The GAE datastore has the concept of relationships. It is implemented by saving a collection of the related objects in a specific attribute. So if you have a blog that has comments. You store a collection of comment objects inside the blog attribute called 'comments'. If a second blog entry references the same comment (which is wierd in this context I know) then that comment is the same root comment for both entries. A change to that comment will be reflected in both entries.
So I was just wondering (couldn't find it in the docs) if you knew what the limit was of related objects for a given attribute. Can you have 1000 comments stored in the "Comments" attribute of the "BlogPost" object? What about 10,000 or a million? there must be some limit. Similarly whats the longest string you can store in a string field - one mb? Baz On Tue, Jun 2, 2009 at 11:53 AM, <[email protected]> wrote: > > I'm not sure what the definitions of "relationships" and "attribute" > are in this context. Can you elaborate on the question? > > Vince > > On Jun 2, 1:43 pm, Baz <[email protected]> wrote: > > > > Do you know the max number of relationships allowed in 1 attribute? > > > > Baz > > > > > > > > On Tue, Jun 2, 2009 at 10:24 AM, <[email protected]> wrote: > > > > > Yes, obviously when you get to that extreme (10,000 CFC instances) the > > > developer is going to have to get smart about designing and accessing > > > the datastore. Note that the CFQUERY and GoogleQuery syntax supports a > > > "range" clause. When you get up to 10,000 entries, it might start to > > > make more sense to query the datastore ("select from blogEntry where > > > category = '#categoryName#' range 1,100") rather than doing batch > > > reads based on keys. > > > > > Vince > > > > > On Jun 2, 1:06 pm, Baz <[email protected]> wrote: > > > > > > > Instead, I store the Google keys for the blogEntry.cfc instances > > > > > within the blogCategory.cfc and read the blogEntry.cfc instances > only > > > > > when needed. > > > > > > If you had 10,000 blog entries or more this will probably break the > app > > > > because you would reach the attribute length limit (which I can't > seem to > > > > find, what is the max attribute size?). In cases like this, when it > comes > > > to > > > > OO db's, I think it is recommended to choose the smaller side of the > > > > relationship to store your data. So instead of storing all posts that > a > > > > category is related too in the category object, you would store all > > > > categories a post is related to in the post object - there will only > be a > > > > few categories per post. To retrieve all posts for a certain category > > > then, > > > > you would do: > > > > > > SELECT FROM Post WHERE Category = 'App Engine' > > > > > > Baz- Hide quoted text - > > > > - Show quoted text - > > > --~--~---------~--~----~------------~-------~--~----~ Open BlueDragon Public Mailing List http://groups.google.com/group/openbd?hl=en official site @ http://www.openbluedragon.org/ !! save a network - trim replies before posting !! -~----------~----~----~----~------~----~------~--~---
