From a5504f05f135ca0f4ce900620fe2874ae57b04f5 Mon Sep 17 00:00:00 2001
From: Dave Gosselin <dave.gosselin@mariadb.com>
Date: Mon, 12 Jan 2026 14:05:40 -0500
Subject: [PATCH] MDEV-38099: Assertion failed in
 st_select_lex::optimize_unflattened_subqueries

When optimizing unflattened subqueries we assert that, if any SELECT in a unit
sets the uncacheable flag with UNCACHEABLE_RAND, then the unit's uncacheable
flag itself should be set likewise.  Put another way, any SELECT in the unit
that is UNCACHEABLE_RAND causes the entire unit to be so marked.

However, this marking was not preserved by SELECT_LEX::register_unit when
registering a new unit.  During that method, the SELECT_LEX's uncacheable
value is updated with the registered unit's uncacheable value but, if the
UNCACHEABLE_RAND marking is present, it is not propagated to the uncacheable
flag of the enclosing unit.

If the incoming unit's uncacheable flag has the UNCACHEABLE_RAND bit set and
if the master unit exists, then set the UNCACHEABLE_RAND flag on the master
unit.
---
 mysql-test/main/gis.result | 10 ++++++++++
 mysql-test/main/gis.test   | 11 +++++++++++
 sql/sql_lex.cc             |  2 ++
 3 files changed, 23 insertions(+)

diff --git a/mysql-test/main/gis.result b/mysql-test/main/gis.result
index 5190e4ff4fd1c..00506d1b0d636 100644
--- a/mysql-test/main/gis.result
+++ b/mysql-test/main/gis.result
@@ -5622,3 +5622,13 @@ t
 #
 # End of 11.6 tests
 #
+#
+# Start of 12.2 tests
+#
+#
+# MDEV-38099:  Assertion failed in st_select_lex::optimize_unflattened_subqueries
+#
+SELECT (WITH cte AS (SELECT st_astext(ST_GeomFromText('POLYGON((1 1,2 2,1 1))'))) SELECT * FROM cte);
+(WITH cte AS (SELECT st_astext(ST_GeomFromText('POLYGON((1 1,2 2,1 1))'))) SELECT * FROM cte)
+POLYGON((1 1,2 2,1 1))
+# End of 12.2 tests
diff --git a/mysql-test/main/gis.test b/mysql-test/main/gis.test
index fd604a363a68b..d3ae097a237b8 100644
--- a/mysql-test/main/gis.test
+++ b/mysql-test/main/gis.test
@@ -3623,3 +3623,14 @@ SELECT ST_ISVALID(ST_GEOMFROMTEXT('POLYGON((0 0, 10 0, 10 10, 0 10, 0 0), (15 15
 --echo #
 --echo # End of 11.6 tests
 --echo #
+
+--echo #
+--echo # Start of 12.2 tests
+--echo #
+
+--echo #
+--echo # MDEV-38099:  Assertion failed in st_select_lex::optimize_unflattened_subqueries
+--echo #
+SELECT (WITH cte AS (SELECT st_astext(ST_GeomFromText('POLYGON((1 1,2 2,1 1))'))) SELECT * FROM cte);
+
+--echo # End of 12.2 tests
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 73d97861325ef..7779411ff8a98 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -11130,6 +11130,8 @@ void st_select_lex::register_unit(SELECT_LEX_UNIT *unit,
   slave= unit;
   unit->master= this;
   uncacheable|= unit->uncacheable;
+  if (master && (unit->uncacheable & UNCACHEABLE_RAND))
+    master->uncacheable|= UNCACHEABLE_RAND;
 
   for(SELECT_LEX *sel= unit->first_select();sel; sel= sel->next_select())
   {