From 2f4f559b837c19ffd2c2bb69f74bffe17fb2f2d6 Mon Sep 17 00:00:00 2001
From: yihong <zouzou0208@gmail.com>
Date: Tue, 15 Jul 2025 10:10:51 +0800
Subject: [PATCH] fix: close issue 59446 make oct("") same as mysql (#61767)

close pingcap/tidb#59446
---
 pkg/expression/builtin_string.go                  |  5 +++++
 pkg/expression/builtin_string_vec.go              |  9 ++++++++-
 tests/integrationtest/r/expression/builtin.result | 15 +++++++++++++++
 tests/integrationtest/t/expression/builtin.test   |  5 +++++
 tests/llmtest/testdata/expression.json            |  6 +++---
 5 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/pkg/expression/builtin_string.go b/pkg/expression/builtin_string.go
index 5a19e49444..154b8c9ec2 100644
--- a/pkg/expression/builtin_string.go
+++ b/pkg/expression/builtin_string.go
@@ -2993,6 +2993,11 @@ func (b *builtinOctStringSig) evalString(ctx EvalContext, row chunk.Row) (string
 		return "", isNull, err
 	}
 
+	// for issue #59446 should return NULL for empty string
+	if len(val) == 0 {
+		return "", true, nil
+	}
+
 	negative, overflow := false, false
 	val = getValidPrefix(strings.TrimSpace(val), 10)
 	if len(val) == 0 {
diff --git a/pkg/expression/builtin_string_vec.go b/pkg/expression/builtin_string_vec.go
index 9a92ed763e..7691c29bbc 100644
--- a/pkg/expression/builtin_string_vec.go
+++ b/pkg/expression/builtin_string_vec.go
@@ -1774,8 +1774,15 @@ func (b *builtinOctStringSig) vecEvalString(ctx EvalContext, input *chunk.Chunk,
 			result.AppendNull()
 			continue
 		}
-		negative, overflow := false, false
+
+		// for issue #59446 should return NULL for empty string
 		str := buf.GetString(i)
+		if len(str) == 0 {
+			result.AppendNull()
+			continue
+		}
+
+		negative, overflow := false, false
 		str = getValidPrefix(strings.TrimSpace(str), 10)
 		if len(str) == 0 {
 			result.AppendString("0")
diff --git a/tests/integrationtest/r/expression/builtin.result b/tests/integrationtest/r/expression/builtin.result
index ee231239e6..38500f943c 100644
--- a/tests/integrationtest/r/expression/builtin.result
+++ b/tests/integrationtest/r/expression/builtin.result
@@ -2007,6 +2007,21 @@ oct("aaaa")	oct("-1.9")	oct("-9999999999999999999999999")	oct("99999999999999999
 select oct(-1.9), oct(1.9), oct(-1), oct(1), oct(-9999999999999999999999999), oct(9999999999999999999999999);
 oct(-1.9)	oct(1.9)	oct(-1)	oct(1)	oct(-9999999999999999999999999)	oct(9999999999999999999999999)
 1777777777777777777777	1	1777777777777777777777	1	1777777777777777777777	1777777777777777777777
+select oct(""), oct(" "), oct(NULL);
+oct("")	oct(" ")	oct(NULL)
+NULL	0	NULL
+drop table if exists t_oct;
+CREATE TABLE t_oct (a VARCHAR(20));
+INSERT INTO t_oct VALUES (''), (' '), (NULL), ('123'), ('abc'), ('0'), ('255');
+SELECT oct(CONCAT(a, '')) FROM t_oct;
+oct(CONCAT(a, ''))
+NULL
+0
+NULL
+173
+0
+0
+377
 select find_in_set("", ""), find_in_set("", ","), find_in_set("中文", "字符串,中文"), find_in_set("b,", "a,b,c,d");
 find_in_set("", "")	find_in_set("", ",")	find_in_set("中文", "字符串,中文")	find_in_set("b,", "a,b,c,d")
 0	1	2	0
diff --git a/tests/integrationtest/t/expression/builtin.test b/tests/integrationtest/t/expression/builtin.test
index 4fee9792b3..733cf7940e 100644
--- a/tests/integrationtest/t/expression/builtin.test
+++ b/tests/integrationtest/t/expression/builtin.test
@@ -899,6 +899,11 @@ insert into t values("中国", cast("国" as binary)), ("中国", ""), ("abc", "
 select instr(a, b) from t;
 select oct("aaaa"), oct("-1.9"),  oct("-9999999999999999999999999"), oct("9999999999999999999999999");
 select oct(-1.9), oct(1.9), oct(-1), oct(1), oct(-9999999999999999999999999), oct(9999999999999999999999999);
+select oct(""), oct(" "), oct(NULL);
+drop table if exists t_oct;
+CREATE TABLE t_oct (a VARCHAR(20));
+INSERT INTO t_oct VALUES (''), (' '), (NULL), ('123'), ('abc'), ('0'), ('255');
+SELECT oct(CONCAT(a, '')) FROM t_oct;
 select find_in_set("", ""), find_in_set("", ","), find_in_set("中文", "字符串,中文"), find_in_set("b,", "a,b,c,d");
 select find_in_set(NULL, ""), find_in_set("", NULL), find_in_set(1, "2,3,1");
 select make_set(0, "12"), make_set(3, "aa", "11"), make_set(3, NULL, "中文"), make_set(NULL, "aa");
diff --git a/tests/llmtest/testdata/expression.json b/tests/llmtest/testdata/expression.json
index facc2e7811..ec814c01b0 100644
--- a/tests/llmtest/testdata/expression.json
+++ b/tests/llmtest/testdata/expression.json
@@ -35587,9 +35587,9 @@
     {
       "sql": "SELECT OCT('')",
       "args": null,
-      "pass": false,
-      "known": true,
-      "comment": "https://github.com/pingcap/tidb/issues/59446"
+      "pass": true,
+      "known": false,
+      "comment": ""
     },
     {
       "sql": "SELECT OCT(8)",