Lessons Learned #544: How to Detect INT Identity Exhaustion Before Inserts Fail.
Recently, I worked on a support case involving an Azure SQL Database table where the customer had reached the maximum value supported by the INT data type. The table used an INT IDENTITY(1,1) column as its primary key. Over time, the generated identity value approached the maximum value supported by INT. Once the available range was exhausted, the application was no longer able to insert new rows. At that point, the column needed to be changed from INT to BIGINT. However, performing this type of migration on a very large table can be a complex and time-consuming operation. The situation is that an INT column uses 4 bytes and supports values from: -2,147,483,648 to: 2,147,483,647. To prevent similar problems in the future, I suggested using the following query to review the current status of all INT IDENTITY columns in the database. The query uses the sys.identity_columns catalog view: SELECT s.name AS SchemaName, t.name AS TableName, c.name AS ColumnName, CONVERT(bigint, c.last_value) AS CurrentIdentityValue, CONVERT(bigint, 2147483647) AS MaximumIntValue, CONVERT(bigint, 2147483647) - ISNULL(CONVERT(bigint, c.last_value), 0) AS RemainingValues, CAST( ISNULL(CONVERT(decimal(20,2), c.last_value), 0) / 2147483647 * 100 AS decimal(6,2) ) AS PercentUsed FROM sys.identity_columns AS c INNER JOIN sys.tables AS t ON c.object_id = t.object_id INNER JOIN sys.schemas AS s ON t.schema_id = s.schema_id WHERE TYPE_NAME(c.system_type_id) = 'int' ORDER BY PercentUsed DESC; I prefer using this query instead of relying on: SELECT COUNT(*) FROM dbo.TableName. The number of rows in a table does not necessarily match the current identity value. Rows might have been deleted, transactions might have been rolled back, and identity values might contain gaps. For this reason, the current identity value is a better indicator of the remaining capacity. Adding this query as a regular preventive check can help identify identity columns that are approaching their limits before they cause application failures. I would like to share with you an example creates a table with an identity seed close to the maximum value supported by INT: DROP TABLE IF EXISTS dbo.IdentityCapacityDemo2; CREATE TABLE dbo.IdentityCapacityDemo2 ( Id INT IDENTITY(2147483600,1) NOT NULL, CreatedDate datetime2(0) NOT NULL CONSTRAINT DF_IdentityCapacityDemo2_CreatedDate DEFAULT SYSUTCDATETIME(), CONSTRAINT PK_IdentityCapacityDemo2 PRIMARY KEY CLUSTERED (Id) ) Insert 20 rows using this command: insert into IdentityCapacityDemo2(CreatedDate) values(SYSUTCDATETIME()) Example of returns: I think runnning this preventive check can help detect identity exhaustion before it affects the application.Lesson Learned #429:Leveraging the Full Range SQL Server INT Data Type: Negative and Positive Values
SQL Server's INT data type, by design, provides a range from -2,147,483,648 to 2,147,483,647. But often, developers only utilize the positive range for primary keys and other identifier fields, effectively wasting half of its potential. What if we could harness this full range to temporarily extend the capacity of an INT column? In this article, we explore this idea in-depth.
