fix(oscar): stop leaking internal ROWNUM column on first page of paginated queries

chat2db-community-server/chat2db-community-plugins/chat2db-community-oscar/pom.xml

@@ -17,6 +17,11 @@
             <groupId>ai.chat2db</groupId>
             <artifactId>chat2db-community-spi</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

chat2db-community-server/chat2db-community-plugins/chat2db-community-oscar/src/main/java/ai/chat2db/plugin/oscar/builder/OscarSqlBuilder.java

@@ -112,20 +112,15 @@ public String buildAlterTable(Table oldTable, Table newTable) {
     public String buildPageLimit(PageLimitRequest request) {
         String sql = request.getSql();
         int startRow = request.getOffset();
-        int pageNo = request.getPageNo();
         int pageSize = request.getPageSize();
         int endRow = startRow + pageSize;
         StringBuilder sqlBuilder = new StringBuilder(sql.length() + 120);
+        sqlBuilder.append(OscarConstants.PAGE_OUTER_SELECT_PREFIX);
         if (startRow > 0) {
-            sqlBuilder.append(OscarConstants.PAGE_OUTER_SELECT_PREFIX);
-        }
-        if (endRow > 0) {
             sqlBuilder.append(OscarConstants.PAGE_INNER_SELECT_PREFIX);
         }
         sqlBuilder.append(SQLConstants.LINE_SEPARATOR).append(sql).append(SQLConstants.LINE_SEPARATOR);
-        if (endRow > 0) {
-            sqlBuilder.append(OscarConstants.PAGE_ROWNUM_FILTER_SQL).append(endRow);
-        }
+        sqlBuilder.append(OscarConstants.PAGE_ROWNUM_FILTER_SQL).append(endRow);
         if (startRow > 0) {
             sqlBuilder.append(OscarConstants.PAGE_AUTO_ROW_ID_FILTER_SQL).append(startRow);
         }

chat2db-community-server/chat2db-community-plugins/chat2db-community-oscar/src/test/java/ai/chat2db/plugin/oscar/builder/OscarSqlBuilderTest.java

@@ -0,0 +1,42 @@
+package ai.chat2db.plugin.oscar.builder;
+
+import ai.chat2db.spi.model.request.PageLimitRequest;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+class OscarSqlBuilderTest {
+
+    @Test
+    void shouldLimitFirstPageWithoutExposingSyntheticRowId() {
+        OscarSqlBuilder builder = new OscarSqlBuilder();
+
+        String sql = builder.buildPageLimit(PageLimitRequest.builder()
+                .sql("SELECT ID, NAME FROM EMPLOYEE")
+                .offset(0)
+                .pageNo(1)
+                .pageSize(10)
+                .build());
+
+        assertEquals("SELECT * FROM ( \nSELECT ID, NAME FROM EMPLOYEE\n ) TMP_PAGE WHERE ROWNUM <= 10", sql);
+        assertFalse(sql.contains("CHAT2DB_AUTO_ROW_ID"));
+    }
+
+    @Test
+    void shouldApplyUpperAndLowerBoundsAfterFirstPage() {
+        OscarSqlBuilder builder = new OscarSqlBuilder();
+
+        String sql = builder.buildPageLimit(PageLimitRequest.builder()
+                .sql("SELECT ID, NAME FROM EMPLOYEE")
+                .offset(10)
+                .pageNo(2)
+                .pageSize(10)
+                .build());
+
+        assertEquals("SELECT * FROM (  SELECT TMP_PAGE.*, ROWNUM CHAT2DB_AUTO_ROW_ID FROM ( \n"
+                        + "SELECT ID, NAME FROM EMPLOYEE\n"
+                        + " ) TMP_PAGE WHERE ROWNUM <= 20 ) WHERE CHAT2DB_AUTO_ROW_ID > 10",
+                sql);
+    }
+}