Re: [google-appengine] Entity groups - does work on a child lock the parent, and vice versa?
From the Python documentation:
When you use the App Engine datastore, every attempt to create,
update, or delete an entity happens in a transaction.
This means, I think, that GAE will perform/create a transaction for
you, in the API, if the put() code is not already inside a
transaction.
So you don't need to code a transaction to create a child object, GAE
will do that for you.
# no need for a transaction here.
Grok(parent=myFoo).put() # python syntax
Code the transaction yourself if you need to modify multiple objects
in the entity group.
2011/1/13 Stephen Johnson onepagewo...@gmail.com:
From the documentation:
While an app is applying changes to entities in an entity group, all other
attempts to update any entity in the group fail at commit time. Because of
this design, using entity groups limits the number of concurrent writes you
can do on any entity in that group. When a transaction starts, App Engine
uses optimistic concurrency control by checking the last update time for the
entity group. Upon commiting a transaction for an entity group, App Engine
again checks the last update time for the entity group. If it has changed
since our initial check, we throw an exception. For an explanation of entity
groups, see Entity Groups.
On Thu, Jan 13, 2011 at 10:48 AM, Mark mar...@gmail.com wrote:
Hi,
Let's say we have an entity group hierarchy like this:
Foo
|
--- Grok
Foo is the entity parent. Any time I add a Grok instance to the
datastore, does the parent Foo instance have to be locked? Example:
Transaction tx = pm.currentTransaction();
try {
tx.begin();
Grok grok = new Grok();
pm.makePersistent(grok);
tx.commit(); // will a parent Foo get locked now?
}
finally {
if (tx.isActive()) {
tx.rollback();
}
I guess the same question then - if I'm performing a transaction on
the parent Foo, will all its Grok instances be locked?
Thanks
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[google-appengine] Entity groups - does work on a child lock the parent, and vice versa?
Hi,
Let's say we have an entity group hierarchy like this:
Foo
|
--- Grok
Foo is the entity parent. Any time I add a Grok instance to the
datastore, does the parent Foo instance have to be locked? Example:
Transaction tx = pm.currentTransaction();
try {
tx.begin();
Grok grok = new Grok();
pm.makePersistent(grok);
tx.commit(); // will a parent Foo get locked now?
}
finally {
if (tx.isActive()) {
tx.rollback();
}
I guess the same question then - if I'm performing a transaction on
the parent Foo, will all its Grok instances be locked?
Thanks
--
You received this message because you are subscribed to the Google Groups
Google App Engine group.
To post to this group, send email to google-appengine@googlegroups.com.
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For more options, visit this group at
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Re: [google-appengine] Entity groups - does work on a child lock the parent, and vice versa?
From the documentation:
While an app is applying changes to entities in an entity group, all other
attempts to update any entity in the group fail at commit time. Because of
this design, using entity groups limits the number of concurrent writes you
can do on any entity in that group. When a transaction starts, App Engine
uses optimistic concurrency
controlhttp://en.wikipedia.org/wiki/Optimistic_concurrency_controlby
checking the last update time for the entity group. Upon commiting a
transaction for an entity group, App Engine again checks the last update
time for the entity group. If it has changed since our initial check, we
throw an exception. For an explanation of entity groups, see Entity
Groupshttp://code.google.com/appengine/docs/java/datastore/transactions.html#Entity_Groups
.
On Thu, Jan 13, 2011 at 10:48 AM, Mark mar...@gmail.com wrote:
Hi,
Let's say we have an entity group hierarchy like this:
Foo
|
--- Grok
Foo is the entity parent. Any time I add a Grok instance to the
datastore, does the parent Foo instance have to be locked? Example:
Transaction tx = pm.currentTransaction();
try {
tx.begin();
Grok grok = new Grok();
pm.makePersistent(grok);
tx.commit(); // will a parent Foo get locked now?
}
finally {
if (tx.isActive()) {
tx.rollback();
}
I guess the same question then - if I'm performing a transaction on
the parent Foo, will all its Grok instances be locked?
Thanks
--
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Google App Engine group.
To post to this group, send email to google-appengine@googlegroups.com.
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.
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