initialValue=N) for non-zero values of N. This is complicated. Depot used to
"initialize" value generators pretty much every time a table schema was
migrated. For TableValueGenerator it could just NOOP if the proper row was in
the sequence table. IdentityValueGenerator was just broken and ignored any
request to configure an initialValue, so it never did anything.
First I looked into preserving this frequent reinitialization behavior, but it
turns out that it's not possible to read the current value of a sequence in
Postgres without modifying it. So trying to do something like:
SELECT setval('"FooRecord_fooId_seq"', max(currval('"FooRecord_fooId_seq"'),
cast(initialValue as bigint)));
doesn't work because you can't call currval() without first having called
nextval() (and furthermore when you do that, the Postgres client grabs a block
of sequence values for this client so that multiple clients can add rows to a
table without having to coordinate with the server and one another to assign a
new value every time a row is inserted).
So I changed Depot around to not reinitialize value generators unless it really
believes that the column in question is newly added. We can't rely on our own
auto-column creation because it's possible for someone to create a column
through a custom entity migration, so instead we just keep track of what
columns we had before we started all of our migrations (automatic and custom)
and check to see if there are any new columns after all is said and done and if
any of those have value generators, we "create" them.
This allows us to just setval() the sequence to the desired initial value
without first reading it.
This all fails if someone renames a column with a value generator. The column
will appear to Depot to be new and it will try to recreate the value generator
on that column. For TableValueGenerators that will basically NOOP and
everything will be just like it was before. For IdentityValueGenerators,
because of the way that Postgres magically creates a tablename_columnname_seq
sequence for identity value generation, when the column is renamed, the
sequence will retain the old column name and when Depot goes to try to setval()
the sequence based on the new column name, it won't exist and the migration
will fail. So at least we're not silently reinitializing the value generator to
its initial value when a column (with an identity value generator) is renamed.
We also don't try to do anything if the initialValue is not 1 (the default). So
we avoid failing or doing anything wrong if those kinds of columns are renamed.
So we only fail if someone renames a column with an identity value generator
with a non-default initial value. Since one can only put a value generator on a
primary key field and an identity value generator generally means you have
something simple like FooRecord with fooId. This means someone is renaming
their simple auto incrementing primary key field which seems extremely unlikely
because those columns usually have an obvious name that you're never going to
change. No problem!
I also haven't fixed this problem for MySQL yet. I can only handle so much
database befuckaroundery in one go.
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table that had field generators on its primary key. The code just blindly
overwrite the supplied primary key and ran the generators anyway.
We now only run the generators if the record has no primary key. This means we
can't use field generators on non-primary-key fields, but I'm not sure we ever
meant to support that in the first place.
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when we're doing a query with primary keys provided by a random caller. We have
know idea where they got those keys or where they have been before we got our
filthy mitts on them.
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fields. Maybe Zell will remind me why this was disallowed, but it seems that to
disallow this is to make FieldOverride useless.
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in the cache as well as records loaded from earlier passes in cases where we
split our query up to avoid database breaking in() clause sizes. Now we track
exactly what we got this time around and report that.
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database and need to provide a defaultValue at the time that you add it, but
don't want to have to define a permanent default value on the field.
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keys. So we can have loadAll(Class,Collection<Comparable>) and
loadAll(Collection<Key>) and not run into type erasure problems. Yay!
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got the primary keys, this goes right to phase two wherein we check the cache
for hits and load the remaining records by primary key (and cache them).
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server or if it's OK to get them from a (potentially slightly out of date)
replica. If you're going to modify rows based on the results of findAllKeys(),
you should probably get them from the master server, if you're just reading
data, you can talk to a replica.
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load or modify the rows that match those keys" pattern so that we can almost
always just magically do the right thing with regard to the cache. Added a
version of deleteAll() that makes use of this.
Also nixed a bunch of checked exception tomfoolery which was almost entirely
unnecessary and now with DatabaseException is completely unnecessary.
A few things remain to be done:
- PrimaryKeySet tries to be "smart" if its passed 0 keys and use
LiteralExp("false") but that causes things to freak out because Depot then
doesn't know what primary class it's dealing with. I'm probably going to make
All and None expressions that match all and none of the records in a table
respectively.
- deleteAll() doesn't currently split its keys into chunks small enough to be
digestible by the database if we match more than 32,768 rows. I'll see if I
can't abstract out that code from FindAllQuery so that we can easily use it
everywhere. It would be cool to handle that a a lower level and allow the
WhereClause to say that it needs to be run in phases, but that would probably
complicate the crap out of the low-level code.
- I need to create PrimaryKey to go between Key and PrimaryKeySet so that we
can avoid duplicating the primary key columns thousands of times in a large
PrimaryKeySet.
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of a checked exception. Invariably, we don't do anything with our
PersistenceExceptions except let them percolate all the way to the top and then
log a warning. We can probably automate the process of logging a warning with
useful information and save ourselves the trouble of doing it manually
everywhere.
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