I am using the Entity Framework 4.1 within an application. One of the requirments is to execute some stored procedures on the database out of which some take quite some time. Further, those stored procedures do not return any results so I need to only start them and forget about them.
Naturally, .NET will wait for these operations to complete so after some time it throws an exception that the "Timeout period has expired".
I know that I could fix that by setting the CommandTimeout property to a higher value, however I am looking for an alternative solution (If such even exists).
Is it possible to execute stored procedures using the Entity Framework as Fire-and-Forget?
Any help will be appreciated.
Regards
Stored procedures don't support fire and forget execution. You can either use plain ADO.NET and execute query asynchronously on separate connection (with BeginExecuteNonQuery). EF doesn't support asynchronous execution. Another more complex way which behaves like fire and forget is creating SQL Job with single step execution your stored procedure. Instead of calling your stored procedure you will call sp_start_job which returns immediately after starting the job and job will execute asynchronously without returning any other result back to your application.
Related
I have two stored procedures, the first one (SP1) creates a table, and the second one (SP2) uses that table.
I cannot run both SP sequentially in one statement.
CALL SP1();
CALL SP2();
I get an error saying " Could not find table/view..."
when SP2 was created, the table existed due to testing SP1, but now I got rid of all the tables that are created temporarily during runtime SP2 doesn't run.
I realize I can just run SP1 and then SP2 and that will work, but there are 39 SPs and they take about 2 hours when running one after another, so waiting would make the process take even longer.
The only solution I can think of is to just leave the tables that are needed and truncate them rather than drop them. If nothing else can be done I will have to do that, but I rather drop them. The person that created this SPs was evil enough to create over 500 of these tables so I don't want them permanently in my schema.
As a side note, these tables are used for debugging mainly so they can be dropped after a few days of execution, once the processes validated.
I wonder if there is any way to ignore the error or something like or any other workaround.
Thanks in advance for your time and expertise.
Regards,
Leonardo
I found a way to run it regardless of the missing tables.
I just had to put each SP in a different DO BEGIN.... END; block, that seems to be only validating one block at a time and since the previous block creates the table that use going to be used on block number 2, everything seems to be working fine.
DO
BEGIN
CALL SP1();
END;
DO
BEGIN
CALL SP2();
END;
and so on.
The blocks have a bit more things in them, I just put the SP call to simplify them.
I am just leaving this here in case someone else has the same problem as I have.
I would still appreciate it if someone has a better solution.
This sounds a lot like that those tables are in fact temporary tables used to "transfer" data between the different stored procedures.
With HANA it is not necessary nor recommended to dynamically create tables for that use.
Instead, use table variables and "hand over" the data via table typed parameters.
That way, no tables have to be created/dropped at runtime at all.
Also, since table variables are effectively handled as internal, session local temporary tables, a lot of overhead is removed (i.e. those tables don't need to take care of logging or concurrent access) which makes them a lot more lightweight and better performing than dynamically created tables.
Another negative aspect of dynamically creating objects is that this always comes with locking of the database catalog, checking for and invalidating potentially dependent objects, and numerous internal caches.
If possible, one really should avoid this if performance is important.
I want to write some (potentially) complex operations on my CosmosDB database, which, most importantly, can consist of multiple CRUD operations, and it is really important of course that if one of operations fails, I can rollback whole transaction. Are javascript stored procedures the only way to achieve this? Would this mean that I would write them as javascript files and execute them using .NET api (because my code is using .NET cosmos db api)? Is this possible?
Thanks in advance
You are absolutely right. For the time being its achievable only through the stored procedures because it has to be run on the server side . You can definitely execute those stored procedures by calling from .net api
var sprocBody = File.ReadAllText(#"..\..\StoredProcedures\spHelloWorld.js");
If you need transactions within a logical partition key, you have options (nothing wrong with different document types in one collection, remember to have a property for type name to distinguish JSON-objects)
1. https://devblogs.microsoft.com/cosmosdb/introducing-transactionalbatch-in-the-net-sdk/ TransactionalBatch
2. https://github.com/Azure/azure-cosmosdb-bulkexecutor-dotnet-getting-started a lib for bulk insert/update operations, also supporting transactions within a partition
I am using a VCL TCPServer components which fires events everytime a data is
received on a tcp port. Within the event data is available into text
parameter of the procedure. Because I want to save this data into mysql
database I am wondering which is the best approach to this problem.
Directly use an INSERT SQL command within the procedure for every data received
or store the data in a memory (i.e. TStrings) and then calling
a function every X (using Timer) minutes excute the INSERT command?
Thanks
Ok Sorry.
It's not really an answer to your question, but do consider the risk of your application failing (for any reason) between receiving the data and executing the INSERT.
If you use a local store of some kind as an intermediate to mitigate this risk, consider the risk of a crash while that store is being updated.
RDBMS vendors go to great lengths to ensure that data that has been accepted by successful completion of an INSERT, UPDATE or similar command will not be lost or corrupted. Can you put in similar effort?
Generally speaking, if you are accepting data piecemeal rather than in bulk, I would probably keep an open connection to the database and insert data as you receive it, and only send an acknowledgement back to the consumer of your application once it has been pushed to the database.
Althoug both Jet/OLE DB parameters are relativly well documented I fail to understand the difference between these two connection parameters:
The first one:
Jet OLEDB:Transaction Commit Mode
(DBPROP_JETOLEDB_TXNCOMMITMODE)
Indicates whether Jet writes data to
disk synchronously or asynchronously
when a transaction is committed.
The second one:
Jet OLEDB:User Commit Sync
(DBPROP_JETOLEDB_USERCOMMITSYNC)
Indicates whether changes that were
made in transactions are written in
synchronous or asynchronous mode.
What's the difference? When to use which?
This is very long, so here's the short answer:
Don't set either of these. The default settings for these two options are likely to be correct. The first, Transaction Commit Mode, controls Jet's implicit transactions, and applies outside of explicit transactions, and is set to YES (asynchronous). The second controls how Jet interacts with its temporary database during an explicit transaction and is set to NO (synchronous). I can't think of a situation where you'd want to override the defaults here. However, you might want to set them explicitly just in case you're running in an environment where the Jet database engine settings have been altered from their defaults.
Now, the long explanation:
I have waded through a lot of Jet-related resources to see if I can find out what the situation here is. The two OLEDB constants seem to map onto these two members of the SetOptionEnum of the top-level DAO DBEngine object (details here for those who don't have the Access help file available):
dbImplicitCommitSync
dbUserCommitSync
These options are there for overriding the default registry settings for the Jet database engine at runtime for any particular connection, or for permanently altering the stored settings for it in the registry. If you look in the Registry for HLKM\Software\Microsoft\Jet\X.X\ you'll find that under the key there for the Jet version you're using there are keys, of which two are these:
ImplicitCommitSync
UserCommitSync
The Jet 3.5 Database Engine Programmer's Guide defines these:
ImplicitCommitSync: A value of Yes indicates that Microsoft Jet will wait for commits to finish. A value other than Yes means that Microsoft Jet will perform commits asynchronously.
UserCommitSync: When the setting has a value of Yes, Microwsoft Jet will wait for commits to finish. Any other value means that Microsoft Jet will perform commits asynchronously.
Now, this is just a restatement of what you'd already said. The frustrating thing is that the first has a default value of NO while the second defaults to YES. If they really were controlling the same thing, you'd expect them to have the same value, or that conflicting values would be a problem.
But the key actually turns out to be in the name, and it reflects the history of Jet in regard to how data writes are committed within and outside of transactions. Before Jet 3.0, Jet defaulted to synchronous updates outside of explicit transactions, but starting with Jet 3.0, IMPLICIT transactions were introduced, and were used by default (with caveats in Jet 3.5 -- see below). So, one of these two options applies to commits OUTSIDE of transactions (dbImplicitCommitSync) and the other for commits INSIDE of transactions (dbUserCommitSync). I finally located a verbose explanation of these in the Jet Database Engine Programmer's Guide (p. 607-8):
UserCommitSynch
The UserCommitSynch setting determines
whether changes made as part of an
explicit transaction...are written to
the database in synchronous mode or
asynchronous mode. The default value...is Yes, which specifies
asynchronous mode. It is not
recommended that you change this value
because in synchronous mode, there is
no guarantee that information has been
written to disk before your code
proceeds to the next command.
ImplicitCommitSync
By default, when
performing operations that add,
delete, or update records outside of
explicit transactions, Microsoft Jet
automatically performs internal
transactions called implicit
transactions that temporarily save
data in its memory cache, and then
later write the data as a chunk to the
disk. The ImplicitCommitSync setting
determines whether changes made by
using implicit transactions are
written to the database in synchronus
mode or asynchronous mode. The default
value...is No, which specifies that
these changes are written to the
database in asynchronous mode; this
provides the best performance. If you
want implicit transactions to be
written to the database in synchronous
mode, change the value...to Yes. If
you change the value...you get
behavior similar to Microsoft Jet
versions 2.x and earlier when you
weren't using explicit transactions.
However, doing so can also impair
performance considerably, so it is not
recommended that you change the value
of this setting.
Note: There is no longer a need to use
explicit transactions to improve the
performance of Microsoft Jet. A
database application using Microsoft
Jet 3.5 should use explicit
transactions only in situations where
there may be a need to roll back
changes. Micosoft Jet can now
automatically perform implicit
transactions to improve performance
whenever it adds, deletes or changes
records. However, implicit
transactions for SQL DML statements
were removed in Microsoft Jet
3.5...see "Removal of Implicit Transactions for SQL DML Statements"
later in this chapter.
That section:
Removal of Implicit Transactions for SQL DML Statements
Even with all the work in Microsoft
Jet 3.0 to eliminate transactions in
order to obtain better performance,
SQL DML statements were still placed
in an implicit transaction. In
Microsoft Jet 3.5, SQL DML statements
are not placed in an implicit
transaction. This substantially
improves performance when running SQL
DML statements that affect many
records of data.
Although this change provides a
substantial performance improvement,
it also introduces a change to the
behavior of SQL DML statements. When
using Microsoft Jet 3.0 and previous
versions that use implicit
transactions for SQL DML statements,
an SQL DML statement rolls back if any
part of the statement is not
completed. When using Microsoft Jet
3.5, it is possible to have some of the records committed by SQL DML
statement while others are not. An
example of this would be when the
Microsoft Jet cache is exceeded. The
data in the cache is written to disk
and the next set of records is
modified and placed in the cache.
Therefore, if the connection is
terminated, it is possible that some
of the records were saved to disk, but
others were not. This is the same
behavior as using DAO looping routines
to update data withoug an explicit
transaction in Microsoft Jet 3.0. If
you want to avoid this behavior, you
need to add explicit transactions
around the SQL DML statement to define
a set of work and you must sacrifice
the performance gains.
Confused yet? I certainly am.
The key point to me seems to me to be that dbUserCommitSync seems to control the way Jet writes to the TEMPORARY database it uses for staging EXPLICIT transactions, while dbImplicitCommitSync relates to where Jet uses its implicit transactions OUTSIDE of an explicit transaction. In other words, dbUserCommitSync controls the behavior of the engine while inside a BeginTrans/CommitTrans loop, while dbImplicitCommitSync controls how Jet behaves in regard to asynch/synch outside of explicit transactions.
Now, as to the "Removal of Implicit Transactions" section: my reading is that implicit transactions apply to updates when you're looping through a recordset outside of a transaction, but no longer apply to a SQL UPDATE statement outside a transaction. It stands to reason that an optimization that improves the performance of row-by-row updates would be good and wouldn't actually help so much with a SQL batch update, which is already going to be pretty darned fast (relatively speaking).
Also note that the fact that it is possible to do it both ways is what enables DoCmd.RunSQL to make incomplete updates. That is, a SQL command that would fail with CurrentDB.Execute strSQL, dbFailOnError, can run to completion if executed with DoCmd.RunSQL. If you turn off DoCmd.SetWarnings, you don't get a report of an error, and you don't get the chance to roll back to the initial state (or, if you are informed of the errors and decide to commit, anyway).
So, what I think is going on is that SQL executed through the Access UI is wrapped in a transaction by default (that's how you get a confirmation prompt), but if you turn off the prompts and there's an error, you get the incomplete updates applied. This has nothing to do with the DBEngine settings -- it's a matter of the way the Access UI executes SQL (and there's an option to turn it off/on).
This contrasts to updates in DAO, which were all wrapped in the implicit transactions starting with Jet 3.0, but starting with Jet 3.5, only sequential updates were wrapped in the implicit transactions -- batch SQL commands (INSERT/UPDATE/DELETE) are not.
At least, that's my reading.
So, in regard to the issue in your actual question, in setting up your OLEDB connection, you'd set the options for the Jet DBEngine for that connection according to what you were doing. It seems to me that the default Jet DBEngine settings are correct and shouldn't be altered -- you want to use implicit transactions for edits where you're walking through a recordset and updating one row at a time (outside of an explicit transaction). On the other hand, you can wrap the whole thing in a transaction and get the same result, so really, this only applies to cases where you're walking a recordset and updating and have not used an explicit transaction, and the default setting seems quite correct to me.
The other setting, UserCommitSync, seems to me to be something you'd definitely want to leave alone as well, as it seems to me to apply to the way Jet interacts with its temp database during an explicit transaction. Setting it to asynchronous would seem to me to be quite dangerous as you'd basically not know the state of the operation at the point that you committed the data.
You'd think that USERCOMMITSYNC=YES would be the option to commit synchronously. And that is the cause of the confusion.
I spent ages googling on this topic because I found that the behavior I was getting with old vb6 applications was not the same as I get in .net oledb/jet4
Now I really should back up what I'm going to say with a link to the actual page(s) I read but I can't find those pages now.
Anyway, I was browsing MSDN website and found a page that described a 'by design' error in Jet3 which transposed the functionality of USERCOMMITSYNC meaning a value of NO gets synchronous commit.
Therefore MS set the default to NO and we get synchronous commit by default. Exactly as described above by David Fenton. A behavior we've all come to accept.
But, the document then went on to explain that the behavior in oledb/Jet4 has been changed. Basically MS fixed their bug and now a setting of USERCOMMITSYNC=YES does what it says.
But did they change the default? I think not because now my explicit transactions are NOT committing synchronously in .Net applications using oledb/jet4.
I have a powershell 2.0 script on an XP OS. The purpose of the script is to extract data from an old database (Sybase) and populate a SQL Server 2008 database. The model that I am using is to create OLEDB connections to the Sybase database. The script calls a series of stored procedures from the Sybase database. The results are used to create an XML string. The XML string is queried for the input data for the SQL Server stored procedures. AFter each data element is created in the SQL Server database the XML string is saved to a file. Every database connection is closed after execution is completed. It is simple model, but uses staggering amounts of memory. For transferring only 1000 rows of data the script memory footprint grows to 3G. When the script completes the memory does not drop. In an attempt to rectify this problem I have added logic to free every variable when not used and call garbage collection in every finally clause of every try block. I am aware that this is overkill, but am trying to find anything that will reduce the memory usage. I am in the processing of looking for a memory trace tool, but I am also looking for expert opinions as to possibly start tracking down this critical issue. I know I am missing something obvious so any advice would be appreciated.
I found the source of the leak. I am using an OLEDB connection to a Sybase Server instance to get data to load into SQL Server. 95% of the leak was isolated to a single function that invoked a Sybase stored procdure. Instead of getting the results in a result set, this procedure had the option of iether returning the results as output parameters or a result set. I initially chose the output parameter option. For reasons that are not clear to me, this output parameter mechanism caused a massive memory leak. I changed the logic to use a result set and the resolved the leak. Not clear why output parameters were an issue, but I found an optional approach that corrected the problem.