Use NVARCHAR for SQL Server

I observed that the SQL Server DDL for Spring Integration metadata tables defines several critical key columns (e.g., REGION, GROUP_KEY, METADATA_KEY) using the VARCHAR data type.

This configuration creates a type mismatch because the Microsoft JDBC Driver, by default, sends string parameters to SQL Server using the Unicode (NVARCHAR) data type.

Potential Impact and Optimization:

This mismatch necessitates an Implicit Conversion by SQL Server on nearly every lookup. 
While functional, this conversion can severely compromise the database's ability to utilize indexes optimally. 
In high-frequency queries involving these key columns, this often forces the database to revert from efficient Index Seek to less efficient Index Scan or Table Scan.

We propose adjusting the relevant VARCHAR columns in the DDL to NVARCHAR. 
This structural alignment eliminates the potential for implicit conversion, ensuring the DDL is consistent with the parameters sent by the MS JDBC driver, and guaranteeing optimal index utilization.

Signed-off-by: Chienlin <[email protected]>

Author: Chienlin1014

spring-integration-jdbc/src/main/resources/org/springframework/integration/jdbc/schema-sqlserver.sql

@@ -1,6 +1,6 @@
 CREATE TABLE INT_MESSAGE  (
 	MESSAGE_ID CHAR(36) NOT NULL,
-	REGION VARCHAR(100) NOT NULL,
+	REGION NVARCHAR(100) NOT NULL,
 	CREATED_DATE DATETIME NOT NULL,
 	MESSAGE_CONTENT IMAGE,
 	constraint INT_MESSAGE_PK primary key (MESSAGE_ID, REGION)
@@ -11,14 +11,14 @@ CREATE INDEX INT_MESSAGE_IX1 ON INT_MESSAGE (CREATED_DATE);
 CREATE TABLE INT_GROUP_TO_MESSAGE  (
 	GROUP_KEY CHAR(36) NOT NULL,
 	MESSAGE_ID CHAR(36) NOT NULL,
-	REGION VARCHAR(100),
+	REGION NVARCHAR(100),
 	constraint INT_GROUP_TO_MESSAGE_PK primary key (GROUP_KEY, MESSAGE_ID, REGION)
 );
 
 CREATE TABLE INT_MESSAGE_GROUP  (
 	GROUP_KEY CHAR(36) NOT NULL,
-	REGION VARCHAR(100) NOT NULL,
-	GROUP_CONDITION VARCHAR(255),
+	REGION NVARCHAR(100) NOT NULL,
+	GROUP_CONDITION NVARCHAR(255),
 	COMPLETE BIGINT,
 	LAST_RELEASED_SEQUENCE BIGINT,
 	CREATED_DATE DATETIME NOT NULL,
@@ -28,7 +28,7 @@ CREATE TABLE INT_MESSAGE_GROUP  (
 
 CREATE TABLE INT_LOCK  (
 	LOCK_KEY CHAR(36) NOT NULL,
-	REGION VARCHAR(100) NOT NULL,
+	REGION NVARCHAR(100) NOT NULL,
 	CLIENT_ID CHAR(36),
 	CREATED_DATE DATETIME NOT NULL,
 	EXPIRED_AFTER DATETIME NOT NULL,
@@ -44,7 +44,7 @@ CREATE TABLE INT_CHANNEL_MESSAGE (
 	MESSAGE_PRIORITY BIGINT,
 	MESSAGE_SEQUENCE BIGINT NOT NULL ,
 	MESSAGE_CONTENT IMAGE,
-	REGION VARCHAR(100) NOT NULL,
+	REGION NVARCHAR(100) NOT NULL,
 	constraint INT_CHANNEL_MESSAGE_PK primary key (REGION, GROUP_KEY, CREATED_DATE, MESSAGE_SEQUENCE)
 );
 
@@ -54,8 +54,8 @@ CREATE INDEX INT_CHANNEL_MSG_DELETE_IDX ON INT_CHANNEL_MESSAGE (REGION, GROUP_KE
 
 
 CREATE TABLE INT_METADATA_STORE  (
-	METADATA_KEY VARCHAR(255) NOT NULL,
-	METADATA_VALUE VARCHAR(4000),
-	REGION VARCHAR(100) NOT NULL,
+	METADATA_KEY NVARCHAR(255) NOT NULL,
+	METADATA_VALUE NVARCHAR(4000),
+	REGION NVARCHAR(100) NOT NULL,
 	constraint INT_METADATA_STORE_PK primary key (METADATA_KEY, REGION)
 );