MDEV-24658: Optimizer trace reads a column not marked for read

mysql-test/main/opt_trace.result

@@ -11156,4 +11156,25 @@ valid_json	json_detailed(json_extract(trace,'$**.expanded_query'))
 1	["Error: failed to escape query string for JSON output"]
 SET NAMES DEFAULT;
 set optimizer_trace=@saved_optimizer_trace;
+#
+# MDEV-24658: Optimizer trace reads a column not marked for read
+#
+set @saved_optimizer_trace=@@optimizer_trace;
+set optimizer_trace='enabled=on';
+create table t1 (i int);
+create table t2 (c int);
+insert into t2 values (1);
+select 1 from (select 1 in (select 1 from t1 where (select 1 from t2 having c)) from t2) as z;
+1
+1
+select json_valid(trace) as valid_json,
+json_detailed(json_extract(trace, '$**.original_condition')) as original_condition
+from information_schema.optimizer_trace;
+valid_json	original_condition
+1	[
+    "(/* select#4 */ select 1 from t2 having 1 <> 0)",
+    "1 <> 0"
+]
+drop table t1, t2;
+set optimizer_trace=@saved_optimizer_trace;
 # End of 10.11 tests

mysql-test/main/opt_trace.test

@@ -1310,4 +1310,34 @@ SET NAMES DEFAULT;
 set optimizer_trace=@saved_optimizer_trace;
 --enable_view_protocol
 
+--echo #
+--echo # MDEV-24658: Optimizer trace reads a column not marked for read
+--echo #
+
+set @saved_optimizer_trace=@@optimizer_trace;
+set optimizer_trace='enabled=on';
+# Disable the view and ps protocols here.  The view protocol
+# renumbers the block printed in the condition.  The ps protocol keeps
+# condition processing in the prepare phase, so the trace read here
+# has no original condition.
+--disable_view_protocol
+--disable_ps_protocol
+
+create table t1 (i int);
+create table t2 (c int);
+insert into t2 values (1);
+
+# t2 has one row, so it is a const/system table whose column c is a known
+# constant.  A table with more than one row can be constant only through a
+# unique key equality, and then the read column stays in the read set.
+select 1 from (select 1 in (select 1 from t1 where (select 1 from t2 having c)) from t2) as z;
+select json_valid(trace) as valid_json,
+       json_detailed(json_extract(trace, '$**.original_condition')) as original_condition
+  from information_schema.optimizer_trace;
+
+drop table t1, t2;
+--enable_ps_protocol
+--enable_view_protocol
+set optimizer_trace=@saved_optimizer_trace;
+
 --echo # End of 10.11 tests

sql/field.cc

@@ -60,7 +60,12 @@ const char field_separator=',';
 // Column marked for read or the field set to read out of record[0]
 bool Field::marked_for_read() const
 {
+  /*
+    (1) A const table's row is read during optimization and remains
+        materialized in record[0], so reading it is safe.
+  */
   return !table ||
+         table->const_table ||  // (1)
          (!table->read_set ||
           bitmap_is_set(table->read_set, field_index) ||
           (!(ptr >= table->record[0] &&