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Fix: SQL Server DDL's VARCHAR usage causes Implicit Conversion on session #3499

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Fix: SQL Server DDL's VARCHAR usage causes Implicit Conversion on session #3499

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4 changes: 2 additions & 2 deletions spring-session-jdbc/src/main/resources/org/springframework/session/jdbc/schema-sqlserver.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ CREATE TABLE SPRING_SESSION (
LAST_ACCESS_TIME BIGINT NOT NULL,
MAX_INACTIVE_INTERVAL INT NOT NULL,
EXPIRY_TIME BIGINT NOT NULL,
PRINCIPAL_NAME VARCHAR(100),
PRINCIPAL_NAME NVARCHAR(100),
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@ronodhirSoumik ronodhirSoumik Dec 19, 2025 •
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question:: using NVARCHAR instead VARCHAR will lower max length capacity
For VARCHAR: 8k Chars but for NVARCHAR: 4k Chars
will that be a concern in this case (in future)?

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@Chienlin1014 Chienlin1014 Jan 14, 2026

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Thanks for the review!

While it is true that NVARCHAR has a lower maximum capacity compared to VARCHAR, the column is explicitly defined as NVARCHAR(100) here, which is well within the 4,000-character limit of NVARCHAR.

Given that PRINCIPAL_NAME typically stores usernames, 100 characters is currently sufficient. Does the team have any roadmap or plans to extend this field's maximum capacity beyond 4,000 characters in the future? > If not, aligning with NVARCHAR would be beneficial to avoid the implicit conversion performance costs caused by the JDBC driver's default behavior.

CONSTRAINT SPRING_SESSION_PK PRIMARY KEY (PRIMARY_ID)
);

Expand All @@ -15,7 +15,7 @@ CREATE INDEX SPRING_SESSION_IX3 ON SPRING_SESSION (PRINCIPAL_NAME);

CREATE TABLE SPRING_SESSION_ATTRIBUTES (
SESSION_PRIMARY_ID CHAR(36) NOT NULL,
ATTRIBUTE_NAME VARCHAR(200) NOT NULL,
ATTRIBUTE_NAME NVARCHAR(200) NOT NULL,
ATTRIBUTE_BYTES IMAGE NOT NULL,
CONSTRAINT SPRING_SESSION_ATTRIBUTES_PK PRIMARY KEY (SESSION_PRIMARY_ID, ATTRIBUTE_NAME),
CONSTRAINT SPRING_SESSION_ATTRIBUTES_FK FOREIGN KEY (SESSION_PRIMARY_ID) REFERENCES SPRING_SESSION(PRIMARY_ID) ON DELETE CASCADE
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