MDEV-37435 Make new vcols created in vcol index substitution inherit name resolution from the select_lex

When a column or alias is the GROUP BY item, and a HAVING conjunct
depends on this column/alias only, the HAVING conjunct could contain
an Item_ref pointing to the GROUP BY Item_field.

If the column/alias happens to the be the expression of a vcol, the
GROUP BY item would be substituted with a newly created vcol
Item_field (MDEV-36132). This causes the Item_ref in HAVING to point
to the new vcol Item_field as well.

Subsequently in the HAVING to WHERE pushdown optimization, the
conjunct is moved to WHERE and fix_fields is called on it, where it
expects the vcol Item_field to have a name resolution context. So we
let the vcol Item_field inherit the context from the select_lex.

Author: mariadb-YuchenPei

mysql-test/suite/vcol/r/order_by_group_by_subst.result

@@ -193,3 +193,32 @@ explain select vc1, vc2 from t group by c + 1, 1 - c;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t	index	NULL	vc1	10	NULL	10000	Using index
 drop table t;
+#
+# MDEV-37435 Assertion `field' failed in virtual bool Item_field::fix_fields(THD *, Item **)
+#
+CREATE TABLE t1 (a INT,a1 INT AS (a) VIRTUAL,INDEX (a1));
+SELECT a FROM t1 GROUP BY a HAVING a>2;
+a
+SELECT a FROM t1 WHERE a=(SELECT a FROM t1 GROUP BY a HAVING a>2);
+a
+drop table t1;
+create table t1 (a int, a1 int as (a+1) virtual, index(a1));
+select a+1 as g from t1 group by g having g>2;
+g
+drop table t1;
+CREATE TABLE t1 (a INT,a1 INT AS (a) VIRTUAL,INDEX (a1));
+CREATE TABLE t2 (b INT,b1 INT AS (b) VIRTUAL,INDEX (b1));
+insert into t1 (a) select seq from seq_1_to_5;
+insert into t2 (b) select seq from seq_1_to_5;
+SELECT a, b FROM t1, t2 GROUP BY a, b HAVING a>2 and b>2;
+a	b
+3	3
+3	4
+3	5
+4	3
+4	4
+4	5
+5	3
+5	4
+5	5
+drop table t1, t2;

mysql-test/suite/vcol/t/order_by_group_by_subst.test

@@ -149,3 +149,22 @@ alter table t
   add index(vc1, vc2);
 explain select vc1, vc2 from t group by c + 1, 1 - c;
 drop table t;
+
+--echo #
+--echo # MDEV-37435 Assertion `field' failed in virtual bool Item_field::fix_fields(THD *, Item **)
+--echo #
+CREATE TABLE t1 (a INT,a1 INT AS (a) VIRTUAL,INDEX (a1));
+SELECT a FROM t1 GROUP BY a HAVING a>2;
+SELECT a FROM t1 WHERE a=(SELECT a FROM t1 GROUP BY a HAVING a>2);
+drop table t1;
+
+create table t1 (a int, a1 int as (a+1) virtual, index(a1));
+select a+1 as g from t1 group by g having g>2;
+drop table t1;
+
+CREATE TABLE t1 (a INT,a1 INT AS (a) VIRTUAL,INDEX (a1));
+CREATE TABLE t2 (b INT,b1 INT AS (b) VIRTUAL,INDEX (b1));
+insert into t1 (a) select seq from seq_1_to_5;
+insert into t2 (b) select seq from seq_1_to_5;
+SELECT a, b FROM t1, t2 GROUP BY a, b HAVING a>2 and b>2;
+drop table t1, t2;

sql/opt_vcol_substitution.cc

@@ -105,6 +105,8 @@ class Vcol_subst_context
   THD *thd;
   /* Indexed virtual columns that we can try substituting */
   List<Field> vcol_fields;
+  /* Name resolution context for new vcol Item_field's */
+  Name_resolution_context *context;
 
   /*
     How many times substitution was done. Used to determine whether to print
@@ -293,6 +295,7 @@ bool substitute_indexed_vcols_for_join(JOIN *join)
   if (!ctx.vcol_fields.elements)
     return false; // Ok, nothing to do
 
+  ctx.context= &join->select_lex->context;
   if (join->conds)
     subst_vcols_in_item(&ctx, join->conds, "WHERE");
   if (join->join_list)
@@ -463,6 +466,7 @@ void subst_vcol_if_compatible(Vcol_subst_context *ctx,
   Item_field *itf= new (thd->mem_root) Item_field(thd, vcol_field);
   if (!itf)
     return; // Out of memory, caller will know from thd->is_error()
+  itf->context= ctx->context;
   bitmap_set_bit(vcol_field->table->read_set, vcol_field->field_index);
   DBUG_ASSERT(itf->fixed());
   thd->change_item_tree(vcol_expr_ref, itf);