I have written a function in PostgreSQL for insertion as follows:
CREATE OR REPLACE FUNCTION public.insert_blog("Url" character)
RETURNS void AS
$BODY$Begin
Insert Into "Blogs"("Url") Values("Url");
End$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION public.insert_blog(character)
OWNER TO postgres;
The above function adds an entry into the Blogs table (Url is a parameter).
I am trying to use this function in .Net Core (Npgsql.EntityFrameworkCore.PostgreSQL) as follows:
[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(Blog blog)
{
if (ModelState.IsValid)
{
//This works fine
var count = _context.Blogs.FromSql("Select insert_blog({0})", blog.Url).Count();
//This doesn't work -- it gives an error of "42601: syntax error at or near "insert_blog""
//var count = _context.Blogs.FromSql("insert_blog #Url={0}", blog.Url).Count();
return RedirectToAction("Index");
}
return View(blog);
}
Can someone tell me why the second command is not working? Also, even if the first command is working, is it the right way?
Since I have to write .FromSql(...).Count() in order for it to work, if I remove .Count() item doesn't get inserted. Can someone tell me why this is happening?
Is there any good article on using .FromSql() or "Using Postgres functions in entity framework core" (I'd guess that this is a new feature and that that's why I couldn't find much data on this)?
Can some one tell me why the second command is not working? Also even if the first command is working, is it the right way?
It's simply just not the way PostgreSQL syntax works. Select insert_blog({0}) is indeed the right way.
Since I have to write .FromSql(...).Count() in order for it to work. If I remove ".Count()" item doesn't get inserted. Can someone tell me why this is happening?
FromSql behaves just like Where and other functions on an IQueryable. Execution is postponed until the results are requested, because it will try to do everything in one database query.
To make sure your query actually gets executed, you need to call a method that returns something other than IQueryable such as .Count() or .ToList(). More info can be found here: https://learn.microsoft.com/en-us/ef/core/querying/overview#when-queries-are-executed
Related
I'm working on a web app in Rust. I'm using Tokio Postgres, Rocket and Tera (this may be relevant).
I'm using the following to connect to my DB which doesn't fail in either case.
(sql_cli, connection) = match tokio_postgres::connect("postgresql://postgres:*my_password*#localhost:8127/*AppName*", NoTls).await{
Ok((sql_cli, connection)) => (sql_cli, connection),
Err(e) => return Err(Redirect::to(uri!(error_display(MyError::new("Failed to make SQLClient").details)))),
};
My query is as follows. I keep my queries in a separate file (I'm self taught and find that easier).
let query= sql_cli.query(mycharactersquery::get_characters(user_id).as_str(), &[]).await.unwrap();
The get characters is as follows. It takes a user ID and should return the characters that they have made in the past.
pub fn get_characters(user_id: i16) -> String {
format!("SELECT * FROM player_characters WHERE user_id = {} ORDER BY char_id ASC;", user_id)
}
In my main file, I have one GET which is /mycharacters/<user_id> which works. This GET returns an HTML file. I have another GET which is /<user_id> which returns a Tera template. The first works fine and loads the characters, the second doesn't: it just loads indefinitely. I initially thought this was to do my lack of familiarity with Tera.
After some troubleshooting, I put some printouts in my code, the one before and after the SQL call work in /mycharacters/<user_id>, but only the one before writes to the terminal in /<user_id>. This makes me think that Tera isn't the issue as it isn't making it past the SQL call.
I've found exactly where it is going wrong, but I don't know why as it isn't giving an error.
Could someone please let me know if there is something obvious that I am missing or provide some assistance?
P.S. The database only has 3 columns, so an actual timeout isn't the cause.
I expected both of these SQL calls to function as I am connected to my database properly and the call is copied from the working call.
I am writing a RIA service, which is also exposed using SOAP.
One of its methods needs to read data from a very big table.
At the beginning I was doing something like:
public IQueryable<MyItem> GetMyItems()
{
return this.ObjectContext.MyItems.Where(x => x.StartDate >= start && x.EndDate <= end);
}
But then I stopped because I was worried about the performance.
As far as I understand MyItemsis fully loaded and "Where" just filters the elements that were loaded at the first access of the property MyItems. Because MyItemswill have really lots of rows, I don't think this is the right approach.
I tried to google a bit the question but no interesting results came up.
So, I was thinking I could create a new instance of the context inside the GetMyItems method and load MyItems selectively. Something like:
public IQueryable<MyItems> GetMyItems(string Username, DateTime Start, DateTime End)
{
using (MyEntities ctx = new MyEntities ())
{
var objQuery = ctx.CreateQuery<MyItems>(
"SELECT * FROM MyItems WHERE Username = #Username AND Timestamp >= #Start AND Timestamp <= #End",
new ObjectParameter("#Username", Username),
new ObjectParameter("#Start", Start),
new ObjectParameter("#End", End));
return objQuery.AsQueryable();
}
}
But I am not sure at all this is the correct way to do it.
Could you please assist me and point out the right approach to do this?
Thanks in advance,
Cheers,
Gianluca.
As far as I understand MyItemsis fully loaded and "Where" just filters the elements that were loaded at the first access of the property MyItems.
No. That's entirely wrong. Don't fix "performance problems" until you actually have them. The code you already have is likely to perform better than the code you propose replacing it with. It certainly won't behave in the way you describe. But don't take my word for it. Use the performance profiler. Use SQL Profiler. And test!
I am writing query like this in zend but I am not getting return result in controller file, then what I have to do for this.
$result=$db->query("insert into geofences (`name`,`description`,`polygon`,
`created_timestamp`,`company_id`)
values ('".$formData ['name']."',
'".$formData['description']."',
GeomFromText('POLYGON(($polygon))'),
now(),'".$formData ['company_id']."')
");
return $result;
after a query() statment you have to fetch the results (if you have a SELECT, SHOW, DESCRIBE and EXPLAIN statement).... i think it uses the standard mysqli classes of PHP!
In your case (an insert statement) you have no result to fetch...i think (i'm not sure but i think this is the case) that it returns true on success and false if the query fails.
Look here and here for reference
I am using code similar to this Support / KB article to return multiple recordsets to my C# program.
But I don't want C# code to be dependant on the physical sequence of the recordsets returned, in order to do it's job.
So my question is, "Is there a way to determine which set of records from a multiplerecordset resultset am I currently processing?"
I know I could probably decipher this indirectly by looking for a unique column name or something per resultset, but I think/hope there is a better way.
P.S. I am using Visual Studio 2008 Pro & SQL Server 2008 Express Edition.
No, because the SqlDataReader is forward only. As far as I know, the best you can do is open the reader with KeyInfo and inspect the schema data table created with the reader's GetSchemaTable method (or just inspect the fields, which is easier, but less reliable).
I spent a couple of days on this. I ended up just living with the physical order dependency. I heavily commented both the code method and the stored procedure with !!!IMPORTANT!!!, and included an #If...#End If to output the result sets when needed to validate the stored procedure output.
The following code snippet may help you.
Helpful Code
Dim fContainsNextResult As Boolean
Dim oReader As DbDataReader = Nothing
oReader = Me.SelectCommand.ExecuteReader(CommandBehavior.CloseConnection Or CommandBehavior.KeyInfo)
#If DEBUG_ignore Then
'load method of data table internally advances to the next result set
'therefore, must check to see if reader is closed instead of calling next result
Do
Dim oTable As New DataTable("Table")
oTable.Load(oReader)
oTable.WriteXml("C:\" + Environment.TickCount.ToString + ".xml")
oTable.Dispose()
Loop While oReader.IsClosed = False
'must re-open the connection
Me.SelectCommand.Connection.Open()
'reload data reader
oReader = Me.SelectCommand.ExecuteReader(CommandBehavior.CloseConnection Or CommandBehavior.KeyInfo)
#End If
Do
Dim oSchemaTable As DataTable = oReader.GetSchemaTable
'!!!IMPORTANT!!! PopulateTable expects the result sets in a specific order
' Therefore, if you suddenly start getting exceptions that only a novice would make
' the stored procedure has been changed!
PopulateTable(oReader, oDatabaseTable, _includeHiddenFields)
fContainsNextResult = oReader.NextResult
Loop While fContainsNextResult
Because you're explicitly stating in which order to execute the SQL statements the results will appear in that same order. In any case if you want to programmatically determine which recordset you're processing you still have to identify some columns in the result.
I'm recently have learned to use Zend Framework. I did a simple CRUD application. But now I want to use a existing database for a more complex application and I want to know how I call a stored procedure in the Model, how to send parameters, how to read the results and store them in an array in PHP. Please. I appreciate any kind of help :)
It's not too hard. Here's an example of a MySQL stored procedure with an IN parameter, an OUT parameter, and a result set:
CREATE PROCEDURE MyProc(IN i INTEGER, OUT o INTEGER)
BEGIN
SELECT i+10 INTO o;
SELECT i, o;
END
You can call this with the query() method, and pass a parameter:
$stmt = $db->query("CALL MyProc(?, #output)", array(25));
print_r( $stmt->fetchAll() );
The trick is that MySQL stored procs might return multiple result sets (if the proc had multiple SELECT queries for instance). So the API must advance through all result sets before you can execute another SQL query. Or else you get the "Commands out of sync" error.
If you use the PDO_MySQL adapter:
while ($stmt->nextRowset()) { }
If you use the MySQLi adapter, you'll find that Zend_Db_Statement_Mysqli doesn't implement nextRowset(), so you have to call the internal mysqli connection object:
while ($db->getConnection()->next_result()) { }
Once you clear the result sets, you can run subsequent SQL queries, for example to fetch the value of the procedure's OUT parameter:
$stmt = $db->query("SELECT #output");
print_r( $stmt->fetchAll() );
Great answer from Bill. Just for completeness, if you encounter:
SQLSTATE[HY000]: General error: 2053
When using this method to get a result set from your procedure, check your arguments. I refactored a method and was passing NULLs as arguments to the procedure as the variables I'd used were out of scope. Once I'd fixed this silly mistake the problem went away (to be replaced by another):
SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other
unbuffered queries are active. Consider using PDOStatement::fetchAll().
I'm using $stmt->fetchAll() though. I switched to using prepare() and execute() in place of query(). Switching to mysqli from pdo_mysql in my Zend_Db config finally got things working for me. I found this information from the following SO question:
Call Multiple Stored Procedures with the Zend Framework
If someone is looking for ZendFramework 2 \ Zend Expressive using Zend\Db :
There is another way to do this using createStatement() method.
// prepare create statement from adapter
$stmt = $this->getAdapter()->createStatement();
$stmt->prepare('CALL myproc("myVal")');
// execute sql query
$records = $stmt->execute();
// manipulate results
if ($records instanceof ResultInterface && $records->isQueryResult()) {
$resultSet = new ResultSet;
$resultSet->initialize($records);
// return records if found
if (count($resultSet)) {
// return array of result set
return $resultSet->toArray();
}
// if no records found
return array()
}
$db = Zend_Db_Table::getDefaultAdapter();
$stmt = $db->query("CALL procedure()");
$data = $stmt->fetchAll();