I'm pretty new to sequelize, though I've worked on node previously I did not use any ORM framework. At present I'm using new SQL DB(which is not supported by sequelize ) and want to connect it using node.js and sequelize( popular ORM for node.js ) by prototyping the existing dialects
The configuration is correct as I've tried it wihtout ORM.
The problem is after configuring the connection with properties the
sequelize.authenticate() doesn't throw any error but doesn't return a promise back
/**
* Test the connection by trying to authenticate
*
* #error 'Invalid credentials' if the authentication failed (even if the database did not respond at all...)
* #return {Promise}
*/
authenticate(options) {
return this.query('SELECT 1+1 AS result', _.assign({ raw: true, plain: true }, options)).return();
}
The return statement doesn't return anything. I've read this post how to create a new dialect. Though it says it is not encouraged to create a new dialect and throws an error if we try to, I think there must be a way to create because if it can be created for other SQL databases then may be there should be a way to do it. This is an open source project on github. Did anyone previously work on this any help is appreciated. Thanks in Advance
Only the 5 dialects are supported and an error will be thrown if you try and use NewSQL.
There is a lot of code in Sequelize to construct queries based on the dialect, so even if you could get past the error (such as forking the repo and changing it) the likelihood of everything working as you expect (or as is documented) is low.
I suggest posting an issue on GitHub to bring that dialect to the project.
Related
I have a multi-tenancy structure set up where each client has a schema set up for them. The structure mirrors the "parent" schema, so any migration that happens needs to happen for each schema identically.
I am using Flask-Script with Flask-Migrate to handle migrations.
What I tried so far is iterating over my schema names, building a URI for them, scoping a new db.session with the engine generated from the URI, and finally running the upgrade function from flask_migrate.
#manager.command
def upgrade_all_clients():
clients = clients_model.query.all()
for c in clients:
application.extensions["migrate"].migrate.db.session.close_all()
application.extensions["migrate"].migrate.db.session = db.create_scoped_session(
options={
"bind": create_engine(generateURIForSchema(c.subdomain)),
"binds": {},
}
)
upgrade()
return
I am not entirely sure why this doesn't work, but the result is that it only runs the migration for the db that was set up when the application starts.
My theory is that I am not changing the session that was originally set up when the manager script runs.
Is there a better way to migrate each of these schemas without setting multiple binds and using the --multidb parameter? I don't think I can use SQLALCHEMY_BINDS in the config since these schemas need to be able to be dynamically created/destroyed.
For those who are encountering the same issue, the answer to my specific situation was incredibly simple.
#manager.command
def upgrade_all_clients():
clients = clients_model.query.all()
for c in clients:
print("Upgrading client '{}'...".format(c.subdomain))
db.engine.url.database = c.subdomain
_upgrade()
return
The database attribute of the db.engine.url is what targets the schema. I don't know if this is the best way to solve this, but it does work and I can migrate each schema individually.
Is there a way to make the logged user (on superset) to make the queries on impala?
I tried to enable the "Impersonate the logged on user" option on Databases but with no success because all the queries run on impala with superset user.
I'm trying to achieve the same! This will not completely answer this question since it does not still work but I want to share my research in order to maybe help another soul that is trying to use this instrument outside very basic use cases.
I went deep in the code and I found out that impersonation is not implemented for Impala. So you cannot achieve this from the UI. I found out this PR https://github.com/apache/superset/pull/4699 that for whatever reason was never merged into the codebase and tried to copy&paste code in my Superset version (1.1.0) but it didn't work. Adding some logs I can see that the configuration with the impersonation is updated, but then the actual Impala query is with the user I used to start the process.
As you can imagine, I am a complete noob at this. However I found out that the impersonation thing happens when you create a cursor and there is a constructor parameter in which you can pass the impersonation configuration.
I managed to correctly (at least to my understanding) implement impersonation for the SQL lab part.
In the sql_lab.py class you have to add in the execute_sql_statements method the following lines
with closing(engine.raw_connection()) as conn:
# closing the connection closes the cursor as well
cursor = conn.cursor(**database.cursor_kwargs)
where cursor_kwargs is defined in db_engine_specs/impala.py as the following
#classmethod
def get_configuration_for_impersonation(cls, uri, impersonate_user, username):
logger.info(
'Passing Impala execution_options.cursor_configuration for impersonation')
return {'execution_options': {
'cursor_configuration': {'impala.doas.user': username}}}
#classmethod
def get_cursor_configuration_for_impersonation(cls, uri, impersonate_user,
username):
logger.debug('Passing Impala cursor configuration for impersonation')
return {'configuration': {'impala.doas.user': username}}
Finally, in models/core.py you have to add the following bit in the get_sqla_engine def
params = extra.get("engine_params", {}) # that was already there just for you to find out the line
self.cursor_kwargs = self.db_engine_spec.get_cursor_configuration_for_impersonation(
str(url), self.impersonate_user, effective_username) # this is the line I added
...
params.update(self.get_encrypted_extra()) # already there
#new stuff
configuration = {}
configuration.update(
self.db_engine_spec.get_configuration_for_impersonation(
str(url),
self.impersonate_user,
effective_username))
if configuration:
params.update(configuration)
As you can see I just shamelessy pasted the code from the PR. However this kind of works only for the SQL lab as I already said. For the dashboards there is an entirely different way of querying Impala that I did not still find out.
This means that queries for the dashboards are handled in a different way and there isn't something like this
with closing(engine.raw_connection()) as conn:
# closing the connection closes the cursor as well
cursor = conn.cursor(**database.cursor_kwargs)
My gut (and debugging) feeling is that you need to first understand the sqlalchemy part and extend a new ImpalaEngine class that uses a custom cursor with the impersonation conf. Or something like that, however it is not simple (if we want to call this simple) as the sql_lab part. So, the trick is to find out where the query is executed and create a cursor with the impersonation configuration. Easy, isnt'it ?
I hope that this could shed some light to you and the others that have this issue. Let me know if you did find out another way to solve this issue, or if this comment was useful.
Update: something really useful
A colleague of mine succesfully implemented impersonation with impala without touching any superset related, but instead working directly with the impyla lib. A PR was open with the code to change. You can apply the patch directly in the impyla src used by superset. You have to edit both dbapi.py and hiveserver2.py.
As a reminder: we are still testing this and we do not know if it works with different accounts using the same superset instance.
I'm writing a small, simple web app in go using the gorm ORM.
Since the database can fail independently of the web application, I'd like to be able to identify errors that correspond to this case so that I can reconnect to my database without restarting the web application.
Motivating example:
Consider the following code:
var mrs MyRowStruct
db := myDB.Model(MyRowStruct{}).Where("column_name = ?", value).First(&mrs)
return &mrs, db.Error
In the event that db.Error != nil, how can I programmatically determine if the error stems from a database connection problem?
From my reading, I understand that gorm.DB does not represent a connection, so do I even have to worry about reconnecting or re-issuing a call to gorm.Open if a database connection fails?
Are there any common patterns for handling database failures in Go?
Gorm appears to swallow database driver errors and emit only it's own classification of error types (see gorm/errors.go). Connection errors do not currently appear to be reported.
Consider submitting an issue or pull request to expose the database driver error directly.
[Original]
Try inspecting the runtime type of db.Error per the advice in the gorm readme "Error Handling" section.
Assuming it's an error type returned by your database driver you can likely get a specific code that indicates connection errors. For example, if you're using PostgreSQL via the pq library then you might try something like this:
import "github.com/lib/pq"
// ...
if db.Error != nil {
pqerr, ok := err.(*pq.Error)
if ok && pqerr.Code[0:2] == "08" {
// PostgreSQL "Connection Exceptions" are class "08"
// http://www.postgresql.org/docs/9.4/static/errcodes-appendix.html#ERRCODES-TABLE
// Do something for connection errors...
} else {
// Do something else with non-pg error or non-connection error...
}
}
Problem
I would like to trace the Uri that will be generated by a LINQ query executed against a Microsoft.WindowsAzure.StorageClient.TableServiceContext object. TableServiceContext just extends System.Data.Services.Client.DataServiceContext with a couple of properties.
The issue I am having is that the query executes fine against our Azure Table Storage instance when we run the web role on a dev machine in debug mode (we are connecting to Azure storage in the cloud not using Dev Storage). I can get the resulting query Uri using Fiddler or just hovering over the statement in the debugger.
However, when we deploy the web role to Azure the query fails against the exact same Azure Table Storage source with a ResourceNotFound DataServiceClientException. We have had ResoureNotFound errors before that dealt with the behavior of FirstOrDefault() on empty tables. This is not the problem here.
As one approach to the problem, I wanted to compare the query Uri that is being generated when the web role is deployed versus when it is running on a dev machine.
Question
Does anyone know a way to get the query Uri for the query that will be sent when the FirstOrDefault() method is called. I know that you can call ToString() on the IQueryable returned from the TableServiceContext but my concern is that when FirstOrDefault() is called the Uri might be further optimized and ToString() on IQueryable might not be what is ultimately sent to the server when FirstOrDefault() is called.
If someone has another approach to the problem I am open to suggestions. It seems to be a general problem with LINQ when trying to determine what will happen when the expression tree is finally evaluated. I am open to suggestions here as well because my LINQ skills could use some improvement.
Sample Code
public void AddSomething(string ProjectID, string Username) {
TableServiceContext context = new TableServiceContext();
var qry = context.Somethings.Where(m => m.RowKey == Username
&& m.PartitionKey == ProjectID);
System.Diagnostics.Trace.TraceInformation(qry.ToString());
// ^ Here I would like to trace the Uri that will be generated
// and sent to the server when the qry.FirstOrDefault() call below is executed.
if (qry.FirstOrDefault() == null) {
// ^ This statement generates an error when the web role is running
// in the fabric
...
}
}
Edit Update and Answer
Steve provided the write answer. Our problem was as exactly described in this post which describes an issue with PartitionKey/RowKey ordering in Single Entity query which was fixed with an update to the Azure OS. This explains the discrepancy between our dev machines and when the web role was deployed to Azure.
When I indicated we had dealt with the ResourceNotFound issue before in our existence checks, we had dealt with it in two ways in our code. One way was using exception handling to deal with the ResourceNotFound error the other way was to put the RowKey first in the LINQ query (as some MS people had indicated was appropriate).
It turns out we have several places where the RowKey was first instead of using the exception handling. We will address this by refactoring our code to target .NET 4 and using the .IgnoreResourceNotFoundException = true property of theTableServiceContext .
Lesson learned (more than once): Don't depend on quirky undocumented behavior.
Aside
We were able to get the query Uri's. They did turn out to be different (as indicated they would be in the blog post). Here are the results:
Query Uri from Dev Fabric
`https://ourproject.table.core.windows.net/Somethings()?$filter=(RowKey eq 'test19#gmail.com') and (PartitionKey eq '41e0c1ae-e74d-458e-8a93-d2972d9ea53c')
Query Uri from Azure Fabric
`https://ourproject.table.core.windows.net/Somethings(RowKey='test19#gmail.com',PartitionKey='41e0c1ae-e74d-458e-8a93-d2972d9ea53c')
I can do one better... I think I know what the problem is. :)
See http://blogs.msdn.com/b/windowsazurestorage/archive/2010/07/26/how-wcf-data-service-changes-in-os-1-4-affects-windows-azure-table-clients.aspx.
Specifically, it used to be the case (in previous Guest OS builds) that if you wrote the query as you did (with the RowKey predicate before the PartitionKey predicate), it resulted in a filter query (while the reverse, PartitionKey preceding RowKey) resulted in the kind of query that raises an exception if the result set is empty.
I think the right fix for you (as indicated in the above blog post) is to set the IgnoreResourceNotFoundException to true on your context.
we've got a real confusing problem. We're trying to test an SQL Bulk Load using a little app we've written that passes in the datafile XML, the schema, and the SQL database connection string.
It's a very straight-forward app, here's the main part of the code:
SQLXMLBULKLOADLib.SQLXMLBulkLoad4Class objBL = new SQLXMLBULKLOADLib.SQLXMLBulkLoad4Class();
objBL.ConnectionString = "provider=sqloledb;Data Source=SERVER\\SERVER; Database=Main;User Id=Username;Password=password;";
objBL.BulkLoad = true;
objBL.CheckConstraints = true;
objBL.ErrorLogFile = "error.xml";
objBL.KeepIdentity = false;
objBL.Execute("schema.xml", "data.xml");
As you can see, it's very simple but we're getting the following error from the library we're passing this stuff to: Interop.SQLXMLBULKLOADLib.dll.
The message reads:
Failure: Attempted to read or write protected memory. This is often an indication that other memory has been corrupted
We have no idea what's causing it or what it even means.
Before this we first had an error because SQLXML4.0 wasn't installed, so that was easy to fix. Then there was an error because it couldn't connect to the database (wrong connection string) - fixed. Now there's this and we are just baffled.
Thanks for any help. We're really scratching our heads!
I am not familiar with this particular utility (Interop.SQLXMLBULKLOADLib.dll), but have you checked that your XML validates to its schema .xsd file? Perhaps the dll could have issues with loading the xml data file into memory structures if it is invalid?
I try to understand your problem ,but i have more doubt in that,
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I know I did something that raised this error message once, but (as often happens) the problem ended up having nothing to do with the error message. Not much help, alas.
Some troubleshooting ideas: try to determine the actual SQL command being generated and submitted by the application to SQL Server (SQL Profiler should help here), and run it as "close" to the database as possible--from within SSMS, using SQLCMD, direct BCP call, whatever is appropriate. Detailing all tests you make and the results you get may help.