Total Storage Data Limited Question
BarrenTeam
Stephen Johnson
Even though you only have one composite index on __key__ (desc), there
are also other indexes you may have. For example, every __key__ has
an ascending index and every property that you have indexed (which may
have been done automatically for you unless you specified otherwise
for example if you're using JDO) will have 2 (yes 2) indexes created
(one ascending and one descending). What's more if those entries are
lists then they will have 1 index entry for each item in the list. So,
ten items in an indexed list field will have 20 index entries (10 for
the ascending index and 10 for the descending index). Also, remember
that the data in the field is copied into the index entry so if you
have indexes on long text fields then you've got problems. Also, if
you are doing a lot of updates/deletes then you can run out of storage
space because AppEngine does soft deletes where it marks items as
deleted and then periodically cleans them up. I myself see that it
takes about 24 hours for storage to be reclaimed and reported in the
dashboard but there has never been any official word that I know of on
how often this happens.
Hope this helps,
Stephen
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BarrenTeam
Stephen Johnson
on properties you don't want indexed.
@Extension(vendorName = "datanucleus", key = "gae.unindexed", value="true")
One caveat is that if you plan to use that property as a composite
index then you'll need to have that property indexed. Unindexed
properties/fields can't be used as part of a composite index.
Also, to reduce you database usage, make sure to use short entity
names (I use 2 letter names) and short property names (I use 3
letter). For properties you can use
@Column(name="abc")
to specify a shorter name for the datastore while using a longer name
in your code, thus putting it all together it will look like
@Persistent
@Column(name="abc")
@Extension(vendorName = "datanucleus", key = "gae.unindexed", value="true")
private int
heyIAmAReallyLongNameButWhoCaresCuzTheDatastoreWillUseTheShortName =
0;
As for your #2 question, I'm not sure what you may have been
experiencing there. But as a warning if you do lots and lots and lots
and lots of deletes you can run in to a situation where there are so
many soft deleted entries in your indexes that when you query the
index the query will timeout because it needs to scan past all those
entries. This has happened to people for example that have deleted all
the entries in a particular entity kind and then aren't able to query
for a period of time. No one but the Googlers really know what's going
on at the lowest levels and so it's kind of a black box at figuring
out some of these side effects that you might encounter. Let me know
if you have any other questions and I'll do my best to try to help out
as will others I'm sure.
Stephen
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BarrenTeam
Stephen Johnson
On Thu, Jul 7, 2011 at 6:24 AM, BarrenTeam <barre...@gmail.com> wrote:
> Thank you again Stephen! :)
> We have solved many of our doubts thanks to your answers :)
>
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