I have a function that finds an oid from a field in a table. According to the docs, the oid field is automatically created and auto incremented. Sounds great.
def teddy_bear_id_by_url(url)
query = "select oid from teddy_bears where url = \"#{url}\""
res = $db.execute(query)
return res
end
Unfortunately this code returns a [] (empty array), when running the query in the sqlite shell gives a 'good' value (e.g. 4).
def teddy_bear_id_by_url(url)
return $db.execute("select oid from teddy_bears where url = '?'", url)
end
The above doesn't work either.
I did indeed check that urlcontains what I think it does.
What might be happening?
There's probably something funny going on in your url that, combined with your string interpolation, is messing up your SQL. Your best bet is to use placeholders with your execute call:
$db.execute("select oid from teddy_bears where url = ?", url)
Related
I'm using Mongoid to access a MongoDB database, however I'm running into an odd problem. It seems like I can only query for records using find_by, as find will always return nil:
invoices = Invoice.find({})
p "invoices"
p invoices
puts ''
invoice = Invoice.find_by({ _id: <ObjectId> })
p "invoice"
p invoice
puts ''
The second query using find_by will return a single record. According to the documentation, find should be returning every record that satisfies the query.
Does anyone have an idea what could be causing this?
Be careful not to confuse the Moped syntax with the Mongoid syntax. For Mongoid, the docs describe the find method:
Find a document or multiple documents by their ids. Will raise an error by default if any of the ids do not match
If you really want every record, Invoice.all can do the trick. (Also be careful with your find_by method. The Mongoid syntax varies from mongo's a bit, so you don't have to have the curlies around your params.)
I am using Sinatra and Sequel with PostgreSQL.
After authentication, I want to welcome the user by printing their name but I cannot get only the value of the user's name from the database, it comes out as a hash.
The query is:
current_user = DB[:users].select(:username).where('password = ?', password).first
and the resulting piece of data is:
Welcome, {:username=>"Rich"}
which looks rather weird, I would prefer it to read "Welcome, Rich".
What am I doing wrong here? I tried the same query without 'first" at the end and that does not work either.
You can either pull the (single) column you selected out of the Hash you are given:
current_user = DB[:users].select(:username).where('password=?', password).first[:username]
Or you can map your results to an array of usernames and pull the first:
# Using a hash in the filter method is simpler than SQL placeholders.
current_user = DB[:users].filter(password:password).select_map(:username).first
But the best way is to get only the user you care about, and then get the name:
# Using [] on a dataset returns the first row matching the criteria
current_user = DB[:users][password:password][:username]
Try Sequel::Dataset#get. Also, as Phrogz points out, Sequel::Dataset#where can take a hash (it will securely escape values to prevent injection attacks).
current_username = DB[:users].where(password: password).get(:username)
There's also Sequel::Dataset#where_single_value, which is optimized for this exact situation:
current_username = DB[:users].select(:username).where_single_value(password: password)
So I have 2 tables actor and actor2role. The latter is a lookup (junction) table to relate actor, role and dvd. I need to create a query with aliases, so I have this method:
def self.remove_duplicate_by_id(id)
offendingActor = self.find(id).actor # get the actor's name
ids = self.find_by_sql("SELECT MIN(id) AS minId, MAX(id) AS maxId, actor FROM `dvd_actor` WHERE actor = '#{offendingActor}'")
rolesForOffender = ids.actor2role # throws error
end
The problem is that ids is not an ActiveRecord object so I can't use the actor2role method (which is a relationship I've established between the 2 tables in Rails and works when you do something like Actor.first.actor2role.
so the questions is: Am I doomed to do this manually and then issue another sql query to recreate what the actor2role method would accomplish or is there some way to do this with Rails objects?
I'd really like to do it all natively if possible because I also have to issue these queries:
UPDATE dvd_actor2role SET actorid = $d->minId WHERE actorId = $d->maxId");
DELETE FROM dvd_actor2role WHERE actorId = $d->maxId LIMIT 1");
Is this even possible?
In the end I went with this which seems to do the trick. If anyone can spot any code that could be optimized, or something inherently wrong (and feels like chiming in) please feel free to comment.
actorObject = self.find_by_id(id) # get the object because we need it below for other queries
offendingActor = actorObject.actor
ids = self.select("MIN(id) AS minId, MAX(id) AS maxId, id, actor").find_by_actor(offendingActor)
rolesForOffender = actorObject.actor2role
rolesForOffender.each do |r|
# first find out if the relationship already exists or we get a SQL error for the foreign key relationship.
exists = Actor2role.where("actorId = ? AND roleId = ?", ids.minId, r.roleId)
if exists.nil?
Actor2role.update_all("actorId = #{ids.minId}, actorId = #{ids.maxId}")
end
end
self.destroy(ids.maxId) # delete this guy in actor table
end
I'm trying to use an Oracle database with ado.net, and it is proving a painful experience. I use Oracle Client (Oracle.Data namespaces).
The following query runs fine from a query window:
UPDATE PRINT_ARGUMENT
SET VALUE = 'Started'
WHERE REQUEST_ID = 1 AND KEYWORD = '{7D066C95-D4D8-441b-AC26-0F4C292A2BE3}'
When I create an OracleCommand however the same thing blows up with ORA-01722. I can't figure out why.
var cmd = cnx.CreateCommand();
cmd.CommandText = #"
UPDATE PRINT_ARGUMENT
SET VALUE = :value
WHERE REQUEST_ID = :requestID AND KEYWORD = :key";
cmd.Parameters.Add(new OracleParameter("requestID", (long)1);
cmd.Parameters.Add(new OracleParameter("key", "{7D066C95-D4D8-441b-AC26-0F4C292A2BE3}");
cmd.Parameters.Add(new OracleParameter("value", "Started");
cnx.Open();
try { int affected = cnx.ExecuteNonQuery(); }
finally { cnx.Close(); }
When I inspect the command in the debugger, the parameters appear to have mapped to the correct types: requestID has OracleDbType.Int64, key and value are both OracleDbType.Varchar2. The values of the parameters are also correct.
This gets even stranger when you consider that I have other queries that operate on the exact same columns (requestID, keyword, value) using the same approach - and they work without a hiccup.
For the record, the column types are requestID NUMBER(10,0); key VARCHAR2(30); value VARCHAR2(2000).
According to Oracle, ORA-01722 'invalid number' means a string failed to convert to a number. Neither of my string values are numbers, neither of the OracleParameters created for them are numeric, and neither
By default, ODP.NET binds parameters by position, not by name, even if they have actual names in the SQL (instead of just ?). So, you are actually binding requestID to :value, key to :requestID and value to :key.
Correct the order of cmd.Parameters.Add in your code, or use BindByName to tell ODP.NET to use the parameter names.
Since you are using named parameters, you have to tell the Oracle client about it. Otherwise your parameters are mixed up (key is assigned to :value):
OracleParameter parameter = new OracleParameter("requestID", (long)1);
parameter.BindByName = true;
cmd.Parameters.Add(parameter);
It's a strange and unexpected behavior, but that's how it is.
I have been looking at the sqlalchemy recipes on their wiki, but don't know which one is best to implement what I am trying to do.
Every row on in my tables have an user_id associated with it. Right now, for every query, I queried by the id of the user that's currently logged in, then query by the criteria I am interested in. My concern is that the developers might forget to add this filter to the query (a huge security risk). Therefore, I would like to set a global filter based on the current user's admin rights to filter what the logged in user could see.
Appreciate your help. Thanks.
Below is simplified redefined query constructor to filter all model queries (including relations). You can pass it to as query_cls parameter to sessionmaker. User ID parameter don't need to be global as far as session is constructed when it's already available.
class HackedQuery(Query):
def get(self, ident):
# Use default implementation when there is no condition
if not self._criterion:
return Query.get(self, ident)
# Copied from Query implementation with some changes.
if hasattr(ident, '__composite_values__'):
ident = ident.__composite_values__()
mapper = self._only_mapper_zero(
"get() can only be used against a single mapped class.")
key = mapper.identity_key_from_primary_key(ident)
if ident is None:
if key is not None:
ident = key[1]
else:
from sqlalchemy import util
ident = util.to_list(ident)
if ident is not None:
columns = list(mapper.primary_key)
if len(columns)!=len(ident):
raise TypeError("Number of values doen't match number "
'of columns in primary key')
params = {}
for column, value in zip(columns, ident):
params[column.key] = value
return self.filter_by(**params).first()
def QueryPublic(entities, session=None):
# It's not directly related to the problem, but is useful too.
query = HackedQuery(entities, session).with_polymorphic('*')
# Version for several entities needs thorough testing, so we
# don't use it yet.
assert len(entities)==1, entities
cls = _class_to_mapper(entities[0]).class_
public_condition = getattr(cls, 'public_condition', None)
if public_condition is not None:
query = query.filter(public_condition)
return query
It works for single model queries only, and there is a lot of work to make it suitable for other cases. I'd like to see an elaborated version since it's MUST HAVE functionality for most web applications. It uses fixed condition stored in each model class, so you have to modify it to your needs.
Here is a very naive implementation that assumes there is the attribute/property self.current_user logged in user has stored.
class YourBaseRequestHandler(object):
#property
def current_user(self):
"""The current user logged in."""
pass
def query(self, session, entities):
"""Use this method instead of :method:`Session.query()
<sqlalchemy.orm.session.Session.query>`.
"""
return session.query(entities).filter_by(user_id=self.current_user.id)
I wrote an SQLAlchemy extension that I think does what you are describing: https://github.com/mwhite/multialchemy
It does this by proxying changes to the Query._from_obj and QueryContext._froms properties, which is where the tables to select from ultimately get set.