MariaDB · mariadb-YuchenPei · Jul 22, 2026
diff --git a/mysql-test/suite/vcol/r/vcol_sargable.result b/mysql-test/suite/vcol/r/vcol_sargable.result
@@ -10,16 +10,24 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	TBL	ref	vcol1	vcol1	5	const	1	
 explain select * from t1 where a+1<=2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	vcol1	vcol1	5	NULL	1	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression `t1`.`a` + 1 -> vcol1 due to failed supertype check
 explain select * from t1 where a+1<2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	vcol1	vcol1	5	NULL	1	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression `t1`.`a` + 1 -> vcol1 due to failed supertype check
 explain select * from t1 where a+1>100;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	vcol1	vcol1	5	NULL	6	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression `t1`.`a` + 1 -> vcol1 due to failed supertype check
 explain select * from t1 where a+1>=100;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	vcol1	vcol1	5	NULL	13	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression `t1`.`a` + 1 -> vcol1 due to failed supertype check
 explain select * from t1 where a+1 between 10 and 12;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	vcol1	vcol1	5	NULL	2	Using index condition
@@ -150,7 +158,7 @@ explain select * from t3 where concat('100', a)=10010;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	ALL	NULL	NULL	NULL	NULL	100	Using where
 Warnings:
-Note	1105	Cannot substitute virtual column expression concat('100',`t3`.`a`) -> vcol1 due to type mismatch
+Note	1105	Cannot substitute virtual column expression concat('100',`t3`.`a`) -> vcol1 due to collation mismatch
 # Character set change
 explain select * from t3 where concat('hello-', a)='abcd';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -182,9 +190,20 @@ a	js1	size1	color
 2	{"size":2, "color":"hue2"}	2	hue2
 3	{"size":3, "color":"hue3"}	3	hue3
 # Index is used:
+## TODO: actually does not work because
+## capacity_limit_is_in_characters() returns false for
+## the expression with type mediumtext, and true for
+## Item_string 'hue5'
+## set collation_connection so that the constant string has the
+## correct collation
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_bin;
 explain select * from t1 where json_unquote(json_extract(js1, '$.color'))='hue5';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	color	color	403	const	1	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression json_unquote(json_extract(`t1`.`js1`,'$.color')) -> color due to failed supertype check
+set collation_connection=@old_collation_connection;
 explain select * from t1 where json_unquote(json_extract(js1, '$.color')) IS NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	color	color	403	const	1	Using index condition
@@ -228,12 +247,18 @@ select collation(json_value(js1, '$.color')) from t1 limit 1;
 collation(json_value(js1, '$.color'))
 utf8mb4_bin
 # If one is fine with _bin comparisons, they can use index access:
+## same problem with capacity_limit_is_in_characters
 alter table t1
 add color1 varchar(100) collate utf8mb4_bin as (json_value(js1, '$.color')),
 add index(color1);
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_bin;
 explain select * from t1 where json_value(js1, '$.color')='hue10';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	color1	color1	403	const	1	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression json_value(`t1`.`js1`,'$.color') -> color1 due to failed supertype check
+set collation_connection=@old_collation_connection;
 alter table t1 drop column color1;
 # Using different collation in column substitution prevents
 # the optimization from working:
@@ -247,19 +272,26 @@ Warnings:
 Note	1105	Cannot substitute virtual column expression json_value(`t1`.`js1`,'$.color') -> color2 due to collation mismatch
 alter table t1 drop column color2;
 # Explicitly specifying the collation helps:
+## TODO: same problem with capacity_limit_is_in_characters
 alter table t1
 add color3 varchar(100) collate utf8mb4_unicode_ci as
 (json_value(js1, '$.color') collate utf8mb4_unicode_ci),
 add index(color3);
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_unicode_ci;
 explain select * from t1
 where
 json_value(js1, '$.color') collate utf8mb4_unicode_ci='hue10';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	color3	color3	403	const	1	Using index condition
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression json_value(`t1`.`js1`,'$.color') collate utf8mb4_unicode_ci -> color3 due to failed supertype check
+set collation_connection=@old_collation_connection;
 #
 # Alternatively, one can store JSON in a column with the same
 # collation as default and then casts are not needed:
 #
+## TODO: same problem with capacity_limit_is_in_characters
 create table t2(
 js1 longtext COLLATE utf8mb4_uca1400_ai_ci DEFAULT NULL CHECK (json_valid(`js1`))
 );
@@ -271,7 +303,9 @@ explain select * from t2
 where
 json_value(js1, '$.color')='hue10';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ref	color3	color3	403	const	1	Using index condition
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	100	Using where
+Warnings:
+Note	1105	Cannot substitute virtual column expression json_value(`t2`.`js1`,'$.color') -> color3 due to failed supertype check
 drop table t1,t2;
 #
 # Test interplay with sargable_casefold optimization:
@@ -387,16 +421,12 @@ EXPLAIN
     "table": {
       "delete": 1,
       "table_name": "t1",
-      "access_type": "range",
-      "possible_keys": ["a1"],
-      "key": "a1",
-      "key_length": "5",
-      "used_key_parts": ["a1"],
+      "access_type": "ALL",
       "rows": 2,
-      "attached_condition": "t1.a1 > 'a'"
+      "attached_condition": "t1.v2 + t1.v3 > 'a'"
     }
   }
 }
 Warnings:
-Warning	1292	Truncated incorrect DECIMAL value: 'a'
+Note	1105	Cannot substitute virtual column expression `t1`.`v2` + `t1`.`v3` -> a1 due to failed supertype check
 drop table t1;
diff --git a/mysql-test/suite/vcol/t/vcol_sargable.test b/mysql-test/suite/vcol/t/vcol_sargable.test
@@ -127,7 +127,17 @@ alter table t1 add index(color);
 select * from t1 limit 3;
 
 --echo # Index is used:
+--echo ## TODO: actually does not work because
+--echo ## capacity_limit_is_in_characters() returns false for
+--echo ## the expression with type mediumtext, and true for
+--echo ## Item_string 'hue5'
+
+--echo ## set collation_connection so that the constant string has the
+--echo ## correct collation
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_bin;
 explain select * from t1 where json_unquote(json_extract(js1, '$.color'))='hue5';
+set collation_connection=@old_collation_connection;
 explain select * from t1 where json_unquote(json_extract(js1, '$.color')) IS NULL;
 explain select * from t1 force index(color)
 where json_unquote(json_extract(js1, '$.color')) IS NOT NULL;
@@ -162,10 +172,14 @@ select * from t1 where size1=10;
 select collation(json_value(js1, '$.color')) from t1 limit 1;
 
 --echo # If one is fine with _bin comparisons, they can use index access:
+--echo ## same problem with capacity_limit_is_in_characters
 alter table t1
   add color1 varchar(100) collate utf8mb4_bin as (json_value(js1, '$.color')),
   add index(color1);
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_bin;
 explain select * from t1 where json_value(js1, '$.color')='hue10';
+set collation_connection=@old_collation_connection;
 alter table t1 drop column color1;
 
 --echo # Using different collation in column substitution prevents
@@ -178,18 +192,23 @@ alter table t1 drop column color2;
 
 
 --echo # Explicitly specifying the collation helps:
+--echo ## TODO: same problem with capacity_limit_is_in_characters
 alter table t1
   add color3 varchar(100) collate utf8mb4_unicode_ci as
   (json_value(js1, '$.color') collate utf8mb4_unicode_ci),
   add index(color3);
+set @old_collation_connection=@@collation_connection;
+set collation_connection=utf8mb4_unicode_ci;
 explain select * from t1
 where
   json_value(js1, '$.color') collate utf8mb4_unicode_ci='hue10';
+set collation_connection=@old_collation_connection;
 
 --echo #
 --echo # Alternatively, one can store JSON in a column with the same
 --echo # collation as default and then casts are not needed:
 --echo #
+--echo ## TODO: same problem with capacity_limit_is_in_characters
 create table t2(
   js1 longtext COLLATE utf8mb4_uca1400_ai_ci DEFAULT NULL CHECK (json_valid(`js1`))
 );

diff --git a/sql/field.cc b/sql/field.cc
@@ -11600,6 +11600,14 @@ void Field::raise_note_cannot_use_key_part(THD *thd,
   }
 }
 
+bool Field::is_supertype(Item *item) const
+{
+  return type_handler()->is_supertype(type_std_attributes(),
+                                      type_extra_attributes(),
+                                      item->type_handler(),
+                                      *item /*Type_std_attributes*/,
+                                      item->type_extra_attributes());
+}
 
 /*
   Give warning for unusable key

diff --git a/sql/field.h b/sql/field.h
@@ -1776,6 +1776,7 @@ class Field: public Value_source
                                       const Data_type_compatibility reason)
                                       const;
   void raise_note_key_become_unused(THD *thd, const String &expr) const;
+  bool is_supertype(Item *item) const;
 protected:
   bool set_warning(unsigned int code, int cuted_increment) const
   {

diff --git a/sql/item.h b/sql/item.h
@@ -2854,6 +2854,14 @@ class Item :public Value_source,
     DBUG_ASSERT(fixed());
     return false;
   }
+  bool is_supertype(Item *item) const
+  {
+    return type_handler()->is_supertype(*this /*Type_std_attributes*/,
+                                        type_extra_attributes(),
+                                        item->type_handler(),
+                                        *item /*Type_std_attributes*/,
+                                        item->type_extra_attributes());
+  }
 
 protected:
   /*

diff --git a/sql/opt_vcol_substitution.cc b/sql/opt_vcol_substitution.cc
@@ -120,7 +120,8 @@ static
 void subst_vcol_if_compatible(Vcol_subst_context *ctx,
                               Item_bool_func *cond,
                               Item **vcol_expr_ref,
-                              Field *vcol_field);
+                              Field *vcol_field,
+                              bool skip_supertype_check= false);
 
 static
 bool collect_indexed_vcols_for_table(TABLE *table, List<Field> *vcol_fields)
@@ -440,41 +441,29 @@ static
 void subst_vcol_if_compatible(Vcol_subst_context *ctx,
                               Item_bool_func *cond,
                               Item **vcol_expr_ref,
-                              Field *vcol_field)
+                              Field *vcol_field,
+                              bool skip_supertype_check)
 {
   Item *vcol_expr= *vcol_expr_ref;
   THD *thd= ctx->thd;
 
   const char *fail_cause= NULL;
-  if (cond)                     /* WHERE substitution (MDEV-39525) */
+  if (cond)
   {
-    if (vcol_expr->type_handler_for_comparison() !=
-        vcol_field->type_handler_for_comparison() ||
-        (vcol_expr->maybe_null() && !vcol_field->maybe_null()))
-      fail_cause="type mismatch";
-    else
-    {
-      CHARSET_INFO *cs= cond ? cond->compare_collation() : NULL;
-      if (vcol_expr->collation.collation != vcol_field->charset() &&
-          cs != vcol_field->charset())
-        fail_cause= "collation mismatch";
-    }
+    if (vcol_expr->collation.collation != vcol_field->charset() &&
+        cond->compare_collation() != vcol_field->charset())
+      fail_cause= "collation mismatch";
   }
-  else                          /* ORDER/GROUP BY substitution */
+  if (!fail_cause && !skip_supertype_check &&
+      !vcol_field->is_supertype(vcol_expr))
   {
-    if (!vcol_field->type_handler()->is_supertype(
-        vcol_field->type_std_attributes(),
-        vcol_field->type_extra_attributes(),
-        vcol_expr->type_handler(),
-        *vcol_expr /*Type_std_attributes*/,
-        vcol_expr->type_extra_attributes()))
       fail_cause="failed supertype check";
-    else if (vcol_expr->maybe_null() && !vcol_field->maybe_null())
-    {
-      /* NOT NULL is not allowed for vcol definition */
-      DBUG_ASSERT(0);
-      fail_cause= "nullability mismatch";
-    }
+  }
+  if (!fail_cause && vcol_expr->maybe_null() && !vcol_field->maybe_null())
+  {
+    /* NOT NULL is not allowed for vcol definition */
+    DBUG_ASSERT(0);
+    fail_cause= "nullability mismatch";
   }
 
   if (fail_cause)
@@ -530,25 +519,41 @@ bool Item::vcol_subst_analyzer(uchar **)
            (((Item_func*)this)->bitmap_bit() & allowed_cmp_funcs))); // (2)
 }
 
+static bool vcol_type_both_bounded(Field *vcol_field, Item *vcol_expr, Item *rhs)
+{
+  return vcol_field->is_supertype(rhs) && vcol_expr->is_supertype(rhs);
+}
 
 Item* Item_bool_rowready_func2::vcol_subst_transformer(THD *thd, uchar *arg)
 {
   DBUG_ASSERT(this->vcol_subst_analyzer(NULL));
   Vcol_subst_context *ctx= (Vcol_subst_context*)arg;
   Field *vcol_field;
   Item **vcol_expr;
+  Item *other= NULL;
 
   if (!args[0]->used_tables() && (vcol_field= is_vcol_expr(ctx, args[1])))
+  {
     vcol_expr= &args[1];
+    if (functype() == EQ_FUNC)
+      other= args[0];
+  }
   else if (!args[1]->used_tables() && (vcol_field= is_vcol_expr(ctx, args[0])))
+  {
     vcol_expr= &args[0];
+    if (functype() == EQ_FUNC)
+      other= args[1];
+  }
   else
     return this; /* No substitution */
 
   DBUG_EXECUTE_IF("vcol_subst_simulate_oom",
                   DBUG_SET("+d,simulate_out_of_memory"););
 
-  subst_vcol_if_compatible(ctx, this, vcol_expr, vcol_field);
+  if (other && vcol_type_both_bounded(vcol_field, *vcol_expr, other))
+    subst_vcol_if_compatible(ctx, this, vcol_expr, vcol_field, true);
+  else
+    subst_vcol_if_compatible(ctx, this, vcol_expr, vcol_field, false);
 
   DBUG_EXECUTE_IF("vcol_subst_simulate_oom",
                   DBUG_SET("-d,vcol_subst_simulate_oom"););
@@ -564,7 +569,11 @@ Item* Item_func_between::vcol_subst_transformer(THD *thd, uchar *arg)
       !args[2]->used_tables() &&
       (vcol_field= is_vcol_expr(ctx, args[0])))
   {
-    subst_vcol_if_compatible(ctx, this, &args[0], vcol_field);
+    if (vcol_type_both_bounded(vcol_field, args[0], args[1]) &&
+        vcol_type_both_bounded(vcol_field, args[0], args[2]))
+      subst_vcol_if_compatible(ctx, this, &args[0], vcol_field, true);
+    else
+      subst_vcol_if_compatible(ctx, this, &args[0], vcol_field, false);
   }
   return this;
 }
@@ -575,7 +584,7 @@ Item* Item_func_null_predicate::vcol_subst_transformer(THD *thd, uchar *arg)
   Vcol_subst_context *ctx= (Vcol_subst_context*)arg;
   Field *vcol_field;
   if ((vcol_field= is_vcol_expr(ctx, args[0])))
-    subst_vcol_if_compatible(ctx, this, &args[0], vcol_field);
+    subst_vcol_if_compatible(ctx, this, &args[0], vcol_field, true);
   return this;
 }
 
@@ -584,6 +593,7 @@ Item* Item_func_in::vcol_subst_transformer(THD *thd, uchar *arg)
 {
   Vcol_subst_context *ctx= (Vcol_subst_context*)arg;
   Field *vcol_field= nullptr;
+  uint i= 1;
 
   /*
     Check that the left hand side of IN() is a virtual column expression and
@@ -592,8 +602,13 @@ Item* Item_func_in::vcol_subst_transformer(THD *thd, uchar *arg)
   if (!(vcol_field= is_vcol_expr(ctx, args[0])) ||
       !compatible_types_scalar_bisection_possible())
     return this;
+  for (; i < arg_count; i++)
+  {
+    if (!vcol_type_both_bounded(vcol_field, args[0], args[i]))
+      break;
+  }
 
-  subst_vcol_if_compatible(ctx, this, &args[0], vcol_field);
+  subst_vcol_if_compatible(ctx, this, &args[0], vcol_field, i == arg_count);
   return this;
 }