Fixed(PS-7745) - (Stored procedure execution fails if contains a func…

…tional index)

https://jira.percona.com/browse/PS-7745

**Problem:**

A Stored Procedure execution fails after some executions when a functional index is present in the SP definition. The error behaves differently depending on the versions I tested:

8.0.23 (PS, Community): It only fails when using a temporary table. After the third execution, all the subsequent executions fail.

8.0.25 (Community): It also fails on normal tables.

How to Repeat

```
DROP PROCEDURE IF EXISTS `sproc`;
DELIMITER $$
CREATE PROCEDURE `sproc`()
BEGIN
DROP TEMPORARY TABLE IF EXISTS `T1`;
CREATE TEMPORARY TABLE `T1`(
`C1` INT,
KEY ( ( `C1` > 0 ) )
);

SELECT 1 FROM ( SELECT 1 `C2` ) `T2`;
END$$
DELIMITER ;
Now if you invoke that procedure 3 times in a row:

mysql> CALL `sproc`(); CALL `sproc`(); CALL `sproc`();
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

ERROR 3107 (HY000): Generated column can refer only to generated columns defined prior to it.
On 8.0.25 (Community) The error is

ERROR 3754 (HY000): Functional index 'functional_index' cannot refer to an auto-increment column.
```

**Cause:**

The issue happens when checks are performed again during a query
in the function `pre_validate_value_generator_expr()`
and column index of the functional index is not available.

**Solution:**

This solution disables some checks if a column index is not available
in the function `pre_validate_value_generator_expr()` during the second
and later queries.
It is safe because these checks are done in the function
`validate_value_generator_expr()` during the first query.
The column index is available there.

mysql-test/suite/rocksdb/r/issue7745.result

@@ -0,0 +1,20 @@
+CREATE PROCEDURE `sproc`()
+BEGIN
+DROP TEMPORARY TABLE IF EXISTS `t1`;
+CREATE TEMPORARY TABLE `t1`(
+`c1` INT,
+KEY ( ( `c1` > 0 ) )
+);
+SELECT 1 FROM ( SELECT 1 `c2` ) `t2`;
+END|
+CALL `sproc`();
+1
+1
+CALL `sproc`();
+1
+1
+CALL `sproc`();
+1
+1
+DROP PROCEDURE `sproc`;
+DROP TEMPORARY TABLE `t1`;

mysql-test/suite/rocksdb/t/issue7745.test

@@ -0,0 +1,18 @@
+--source include/have_rocksdb.inc
+
+DELIMITER |;
+CREATE PROCEDURE `sproc`()
+BEGIN
+	DROP TEMPORARY TABLE IF EXISTS `t1`;
+	CREATE TEMPORARY TABLE `t1`(
+		`c1` INT,
+		KEY ( ( `c1` > 0 ) )
+	);
+	SELECT 1 FROM ( SELECT 1 `c2` ) `t2`;
+END|
+DELIMITER ;|
+
+CALL `sproc`(); CALL `sproc`(); CALL `sproc`();
+
+DROP PROCEDURE `sproc`;
+DROP TEMPORARY TABLE `t1`;

sql/item.cc

@@ -1037,7 +1037,6 @@ bool Item_field::check_function_as_value_generator(uchar *checker_args) {
   }
 
   int fld_idx = func_args->col_index;
-  assert(fld_idx > -1);
 
   /*
     Don't allow the GC (or default expression) to refer itself or another GC
@@ -1046,7 +1045,7 @@ bool Item_field::check_function_as_value_generator(uchar *checker_args) {
   if ((func_args->source != VGS_CHECK_CONSTRAINT) &&
       (field->is_gcol() ||
        field->has_insert_default_general_value_expression()) &&
-      field->field_index() >= fld_idx) {
+      (fld_idx >= 0 && field->field_index() >= fld_idx)) {
     func_args->err_code = (func_args->source == VGS_GENERATED_COLUMN)
                               ? ER_GENERATED_COLUMN_NON_PRIOR
                               : ER_DEFAULT_VAL_GENERATED_NON_PRIOR;