test: Add unit and integration tests for limit/offset support in OpenGaussDialect

- Implemented unit tests for the `OpenGaussDialect` limit/offset support using `LimitHandler`.
- Tested SQL generation for queries with and without offset.
  - `testProcessSqlWithOffset`: Validates SQL query with limit and offset values.
  - `testProcessSqlWithoutOffset`: Validates SQL query with only limit value.
  - `testSupportsLimit`: Ensures `supportsLimit()` returns true.
- Structured tests in `OpenGaussDialectLimitHandlerTest.java`.
- Verified the proper handling of limit and offset logic in OpenGaussDialect.

openGaussDialect/.gitignore

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+/target/

openGaussDialect/src/test/java/org/hibernate/dialect/entity/pagination/TestEntity.java

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+package org.hibernate.dialect.entity.pagination;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Entity
+@Table(name = "test_pagination")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class TestEntity {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+    private String name;
+}

openGaussDialect/src/test/java/org/hibernate/dialect/integration/OpenGaussDialectPaginationIntegrationTest.java

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+package org.hibernate.dialect.integration;
+
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.hibernate.dialect.entity.pagination.TestEntity;
+import org.hibernate.dialect.util.HibernateUtil;
+import org.hibernate.query.Query;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+public class OpenGaussDialectPaginationIntegrationTest {
+
+    private static SessionFactory sessionFactory;
+
+    @BeforeAll
+    public static void init() {
+        sessionFactory = HibernateUtil.getSessionFactory(TestEntity.class);
+        Session session = sessionFactory.openSession();
+        session.beginTransaction();
+        session.createQuery("delete from TestEntity").executeUpdate();
+        for (int i = 1; i <= 100; i++) {
+            TestEntity entity = new TestEntity();
+            entity.setName("Name " + i);
+            session.save(entity);
+        }
+
+        session.getTransaction().commit();
+        session.close();
+    }
+
+    @AfterAll
+    public static void tearDown() {
+        if (sessionFactory != null) {
+            sessionFactory.close();
+        }
+    }
+
+    @Test
+    public void testPaginationWithOffset() {
+        Session session = sessionFactory.openSession();
+        int pageSize = 10;
+        int pageNumber = 3;
+        String hql = "from TestEntity order by id";
+        Query<TestEntity> query = session.createQuery(hql, TestEntity.class);
+        query.setFirstResult(pageNumber * pageSize); // 设置 offset
+        query.setMaxResults(pageSize); // 设置 limit
+        List<TestEntity> results = query.list();
+        Assertions.assertEquals(pageSize, results.size());
+        Assertions.assertEquals(31L, results.get(0).getId());
+        Assertions.assertEquals(40L, results.get(results.size() - 1).getId());
+        session.close();
+    }
+
+    @Test
+    public void testPaginationWithoutOffset() {
+        Session session = sessionFactory.openSession();
+        int pageSize = 10;
+        String hql = "from TestEntity order by id";
+        Query<TestEntity> query = session.createQuery(hql, TestEntity.class);
+        query.setMaxResults(pageSize);
+        List<TestEntity> results = query.list();
+        Assertions.assertEquals(pageSize, results.size());
+        Assertions.assertEquals(1L, results.get(0).getId());
+        Assertions.assertEquals(10L, results.get(results.size() - 1).getId());
+        session.close();
+    }
+}

openGaussDialect/src/test/java/org/hibernate/dialect/unit/OpenGaussDialectLimitHandlerTest.java

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+package org.hibernate.dialect.unit;
+
+import org.hibernate.dialect.OpenGaussDialect;
+import org.hibernate.dialect.pagination.LimitHandler;
+import org.hibernate.engine.spi.RowSelection;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class OpenGaussDialectLimitHandlerTest {
+    @Test
+    public void testProcessSqlWithOffset() {
+        OpenGaussDialect dialect = new OpenGaussDialect();
+        LimitHandler limitHandler = dialect.getLimitHandler();
+        String originalSql = "SELECT * FROM test_table";
+        RowSelection selection = new RowSelection();
+        selection.setFirstRow(10); // offset
+        selection.setMaxRows(20);  // limit
+        String processedSql = limitHandler.processSql(originalSql, selection);
+        String expectedSql = "SELECT * FROM test_table limit ? offset ?";
+        Assertions.assertEquals(expectedSql, processedSql);
+    }
+
+    @Test
+    public void testProcessSqlWithoutOffset() {
+        OpenGaussDialect dialect = new OpenGaussDialect();
+        LimitHandler limitHandler = dialect.getLimitHandler();
+        String originalSql = "SELECT * FROM test_table";
+        RowSelection selection = new RowSelection();
+        selection.setMaxRows(20);  // limit
+        String processedSql = limitHandler.processSql(originalSql, selection);
+        String expectedSql = "SELECT * FROM test_table limit ?";
+        Assertions.assertEquals(expectedSql, processedSql);
+    }
+
+    @Test
+    public void testSupportsLimit() {
+        OpenGaussDialect dialect = new OpenGaussDialect();
+        LimitHandler limitHandler = dialect.getLimitHandler();
+        Assertions.assertTrue(limitHandler.supportsLimit());
+    }
+}