for: used in a server-side python script light-weight supports MySQL what I need to do: insert (filename, file size, file md5, the file itself) into (string, int, string, BLOB) columns if the same file (checksum + filename) does not exist in db thx

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  • using Hibernate to loading 20K products, modifying the entity and updating to db

    - by Blankman
    I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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  • Fluent nHibernate - How to map a non-key column on a junction table?

    - by The Matt
    Taking an example that is provided on the Fluent nHibernate website, I need to extend it slightly: I need to add a 'Quantity' column to the StoreProduct table. How would I map this using nHibernate? An example mapping is provided for the given scenario above, but I'm not sure how I would get the Quantity column to map to a property on the Product class: public class StoreMap : ClassMap<Store> { public StoreMap() { Id(x => x.Id); Map(x => x.Name); HasMany(x => x.Employee) .Inverse() .Cascade.All(); HasManyToMany(x => x.Products) .Cascade.All() .Table("StoreProduct"); } }

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  • Higher level database layer for Android?

    - by sweetiecakes
    Are there any good database abstraction layers/object relational mappers/ActiveRecord implementations/whatever they are called for Android? I'm aware that db4o is officially supported, but it has quite a large footprint and I'd rather use a more conventional database (SQLite).

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  • JPA and hibernate for Flex

    - by dejaninic
    I'm using JPA but I'm not sure how to use it for relation between two classes. I need to connect them @OneToMany. I have done this before but forgot. Is there any good tutorial for this or an example that is easy to understand. By the way this is a Flex application where I'm using BlazeDS for connection between Java and Flex.

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  • Hibernate Many-To-One Foreign Key Default 0

    - by user573648
    I have a table where the the parent object has an optional many-to-one relationship. The problem is that the table is setup to default the fkey column to 0. When selecting, using fetch="join", etc-- the default of 0 on the fkey is being used to try over and over to select from another table for the ID 0. Of course this doesn't exist, but how can I tell Hibernate to treat a value of 0 to be the same as NULL-- to not cycle through 20+ times in fetching a relationship which doesn't exist? <many-to-one name="device" lazy="false" class="Device" not-null="true" access="field" cascade="none" not-found="ignore"> <column name="DEVICEID" default="0" not-null="false"/>

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  • MySQL Hibernate sort on 2 columns

    - by sammichy
    I have a table as follows Table item { ID - Primary Key content - String published_date - When the content was published create_date - When this database entry was created } Every hour (or specified time interval) I run a process to update this table with data from different sources (websites). I want to display the results according to the following rules. 1. The entries created each time the process runs should be grouped together. So the entries from the 2nd process run will always be after the entries from the first process run even if the published_date of an entry from the first run is after the published_date of an entry from the 2nd run. 2. Within the grouping by run, the entries by sorted by published_date 3. Another restriction is that I prefer that data from the same source not be grouped together. If I do the sort by create_date, published_date I will end up with data from source a, data from source b etc. I prefer that the data within each hour be mixed up for better presentation If I add a column to this table and store a counter which increments each time the process is run, it is possible to create a query to sort first by counter and then by published_dt. Is there a way to do it without adding a field? I'm using Hibernate over MySQL. e.g. Hour 1 (run 1) 4 rows collected from site a (rows 1-4) 3 rows collected from site b (rows 5-7) hour 2 (run 2) 2 row collected from site a (rows 8-9) 3 rows collected from site b (rows 10-12) ... After each run, new records are added to the database from each website. The create date is the time when the record was created in the database. The published date is part of the content and is read in from the external source. When the results are displayed I would like rows to be grouped together based on the hour they were published in. So rows 1-7 would be displayed before rows 8-12. Within each hourly grouping, I would like to sort the results by published date (timestamp). This is necessary so that the posts from all the sites collected in that hour are not grouped together but rather mixed in with each other.

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  • Hibernate Annotation for Entity existing in more than 1 catalog

    - by user286395
    I have a Person entity mapped by Hibernate to a database table in a database catalog "Active". After a period of time, records in this database table in the "Active" catalog are archived/moved to an exact copy of the table in a database Catalog "History". I have the need to retrieve from both the Active and History Catalogs. Is there a better way to model this with Hibernate annotations than making an abstract class that 2 classes extend from. This is what I have now. @MappedSuperclass public abstract class Person { @Id private Integer id; private String name; } @Entity @Table(name="Person", catalog="Active") public class PersonActive extends Person { } @Entity @Table(name="Person", catalog="History") public class PersonHistory extends Person { }

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