When Grails creates a table from a domain object, is it possible to specify the column order? I'd like it to preserve the column order as specified in the domain. Instead, it seems to be mostly alphabetical. I could not find anything in the documentation. I've found this article that details specifying constraints, but that did not appear to fix the issue for database columns.
Example:
class Foo {
Long id
String zee
Integer baz
Integer bar
}
I'd like the database columns to then be ordered as:
id | zee | baz | bar
Instead I get something closer to:
id | bar | baz | zee
You can always create the DB outside of Grails and put the columns in whatever order you wish and Grails will happily use the schema you provide (assuming only the column ordering is different from what it wants to create by default)
An even better option, as #Burt pointed out, is to use the database migration plugin to create (and manage) the database. It lets you have fine-grained control over the database in a database-agnostic way and also has the massive advantage of making your DB schema and schema changes versioned along with your code, for both upgrades and rollbacks.
This is the only way to do it as I know. Use static constraints and write them with your order
class Foo {
Long id
String zee
Integer baz
Integer bar
}
static constraints = {
id()
zee()
baz()
bar()
}
Related
I'm building a rails app for managing a queue of work items. I have several types of users ("access levels") to whom I want to auto-assign these work items.
The end goal is an "Auto-assign" button on one of my views that will automatically grab the next work item based on a priority, which is defined by the users's access level.
I'm trying to set up a class method in my work_item model to automatically sort work items by type based on the user's access level. I am looking at something like this:
def self.auto_assign_next(access_level)
case
when access_level = 2
where("completed = 'f'").order("requested_time ASC").limit(1)
when access_level > 2
where("completed = 'f'").order("CASE WHEN form='supervisor' THEN 1 WHEN form='installer' THEN 2 WHEN form='repair' THEN 3 WHEN form='mail' THEN 4 WHEN form='hp' THEN 5 ELSE 6 END").limit(1)
end
This isn't very DRY, though. Ideally I'd like the sort order to be configurable by administrators, so maybe setting up a separate table on which the sort order is kept would be best. The problem with that idea is that I have no idea how to pass the priority order on that table to the [postgre]SQL query. I'm new to SQL in general and somewhat lost with this one. Does anybody have any suggestions as to how this should be handled?
One fairly simple approach starts with turning your case statement into a new table, listing form values versus what precedence value they should be sorted by:
id | form | precedence
-----------------------------------
1 | supervisor | 1
2 | installer | 2
(etc)
Create a model for this, say, FormPrecedences (not a great name, but I don't totally grok your data model so pick one that better describes it). Then, your query can look like this (note: I'm assuming your current model is called WorkItems):
when access_level > 2
joins("LEFT JOIN form_precedences ON form_precedences.form = work_items.form")
.where("completed = 'f'")
.order("COALESCE(form_precedences.precedence, 6)")
.limit(1)
The way this works isn't as complicated as it looks. A "left join" in SQL simply takes all the rows of the table on the left (in this case, work_items) and, for each row, finds all the matching rows from the table on the right (form_precedences, where "matching" is defined by the bit after the "ON" keyword: form_precedences.form = work_items.form), and emits one combined row. If no match is found, a LEFT JOIN will still emit a row, but with all the right-hand values being NULL. A normal join would skip any rows with no right-hand match found.
Anyway, with the precedence data joined on to our work items, we can just sort by the precedence value. But, in case no match was found during the join above, that value will be NULL -- so, I use COALESCE (which returns the first of its arguments that's not NULL) to default to a precedence of 6.
Hope that helps!
I have a POGO we'll call Foo and it has a list of Bars. In the database, these are simple integers, but they're stored in a separate table (Foo_Bars)
class Foo {
String name
...
static hasMany = [bars:Integer]
...
}
So my question is, how do I create a query to find all Foos that with bars that are in a list. I know how I would write it in SQL.
SELECT * FROM foo, foo_bars
WHERE foo.id = foo_bars.foo_id
AND foo_bars.bars_integer IN (11, 15, 52)
But I figure there must be a simpler way, using GORM or HQL. How would I write this?
but what exactly you want to achieve? list of Foo's where bars is equal to (11,15,52), or ONE OF bars is in the list or the list of bars contain each of given list?
either way, I doubt you can do it in criteria or using a dynamic finder, I'm trying to do it in an unit test and nothing worked
I would go with creating another domain class like
class FooBar {
Foo foo
Integer integer
}
which would create exactly the same database table as you already have, and then querying would be much simpler
I have three rails objects: User, DemoUser and Stats. Both the User and the DemoUser have many stats associated with them. The User and Stats tables are stored on Postgresql (using ActiveRecord). The DemoUser is stored in redis. The id for the DemoUser is a (random) string. The id for the User is a (standard-rails) incrementing integer.
The stats table has a user_id column that can contain either the User id or the DemoUser id. For that reason, the user_id column is a string, rather than an integer.
There isn't an easy way to translate from the random string to an integer, but there's a very easy way to translate the integer id to a string (42 -> "42"). The ids are guaranteed not to overlap (there won't be a User instance with the same id as a DemoUser, ever).
I have some code that manages those stats. I'd like to be able to pass over a some_user instance (which can either be a DemoUser or a User) and then be able to use the id to fetch Stats, update them etc. Also would be nice to be able to define a has_many for the User model, so I can do things like user.stats
However, operations like user.stats would create a query like
SELECT "stats".* FROM "stats" WHERE "stats"."user_id" = 42
which then breaks with PG::UndefinedFunction: ERROR: operator does not exist: character varying = integer
Is there a way to either let the database (Postgresql), or Rails do auto-translation of the ids on JOIN? (the translation from integer to string should be simple, e.g. 42 -> "42")
EDIT: updated the question to try to make things as clear as possible. Happy to accept edits or answer questions to clarify anything.
You can't define a foreign key between two types that don't have built-in equality operators.
The correct solution is to change the string column to be an integer.
In your case you could create a user-defined = operator for varchar = string, but that would have messy side effects elsewhere in the database; for example, it would allow bogus code like:
SELECT 2014-01-02 = '2014-01-02'
to run without an error. So I'm not going to give you the code to do that. If you truly feel it's the only solution (which I don't think is likely to be correct) then see CREATE OPERATOR and CREATE FUNCTION.
One option would be to have separate user_id and demo_user_id columns in your stats table. The user_id would be an integer that you could use as a foreign key to the users table in PostgreSQL and the demo_user_id would be a string that would link to your Redis database. If you wanted to treat the database properly, you'd use a real FK to link stats.user_id to users.id to ensure referential integrity and you'd include a CHECK constraint to ensure that exactly one of stats.user_id and stats.demo_user_id was NULL:
check (user_id is null <> demo_user_id is null)
You'll have to fight ActiveRecord a bit to properly constrain your database of course, AR doesn't believe in fancy things like FKs and CHECKs even though they are necessary for data integrity. You'd have to keep demo_user_id under control by hand though, some sort of periodic scan to make sure they link up with values in Redis would be a good idea.
Now your User can look up stats using a standard association to the stats.user_id column and your DemoUser can use stats.demo_user_id.
For the time being, my 'solution' is not to use a has_many in Rails, but I can define some helper functions in the models if necessary. e.g.
class User < ActiveRecord::Base
# ...
def stats
Stats.where(user_id: self.id.to_s)
end
# ...
end
also, I would define some helper scopes to help enforce the to_s translation
class Stats < ActiveRecord::Base
scope :for_user_id, -> (id) { where(user_id: id.to_s) }
# ...
end
This should allow calls like
user.stats and Stats.for_user_id(user.id)
I think I misunderstood a detail of your issue before because it was buried in the comments.
(I strongly suggest editing your question to clarify points when comments show that there's something confusing/incomplete in the question).
You seem to want a foreign key from an integer column to a string column because the string column might be an integer, or might be some unrelated string. That's why you can't make it an integer column - it's not necessarily a valid number value, it might be a textual key from a different system.
The typical solution in this case would be to have a synthetic primary key and two UNIQUE constraints instead, one for keys from each system, plus a CHECK constraint preventing both from being set. E.g.
CREATE TABLE my_referenced_table (
id serial,
system1_key integer,
system2_key varchar,
CONSTRAINT exactly_one_key_must_be_set
CHECK (system1_key IS NULL != system2_key IS NULL),
UNIQUE(system1_key),
UNIQUE(system2_key),
PRIMARY KEY (id),
... other values ...
);
You can then have a foreign key referencing system1_key from your integer-keyed table.
It's not perfect, as it doesn't prevent the same value appearing in two different rows, one for system1_key and one for system2_key.
So an alternative might be:
CREATE TABLE my_referenced_table (
the_key varchar primary key,
the_key_ifinteger integer,
CONSTRAINT integerkey_must_equal_key_if_set
CHECK (the_key_ifinteger IS NULL OR (the_key_ifinteger::varchar = the_key)),
UNIQUE(the_key_ifinteger),
... other values ...
);
CREATE OR REPLACE FUNCTION my_referenced_table_copy_int_key()
RETURNS trigger LANGUAGE plpgsql STRICT
AS $$
BEGIN
IF NEW.the_key ~ '^[\d]+$' THEN
NEW.the_key_ifinteger := CAST(NEW.the_key AS integer);
END IF;
RETURN NEW;
END;
$$;
CREATE TRIGGER copy_int_key
BEFORE INSERT OR UPDATE ON my_referenced_table
FOR EACH ROW EXECUTE PROCEDURE my_referenced_table_copy_int_key();
which copies the integer value if it's an integer, so you can reference it.
All in all though I think the whole idea is a bit iffy.
I think I may have a solution for your problem, but maybe not a massively better one:
class User < ActiveRecord::Base
has_many :stats, primary_key: "id_s"
def id_s
read_attribute(:id).to_s
end
end
Still uses a second virtual column, but maybe more handy to use with Rails associations and is database agnostic.
As well as associations between different domain classes, GORM also supports mapping of basic collection types. . For example, the following class creates a nicknames association that is a Set of String instances
class Person {
static hasMany = [nicknames:String]
}
This will store the nicknames in a separate table person_nicknames:
---------------------------------------------
| person_id | nickname |
---------------------------------------------
| 1 | Fred |
---------------------------------------------
By default both columns are nullable and there are no indices present. I would like to make the following changes
make both columns not null
put a composite unique index on (person_id, nickname)
Obviously I could just run an SQL script to make these changes, but is it possible for me to express this in the domain model, so that GORM does it when creating and updating the schema?
No, this presently isn't possible. You can fake it by making Nickname an explicit domain class (Andre Steingress gives an example in the question comments), but otherwise you have to write a migration.
You can use joinTable and basic collection types.
http://grails.org/doc/2.4.3/ref/Database%20Mapping/joinTable.html
You can specify SQL behavior with column mapping:
http://grails.org/doc/2.4.3/ref/Database%20Mapping/column.html
So I am new to Rails, and OO programming in general. I have some grasp of the MVC architecture. My goal is to make a (nearly) completely dynamic plug-and-play plotting web server. I am fairly confused with params, forms, and select helpers.
What I want to do is use Rails drop downs to basically pass parameters as strings to my controller, which will use the params to select certain column data from my database and plot it dynamically. I have the latter part of the task working, but I can't seem to pass values from my view to controller.
For simplicity's sake, say my database schema looks like this:
--------------Plot---------------
|____x____|____y1____|____y2____|
| 1 | 1 | 1 |
| 2 | 2 | 4 |
| 3 | 3 | 9 |
| 4 | 4 | 16 |
| 5 | 5 | 25 |
...
and in my Model, I have dynamic selector scopes that will let me select just certain columns of data:
in Plot.rb
class Plot < ActiveRecord::Base
scope :select_var, lambda {|varname| select(varname)}
scope :between_x, lambda {|x1,x2| where("x BETWEEN ? and ?","#{x1}","#{x2}")}
So this way, I can call:
irb>>#p1 = Plot.select_var(['x','y1']).between_x(1,3)
and get in return a class where #p1.x and #p1.y1 are my only attributes, only for values between x=1 to x=4, which I dynamically plot.
I want to start off in a view (plot/index), where I can dynamically select which variable names (table column names), and which rows from the database to fetch and plot. The problem is, most select helpers don't seem to work with columns in the database, only rows.
So to select columns, I first get an array of column names that exist in my database with a function I wrote.
Plots Controller
def index
d=Plot.first
#tags = d.list_vars
end
So #tags = ['x','y1','y2']
Then in my plot/index.html.erb I try to use a drop down to select wich variables I send back to the controller.
index.html.erb
<%= select_tag( :variable, options_for_select(#plots.first.list_vars,:name,:multiple=>:true) )%>
<%= button_to 'Plot now!', :controller =>"plots/plot_vars", :variable => params[:variable]%>
Finally, in the controller again
Plots controller
...
def plot_vars
#plot_data=Plot.select_vars([params[:variable]])
end
The problem is everytime I try this (or one of a hundred variations thereof), the params[:variable] is nill.
How can I use a drop down to pass a parameter with string variable names to the controller?
Sorry its so long, I have been struggling with this for about a month now. :-( I think my biggest problem is that this setup doesn't really match the Rails architecture. I don't have "users" and "articles" as individual entities. I really have a data structure, not a data object. Trying to work with the structure in terms of data object speak is not necessarily the easiest thing to do I think.
For background: My actual database has about 250 columns and a couple million rows, and they get changed and modified from time to time. I know I can make the database smarter, but its not worth it on my end. I work at a scientific institute where there are a ton of projects with databases just like this. Each one has a web developer that spends months setting up a web interface and their own janky plotting setups. I want to make this completely dynamic, as a plug-and-play solution so all you have to do is specify your database connection, and this rails setup will automatically show and plot which data you want in it. I am more of a sequential programmer and number cruncher, as are many people here. I think this project could be very helpful in the end, but its difficult to figure out for me right now.