From 74b0c7840905f3f131347b67d414667d571f90c6 Mon Sep 17 00:00:00 2001
From: Anway Durge <durgeanway@gmail.com>
Date: Thu, 1 Oct 2026 10:31:41 +0530
Subject: [PATCH] MDEV-41171 SQL_SELECT_LIMIT and FOUND_ROWS() on the
 I_S.TABLES fast path

Set limit_found_rows from matching rows sent on the fast path so
FOUND_ROWS() matches the fallback path when SQL_CALC_FOUND_ROWS is
not used.
---
 mysql-test/main/mdev_31342.result | 22 +++++++++++++++++++
 mysql-test/main/mdev_31342.test   | 35 +++++++++++++++++++++++++++++++
 sql/sql_show.cc                   |  2 ++
 3 files changed, 59 insertions(+)

diff --git a/mysql-test/main/mdev_31342.result b/mysql-test/main/mdev_31342.result
index d6c37d912b3..e59d1092309 100644
--- a/mysql-test/main/mdev_31342.result
+++ b/mysql-test/main/mdev_31342.result
@@ -841,3 +841,25 @@ LIMIT 1;
 TABLE_NAME
 tb3
 DROP DATABASE mdev41167;
+#
+# MDEV-41171: @@sql_select_limit and FOUND_ROWS() on the fast path
+#
+CREATE DATABASE mdev41171;
+CREATE TABLE mdev41171.t1(i INT);
+CREATE TABLE mdev41171.t2(i INT);
+CREATE TABLE mdev41171.t3(i INT);
+SET @@session.sql_select_limit=2;
+SELECT TABLE_CATALOG FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA='mdev41171';
+SET @@session.sql_select_limit=DEFAULT;
+SELECT 1;
+1
+1
+SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA='mdev41171';
+TABLE_NAME
+t1
+t2
+t3
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+3
+DROP DATABASE mdev41171;
diff --git a/mysql-test/main/mdev_31342.test b/mysql-test/main/mdev_31342.test
index 86f626f9e5e..4d642b6dff9 100644
--- a/mysql-test/main/mdev_31342.test
+++ b/mysql-test/main/mdev_31342.test
@@ -323,3 +323,38 @@ SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
 WHERE TABLE_SCHEMA='mdev41167' AND (TABLE_NAME='tb3' OR TABLE_CATALOG='nope')
 LIMIT 1;
 DROP DATABASE mdev41167;
+
+--echo #
+--echo # MDEV-41171: @@sql_select_limit and FOUND_ROWS() on the fast path
+--echo #
+CREATE DATABASE mdev41171;
+CREATE TABLE mdev41171.t1(i INT);
+CREATE TABLE mdev41171.t2(i INT);
+CREATE TABLE mdev41171.t3(i INT);
+SET @@session.sql_select_limit=2;
+# CALL (used by --sp-protocol) sets sql_select_limit=HA_POS_ERROR, so
+# do not compare the row list. Capture FOUND_ROWS() immediately.
+--disable_result_log
+SELECT TABLE_CATALOG FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA='mdev41171';
+--enable_result_log
+--disable_query_log
+--disable_result_log
+let $n= query_get_value(SELECT FOUND_ROWS(), FOUND_ROWS(), 1);
+--enable_result_log
+--enable_query_log
+if (`SELECT $SP_PROTOCOL = 0`)
+{
+  if ($n != 2)
+  {
+    --echo # sql_select_limit=2 returned $n rows
+    --die
+  }
+}
+SET @@session.sql_select_limit=DEFAULT;
+SELECT 1;
+--sorted_result
+SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA='mdev41171';
+--disable_ps_protocol
+SELECT FOUND_ROWS();
+--enable_ps_protocol
+DROP DATABASE mdev41171;
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index a7ae9626aa3..e4b07b942f9 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -10295,6 +10295,8 @@ bool get_schema_tables_result(JOIN *join,
           }
           plan->fp_state= IS_table_read_plan::FP_STREAMING;
         }
+        /* FOUND_ROWS() without SQL_CALC_FOUND_ROWS is rows sent. */
+        thd->limit_found_rows= plan->sent_rows;
         my_eof(thd);
         result= 1;
       }