What is the RetainSameConnection Property of OLEDB Connection in SSIS?

I recently wrote about How to Use Temp Table in SSIS. One of the requirements to successfully reuse a temporary table across multiple tasks in SSIS is to set the RetainSameConnection property of the OLEDB Connection to TRUE. In this post, I will discuss the property and also use a Profiler Trace to find out its behavior.

The RetainSameConnection Property

RetainSameConnection is a property of an OLEDB Connection Manager. The default value of this property is FALSE. This default value makes SSIS execution engine open a new OLEDB connection for each task that uses the connection and closes that connection when the task is complete. I believe the idea behind this is to not block a connection to a server unnecessarily and release it until it is needed again. And it makes sense too because some packages can run for an extended duration and may not need to be connected to an OLEDB server all the time. For example, an OLEDB in not required to be open while parsing text files, sending emails, ETL operations not involving the OLEDB server in question etc. Releasing connections unless really required can be certainly helpful on busy servers because SQL Server needs some memory for each open connection.

On the other hand, some scenarios require a persistent connection e.g. temporary table reuse across multiple tasks. We can set the property value to TRUE and then it will open just one OLEDB connection with a server and keep it alive until the end of the package execution. The property can be set via the Properties window for the OLEDB Connection Manager.

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The Temporary Table Scenario

Local temporary tables (with a # in front of their name) in SQL Server are scoped to a session. SQL Server drops them when the session is closed. This means, local temporary tables created in one session are not available in another session. In SSIS, with the RetainSameConnection set to FALSE (the default), a new session is opened for each task. Therefore, temporary tables created by a task are not available to another task.

Demo

I have a demo package with two Execute SQL Tasks and one OLEDB Connection Manager. The Execute SQL Tasks have a simple SELECT statement and they both use the same connection manager.

aalamrangi.wordpress.com-SSISRetainSameConnection1

I have a Profiler Trace to monitor the number of connections created by the SSIS package.

The first execution of the package is with the RetainSameConnection set to the default value of FALSE. The trace captures two pairs of login/logout events, one for each task. The second execution is with the property value set to TRUE. This time, the trace captures only one pair of login/logout events.

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Conclusion

In most cases, the default value of RetainSameConnection=FALSE will be suitable. A developer should make a decision to enable it when the package tasks really need a persistent connection. In addition to the temporary table reuse, a TRUE value for this property can also be useful in managing transactions and reducing the number of recurring connection requests to a server.

How to Have Standard Event Logging in SSIS and Avoid Traps

Event logging in SSIS gives a lot of valuable information about the run-time behavior and execution status of the SSIS package. Having a common minimum number of events is good for consistency in reports and general analysis. Lets say your team wants to ensure that all packages must log at least OnError, OnWarning, OnPreExecute and OnPostExecute events. If the package has a DataFlowTask then the BufferSizeTuning should also be logged. The developer can include more events to log as required but these mentioned previously are the minimum that must be included.

You can create pre-deployment checklists or documentation to ensure this minimum logging. Probably you already have that. As the number of developers and/or packages increase, it becomes difficult to ensure consistency in anything, not just for event logging. Therefore documentation, checklists and training are helpful to an extent only. Your requirement could be more complex than my five-event example above and thus more prone to to oversight.

The easiest way to ensure a common logging implementation would be a logging template that has all the minimum event pre-selected. The developer should just need to apply that to the package.

Event Logging in SSIS with a Template

I assume that you are already familiar with the concepts of event logging in SSIS so this post is not going to be a beginners level introduction to event logging. I will rather discuss options to have a minimum standard event logging across SSIS packages and teams with minimal effort. I’ll also mention some traps to avoid.

I am using a demo SSIS package with two Data Flow Tasks and an Execute SQL Task. I have enabled event logging in SSIS for the first few events at the package level for the sake of demonstration. The logging configuration options for the package node (which is the top node) are shown in the first image.

Image 1 - Logging configuration window for the package node
Image 1 – Event logging configuration window for the package node

The logging options at the child container node Data Flow Task 1 are shown in the second image. The configuration for other Data Flow and the Execute SQL Task look the same.

Image 2 - Logging configuration window at the child container node
Image 2 – Event logging configuration window at the child container node

The check marks for the tasks are grayed out which means they are inheriting the logging options from their parent, i.e. the package. To disable logging for a task, remove its check mark in the left tree view window.

TIP: Logging can also be disabled by going to the Control Flow canvas and changing the LoggingMode property of the task to Disabled.

The Trick

Now look at the bottom of the images again. Notice the Load… and Save… buttons? They do exactly what they say. You can set your logging options and save them as an XML template. Later, this XML template can be loaded into other packages to enable the same logging options.

The XML template file has nodes for each event. For example, the logging options for OnError event are saved like this –


-<EventsFilter Name="OnError">

-<Filter>

<Computer>true</Computer>

<Operator>true</Operator>

<SourceName>true</SourceName>

<SourceID>true</SourceID>
<ExecutionID>true</ExecutionID>

<MessageText>true</MessageText>

<DataBytes>true</DataBytes>

</Filter>

</EventsFilter>

Notice that the XML just mentions the event name, not the name of any task. This means that when the template file is loaded, this logging option will be set for any task where the event is applicable. More on this later.

The Traps

The OnError event is a generic event applicable to all tasks. Lets talk about events that are specific to tasks. For example, the BufferSizeTuning event is applicable just to the Data Flow Tasks, not Execute SQL Tasks.

When I proceed to set logging for BufferSizeTuning event, I have to set it individually in the Data Flow Task tree node. Notice the message at the bottom of the second image that says –

To enable unique logging options for this container, enable logging for it in the tree view.

This message is important in the context of saving and loading a template file too. When I save a template file, the logging options of just that tree view node are saved. For example, the BufferSizeTuning event will be saved in the template only if I am at the Data Flow task in the tree view. It will not be saved if I am at the Package or the Execute SQL task in the tree view.

The reverse is also true. When I load a template, its logging options are applied to just that node which I select in the tree view. For example, if I load a template at the Data Flow Task 1, the options will not be applied to the Data Flow Task 2 or the Execute SQL Task. If the template has an event that is not applicable to the task then that event’s settings will be ignored. For example, the BufferSizeTuning event logging option is meant for Data Flow Tasks so it will be ignored for the Execute SQL Task. The fact that non-relevant options are ignored can be helpful for us to consolidate all logging options in a single template file.

Conclusion

A package level Save and Load of a logging template is straight forward. But if you need to have logging for events that are specific to a task type, then consider creating a logging template for each type of task. Also, if your logging configuration requires anything else than the package level settings, remember to load the template for each task in the tree view.

Number of Template Files How Pros and Cons
Individual File per Task Create one template file for each type of task. The file will have events applicable to that task. Pros –
Easier to know what type of tasks have a template and which ones do not.Cons –
More files to manage.
Single File for All Tasks Create a template file for each task. Then copy all event options in a single XML file. Pros –
One file is easier to manage.Cons –
Not obvious which tasks are include. Need to put in comments in the XML file.

How to Use Temp Table in SSIS

Using a temporary table in SSIS, especially in a Data Flow Task, could be challenging. SSIS tries to validate tables and their column metadata at design time. As the Temp table does not exist at the design time, SSIS cannot validate its metadata and throws an error. I will present a pretty straight forward solution here to trick SSIS into believing that the Temp table actually exists and proceed as normal.

Temporary Table Reference Across Two Tasks

To begin with, I will demonstrate that a Temp table can be referenced across two tasks. Add two Execute SQL Tasks in your package. Both of them use the same OLEDB connection. The first task creates a Local Temp table and inserts one row into it. The second task tries to insert one more row in the same table.

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TSQL script in the first task –

/* Create a LOCAL temp table*/
IF
(
Object_id('[tempdb].[dbo].[#LocalTable]')
IS NOT NULL
)
DROP TABLE
[tempdb].[dbo].[#LocalTable]
GO

CREATE TABLE [#LocalTable]
(
id INT IDENTITY,
label VARCHAR(128)
);
GO

/* Insert one row */
INSERT INTO [#LocalTable]
(label)
VALUES ('First row');
GO

TSQL script in the second task –

/* Insert one row */
INSERT INTO [#LocalTable]
(label)
VALUES ('Second row');
GO

Invalid Object Name Error

When executed, the SSIS package gives the following error because the second task cannot see the Temp table created in the first task. Local Temp tables are specific to a connection. When SSIS switches from one task to another, it resets the connection so the Local Temp table is also dropped.

Error: 0xC002F210 at ESQLT-InsertSecondRow
, Execute SQL Task: Executing the query
&quot;/* Insert second row */
INSERT INTO [#LocalTable]...&quot;
failed with the following error:
&quot;Invalid object name '#LocalTable'.&quot;.
Possible failure reasons:
Problems with the query
, &quot;ResultSet&quot; property not set correctly
, parameters not set correctly
, or connection not established correctly.
Task failed: ESQLT-InsertSecondRow
Warning: 0x80019002 at SSIS-DemoTempTable:
SSIS Warning Code DTS_W_MAXIMUMERRORCOUNTREACHED.
The Execution method succeeded, but the number
of errors raised (1) reached the maximum
allowed (1); resulting in failure. This occurs
when the number of errors reaches the number
specified in MaximumErrorCount. Change the
MaximumErrorCount or fix the errors.
SSIS package &quot;SSIS-DemoTempTable.dtsx&quot;
finished: Failure.

The Fix

The fix is pretty simple. Right-click on the OLEDB connection manager and go to the Properties window. Change the RetainSameConnection property to True. This will force the connection manager to keep the same connection open. I have another post with more details about the RetainSameConnection property of OLEDB connection managers.

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This fixes the error and the package executes successfully.

Temporary Table in a Data Flow Task

Now let me demonstrate that a Temp table can be used in a Data Flow Task.

Add a Data Flow Task to the package.

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In the Data Flow task, add an OLEDB source that will use the same OLEDB connection as used by the Execute SQL Tasks earlier. In the OLEDB Source Editor window, there is no way to find our Local Temp table in the list so close the Editor window.

The Development Workaround

Open a SSMS query window and connect to the SQL Server used in the OLEDB connection. Now create a Global Temp table with the same column definition. You can just copy the CREATE TABLE script and add one more # symbol to the table name.

The Global Temp table is just a development workaround for the restriction imposed by the volatility of the Local Temp table. You can even use an actual physical table instead of the Global Temp table. We will switch to the Local Temp table in the end of this post and then the Global Temp table (or the actual physical table) can be dropped.

Script –

/* Create a GLOBAL temp table
with the same schema as the
earlier LOCAL temp table.
Note the ## in the table name */

CREATE TABLE [##LocalTable]
(
id INT IDENTITY,
label VARCHAR(128)
);
GO

Come back to the SSIS Control Flow. Create a new package scoped variable of String data type. Give it the name TableName and put the Global Temp table name as its value.

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Go to the Data Flow > OLEDB Source and double click to open the OLEDB Source Editor window. Choose the Data Access Mode as Table name or view name variable. In the Variable name drop-down, choose the new variable that we created. This means that now the OLEDB Source is going to use the GLOBAL Temp table. Of course, it is not the same as the LOCAL Temp table but we will get to that in a minute. Click on the Columns tab to load the table metadata. Then click on OK to close the OLEDB Source Editor.

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Now add a Flat File Destination and configure its properties. I’ll not go into those details. Please let me know in the comments or via email if you need information on how to configure a Flat File Destination.

The final Data Flow Task looks like this.

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You can execute the package now to verify if it runs successfully. Although it will run fine, the flat file will not have rows because the source of the data is the Global Temp table, not the Local Temp table populated by the Execute SQL Tasks.

A Global Temp table (or a physical table) is common to all users so it could cause issues in multi-user environments. Local Temp tables are specific to a connection, hence more scalable. All that is needed now is to remove one # in the variable value and the OLEDB Source will point to the correct Local Temp table. To clean up, you can drop the Global Temp table.

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The flat file will have the rows inserted by the Execute SQL Tasks.

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Avoid Validation

Subsequent runs of the package will show validation errors because the Local Temp table is not available when the package starts. To go around this, you can set the DelayValidation property of the package to TRUE. As the package is the parent container for all other tasks, this property will be applied to all tasks in the package. If you do not wish to disable validation for all tasks, then you can set it for individual tasks, i.e. the first Execute SQL Task and the Data Flow Task. Again, the Data Flow Task may contain multiple sources, destinations and transformations and you may not want to disable validation for all of them. In that case you can be more granular and set just the ValidateExternalMetadata property of the OLEDB Source to FALSE.

Further Reading:

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How To Manage SQL Server Job Failure Emails with MS Outlook Conditional Formatting

Some scheduled jobs send failure emails upon an error and DBAs need to remember to fix the job and re-execute it. I use filter rules in MS Outlook to organize my inbox by redirecting all the scheduled job emails to a separate folder. In addition to that, I use conditional formatting rules to keep track of action items as pending or done. The conditional formatting rules highlight the job failure emails with the red color and turn them green when marked complete as shown in the following image.

JobEmailsAsTasksExpected

Create a Conditional Formatting Rule to Highlight a Failed Job Email in Red:

Navigate to the folder where you would like to modify the view. You can even customize your main Inbox folder view, if that is where your emails are. Right-click on the header row and go to View Settings.

JobEmailsAsTasks1

Click on Conditional Formatting.

JobEmailsAsTasks2

In the Conditional Formatting window, click on Add and rename the new untitled rule. Then change the font color to red and click on Condition.

JobEmailsAsTasks3

In the Filter window, put a sufficiently unique text phrase from the error email that can distinguish it from good emails. Also specify in the drop-down where exactly the filter should look for the text phrase i.e. just in the email subject or, email body or both.

My emails have the following text in the email body that I can use for identification –

STATUS:  Failed

Now this a simple example with a text phrase for filtering but you can use other criteria in More Choices and Advanced tabs too for more complex scenarios as necessary. If you get emails with different text patterns then you can always create a new rule for each phrase.

JobEmailsAsTasks4

That is it. Click on OK to come back to your inbox and verify that the error emails have a red font.

Create a Conditional Formatting Rule to Highlight a Failed Job Email in Green After Resolution:

Now we want another rule that will change the red email to a green one when it is marked as complete. Add another Conditional Formatting rule, rename it and change the font color to green and click on Condition.

JobEmailsAsTasks5

In the filter window, follow the same steps as in the previous red rule. Then go the More Choices tab.

JobEmailsAsTasks6

In the More Choices tab, check the Only Items which: and select the drop-down value of are marked complete.

JobEmailsAsTasks7

Back in the Conditional Formatting window, move the green job up. This is important otherwise the red rule will override the effects of the green rule.

JobEmailsAsTasks8

The final window will look like this.

JobEmailsAsTasks9Final

Now when ever the issue from the failure email is resolved, just right-click on the email, go to Follow Up, select Mark Complete. The email will turn green.

JobEmailsAsTasks10

How To Connect SSMS to ALWAYSON Read-Only Secondary Database

The databases in PRIMARY availability group can be used for read-write access. The databases in the SECONDARY availability group can be used just for read-only access.

An attempt to connect to a SECONDARY availability group database with a normal connection, which is read-write by default, shows the following error message –

Msg 978, Level 14, State 1, Line 1

The target database ('AGDemoDB') is in an
availability group and is currently accessible
for connections when the application intent is
set to read only. For more information about
application intent, see SQL Server Books Online.

To resolve the issue, the connection string needs to have the Application Intent = ReadOnly parameter. How do you pass parameters in a SSMS connection?

SSMS has many options that are not too obvious. One of them is to provide additional connection parameter options. All that is needed to resolve the above error is to use the Additional Connection Parameters screen in the connection dialog and put the parameter there.

AG_ReadOnlyIntent01

The keyword should not have any spaces.

AG_ReadOnlyIntent02

Further reading:

The AlwaysOn Professional MSDN blog has more examples of connection strings for various applications.

You may also like to review the Application Intent Filtering feature of AlwaysOn at this and this link.

How to Avoid Orphan Users in SQL Server ALWAYSON, Create Logins Correctly

SQL Server logins are stored in the [master] database. System databases (master, model, msdb and tempdb) cannot be included in an availability group so a login created on the PRIMARY replica will not show up on the SECONDARY replica automatically. It has to be created manually on the SECONDARY replica.

Logins have an SID associated with them. When a Windows authentication login is created in SQL Server, it uses the SID from the Windows Active Directory. So the SID for such a login will be the same on every SQL Server in the network domain.

When a SQL authentication login is created, it gets a new auto-generated SID assigned by the SQL Server. This auto-generated SID will be different in each SQL Server even if the login name and the password combination are the same.

The database users are mapped to the logins internally using the SID, not the login name/user name. There are some situations where the SID may have a mismatch, e.g. when a database is restored to a different server where the supposedly matching login already exists, or a login is dropped and recreated without consideration to the mapped users, or a login is recreated between a database detach and reattach etc. Such users that do not have a login with a matching SID are known as orphan users. This SID mismatch means that although an application or a user can connect to the server using the login, but it can not access the database.

The following options with varying degree of effectiveness can be used to fix the SID mapping between a login and an orphan user –

  • Drop and recreate the user in the restored database. Of course the user permissions will get deleted too and have to be granted again.
  • Drop and recreate the login with same SID as the restored database. This is a definite no-no if there are other databases on the server linked to that login. It will only complicate matters.
  • Run the system stored procedure sp_change_users_login. It has parameters to just report, fix one or fix all orphans. But the stored procedure is now marked as deprecated so there are no guarantees of future availability.
  • ALTER the user (there are some restrictions, like there cannot be a one-to many mapping etc.) –
    USE [MyUserDBName]
    GO
    ALTER USER someuser WITH LOGIN = somelogin
    

    As the user databases on the SECONDARY replica are read-only, the role of the SECONDARY server has to be changed to PRIMARY by doing a failover before the above ALTER command can be executed.

All of this can be avoided if the login is created correctly on the SECONDARY replica. We just have to make sure that the SID for the login on the SECONDARY replica matches the PRIMARY replica.

Let us begin with creating a new login on the PRIMARY replica of an existing Availability Group –

/* On the PRIMARY replica */

-- Create the Login
USE [master]
GO
CREATE LOGIN [TestLogin]
WITH PASSWORD=N'abc123#'
, DEFAULT_DATABASE=[master]
GO

Grant privileges to this login if necessary. They will NOT automatically replicate to the SECONDARY replica. Now find the SID of this new login.

-- Get the SID for the new Login
SELECT name, sid 
FROM sys.server_principals 
WHERE name = 'TestLogin'

/* Results:
name          sid
TestLogin     0x8EA0E033BD83524180CF813A20C5265B
*/

On the SECONDARY replica, create the login with the same SID. The GUI wizard to create logins does not have this feature to specify the SID, so the login has to be created using TSQL with an additional parameter.

/* On the SECONDARY replica */
-- Create the Login with the same SID as
-- the PRIMARY replica
CREATE LOGIN [TestLogin]
WITH PASSWORD=N'abc123#'
-- use the SID retrieved above
, SID = 0x8EA0E033BD83524180CF813A20C5265B
, DEFAULT_DATABASE=[master]
GO

Grant the same privileges to this login as done on the PRIMARY replica.

Now go back to the PRIMARY replica and create database user mapped to the login and grant required permissions at the database level. This new database user will be automatically replicated on the SECONDARY replica with its permissions and correctly map to the login. No action on SECONDARY required because the user database is in an Availability Group that is synced across replicas.

Further reading:
For the sake of completeness, I must mention the widely cited KB 918992 article (How to transfer logins and passwords between instances of SQL Server) which provides a stored procedure [sp_rev_login] to move the logins from one server to another. This stored procedure generates the CREATE LOGIN script with the password hash and the SID. You would need that stored procedure only if you don’t have access to the clear text passwords or, if you want to include that script as a scheduled job but not hardcode the password in the job. If you do not have those constraints then you can simply use the steps described in my blog post here.

How to Concatenate SSIS Variables with a For Loop Container

Variable value concatenation in SSIS is usually done with a Script Task. I am going to demonstrate variable concatenation with a For Loop Container in this post while working on a real world scenario of sending all files from a folder as email attachments.

Drag a ForEach Loop Container in the Control Flow. Then drag a For Loop Container within the ForEach Loop Container. There are no other tasks in these two containers. Finally add a Send Mail Task to the Control Flow and join it to the ForEach Loop Container with a precedence constraint.

The final package looks like this.

Concat1-Package

ForEach Loop Container is used to iterate through all files in a folder and return their full paths. For Loop Container will concatenate the file paths in a variable. Send Mail Task will use the concatenated file paths as an attachment list in an email.

Declare two variables of string type at the package level. Variable @[User::FELC_Iterate] will hold the single file path returned by the ForEach Loop. Variable @[User::FLC_Concat] will hold the concatenated list of file paths passed from the other variable.

Concat2-Variables

Double click the ForEach Loop Container to open the properties editor. In the Collections tab, give the folder path and select the radio button for fully qualified file name. You can also set the filter for the file types (e.g. *.txt, *.xls etc.). I let it be at its default of all files (i.e. *.*).

Concat3-FELCEditorCollectionsTab

In the Variable Mappings tab, set the variable @[User::FELC_Iterate] to index zero so that it can hold the file paths returned by the ForEach Loop Container. Click OK to close the editor.

Concat4-FELCEditorVariableMappingsTab

Now double click the For Loop Container to open its properties editor. Set the InitExpression to –

@[User::FLC_Concat] = @[User::FLC_Concat] + @[User::FELC_Iterate] + "|"

This expression will append the @[User::FELC_Iterate] value coming from the outer ForEach Loop along with a pipe symbol to the @[User::FLC_Concat] in each iteration. The pipe symbol is the separator required by the Send Mail Task if there are multiple files as attachments.

One iteration of the For Loop will suffice our requirement to append the variable value. So set EvalExpression to 1<0, or any improbable boolean condition. The For Loop executes once and then evaluates this condition to see if it can go for another execution. The improbable condition will exit the loop on second iteration because the condition will evaluate to FALSE. Click OK to close the editor.

Concat5-ForLoopEditor

Double click the Send Mail Task to open its editor. Setup the SMTP connection and other fields in the Mail tab. In the Expressions tab, add an expression for FileAttachments to use the @[User::FLC_Concat] variable. Click OK to close the editor.

Concat6-SendMailTaskEditorExpressions

Execute the package and the file paths are concatenated as shown on the Locals window. These files would be emailed as attachments.

Concat7-LocalsWindowVariableValues

How to Log SSIS Variable Values During Execution in the Event Log

Log entries created during the execution of an SSIS package help in monitoring, analysis, and issue resolution. In addition to logging events, you might want to capture the run-time values of variables in the package. I couldn’t find a native feature to log SSIS variable values so the following post shows how I did it.

The Setup

For this demo, I’ll do an INSERT operation on a table named TableA and use variables to save the before and after INSERT row count. The TableA is always blank at the beginning of the package i.e. the row count is zero. The Execute SQL Task named ESQLT-InsertRowsInTableA inserts 502 rows in TableA. The simple package looks like the image below. If you are wondering about the funny prefixes in the object names then you can read about my naming conventions mentioned in my other blog post.

Log SSIS Variable Value 1 - Package

I have two integer variables named rcTableA_PreRefresh and rcTableA_PostRefresh scoped at the package level.

Log SSIS Variable Value 2 - Variables Init Zero

Enable the Event

A log entry is generated when an event is triggered. Each object in SSIS has its own events that can be logged. I’ll use the event called OnVariableValueChanged, which as the name denotes, is triggered whenever the value of the variable changes. This event is disabled by default. To enable it, go to the Properties window of the variable and make the RaiseChangedEvent property to True. It must be enabled for each variable individually.

Log SSIS Variable Value 3 - Variable Properties

Next, I include the OnVariableValueChanged event in the logging configuration. It has to be included at the container level where the variables are scoped to. In my case, at the package level. I’m using the SSIS Log Provider for SQL Server in this package.

Log SSIS Variable Value 44 - Configure Log

Then I execute the package and look at the [dbo].[sysssislog] table for the log entries.

Log SSIS Variable Value 5 - Log Entries 1

There are some log entries but something is missing. I see the OnVariableValueChanged event logged for the Post Refresh variable but not the Pre Refresh variable.

The reason is that the initial value of the variable is set to zero in the package. The row count of a brand new empty table is also zero. So there was no change in variable value. The OnVariableValueChanged event fires only when the value actually changes! Overwriting with the same value doesn’t fulfill this condition.

To resolve that, I change the initial values in the package to -1. Now even if the row count turns out to be zero, the variable value will still change from -1 to zero. The COUNT function can’t count below zero, can it?

Log SSIS Variable Value 6 - Variables Init Minus One

I run the package again and check out the [dbo].[sysssislog] table.

Log SSIS Variable Value 7 - Log Entries 2

Things are better. The OnVariableValueChanged event for both the variables show up in the log. But the variable values are still not there.

Log SSIS Variable

The reason for missing values is that the event logging just captures the fact that the variable value changed. It doesn’t capture the value by itself. I’ll make an addition to the event handler to get the variable values too. I add an Execute SQL Task to the package level event handler for OnVariableValueChanged event.

Log SSIS Variable Value 8 - Event Handler

The General tab of the Execute SQL Task has the following properties and SQL command –

Log SSIS Variable Value 8 - Event Handler - ESQLT 1

INSERT INTO [dbo].[sysssislog]
([event]
,[computer]
,[operator]
,[ source]
,[sourceid]
,[executionid]
,[starttime]
,[endtime]
,[datacode]
,[databytes]
,[message])
VALUES
('*SSIS-OnVariableValueChanged' -- Custom event name
,? -- param 0
,? -- param 1
,? -- param 2
,? -- param 3
,? -- param 4
,? -- param 5
,? -- param 6
,0 -- Zero
,'' -- Blank string
,?) -- param 7

Notice that I precede the custom event name with an asterisk to differentiate it from the log entries created by the system.

The Parameter Mapping tab of the Execute SQL Task has the following properties –

Log SSIS Variable Value 9 - Event Handler - ESQLT 2

Pay attention to the System::VariableValue (last variable) in this screen. Its data type is LONG, which is appropriate for the numeric row counts in my example. You may have different data types for your variables. Do adjust the data type and length appropriately. Using a wrong type could lead to no value logged at all.

I run the package again and this time, the variable values are also logged in the table.

Log SSIS Variable Value 10 - Log Entries 2

Summary

A single event handler will take care of all variables in that scope. In my case, two package scoped variables are handled by a single package level event handler.

The variable value really has to change to fire the event.

The OnVariableValueChanged event is triggered for the container that has the variable in its scope. The container triggering the change in variable value could be different than the container that has the variable in its scope. In my demo, the variables were scoped to the package. Even though an Execute SQL Task is changing the variable values, I still put the event handler at the package level. As another example, assume there is a variable declared in the scope of a ForEachLoop container and there is a Script Task in the ForEachLoop. The Script Task changes the variable value. The OnVariableValueChanged event will be triggered for the ForEachLoop task.

I have used the default [sysssislog] logging table to log my variable values. You can easily use a different custom table by changing the OLEDB connection and making appropriate changes to the INSERT statement.

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TSQL Gotcha – Order of expressions for a range search with BETWEEN

Do you trust your users to always pass range search parameters in the correct order? Or do the users trust that the code will take care of a small thing like parameter ordering?

If you have a stored procedure or a script that accepts two parameters to do a range search using a BETWEEN keyword (or maybe with a >= and <=) then it is important to verify that the start expression and end expression are in the correct order. The correct order for numeric values is smaller value before a larger value. The correct order for character values is the dictionary order. A user might pass on the expression values the wrong way around and see no results returned.

The following demonstration has a small check for the correct order of values and to do a quick reorder to fix any issues. To help things a bit more, instead of using generic variable names like @param1 and @param2, they can be made self-documenting by being descriptive like @begin_param and @end_param.

Demonstration with numeric values:

declare @DemoTableNumeric table 
(col1 int)

-- Insert 10 rows in the demo table
insert into @DemoTableNumeric (col1)
values 
(1),(2),(3),(4),(5),
(6),(7),(8),(9),(10)

-- verify data
select * 
from @DemoTableNumeric

declare 
@param1 int, 
@param2 int

-- Assign values
-- Note: Param1 &gt; Param2
select 
@param1 = 7, 
@param2 = 4

-- The following return zero rows
-- because the first expression is
-- greater than the second expression
-- It is a wrong order of values.
select * 
from @DemoTableNumeric
where 
col1 between @param1 and @param2

select * 
from @DemoTableNumeric
where 
col1 &gt;= @param1 and col1 &lt;= @param2

-- It is important to verify the expression
-- values and reorder them if necessary
-- The following IF condition does that
if @param1 &gt; @param2
begin
	declare @temp int
	set @temp = @param1
	set @param1 = @param2
	set @param2 = @temp
end

-- Now both queries return rows
select * 
from @DemoTableNumeric
where 
col1 between @param1 and @param2

select * 
from @DemoTableNumeric
where 
col1 &gt;= @param1 and col1 &lt;= @param2

Demonstration with character values:

declare @DemoTableChar table 
(col1 varchar(10))

insert into @DemoTableChar (col1)
values
('Alpha'),
('Golf'),
('Kilo'),
('Oscar'),
('Tango'),
('Zulu')

-- verify data
select * 
from @DemoTableChar

declare 
@param1 varchar(10), 
@param2 varchar(10)

-- Note: Param1 &gt; Param2
select 
@param1 = 'Tango', 
@param2 = 'Golf'

-- This returns zero rows
-- because the first expression is
-- greater than the second expression
-- It is a wrong order of values.
select * 
from @DemoTableChar
where 
col1 between @param1 and @param2

select * 
from @DemoTableChar
where 
col1 &gt;= @param1 and col1 &lt;= @param2

-- It is important to verify the expression
-- values and reorder them if necessary
if @param1 &gt; @param2
begin
	declare @temp varchar(10)
	set @temp = @param1
	set @param1 = @param2
	set @param2 = @temp
end

-- Now both queries return rows
select * 
from @DemoTableChar
where 
col1 between @param1 and @param2

select * 
from @DemoTableChar
where 
col1 &gt;= @param1 and col1 &lt;= @param2