Commit 963e94ce authored by unknown's avatar unknown
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A fix and a test case for Bug#9520 "SELECT DISTINCT crashes server 

with cursor". The patch refactors do_select/sub_select
functions, which implement the nested loop algorithm, and reuses them to
fetch rows for cursors as well.
Pushing with view.test failing (--ps-protocol).


sql/sql_prepare.cc:
   Cursor::fetch() now returns void
sql/sql_select.cc:
  A fix for Bug#9520 "SELECT DISTINCT crashes server with cursor":
  * rename sub_select returns codes to be able to track down what's going
    on in which case.
  * move record processing and outer join record processing to a separate
    function, out of sub_select read-record loop.
  * use generalized sub_select() nested loop function for
  cursors instead of own loop implementation used in Cursor::fetch() before
sql/sql_select.h:
  Replace all return values of sub_select family with enum.
  Add JOIN::resume_nested_loop flag to indicate we are restarting the nested loop
  for execution of next chunk of cursor's rows.
tests/mysql_client_test.c:
  A test case for Bug#9520 "SELECT DISTINCT crashes server with cursor"
parent e9cc39c4

sql/sql_prepare.cc

+1 −1
Original line number Diff line number Diff line
@@ -2223,7 +2223,7 @@ void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length) 
    my_pthread_setprio(pthread_self(), QUERY_PRIOR);



  thd->protocol= &thd->protocol_prep;		// Switch to binary protocol

  (void) stmt->cursor->fetch(num_rows);

  stmt->cursor->fetch(num_rows);

  thd->protocol= &thd->protocol_simple;         // Use normal protocol



  if (!(specialflag & SPECIAL_NO_PRIOR))

sql/sql_select.cc

+381 −353

File changed.

Preview size limit exceeded, changes collapsed.

sql/sql_select.h

+16 −2
Original line number Diff line number Diff line
@@ -91,7 +91,15 @@ enum join_type { JT_UNKNOWN,JT_SYSTEM,JT_CONST,JT_EQ_REF,JT_REF,JT_MAYBE_REF, 


class JOIN;



typedef int (*Next_select_func)(JOIN *,struct st_join_table *,bool);

enum enum_nested_loop_state

{

  NESTED_LOOP_KILLED= -2, NESTED_LOOP_ERROR= -1,

  NESTED_LOOP_OK= 0, NESTED_LOOP_NO_MORE_ROWS= 1,

  NESTED_LOOP_QUERY_LIMIT= 3, NESTED_LOOP_CURSOR_LIMIT= 4

};



typedef enum_nested_loop_state

(*Next_select_func)(JOIN *, struct st_join_table *, bool);

typedef int (*Read_record_func)(struct st_join_table *tab);
@@ -162,6 +170,11 @@ class JOIN :public Sql_alloc 
  uint	   send_group_parts;

  bool	   sort_and_group,first_record,full_join,group, no_field_update;

  bool	   do_send_rows;

  /*

    TRUE when we want to resume nested loop iterations when

    fetching data from a cursor

  */

  bool     resume_nested_loop;

  table_map const_table_map,found_const_table_map,outer_join;

  ha_rows  send_records,found_records,examined_rows,row_limit, select_limit;

  /*
@@ -263,6 +276,7 @@ class JOIN :public Sql_alloc 
    sort_and_group= 0;

    first_record= 0;

    do_send_rows= 1;

    resume_nested_loop= FALSE;

    send_records= 0;

    found_records= 0;

    fetch_limit= HA_POS_ERROR;
@@ -374,7 +388,7 @@ class Cursor: public Sql_alloc, public Item_arena 
  void reset_thd(THD *thd);



  int open(JOIN *join);

  int fetch(ulong num_rows);

  void fetch(ulong num_rows);

  void reset() { join= 0; }

  bool is_open() const { return join != 0; }

  void close();

tests/mysql_client_test.c

+54 −0
Original line number Diff line number Diff line
@@ -12854,6 +12854,59 @@ static void test_bug9159() 
  myquery(rc);

}





/* Crash when opening a cursor to a query with DISTICNT and no key */



static void test_bug9520()

{

  MYSQL_STMT *stmt;

  MYSQL_BIND bind[1];

  char a[6];

  ulong a_len;

  int rc, row_count= 0;



  myheader("test_bug9520");



  mysql_query(mysql, "drop table if exists t1");

  mysql_query(mysql, "create table t1 (a char(5), b char(5), c char(5),"

                     " primary key (a, b, c))");

  rc= mysql_query(mysql, "insert into t1 values ('x', 'y', 'z'), "

                  " ('a', 'b', 'c'), ('k', 'l', 'm')");

  myquery(rc);



  stmt= open_cursor("select distinct b from t1");



  /*

    Not crashes with:

    stmt= open_cursor("select distinct a from t1");

  */



  rc= mysql_stmt_execute(stmt);

  check_execute(stmt, rc);



  bzero(bind, sizeof(bind));

  bind[0].buffer_type= MYSQL_TYPE_STRING;

  bind[0].buffer= (char*) a;

  bind[0].buffer_length= sizeof(a);

  bind[0].length= &a_len;



  mysql_stmt_bind_result(stmt, bind);



  while (!(rc= mysql_stmt_fetch(stmt)))

    row_count++;



  DIE_UNLESS(rc == MYSQL_NO_DATA);



  printf("Fetched %d rows\n", row_count);

  DBUG_ASSERT(row_count == 3);



  mysql_stmt_close(stmt);



  rc= mysql_query(mysql, "drop table t1");

  myquery(rc);

}





/*

  Read and parse arguments and MySQL options from my.cnf

*/
@@ -13079,6 +13132,7 @@ static struct my_tests_st my_tests[]= { 
  { "test_bug8722", test_bug8722 },

  { "test_bug8880", test_bug8880 },

  { "test_bug9159", test_bug9159 },

  { "test_bug9520", test_bug9520 },

  { 0, 0 }

};