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MDEV-20516: Assertion `!lex->proc_list.first && !lex->result && !lex->param_list.elements' failed in mysql_create_view

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Execution of the CREATE VIEW statement sent via binary protocol
where the flags of the COM_STMT_EXECUTE request a cursor to be opened
before running the statement results in an assert failure.

This assert fails since the data member thd->lex->result has not null
value pointing to an instance of the class Select_materialize.
The data member thd->lex->result is assigned a pointer to the class
Select_materialize in the function mysql_open_cursor() that invoked
in case the packet COM_STMT_EXECUTE requests a cursor to be opened.

After thd->lex->result is assigned a pointer to an instance of the
class Select_materialize the function mysql_create_view() is called
(indirectly via the function mysql_execute_statement()) and the assert
fails.

The assert
  DBUG_ASSERT(!lex->proc_list.first && !lex->result &&
              !lex->param_list.elements);

was added by the commit 591c06d4b7.
Unfortunately , the condition
  !lex->result
was specified incorrect. It was supposed that the thd->lex->result
is set only by parser on handling the clauses SELECT ... INTO
but indeed it is also set inside mysql_open_cursor() and
that fact was missed by the assert's condition.

So, the fix for this issue is to just remove the condition
  !lex->result
from the failing assert.
This commit is contained in:
Dmitry Shulga
2022-01-22 12:46:06 +07:00
parent faaecc8fcf
commit f99d141cd2
2 changed files with 46 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
sql/sql_view.cc
View File

@ -408,8 +408,18 @@ bool mysql_create_view(THD *thd, TABLE_LIST *views,
bool res= FALSE;
DBUG_ENTER("mysql_create_view");
/* This is ensured in the parser. */
DBUG_ASSERT(!lex->proc_list.first && !lex->result &&
/*
This is ensured in the parser.
NOTE: Originally, the assert below contained the extra condition
&& !lex->result
but in this form the assert is failed in case CREATE VIEW run under
cursor (the case when the byte 'flags' in the COM_STMT_EXECUTE packet has
the flag CURSOR_TYPE_READ_ONLY set). For the cursor use case
thd->lex->result is assigned a pointer to the class Select_materialize
inside the function mysql_open_cursor() just before handling of a statement
will be started and the function mysql_create_view() called.
*/
DBUG_ASSERT(!lex->proc_list.first &&
!lex->param_list.elements);
/*

34
tests/mysql_client_test.c
View File

@ -20013,6 +20013,39 @@ static void test_mdev24827()
myquery(rc);
}
static void test_mdev_20516()
{
MYSQL_STMT *stmt;
int rc;
unsigned long cursor= CURSOR_TYPE_READ_ONLY;
myheader("test_mdev_20516");
rc= mysql_query(mysql, "DROP TABLE IF EXISTS t1");
myquery(rc);
rc= mysql_query(mysql, "CREATE TABLE t1(a INT)");
myquery(rc);
const char* query=
"CREATE VIEW v1 AS SELECT * FROM t1";
stmt= mysql_stmt_init(mysql);
check_stmt(stmt);
rc= mysql_stmt_prepare(stmt, query, strlen(query));
check_execute(stmt, rc);
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_CURSOR_TYPE, &cursor);
check_execute(stmt, rc);
rc= mysql_stmt_execute(stmt);
check_execute(stmt, rc);
rc= mysql_query(mysql, "DROP TABLE t1");
myquery(rc);
}
#ifndef EMBEDDED_LIBRARY
#define MDEV19838_MAX_PARAM_COUNT 32
#define MDEV19838_FIELDS_COUNT 17
@ -20163,6 +20196,7 @@ static void test_mdev19838()
#endif // EMBEDDED_LIBRARY
static struct my_tests_st my_tests[]= {
{ "test_mdev_20516", test_mdev_20516 },
{ "test_mdev24827", test_mdev24827 },
{ "test_mdev_26145", test_mdev_26145 },
{ "disable_query_logs", disable_query_logs },