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Today, let’s see how our Support Engineers fix this Amazon Redshift error for our customers.

 

Amazon Redshift ERROR: 1023 DETAIL: Serializable isolation violation

 
In Amazon Redshift, concurrent operations are supported in a protective way using the concept of Serializable Isolation.

If the result of the serial running of the concurrent execution is the same as their concurrent execution, those transactions are considered serializable and it can be run safely.

When Amazon Redshift detects a serializable isolation error, we can see an error message as follows:

ERROR: 1023 DETAIL: Serializable isolation violation on the table in Redshift

Now let’s see how we can fix this serializable isolation error by using the following methods:

• We can force the serialization by locking every table in each session.
• We can move the operations that do not have to be in the same transaction for atomicity outside of the transaction.

Now, let’s discuss both methods in detail.
 

Force the serialization by locking every table

 
The LOCK command restricts access to the database tables. It obstructs operations and results in serializable isolation errors. When using the LOCK command, we must ensure the following points:

• We must lock every table affected by the transaction.
• Also, lock the tables in the same order regardless of the order of operation.
• Lock every table before performing the operation.

Move operations that do not have to be in the same transaction for atomicity outside of the transaction

 
This method applies if two independent operations inside two transactions compared each other in a way that could affect the outcome of the other transaction. Consider the following sessions A and B start a transaction:

SessionA_AmazonRedshift = # BEGIN;

SessionB_AmazonRedshift = # BEGIN;

Now, the result of the SELECT statement in one transaction could affect by the INSERT statement in the other.

If we serially run the following statements in any order, one of the SELECT statements returns one more row than if the transactions run simultaneously.

If there is no order for which the operations could be run serially, it would produce the same result as when run simultaneously, the final operation results in a serializable isolation error.

SessionA_AmazonRedshift=# select * from tab1;
SessionA_AmazonRedshift =# insert into tab2 values (1);

sessionB_AmazonRedshift =# insert into tab1 values (1);
SessionB_AmazonRedshift =# select * from tab2

The SELECT statement result is not important, we can move the SELECT statements outside of their transactions, as shown in the following examples:

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

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

Here, both INSERT statements do not affect each other. There is at the minimum of one order in which the transactions can run serially. Therefore, it produces the same result as if run the transactions at the same time.

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Conclusion

 
To conclude, today we saw how our Support Engineers resolve the error ‘Amazon Redshift ERROR: 1023 DETAIL: Serializable isolation violation’ for our AWS Customers.