I am implementing a SSIS package and currently trying to do the following.
Truncate the destination table
Fetch the data by executing the stored procedure and insert it into the destination table.
I have created an Execute SQL task to address step 1 and dataflow with oledb source and oledb destination to address the second point. It been working successfully so far but isn't working for one my stored procedure that uses temp tables.
When I edit the oledb source and click the preview button, I get the error no column returned
I know that SSIS has an issue with generating column while executing stored procedures that depend on temp tables. I have converted the stored proc to use temporary table variables and its now able to return columns in SSIS when I do a preview. The only downside is that the stored procedure is taking longer time to execute. Its taking 1 hour 15 mins as compared to 15 mins while using temp tables.
I did see a suggestion to use SET FMTONLY before executing the stored procedure as an alternate solution to changing to temp table variables but that didn't seem to work as I am getting syntax or permission denied error.
Could somebody tell me a solution to my problem which does not compromise on the performance.
Sounds like you've already read all the approaches to using Temp tables in SSIS, including the IF 1=0... trick? If you haven't seen that one yet, google it.
You say that using Table Variables causes your stored procedure to take about 5 times longer than using Temp Tables. The most likely reason for that is that you are indexing your temp tables but not your table variables. If you didn't know that table variables can be indexed, they can. You might try that.
Finally, a solution that you haven't mentioned is that you can replace your temporary table with a real table that gets truncated when you're done using it.
Short comment:
Try EXEC WITH RESULT SETS and specify the metadata yourself for a proc with temp tables; or use the Script Component as a source and specify the Output columns yourself.
Long comment:
Technically speaking, it is the driver/database you are using in SSIS that would decide the behavior when working with temp tables.
Metadata is an important factor when using SSIS's pipeline components. By metadata, I mean the names of the columns, their data types etc that a pipeline component uses. When designing a data flow, someone/something should provide this metadata to the components that require it.
In most cases, SSIS automatically retreives the metadata. Components that do not connect to a external data source, like Conditional Split etc, get their metadata from the other components they are connected to. For the pipeline components that connect to a external data source (like Oledb source, oledb destination, Lookup etc.), SSIS provides a mechanism to get this metadata without human involvement. This mechanism involves the driver connecting to the database and retrieving the metadata of the output. If the driver/database is capable of returning the metadata, then that metadata is used. If the driver/database is incapable, then you get the errors you are seeing. The rest of my comments are based on the assumption that you are using a SQL Server database in your question.
When working with a SQL Server database in SSIS, typically, we use the native client drivers provided by Microsoft. When trying to get the metadata, these drivers try to get the metadata without actually executing the SQL Statement (actual execution can have side effects; and also, might take more than a few seconds/minutes/hours; and you dont want side effects and long wait times during package design time.) So to get the metadata, the driver relies on the metadata of the actual objects used in the sql command. If the command uses a physical table or view, SQL Server already has the metadata available and can supply it to the driver. If it is a temp table, SQL Server does not have the metadata until it can create the temp table. If using FMT ONLY option, you can use it in such a way to create the temp tables, but avoid any heavy processing/side affects and thus be able to retrieve metadata without penalties. Post 2012, these native client drivers rely on some newer functionality to retrieve metadata than the drivers before 2012. In 2012 and after, the driver uses the sp_describe_first_result_set proc to retrieve metadata. So, whether you can get metadata or not is determined by the ability of the sp_describe_first_result_set proc.
So while SSIS can automatically get the metadata (because of the driver/database), it does not automatically get the metadata in some cases (again because of the driver/database). In cases involving the second scenario, some other process (typically a human) can help the driver infer metadata or provide the metadata to the component directly.
To help the driver, in case of SQL Server 2012 and after, you can use the WITH RESULTSETS clause to specify the output metadata. When this clause is present, the driver will use it and doesnt try to query the metadata from system objects; and thus avoid the error which you would otherwise get. If you are using the drivers that came with SQL Server 2008, you can use FMT ONLY. This option is at the driver/database level.
Another option could be to use a Script Component as the Source and in the Output columns, you can specify the columns/metadata. SSIS would not try to retrieve metadata from the datasource in this case, but would rely on the definitions you provided in the Output section of the Script Component.
As you can see, both options involve a human (or some other process) specifying the metadata instead of SSIS trying to retrieve the metadata in an automated fashion. I would prefer the first option if working with SQL Server and the second option if working with databases like MySql.
Related
I have a package that is essentially trying to copy 26 tables from oracle to sql server.
Its not a complete table copy, we are looking for records that belong to certain 'Regions' of our company.
I pull the data from oracle
I started just doing this with elbow grease, but each of the 26 tables required several variable to do the deletes, the fetches etc.
Long story short, I decided to use variables to represent the table names (source, temp and target).
This allowed me to copy/paste one sequence and effectively bypass a lot of click click in bids.
The problem I am running into is that the meta data seems to be very fragile. Sequences all seem to run on their owwn, but when i run the whole package, it breaks. And never in the same place.
Is this approach just a bad idea w/ SSIS?
So just to take this off the board....
Each sequence container had the following ops
Script task - set variables
Execute SQL task - delete from temp
data flow SourceToTemp -
ole db source - used a generic select * from tbl to temp_tbl
derived column1 - insert a timestamp column
oledb destination - map all the columns into a temp table (**THIS IS THE BIG PROBLEM CHILD)
Execute SQL task - delete from target
Execute SQL task - insert target select from temp
the oleDB destination is the piece that kept breaking.
Since it references variables, I had to be very careful at design time to set the variables correctly before opening one of the data flows.
I am pretty sure this is the problem. Since I can not say w/ certainty when SSIS refreshes meta data in the design environment, I cant be sure if/when sequence X refreshed while the variables were set to support sequence Y.
So while it conceptually should work at run time, dev time is a change control night mare.
I have changed all the oleDB destinations to point to a hard table name. this is really a small concession since there are 4 sql statements that are still driven by variables. (saving me a lot of clicking and typing)
This small change has eliminated the 'shifting sands' problem.
Take-a-way lesson : dont have an oledb destination be basesd on a variable.
thanks for the comments
I am creating an ETL in SSIS in which I which I want my data source to be a restricted query, like select * from table_name where id='Variable'. This variable is what I defined as User created variable.
I do not understand how I can have my source query interact with the SSIS scoped Variable.
The only present options are
Table
Table from variable
SQL Command
SQL command from a variable
What I want is to have a SQL statement having a variable as parameter
Simple. Choose SQL command as the Data Access Mode. Enter your query with a question mark as a parameter placeholder. Then click the Parameters button and map your variable to Parameter0 in the Set Query Parameters dialog:
More information is available on MSDN.
An inferior alternative to #Edmund's approach is to use an Expression on another Variable to build your string. Assuming you have #[User::FirstName] already defined, you would then create another variable, #[User::SourceQuery].
In the properties for this variable, set EvaluateAsExpression to True and then set an Expression like "SELECT FirstName, LastName, FROM Person.Person WHERE FirstName = '" + #[User::FirstName] +"'" The double quotes are required because we are building an SSIS String.
There are two big reasons this approach should not be implored.
Caching
This approach is going to bloat your plan cache in SQL Server with N copies of essentially the same query. The first time it runs and the value is "Edmund" SQL Server will create an execution plan and save it (because it can be expensive to build them). You then run the package and the value is "Bill". SQL Server checks to see if it has a plan for this. It doesn't, it only has one for Edmund and so it creates another copy of the plan, this time hard coded to Bill. Lather-rinse-repeat and watch your available memory dwindle until it unloads some plans.
By using the parameter approach, when the plan is submitted to SQL Server, it should be creating a parameterized version of the plan internally and assumes that all parameters supplied will result in equal costing executions. Generally speaking, this is the desired behaviour.
If your database is optimized for ad-hoc workload (it's a setting turned off by default), that should be mitigated as every plan is going to get parameterized.
SQL Injection
The other big nasty you will run into with building your own string is that you open yourself up to SQL Injection attacks or at the least, you can get runtime errors. It's as simple as having a value of "d'Artagnan." That single quote will cause your query to fail resulting in package failure. Changing the value to "';DROP TABLE Person.Person;--" will result in great pain.
You might think it's trivial to safe quote everything but the effort of implementing it consistently everywhere you query is beyond what your employer is paying you. All the more so since there is native functionality provided to do the same thing.
When using OLEDB Connection manager (with SQL Server Native Client 11.0 provider in my case) you can catch an error like this:
Parameters cannot be extracted from the SQL command. The provider
might not help to parse parameter information from the command. In
that case, use the "SQL command from variable" access mode, in which
the entire SQL command is stored in a variable.
So you need to explicitly specify database name in OLEDB Connection manager properties. Otherwise SQL Server Native Client can use different database name then you mean (e.g. master in MSSQL Server).
For some cases you can explicitly specify database name for each database object used in query, e.g.:
select Name
from MyDatabase.MySchema.MyTable
where id = ?
I can only find a solution for using temp table in OLE DB source.
But I can't find a solution for ADO.NET source. How can I successfully use temp table in the ADo.NET source in SSIS package?
I find working with temporary tables in SSIS more pain than they are usually worth. I hope your experience is better.
Create an ADO.NET connection. In the properties of the Connection Manager set the value of RetainSameConnection from false to true. This will allow the temporary table created to be in existence for the duration of the package execution by preventing connection pooling from swapping out threads.
My trouble extends from getting the metadata set up correctly. To get around this, I create a variable, QuerySource, that queries a physical table that mirrors what the temporary table will look like. SELECT S.src_id, S.src_value FROM dbo.SRC AS S; This allows the data flow to establish the correct meta data for the downstream components. I manually use this query in the ADO.NET source. Once that's done, I will need to change the query to use the temporary table, ##SRC. Unlike the OLE DB Source component, you cannot set this property inside the Data Flow task.
Once the data flow work is completed, back in the Control Flow, view the Properties of the Data Flow Task. Change the Delay Validation from false to true. This will prevent any design time validation from firing which is needed once we remove the non-temporary table "scaffolding." Next find the Expressions and click the ellipses (...). In the drop down, you should see the name of your ADO.NET source. I had renamed mine so I saw [ADONET Src].[TableOrViewName] and [ADONET Src].[SqlCommand] in the drop down list. I selected [ADONET Src].[SqlCommand] and as my value, I used #[User::SrcQuery].
I ran the package to ensure it still worked. It did. I then changed the value of my query to be SELECT S.src_id, S.src_value FROM ##SRC AS S; I reran and this time it correctly pulled data from my temporary table.
If you are using SQL Server 2012 as your source, you might be able to make it easier on yourself by using the WITH RESULT SETS option of the EXECUTE statement to explicitly describe your temporary tables metadata.
I have a reporting database and have to transfer data from that to another server where we run some other reports or functions on Data. What is the best way to transfer data periodically like months or by-weekly. I can use SSIS but is there anyway I can put some where clause on what rows should be extracted from the source database? like i only want to extract data for a current month. Please do let me know.
Thanks,
Vivek
For scheduling periodic extractions, I'd leave to that SQL Agent.
As for restricting the results by some condition, that's an easy thing. Instead of this (and you should always use SQL Command or SQL Command From Variable over Table Name/Table Name From Variable as they are faster)
Add a parameter. If you're use OLE DB connection manager, your indicator for a variable is ?. ADO.NET will be #parameterName
Now, wire the filter up by clicking the Parameters... button. With OLE DB, it's ordinal position starting at 0. If you wanted to use the same parameter twice, you will have to list it each time or use the ADO.NET connection manager.
The biggest question you will have to answer is how do I identify what row(s) need to go. Possibilities are endless: query into the target database and find most recent modified date for a table or highest key value. You could create a local table that tracks what's been sent and query that. You could perform an incremental load / ETL Instrumentation to identify new/updated/unchanged rows, etc.
I am writing a basic file dump from one database to another. I am using SSIS 2008 and creating several packages to transform the data I have from a MSSQL 2010 database to a MYSQL 5.1 database.
All the connections are set up and records can be tranfered between the two databases but I would like to use temp tables in the transform processes and use the temp table as the MSSQL source in a dataflow task to dump the table in an awaiting MYSQL table.
I have been having problems setting this up. I am using an OLEDB connection and have set the RetainSameConnection property as well as the DelayValidation property to true. When setting up the source figure as the source from the MSSQL database I cannot find the temp table I have created in an earlier task from the control flow. I am using the same connection manager for these two tasks.
Anyone have any ideas or experience with this?
As a simple example one task does..
SELECT *
INTO #TMP
FROM CUSTOMERS
(This is a simplified example and I relize in this case I could just use the Customers table so bear with me)
Is it possible to use this temp table in a dataflow operation as the source table?
As I mentioned in my comment, not much of a solution and more of a workaround. SSIS uses the shape of result sets to bind properties in tasks. As temp tables are not always available in the database this can cause errors in SSIS even if you set DelayValidation to true.
My solution is to create an SSIS schema in whichever database you're connecting to. The reasons for doing so are security and clear separation of objects that are only used within SSIS packages - primarily staging tables.
Instead of throwing tables in your dbo schema (you shouldn't be anyway, shame on you) you'd create them in the SSIS schema. A typical data flow would truncate the table when it begins, load values and perform whatever operations are required, optionally truncating it when complete. As long as the table is always available SSIS can examine the shape of result sets.
You should not use temp tables as the source as it will not recognize the columns for the select. use table variables or CTEs instead.