Re: Implementation for Deleting Entities from an Aggregate
"Paul Rayner [email protected] [domaindrivendesign]" <[email protected]> Fri, 2 Sep 2016 17:46:05 -0600
| Newsgroups | gmane.comp.programming.domain-driven-design |
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| Message-ID | <CAKKp0qhOW8scAS=3DaFxj9wtkb-qdyipjuWFvHhvkCWOLxoz2Q@mail.gmail.com> |
--94eb2c07cf1473aa61053b8ef14b Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable I would explore making Comments its own aggregate. On Fri, Sep 2, 2016 at 12:35 PM, Caleb Cushing [email protected] [domaindrivendesign] <[email protected]> wrote: > > > are you using an ORM? that can matter, also does your system need to be > distributed? is there any polyglot persistence? using events is fine but > it's one of the more complicated ways of removing an entity from the > aggregate, imho. Some complex situations do require this though. > > On Fri, Sep 2, 2016 at 12:52 PM [email protected] > [domaindrivendesign] <[email protected]> wrote: > >> >> >> Greetings, >> >> >> I have modeled a simple Social Network, but I am running into a bit of a= n >> implementation conundrum, when it comes to figuring out the best way to >> delete a specific Entity from within an Aggregate. I was hoping that I >> might be able to find some guidance. >> >> >> Since my model is a fairly obvious one, I can jump right into my issue. >> What I have is a Post Aggregate that can contain multiple Comment >> Entities. A well-trafficked Post can contain hundred, or even thousands= , >> of Comments. Part of the business requirements is that a User can remov= e >> his/her Comment from a Post. The scenario also holds true for edits to = a >> Comment, so I imagine that I am facing the same issue with each. What t= hat >> issue is, would be what is the best implementation route for removing a >> single Comment on a Post, considering the potentially large number of >> Comments that can exist? >> >> >> The potential solution that I see would be: >> >> >> - A RemoveComment command is used by an Application Service, >> containing the identifier of the Post that Comment belongs to, as wel= l as >> the identifier of the Comment, itself. >> - The Command Handler will invoke the RemoveComment() method on the >> Post Entity. >> - The RemoveComment() method will raise a CommentRemoved Event. >> - The Event Handler will invoke a Domain Service to handle the CRUD-y >> operation. >> >> On the surface, at least, I feel that this makes sense. My issue with >> it, though, is that I would need to load the Post to invoke the >> RemoveComment() method, which means that I incur a load operation before= I >> can remove. If I have hundreds, or thousands, of Comments on a Post, it >> seems excessive to want to load them all to just delete one. I suppose >> that I can have the Aggregate Root not load Comments as part of the init= ial >> Get() operation, and expose a LoadComments() method on the Aggregate Roo= t. >> I will likely need to do something like that, anyhow, because I would no= t >> want to be incurring the performance penalty for loading and transferrin= g >> every Comment when someone first views a Post. >> >> If I could get some feedback as to if this is a sane approach, it would >> be most appreciated. >> >> Thanks! >> >> Joseph >> >> >> -- > Caleb Cushing > > http://xenoterracide.com > >=20 > --94eb2c07cf1473aa61053b8ef14b Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <head> <style type=3D"text/css"> <!-- /* start of attachment style */ .ygrp-photo-title{ clear: both; font-size: smaller; height: 15px; overflow: hidden; text-align: center; width: 75px; } div.ygrp-photo{ background-position: center; background-repeat: no-repeat; background-color: white; border: 1px solid black; height: 62px; width: 62px; } div.photo-title=20 a, div.photo-title a:active, div.photo-title a:hover, div.photo-title a:visited { text-decoration: none;=20 } div.attach-table div.attach-row { clear: both; } div.attach-table div.attach-row div { float: left; /* margin: 2px;*/ } p { clear: both; padding: 15px 0 3px 0; overflow: hidden; } div.ygrp-file { width: 30px; valign: middle; } div.attach-table div.attach-row div div a { text-decoration: none; } div.attach-table div.attach-row div div span { font-weight: normal; } div.ygrp-file-title { font-weight: bold; } /* end of attachment style */ --> </style> </head> <html> <head> <style type=3D"text/css"> <!-- #ygrp-mkp { border: 1px solid #d8d8d8; font-family: Arial; margin: 10px 0; padding: 0 10px; } #ygrp-mkp hr { border: 1px solid #d8d8d8; } #ygrp-mkp #hd { color: #628c2a; font-size: 85%; font-weight: 700; line-height: 122%; margin: 10px 0; } #ygrp-mkp #ads { margin-bottom: 10px; } #ygrp-mkp .ad { padding: 0 0; } #ygrp-mkp .ad p { margin: 0; } #ygrp-mkp .ad a { color: #0000ff; text-decoration: none; } --> </style> </head> <body> <!-- |**|begin egp html banner|**| --> <br><br> <!-- |**|end egp html banner|**| --> <div dir=3D"ltr">I would explore making Comments its own aggregate.=C2=A0</= div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Fri, Sep 2= , 2016 at 12:35 PM, Caleb Cushing <a href=3D"mailto:[email protected]= ">[email protected]</a> [domaindrivendesign] <span dir=3D"ltr"><<a= href=3D"mailto:[email protected]" target=3D"_blank">domai= [email protected]</a>></span> wrote:<br><blockquote class=3D= "gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding= -left:1ex"> <u></u> =20 <div style=3D"background-color:#fff"> <span style=3D"display:none">=C2=A0</span> <div> <div> <div> =20=20=20=20=20=20 =20=20=20=20=20=20 <p></p><div dir=3D"ltr">are you using an ORM? that can matter, also d= oes your system need to be distributed? is there any polyglot persistence? = using events is fine but it's one of the more complicated ways of remov= ing an entity from the aggregate, imho. Some complex situations do require = this though.</div><span class=3D""><br><div class=3D"gmail_quote"><div dir= =3D"ltr">On Fri, Sep 2, 2016 at 12:52 PM <a href=3D"mailto:joseph.ferris@gm= ail.com" target=3D"_blank">[email protected]</a> [domaindrivendesign]= <<a href=3D"mailto:[email protected]" target=3D"_blank= ">domaindrivendesign@<wbr>yahoogroups.com</a>> wrote:<br></div><blockquo= te class=3D"gmail_quote" style=3D"border-left:1px #ccc solid"> =20=20=20=20=20=20=20=20 <div> <br><br> <p><span>Greetings,</span></p><p><span><br></span></p><p><span>I have model= ed a simple Social Network, but I am running into a bit of an implementatio= n conundrum, when it comes to figuring out the best way to delete a specifi= c Entity from within an Aggregate.=C2=A0 I was hoping that I might be able = to find some guidance.</span></p><p><span><br></span></p><p><span>Since my = model is a fairly obvious one, I can jump right into my issue.=C2=A0 What I= have is a Post Aggregate that can contain multiple Comment Entities.=C2=A0= A well-trafficked Post can contain hundred, or even thousands, of Comments= .=C2=A0 Part of the business requirements is that a User can remove his/her= Comment from a Post.=C2=A0 The scenario also holds true for edits to a Com= ment, so I imagine that I am facing the same issue with each.=C2=A0 What th= at issue is, would be what is the best implementation route for removing a = single Comment on a Post, considering the potentially large number of Comme= nts that can exist?</span></p><p><span><br></span></p><p><span>The potentia= l solution that I see would be:</span></p><p></p><ul><li>A RemoveComment co= mmand is used by an Application Service, containing the identifier of the P= ost that Comment belongs to, as well as the identifier of the Comment, itse= lf.</li><li>The Command Handler will invoke the RemoveComment() method on t= he Post Entity.</li><li>The RemoveComment() method will raise a CommentRemo= ved Event.</li><li>The Event Handler will invoke a Domain Service to handle= the CRUD-y operation.</li></ul><div>On the surface, at least, I feel that = this makes sense.=C2=A0 My issue with it, though, is that I would need to l= oad the Post to invoke the RemoveComment() method, which means that I incur= a load operation before I can remove.=C2=A0 If I have hundreds, or thousan= ds, of Comments on a Post, it seems excessive to want to load them all to j= ust delete one.=C2=A0 I suppose that I can have the Aggregate Root not load= Comments as part of the initial Get() operation, and expose a LoadComments= () method on the Aggregate Root.=C2=A0 I will likely need to do something l= ike that, anyhow, because I would not want to be incurring the performance = penalty for loading and transferring every Comment when someone first views= a Post.</div><div><br></div><div>If I could get some feedback as to if thi= s is a sane approach, it would be most appreciated.</div><div><br></div><di= v>Thanks!</div><div><br></div><div>Joseph</div> <br> <br> <div width=3D"1" style=3D"color:white"></div> <p></p></div></blockquote></div></span><div dir=3D"ltr">-- <br></div><div d= ata=3D"https://ci4.googleusercontent.com/proxy/CpYzkcDKjPf-NqFCSu4GBqoQ_5P1= dDkfTMWPGDqglo-e-uanL4gIS02e2U0=3Ds0-d-e1-ft#http://gmail_signature"><div d= ir=3D"ltr">Caleb Cushing<div><br></div><div><a href=3D"http://xenoterracide= .com" target=3D"_blank">http://xenoterracide.com</a></div></div></div> <p></p> </div> =20=20=20=20=20 =20=20=20=20 <div style=3D"color:#fff;min-height:0"></div> </div> =20=20 </blockquote></div><br></div> <!-- |**|begin egp html banner|**| --> <br> <br> <!-- |**|end egp html banner|**| --> <div width=3D"1" style=3D"color: white; 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