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  • how to delete fk children in nhibernate

    - by frosty
    I would like to delete the ICollection PriceBreaks from Product. I'm using the following method. However they dont seem to delete. What am i missing. When i step thru. i notice that "product.PriceBreaks.Clear();" doesn't actually clear the items. Do i need to flush or something? public void RemovePriceBreak(int productId) { using (ISession session = EStore.Domain.Helpers.NHibernateHelper.OpenSession()) using (ITransaction transaction = session.BeginTransaction()) { var product = session.Get<Product>(productId); product.PriceBreaks.Clear(); session.SaveOrUpdate(product); transaction.Commit(); } } Here are my hbm files <class name="Product" table="Products"> <id name="Id" type="Int32" column="Id" unsaved-value="0"> <generator class="identity"/> </id> <property name="CompanyId" column="CompanyId" type="Int32" not-null="true" /> <property name="Name" column="Name"/> <set name="PriceBreaks" table="PriceBreaks" generic="true" cascade="all-delete-orphan" inverse="true" > <key column="ProductId" /> <one-to-many class="EStore.Domain.Model.PriceBreak, EStore.Domain" /> </set> </class> <class name="PriceBreak" table="PriceBreaks"> <id name="Id" type="Int32" column="Id" unsaved-value="0"> <generator class="identity"/> </id> <many-to-one name="Product" column="ProductId" not-null="true" cascade="all" class="EStore.Domain.Model.Product, EStore.Domain" /> </class> My Entities public class Product { public virtual int Id { get; set; } public virtual ICollection<PriceBreak> PriceBreaks { get; set; } public virtual void AddPriceBreak(PriceBreak priceBreak) { priceBreak.Product = this; PriceBreaks.Add(priceBreak); } } public class PriceBreak { public virtual int Id { get; set; } public virtual Product Product { get; set; } }

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  • Different behaviour using unidirectional or bidirectional relation

    - by sinuhepop
    I want to persist a mail entity which has some resources (inline or attachment). First I related them as a bidirectional relation: @Entity public class Mail extends BaseEntity { @OneToMany(mappedBy = "mail", cascade = CascadeType.ALL, orphanRemoval = true) private List<MailResource> resource; private String receiver; private String subject; private String body; @Temporal(TemporalType.TIMESTAMP) private Date queued; @Temporal(TemporalType.TIMESTAMP) private Date sent; public Mail(String receiver, String subject, String body) { this.receiver = receiver; this.subject = subject; this.body = body; this.queued = new Date(); this.resource = new ArrayList<>(); } public void addResource(String name, MailResourceType type, byte[] content) { resource.add(new MailResource(this, name, type, content)); } } @Entity public class MailResource extends BaseEntity { @ManyToOne(optional = false) private Mail mail; private String name; private MailResourceType type; private byte[] content; } And when I saved them: Mail mail = new Mail("[email protected]", "Hi!", "..."); mail.addResource("image", MailResourceType.INLINE, someBytes); mail.addResource("documentation.pdf", MailResourceType.ATTACHMENT, someOtherBytes); mailRepository.save(mail); Three inserts were executed: INSERT INTO MAIL (ID, BODY, QUEUED, RECEIVER, SENT, SUBJECT) VALUES (?, ?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE, MAIL_ID) VALUES (?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE, MAIL_ID) VALUES (?, ?, ?, ?, ?) Then I thought it would be better using only a OneToMany relation. No need to save which Mail is in every MailResource: @Entity public class Mail extends BaseEntity { @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true) @JoinColumn(name = "mail_id") private List<MailResource> resource; ... public void addResource(String name, MailResourceType type, byte[] content) { resource.add(new MailResource(name, type, content)); } } @Entity public class MailResource extends BaseEntity { private String name; private MailResourceType type; private byte[] content; } Generated tables are exactly the same (MailResource has a FK to Mail). The problem is the executed SQL: INSERT INTO MAIL (ID, BODY, QUEUED, RECEIVER, SENT, SUBJECT) VALUES (?, ?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE) VALUES (?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE) VALUES (?, ?, ?, ?) UPDATE MAILRESOURCE SET mail_id = ? WHERE (ID = ?) UPDATE MAILRESOURCE SET mail_id = ? WHERE (ID = ?) Why this two updates? I'm using EclipseLink, will this behaviour be the same using another JPA provider as Hibernate? Which solution is better?

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  • NHibernate Many to Many delete all my data in the table

    - by Daoming Yang
    I would love to thank @Stefan Steinegger and @David helped me out yesterday with many-to-many mapping. I have 3 tables which are "News", "Tags" and "News_Tags" with Many-To-Many relationship and the "News_Tags" is the link table. If I delete one of the news records, the following mappings will delete all my news records which have the same tags. One thing I need to notice, I only allowed unique tag stored in the "Tag" table. This mapping make sense for me, it will delete the tag and related News records, but how can I implement a tagging system with NHibernate? Can anyone give me some suggestion? Many thanks. Daoming. News Mapping: <class name="New" table="News" lazy="false"> <id name="NewID"> <generator class="identity" /> </id> <property name="Title" type="String"></property> <property name="Description" type="String"></property> <set name="TagsList" table="New_Tags" lazy="false" inverse="true" cascade="all"> <key column="NewID" /> <many-to-many class="Tag" column="TagID" /> </set> </class> Tag Mapping: <class name="Tag" table="Tags" lazy="false"> <id name="TagID"> <generator class="identity" /> </id> <property name="TagName" type="String"></property> <property name="DateCreated" type="DateTime"></property> <!--inverse="true" has been defined in the "News mapping"--> <set name="NewsList" table="New_Tags" lazy="false" cascade="all"> <key column="TagID" /> <many-to-many class="New" column="NewID" /> </set> </class>

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  • JPA 2.0 @OrderColumn annotation in Hibernate 3.5

    - by peperg
    I'm trynig to use @OrderColumn annotation with Hibernate 3.5 @OneToMany(mappedBy = "parent",fetch=FetchType.EAGER, cascade=CascadeType.ALL) @OrderColumn(name = "pos") private List<Children> childrenCollection; When retrieving data everyting works fine. But I can't make it to reorded elements in List and save new order to database.

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  • MySQL won't use index for query?

    - by Jack Sleight
    I have this table: CREATE TABLE `point` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `siteid` INT(11) NOT NULL, `lft` INT(11) DEFAULT NULL, `rgt` INT(11) DEFAULT NULL, `level` SMALLINT(6) DEFAULT NULL, PRIMARY KEY (`id`), KEY `point_siteid_site_id` (`siteid`), CONSTRAINT `point_siteid_site_id` FOREIGN KEY (`siteid`) REFERENCES `site` (`id`) ON DELETE CASCADE ) ENGINE=INNODB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci And this query: SELECT * FROM `point` WHERE siteid = 1; Which results in this EXPLAIN information: +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | 1 | SIMPLE | point | ALL | point_siteid_site_id | NULL | NULL | NULL | 6 | Using where | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ Question is, why isn't the query using the point_siteid_site_id index?

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  • postgresql drop table

    - by Russell
    I have two tables (tbl and tbl_new) that both use the same sequence (tbl_id_seq). I'd like to drop one of those tables. On tbl, I've removed the modifier "not null default nextval('tbl_id_seq'::regclass)" but that modifier remains on tbl_new. I'm getting the following error: ERROR: cannot drop table tbl because other objects depend on it DETAIL: default for table tbl_new column id depends on sequence tbl_id_seq After reviewing http://www.postgresql.org/docs/9.1/static/sql-droptable.html It looks like there is only CASCADE and RESTRICT as options.

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  • Sort months ( with strings ) algorithm

    - by Oscar Reyes
    I have this months array: ["January", "March", "December" , "October" ] And I want to have it sorted like this: ["January", "March", "October", "December" ] I'm currently thinking in a "if/else" horrible cascade but I wonder if there is some other way to do this. The bad part is that I need to do this only with "string" ( that is, without using Date object or anything like that ) What would be a good approach?

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  • Doctrine join enitiy or null

    - by Medvedev
    I have an entity Entity\User with avatar: /** * @ORM\OneToOne(targetEntity="Entity\Avatar", cascade={"remove"}, fetch="LAZY") */ protected $avatar; And Entity\Message entity /** * @ORM\ManyToOne(targetEntity="Entity\User") */ protected $user; When i try to load all messages with users and avatars. But not all user have avatar. SELECT m, u, a FROM Entity\Message m JOIN m.user u JOIN u.avatar a ORDER BY m.id DESC How to load all messages with user who avatars and who does not have?

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  • Proper way to use multiple stylesheets...so it WORKS?

    - by thatryan
    I am making a site where I need to have styles separated for layout, colors and typography. So basically I took my main style sheet and just copied it 3 times, and in removed everything but coloring from one, everything but type related in another and etc. But when I link to them now there must be some cascade issue or something, because a lot of the type stuff is not being applied. Is there a proper way to do this?

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  • Postgresql constraint

    - by Ryan
    I cannot seem to get this right, I am trying to modify a field to be a foreign key, with cascading delete... what am i doing wrong? ALTER TABLE my_table ADD CONSTRAINT $4 FOREIGN KEY my_field REFERENCES my_foreign_table ON DELETE CASCADE;

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  • How to build a test suite in watir?

    - by karlthorwald
    I have some single watir.rb scripts that use IE and are written in a standard watir way. How do I create a test suite that combines them? Is it possible to enumerate the files that should be included in the test suite? Is it possible to auto include single test files into a test suite by subidr? Can I cascade (include other watir suites in watir suites)?

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  • NHibernate - Saving simple parent-child relationship generates unnecessary selects with assigned id

    - by Alice
    Entities: public class Parent { virtual public long Id { get; set; } virtual public string Description { get; set; } virtual public ICollection<Child> Children { get; set; } } public class Child { virtual public long Id { get; set; } virtual public string Description { get; set; } virtual public Parent Parent { get; set; } } Mappings: public class ParentMap : ClassMap<Parent> { public ParentMap() { Id(x => x.Id).GeneratedBy.Assigned(); Map(x => x.Description); HasMany(x => x.Children) .AsSet() .Inverse() .Cascade.AllDeleteOrphan(); } } public class ChildMap : ClassMap<Child> { public ChildMap() { Id(x => x.Id).GeneratedBy.Assigned(); Map(x => x.Description); References(x => x.Parent) .Not.Nullable() .Cascade.All(); } } and using (var session = sessionFactory.OpenSession()) using (var transaction = session.BeginTransaction()) { var parent = new Parent { Id = 1 }; parent.Children = new HashSet<Child>(); var child1 = new Child { Id = 2, Parent = parent }; var child2 = new Child { Id = 3, Parent = parent }; parent.Children.Add(child1); parent.Children.Add(child2); session.Save(parent); transaction.Commit(); } this codes generates following sql NHibernate: SELECT child_.Id, child_.Description as Descript2_0_, child_.Parent_id as Parent3_0_ FROM [Child] child_ WHERE child_.Id=@p0;@p0 = 2 [Type: Int64 (0)] NHibernate: SELECT child_.Id, child_.Description as Descript2_0_, child_.Parent_id as Parent3_0_ FROM [Child] child_ WHERE child_.Id=@p0;@p0 = 3 [Type: Int64 (0)] NHibernate: INSERT INTO [Parent] (Description, Id) VALUES (@p0, @p1);@p0 = NULL[Type: String (4000)], @p1 = 1 [Type: Int64 (0)] NHibernate: INSERT INTO [Child] (Description, Parent_id, Id) VALUES (@p0, @p1, @p2);@p0 = NULL [Type: String (4000)], @p1 = 1 [Type: Int64 (0)], @p2 = 2 [Type:Int64 (0)] NHibernate: INSERT INTO [Child] (Description, Parent_id, Id) VALUES (@p0, @p1, @p2);@p0 = NULL [Type: String (4000)], @p1 = 1 [Type: Int64 (0)], @p2 = 3 [Type:Int64 (0)] Why are these two selects generated and how can I remove it?

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  • Contour graphs in JS or PHP ?

    - by vince83000
    Hi everybody, For a web application, I have to make a scientific graph. You can see an example here : http://www.ego-network.org/monitoring/plot_deployment.php?glider=eudoxus&deployment=Cascade&posti=4&postj=scaptemperature_lastweek&pposti=4&ppostj=scaoxygen_lastweek&hchk=&defsct=default_scatter I have 2 coordinates, time and depth, and I want the temperature to be represent by a color, exactly like the example. Someone know how to make this king of graph ? Thanks !

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  • How to write my own global lock / unlock functions for PostgreSQL

    - by rafalmag
    I have postgresql (in perlu) function getTravelTime(integer, timestamp), which tries to select data for specified ID and timestamp. If there are no data or if data is old, it downloads them from external server (downloading time ~300ms). Multiple process use this database and this function. There is an error when two process do not find data and download them and try to do an insert to travel_time table (id and timestamp pair have to be unique). I thought about locks. Locking whole table would block all processes and allow only one to proceed. I need to lock only on id and timestamp. pg_advisory_lock seems to lock only in "current session". But my processes uses their own sessions. I tried to write my own lock/unlock functions. Am I doing it right? I use active waiting, how can I omit this? Maybe there is a way to use pg_advisory_lock() as global lock? My code: CREATE TABLE travel_time_locks ( id_key integer NOT NULL, time_key timestamp without time zone NOT NULL, UNIQUE (id_key, time_key) ); ------------ -- Function: mylock(integer, timestamp) DROP FUNCTION IF EXISTS mylock(integer, timestamp) CASCADE; -- Usage: SELECT mylock(1, '2010-03-28T19:45'); -- function tries to do a global lock similar to pg_advisory_lock(key, key) CREATE OR REPLACE FUNCTION mylock(id_input integer, time_input timestamp) RETURNS void AS $BODY$ DECLARE rows int; BEGIN LOOP BEGIN -- active waiting here !!!! :( INSERT INTO travel_time_locks (id_key, time_key) VALUES (id_input, time_input); EXCEPTION WHEN unique_violation THEN CONTINUE; END; EXIT; END LOOP; END; $BODY$ LANGUAGE 'plpgsql' VOLATILE COST 1; ------------ -- Function: myunlock(integer, timestamp) DROP FUNCTION IF EXISTS myunlock(integer, timestamp) CASCADE; -- Usage: SELECT myunlock(1, '2010-03-28T19:45'); -- function tries to do a global unlock similar to pg_advisory_unlock(key, key) CREATE OR REPLACE FUNCTION myunlock(id_input integer, time_input timestamp) RETURNS integer AS $BODY$ DECLARE BEGIN DELETE FROM ONLY travel_time_locks WHERE id_key=id_input AND time_key=time_input; RETURN 1; END; $BODY$ LANGUAGE 'plpgsql' VOLATILE COST 1;

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  • Hibernate Persistence problems with Bean Mapping (Dozer)

    - by BuffaloBuffalo
    I am using Hibernate 3, and having a particular issue when persisting a new Entity which has an association with an existing detached entity. Easiest way to explain this is via code samples. I have two entities, FooEntity and BarEntity, of which a BarEntity can be associated with many FooEntity: @Entity public class FooEntity implements Foo{ @Id private Long id; @ManyToOne(targetEntity = BarEntity.class) @JoinColumn(name = "bar_id", referencedColumnName = "id") @Cascade(value={CascadeType.ALL}) private Bar bar; } @Entity public class BarEntity implements Bar{ @Id private Long id; @OneToMany(mappedBy = "bar", targetEntity = FooEntity.class) private Set<Foo> foos; } Foo and Bar are interfaces that loosely define getters for the various fields. There are corresponding FooImpl and BarImpl classes that are essentially just the entity objects without the annotations. What I am trying to do is construct a new instance of FooImpl, and persist it after setting a number of fields. The new Foo instance will have its 'bar' member set to an existing Bar (runtime being a BarEntity) from the database (retrieved via session.get(..)). After the FooImpl has all of its properties set, Apache Dozer is used to map between the 'domain' object FooImpl and the Entity FooEntity. What Dozer is doing in the background is instantiating a new FooEntity and setting all of the matching fields. BarEntity is cloned as well via instantiation and set the FooEntity's 'bar' member. After this occurs, passing the new FooEntity object to persist. This throws the exception: org.hibernate.PersistentObjectException: detached entity passed to persist: com.company.entity.BarEntity Below is in code the steps that are occurring FooImpl foo = new FooImpl(); //returns at runtime a persistent BarEntity through session.get() Bar bar = BarService.getBar(1L); foo.setBar(bar); ... //This constructs a new instance of FooEntity, with a member 'bar' which itself is a new instance that is detached) FooEntity entityToPersist = dozerMapper.map(foo, FooEntity.class); ... session.persist(entityToPersist); I have been able to resolve this issue by either removing or changing the @Cascade annotation, but that limits future use for say adding a new Foo with a new Bar attached to it already. Is there some solution here I am missing? I would be surprised if this issue hasn't been solved somewhere before, either by altering how Dozer Maps the children of Foo or how Hibernate reacts to a detached Child Entity.

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  • Default subclass objects in Sqlalchemy?

    - by Timmy
    im using the example from the pylons book orm.mapper(Comment, comment_table) orm.mapper(Tag, tag_table) orm.mapper(Nav, nav_table, polymorphic_on=nav_table.c.type, polymorphic_identity='nav') orm.mapper(Section, section_table, inherits=Nav, polymorphic_identity='section') orm.mapper(Page, page_table, inherits=Nav, polymorphic_identity='page', properties={ 'comments':orm.relation(Comment, backref='page', cascade='all'), 'tags':orm.relation(Tag, secondary=pagetag_table) }) i am mostly copying from this, but is there a simple way have a default Page that gets referenced, but if users requests a change, create a new Page object? thanks i want something similar to this class DefaultPage(Page): __init__(self): self.a = a self.b = b self.c = c orm.mapper(DefaultPage, None, inherits=Nav, yada yada )

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  • How do I delete orphan entities using hibernate and JPA on a many-to-many relationship?

    - by user368453
    I want to delete orphan entities using hibernate and JPA on a many-to-many relationship but all that I found was this atibute the attribute. org.hibernate.annotations.CascadeType.DELETE_ORPHAN ( i.e. @Cascade(value={org.hibernate.annotations.CascadeType.DELETE_ORPHAN) ), which works only for one-to-many relationships. I want to know if I can delete the orphan ones on my many-to-many relationship. I´d be happy if anyone could help me... Thanks in advance !

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  • hibernate many to many only save the new object and between table

    - by Joe
    I have the following tables: Student Student_Course Course Now when I create a student I only want to create a user and add a row to student_course. The "problem" I have is that when I set the set of courses in Student to cascade="save-update" that an update is also invoked on course. I was wondering if there was a way to prevent this.

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  • Phpmyadmin mysql foreign key help

    - by Alan
    Hey guys i'm using phpmyadmin (php & mysql) and i'm having alot of trouble linking the tables using foreign keys. I'm getting negative values for the field countyId (which is the foriegn key). However it is linking to my other table fine and it's cascading fine. So when I go to add data there will be a drop box for the CountyId and the vlaues will look something like this, " -1 1- " Here is my alter statement, ALTER TABLE Baronies ADD FOREIGN KEY (CountyId) REFERENCES Counties (CountyId) ON DELETE CASCADE

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  • delete hibernate entity question?

    - by ylazez
    i want to delete a row and cascade all foreign keys in hibernate i am new to hibernate and i want to know if there's a method to delete an entity session.delete(); like the session.save and session.update methods in hibernate?

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  • OpenCV haar training for static image

    - by Evl-ntnt
    I trying to train haar cascade classificator for card suite detection (which no rotation and has no distortion on image) For example I have file Clubs.png which contents clubs image on white background 20x20 pixels This tutorial is so tangled http://note.sonots.com/SciSoftware/haartraining.html My image varies only in sizes, no distortion or angling. Which commands I must enter in aim to get Clubs.xml file?

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  • Generate Delete Statement From Foreign Key Relationships in SQL 2008 ?

    - by Element
    Is it possible via script/tool to generate a delete statement based on the tables fk relations. i.e. I have the table: DelMe(ID) and there are 30 tables with fk references to its ID that I need to delete first, is there some tool/script that I can run that will generate the 30 delete statements based on the FK relations for me ? (btw I know about cascade delete on the relations, I can't use it in this existing db) I'm using Microsoft SQL Server 2008

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  • C#: Optional Parameters - Pros and Pitfalls

    - by James Michael Hare
    When Microsoft rolled out Visual Studio 2010 with C# 4, I was very excited to learn how I could apply all the new features and enhancements to help make me and my team more productive developers. Default parameters have been around forever in C++, and were intentionally omitted in Java in favor of using overloading to satisfy that need as it was though that having too many default parameters could introduce code safety issues.  To some extent I can understand that move, as I’ve been bitten by default parameter pitfalls before, but at the same time I feel like Java threw out the baby with the bathwater in that move and I’m glad to see C# now has them. This post briefly discusses the pros and pitfalls of using default parameters.  I’m avoiding saying cons, because I really don’t believe using default parameters is a negative thing, I just think there are things you must watch for and guard against to avoid abuses that can cause code safety issues. Pro: Default Parameters Can Simplify Code Let’s start out with positives.  Consider how much cleaner it is to reduce all the overloads in methods or constructors that simply exist to give the semblance of optional parameters.  For example, we could have a Message class defined which allows for all possible initializations of a Message: 1: public class Message 2: { 3: // can either cascade these like this or duplicate the defaults (which can introduce risk) 4: public Message() 5: : this(string.Empty) 6: { 7: } 8:  9: public Message(string text) 10: : this(text, null) 11: { 12: } 13:  14: public Message(string text, IDictionary<string, string> properties) 15: : this(text, properties, -1) 16: { 17: } 18:  19: public Message(string text, IDictionary<string, string> properties, long timeToLive) 20: { 21: // ... 22: } 23: }   Now consider the same code with default parameters: 1: public class Message 2: { 3: // can either cascade these like this or duplicate the defaults (which can introduce risk) 4: public Message(string text = "", IDictionary<string, string> properties = null, long timeToLive = -1) 5: { 6: // ... 7: } 8: }   Much more clean and concise and no repetitive coding!  In addition, in the past if you wanted to be able to cleanly supply timeToLive and accept the default on text and properties above, you would need to either create another overload, or pass in the defaults explicitly.  With named parameters, though, we can do this easily: 1: var msg = new Message(timeToLive: 100);   Pro: Named Parameters can Improve Readability I must say one of my favorite things with the default parameters addition in C# is the named parameters.  It lets code be a lot easier to understand visually with no comments.  Think how many times you’ve run across a TimeSpan declaration with 4 arguments and wondered if they were passing in days/hours/minutes/seconds or hours/minutes/seconds/milliseconds.  A novice running through your code may wonder what it is.  Named arguments can help resolve the visual ambiguity: 1: // is this days/hours/minutes/seconds (no) or hours/minutes/seconds/milliseconds (yes) 2: var ts = new TimeSpan(1, 2, 3, 4); 3:  4: // this however is visually very explicit 5: var ts = new TimeSpan(days: 1, hours: 2, minutes: 3, seconds: 4);   Or think of the times you’ve run across something passing a Boolean literal and wondered what it was: 1: // what is false here? 2: var sub = CreateSubscriber(hostname, port, false); 3:  4: // aha! Much more visibly clear 5: var sub = CreateSubscriber(hostname, port, isBuffered: false);   Pitfall: Don't Insert new Default Parameters In Between Existing Defaults Now let’s consider a two potential pitfalls.  The first is really an abuse.  It’s not really a fault of the default parameters themselves, but a fault in the use of them.  Let’s consider that Message constructor again with defaults.  Let’s say you want to add a messagePriority to the message and you think this is more important than a timeToLive value, so you decide to put messagePriority before it in the default, this gives you: 1: public class Message 2: { 3: public Message(string text = "", IDictionary<string, string> properties = null, int priority = 5, long timeToLive = -1) 4: { 5: // ... 6: } 7: }   Oh boy have we set ourselves up for failure!  Why?  Think of all the code out there that could already be using the library that already specified the timeToLive, such as this possible call: 1: var msg = new Message(“An error occurred”, myProperties, 1000);   Before this specified a message with a TTL of 1000, now it specifies a message with a priority of 1000 and a time to live of -1 (infinite).  All of this with NO compiler errors or warnings. So the rule to take away is if you are adding new default parameters to a method that’s currently in use, make sure you add them to the end of the list or create a brand new method or overload. Pitfall: Beware of Default Parameters in Inheritance and Interface Implementation Now, the second potential pitfalls has to do with inheritance and interface implementation.  I’ll illustrate with a puzzle: 1: public interface ITag 2: { 3: void WriteTag(string tagName = "ITag"); 4: } 5:  6: public class BaseTag : ITag 7: { 8: public virtual void WriteTag(string tagName = "BaseTag") { Console.WriteLine(tagName); } 9: } 10:  11: public class SubTag : BaseTag 12: { 13: public override void WriteTag(string tagName = "SubTag") { Console.WriteLine(tagName); } 14: } 15:  16: public static class Program 17: { 18: public static void Main() 19: { 20: SubTag subTag = new SubTag(); 21: BaseTag subByBaseTag = subTag; 22: ITag subByInterfaceTag = subTag; 23:  24: // what happens here? 25: subTag.WriteTag(); 26: subByBaseTag.WriteTag(); 27: subByInterfaceTag.WriteTag(); 28: } 29: }   What happens?  Well, even though the object in each case is SubTag whose tag is “SubTag”, you will get: 1: SubTag 2: BaseTag 3: ITag   Why?  Because default parameter are resolved at compile time, not runtime!  This means that the default does not belong to the object being called, but by the reference type it’s being called through.  Since the SubTag instance is being called through an ITag reference, it will use the default specified in ITag. So the moral of the story here is to be very careful how you specify defaults in interfaces or inheritance hierarchies.  I would suggest avoiding repeating them, and instead concentrating on the layer of classes or interfaces you must likely expect your caller to be calling from. For example, if you have a messaging factory that returns an IMessage which can be either an MsmqMessage or JmsMessage, it only makes since to put the defaults at the IMessage level since chances are your user will be using the interface only. So let’s sum up.  In general, I really love default and named parameters in C# 4.0.  I think they’re a great tool to help make your code easier to read and maintain when used correctly. On the plus side, default parameters: Reduce redundant overloading for the sake of providing optional calling structures. Improve readability by being able to name an ambiguous argument. But remember to make sure you: Do not insert new default parameters in the middle of an existing set of default parameters, this may cause unpredictable behavior that may not necessarily throw a syntax error – add to end of list or create new method. Be extremely careful how you use default parameters in inheritance hierarchies and interfaces – choose the most appropriate level to add the defaults based on expected usage. Technorati Tags: C#,.NET,Software,Default Parameters

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  • MySQL Cluster 7.3 Labs Release – Foreign Keys Are In!

    - by Mat Keep
    0 0 1 1097 6254 Homework 52 14 7337 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary (aka TL/DR): Support for Foreign Key constraints has been one of the most requested feature enhancements for MySQL Cluster. We are therefore extremely excited to announce that Foreign Keys are part of the first Labs Release of MySQL Cluster 7.3 – available for download, evaluation and feedback now! (Select the mysql-cluster-7.3-labs-June-2012 build) In this blog, I will attempt to discuss the design rationale, implementation, configuration and steps to get started in evaluating the first MySQL Cluster 7.3 Labs Release. Pace of Innovation It was only a couple of months ago that we announced the General Availability (GA) of MySQL Cluster 7.2, delivering 1 billion Queries per Minute, with 70x higher cross-shard JOIN performance, Memcached NoSQL key-value API and cross-data center replication.  This release has been a huge hit, with downloads and deployments quickly reaching record levels. The announcement of the first MySQL Cluster 7.3 Early Access lab release at today's MySQL Innovation Day event demonstrates the continued pace in Cluster development, and provides an opportunity for the community to evaluate and feedback on new features they want to see. What’s the Plan for MySQL Cluster 7.3? Well, Foreign Keys, as you may have gathered by now (!), and this is the focus of this first Labs Release. As with MySQL Cluster 7.2, we plan to publish a series of preview releases for 7.3 that will incrementally add new candidate features for a final GA release (subject to usual safe harbor statement below*), including: - New NoSQL APIs; - Features to automate the configuration and provisioning of multi-node clusters, on premise or in the cloud; - Performance and scalability enhancements; - Taking advantage of features in the latest MySQL 5.x Server GA. Design Rationale MySQL Cluster is designed as a “Not-Only-SQL” database. It combines attributes that enable users to blend the best of both relational and NoSQL technologies into solutions that deliver web scalability with 99.999% availability and real-time performance, including: Concurrent NoSQL and SQL access to the database; Auto-sharding with simple scale-out across commodity hardware; Multi-master replication with failover and recovery both within and across data centers; Shared-nothing architecture with no single point of failure; Online scaling and schema changes; ACID compliance and support for complex queries, across shards. Native support for Foreign Key constraints enables users to extend the benefits of MySQL Cluster into a broader range of use-cases, including: - Packaged applications in areas such as eCommerce and Web Content Management that prescribe databases with Foreign Key support. - In-house developments benefiting from Foreign Key constraints to simplify data models and eliminate the additional application logic needed to maintain data consistency and integrity between tables. Implementation The Foreign Key functionality is implemented directly within MySQL Cluster’s data nodes, allowing any client API accessing the cluster to benefit from them – whether using SQL or one of the NoSQL interfaces (Memcached, C++, Java, JPA or HTTP/REST.) The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL In addition, the MySQL Cluster implementation supports the online adding and dropping of Foreign Keys, ensuring the Cluster continues to serve both read and write requests during the operation. An important difference to note with the Foreign Key implementation in InnoDB is that MySQL Cluster does not support the updating of Primary Keys from within the Data Nodes themselves - instead the UPDATE is emulated with a DELETE followed by an INSERT operation. Therefore an UPDATE operation will return an error if the parent reference is using a Primary Key, unless using CASCADE action, in which case the delete operation will result in the corresponding rows in the child table being deleted. The Engineering team plans to change this behavior in a subsequent preview release. Also note that when using InnoDB "NO ACTION" is identical to "RESTRICT". In the case of MySQL Cluster “NO ACTION” means “deferred check”, i.e. the constraint is checked before commit, allowing user-defined triggers to automatically make changes in order to satisfy the Foreign Key constraints. Configuration There is nothing special you have to do here – Foreign Key constraint checking is enabled by default. If you intend to migrate existing tables from another database or storage engine, for example from InnoDB, there are a couple of best practices to observe: 1. Analyze the structure of the Foreign Key graph and run the ALTER TABLE ENGINE=NDB in the correct sequence to ensure constraints are enforced 2. Alternatively drop the Foreign Key constraints prior to the import process and then recreate when complete. Getting Started Read this blog for a demonstration of using Foreign Keys with MySQL Cluster.  You can download MySQL Cluster 7.3 Labs Release with Foreign Keys today - (select the mysql-cluster-7.3-labs-June-2012 build) If you are new to MySQL Cluster, the Getting Started guide will walk you through installing an evaluation cluster on a singe host (these guides reflect MySQL Cluster 7.2, but apply equally well to 7.3) Post any questions to the MySQL Cluster forum where our Engineering team will attempt to assist you. Post any bugs you find to the MySQL bug tracking system (select MySQL Cluster from the Category drop-down menu) And if you have any feedback, please post them to the Comments section of this blog. Summary MySQL Cluster 7.2 is the GA, production-ready release of MySQL Cluster. This first Labs Release of MySQL Cluster 7.3 gives you the opportunity to preview and evaluate future developments in the MySQL Cluster database, and we are very excited to be able to share that with you. Let us know how you get along with MySQL Cluster 7.3, and other features that you want to see in future releases. * Safe Harbor Statement This information is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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