That clears it all up, thank you. Baz
On Tue, Jun 2, 2009 at 1:53 PM, <[email protected]> wrote: > > What you're describing is the JDO layer that's implemented on top of > the GAE datastore low-level API; the JDO layer has the concept of > relationships, the GAE low-level API doesn't. It looks like the JDO > layer implements relationships by managing keys "under the covers" > exactly as I described previously. Take a look at this page: > > http://code.google.com/appengine/docs/java/datastore/relationships.html > > What they describe as "unowned relationships" is exactly what I > described previously for my BlogCFC implementation--the programmer > manages the keys manually himself. What they describe as "owned > relationships" are a set of conventions and persistence annotations > that let the JDO layer handle the key management automatically (again, > very similar to what I described for a future enhancement for BD, so > we have a good model to mimic). > > The only limit I can find is that a datastore Entity (the fundamental > unit of storage in the GAE datastore) is limited to 1MB. Each > "relationshp" is basically a Key, so I'd guess you can have as many as > you want until you break the 1MB entity limit. Even then, the JDO > layer (or BD CFC persistence layer) could exceed that limit by > "chaining" entities. Same for strings--you're limited to 1MB unless > you implemented some sort of entity chaining mechanism to exceed this > limit. > > Vince > > On Jun 2, 4:02 pm, Baz <[email protected]> wrote: > > > > 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 -- 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 !! -~----------~----~----~----~------~----~------~--~---
