Why mssql jdbc 9.4.0.jre8 driver generating VARCHAR(8000) for a column annotated with @Column(length=4000, columnDefinition = "VARCHAR(4000)")?

Question

I am using hibernate 5.6.15 Final, SQLSERVER2016DIALECT, and mssql-jdbc-9.4.0.jre8 I have declared following field defintion in my entity class:

@Type(type ="org.hibernate.type.StringType") @Column(name = data_string", length = 4000, nullable= true, updatable = true, columnDefinition = "VARCHAR(4000)")       private String DataString;

Despite specifying columnDefinition = "VARCHAR(4000)", Hibernate is generating the column as VARCHAR(8000) in its queries. This is causing issues with implicit conversions in my SQL Server database. The table is defined in SQL Server as:

CREATE TABLE CUST_DATA ( DATA_STRING VARCHAR(4000) NULL, );

Questions:

1.Why MSSQL JDBC 9.4.0.jre8 overriding the specified length of 4000 and generating VARCHAR(8000)?

2.Is there a way to enforce the correct length in the generated query?

Answer 1

• @pavan naik Here are some insights and potential solutions:
  1. Why MSSQL JDBC 9.4.0.jre8 is overriding the specified length of 4000 and generating VARCHAR(8000)?
  This issue might be related to how Hibernate and the SQL Server dialect handle VARCHAR lengths. SQL Server has a maximum row size limit, and when the length of a VARCHAR column exceeds 4000 characters, it might automatically convert it to VARCHAR(MAX) or a larger size to accommodate potential data growth. This behavior can sometimes be influenced by the JDBC driver and the SQL Server dialect used in Hibernate.
  2. How to enforce the correct length in the generated query?
  To ensure that Hibernate generates the correct column length, you can try the following approaches: a. Use @Column with length attribute: Ensure that you are correctly specifying the length attribute in the @Column annotation: Java

    @Column(name = "data_string", length = 4000, nullable = true, updatable = true, columnDefinition = "VARCHAR(4000)")
  

  b. Use @Type annotation: Make sure the @Type annotation is correctly applied: Java

    @Type(type = "org.hibernate.type.StringType")
  

  c. Custom Dialect: If the above steps do not resolve the issue, you might need to create a custom SQL Server dialect that explicitly handles the VARCHAR length correctly. Here’s an example of how you can extend the SQL Server dialect: Java

    public
  

  Then, configure Hibernate to use this custom dialect in your hibernate.cfg.xml or application.properties: XML

    <property name="hibernate.dialect">
  

  or

    hibernate.dialect
  

  These steps should help enforce the correct column length in the generated SQL queries

Answer 2

Hi @PAVAN NAIK

I am using hibernate 5.6.15 Final, SQLSERVER2016DIALECT, and mssql-jdbc-9.4.0.jre8

The annotation of the columnDefinition might be ignored or overwritten by the dialect’s default behavior when the schema is generated via Hibernate.

Try upgrading to the latest stable version of the JDBC driver which may help resolve the issue.

Best regards,

Cosmog

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