Serializable Isolation Violation on Table in Redshift Simplified: A Comprehensive Guide 101

In this tutorial, you will learn how to resolve Serializable Isolation Violation on Table errors in Redshift. Unlike what some users may believe, it is possible to run transactions concurrently on a single Redshift table. That said, these concurrent transactions will be successful only if the processes will produce the same results as when they are applied serially. If you run concurrent transactions that produce different results from when they are applied serially, your Redshift table will display the Serializable Isolation Violation on Table Error.

Read along to learn more about why the Serializable Isolation Violation on Table error occurs and how to solve it.

Table of Contents

• What is Amazon Redshift?
  • Benefits of Amazon Redshift
• What is Serialization isolation?
• How to Solve Serializable Isolation Violation on Table Error?
  • Use the LOCK command to Force Serialization
  • Run both Transactions Serially
  • Abort One Transaction Entirely
• Conclusion

What is Amazon Redshift?

Amazon Redshift is a Data Warehouse that offers data storage opportunities to businesses and programmers. This service also allows you to analyze your data to generate detailed insights for your business decisions. 

To enable Redshift users to get the best out of their databases, Redshift offers a variety of functions. Some of these features are:

• Concurrent Scaling: This feature allows you to quickly run massive queries when your data needs outsize basic Redshift clusters. With concurrent scaling, you can run your queries rapidly irrespective of their number.
• Data Sharing: The purpose of the Data Sharing feature is to display data in clusters on multiple clusters without moving the data manually. Data sharing facilitates inter-team communication.
• Federated Queries: The Amazon Redshift Federated Query lets users integrate queries outside Amazon Redshift with data in Redshift clusters.

Benefits of Amazon Redshift

Thanks to its features, Redshift users enjoy the following benefits of Amazon Redshift: 

• Redshift analyzes databases quickly. It can process a thousand queries in seconds.
• It is easy to use. It adopts the same interface as MySQL to help users navigate the service efficiently.
• Redshift is affordable. It offers a flexible pricing model where businesses can choose to pay for the data warehousing services on a reserved or on-demand basis. Small companies which rarely use the Data Warehouse tend to pay by demand. On the other hand, larger companies that use the storage consistently pay on a reserved basis. 
• It is scalable. Redshift lets its users increase the size of their database when their storage needs grow. Also, you only pay for the memory size you use.
• With Redshift, you can rest assured that your data will enjoy secure protection. The system offers VPCs (Virtual Private Cloud), which hosts users’ data in isolated networks.

Despite its helpful features and numerous benefits, Amazon Redshift still has a few limitations. For instance, you can only run concurrent transactions to a single table if they will produce the same results as when you apply them serially. In technical terms, Redshift users must follow the Serializable Isolation on Table rule to run concurrent transactions in a single table.

What is Serialization Isolation?

Serialization Isolation is an SQL Transaction that treats concurrent transactions as if they were applied in serial order. As such, this behavior only supports concurrent transactions that produce the same results as their serial combinations. Redshift is one of the Amazon services that support this transaction level. When users apply concurrent transactions that generate different results from their serial combinations to the same Redshift table, the system displays a Serializable Isolation Violation on Table error.

Examples of concurrent operations that won’t generate Serializable Isolation Violation on Table errors are COPY and INSERT. If you apply these transactions to one table simultaneously, you’ll still get the same results as when you run them serially.

However, if you apply SELECT and INSERT transactions concurrently, the results will differ from when you enable them in serial order. Running these transactions serially will make the SELECT command yield extra rows than when it was first applied. 

On the other hand, the SELECT command may retain the original number of rows of its results if it is applied concurrently with an INSERT transaction. So, your Redshift table will display a serialization isolation error if you run the SELECT and INSERT transactions concurrently. 

You can prevent this problem by applying each transaction serially. Nevertheless, serial combinations of multiple transactions won’t eliminate the Serialization Isolation Violation on Table error. 

If you apply a new transaction to a Redshift table before the previous one commits, your Redshift table may also display a Serializable Isolation Violation on Table error. Again, you can easily avoid this issue by waiting for one transaction to end before applying another. 

How to Solve Serializable Isolation Violation on Table Error?

We’ve already discussed the actions that result in Serializable Isolation Violation on Table errors, and how to avoid them. But what do you do when your Redshift table has canceled a transaction due to the Serializable Isolation Violation on Table error?

There are three ways to resolve the Serializable Isolation Violation on Table errors:

1) Use the LOCK command to Force Serialization

Another way to resolve this issue is to lock all the operations that might lead to Serializable Isolation Violation on Table errors. This may include:

• Lock all tables in the target cluster in the same order that you created them. Don’t worry about the order in which you’ve applied transactions to them. This will help you avoid the Serializable Isolation Violation on Table error.
• Lock only the tables affected by the concurrent transactions. 
• Lock all your tables before you begin the transactions. Then, open them after completing the transactions.

2) Run both Transactions Serially

You can separate the transactions, and run them in serial order. If the concurrent transactions are SELECT and INSERT, you can remove the SELECT transaction from the previous session and run it as a new transaction. This time, you need to apply both transactions to the table in serial order. 

While running both transactions, remember to wait for the first transaction to end before applying a new transaction. This will prevent the transactions from generating another Serializable Isolation Violation on Table error.

3) Abort One Transaction Entirely

You can also choose to remove the less important transaction and retain the sessions. For example, you might have applied the SELECT and INSERT transactions concurrently in two sessions. To solve the Serializable Isolation Violation on Table error, you can take the SELECT statement out of the affected sessions:

Here’s how the new transaction should look like:

Session1_Redshift=# BEGIN;
Session1_Redshift   = #  insert into tab1 values ( 1 )
Session1_Redshift  = # END ;
Session1 _Redshift  # select  * from tab2

Session2_Redshift # select  * from tab1;
Session2_Redshift = #BEGIN;
Session2_Redshift = # insert into tab2 values ( 1 )
Session2_Redshift  = #END;

Conclusion

You have just learned how to solve the Serializable Isolation Violation on Table error problem. Follow the same steps to resolve the errors when they occur. You can also avoid this error by applying the tips discussed in the guidelines above.

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