From 07dc1436af2324b9b31ead30bc3808952c8cba7e Mon Sep 17 00:00:00 2001
From: Syngnat <92659908+Syngnat@users.noreply.github.com>
Date: Wed, 8 Jul 2026 11:51:05 +0800
Subject: [PATCH 1/2] perf(oceanbase): use FETCH FIRST for Oracle auto limit

---
 frontend/src/utils/queryAutoLimit.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/frontend/src/utils/queryAutoLimit.ts b/frontend/src/utils/queryAutoLimit.ts
index b0383c5..053bea6 100644
--- a/frontend/src/utils/queryAutoLimit.ts
+++ b/frontend/src/utils/queryAutoLimit.ts
@@ -322,7 +322,7 @@ export const applyQueryAutoLimit = (
     if (offsetPos >= 0 && (fromPos < 0 || offsetPos > fromPos)) return { sql, applied: false, maxRows };
     const forPos = findTopLevelKeyword(main, 'for');
     if (forPos >= 0 && (fromPos < 0 || forPos > fromPos)) return { sql, applied: false, maxRows };
-    return { sql: `SELECT * FROM (${main.trimEnd()}) WHERE ROWNUM <= ${maxRows}${tail}`, applied: true, maxRows };
+    return { sql: `${main.trimEnd()} FETCH FIRST ${maxRows} ROWS ONLY${tail}`, applied: true, maxRows };
   }
 
   const offsetPos = findTopLevelKeyword(main, 'offset');

From 5712b39cf9c512712cabfbcef4bf38286bd5b404 Mon Sep 17 00:00:00 2001
From: Syngnat <92659908+Syngnat@users.noreply.github.com>
Date: Wed, 8 Jul 2026 11:52:06 +0800
Subject: [PATCH 2/2] test(oceanbase): expect Oracle auto limit FETCH FIRST

---
 frontend/src/utils/queryAutoLimit.test.ts | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/frontend/src/utils/queryAutoLimit.test.ts b/frontend/src/utils/queryAutoLimit.test.ts
index dbaee51..957c009 100644
--- a/frontend/src/utils/queryAutoLimit.test.ts
+++ b/frontend/src/utils/queryAutoLimit.test.ts
@@ -40,9 +40,9 @@ describe('applyQueryAutoLimit', () => {
     ['dameng'],
     ['dm'],
     ['dm8'],
-  ])('adds ROWNUM limit for %s connections', (dbType) => {
+  ])('adds FETCH FIRST limit for %s connections', (dbType) => {
     expect(applyQueryAutoLimit('SELECT * FROM MYCIMLED.EDC_LOG', dbType, 500).sql)
-      .toBe('SELECT * FROM (SELECT * FROM MYCIMLED.EDC_LOG) WHERE ROWNUM <= 500');
+      .toBe('SELECT * FROM MYCIMLED.EDC_LOG FETCH FIRST 500 ROWS ONLY');
   });
 
   it.each([
@@ -61,8 +61,8 @@ describe('applyQueryAutoLimit', () => {
   });
 
   it.each([
-    ['oracle', 'SELECT * FROM (SELECT * FROM users) WHERE ROWNUM <= 500'],
-    ['dm8', 'SELECT * FROM (SELECT * FROM users) WHERE ROWNUM <= 500'],
+    ['oracle', 'SELECT * FROM users FETCH FIRST 500 ROWS ONLY'],
+    ['dm8', 'SELECT * FROM users FETCH FIRST 500 ROWS ONLY'],
     ['mssql', 'SELECT TOP 500 * FROM users'],
     ['postgresql', 'SELECT * FROM users LIMIT 500'],
     ['gauss-db', 'SELECT * FROM users LIMIT 500'],
@@ -76,12 +76,17 @@ describe('applyQueryAutoLimit', () => {
 
   it('keeps trailing semicolon and comments after injected Oracle limit', () => {
     expect(applyQueryAutoLimit('SELECT * FROM MYCIMLED.EDC_LOG; -- preview', 'oracle', 500).sql)
-      .toBe('SELECT * FROM (SELECT * FROM MYCIMLED.EDC_LOG) WHERE ROWNUM <= 500; -- preview');
+      .toBe('SELECT * FROM MYCIMLED.EDC_LOG FETCH FIRST 500 ROWS ONLY; -- preview');
   });
 
-  it('uses Oracle 11g compatible ROWNUM limit for simple table queries', () => {
+  it('uses Oracle FETCH FIRST limit for simple table queries', () => {
     expect(applyQueryAutoLimit('select 1 from xxx', 'oracle', 500).sql)
-      .toBe('SELECT * FROM (select 1 from xxx) WHERE ROWNUM <= 500');
+      .toBe('select 1 from xxx FETCH FIRST 500 ROWS ONLY');
+  });
+
+  it('keeps ORDER BY semantics with Oracle FETCH FIRST', () => {
+    expect(applyQueryAutoLimit('SELECT * FROM users ORDER BY created_at DESC', 'oracle', 100).sql)
+      .toBe('SELECT * FROM users ORDER BY created_at DESC FETCH FIRST 100 ROWS ONLY');
   });
 
   it('does not add another generic limit when SQL already limits rows', () => {