Assertion `0' failed in Item_sum_field::get_tmp_table_field()

CREATE TABLE t1 (i INT);

INSERT INTO t1 VALUES (1),(2);

SELECT DISTINCT VAR_POP(1) FROM t1 GROUP BY @a := 's';

mysqld: /src/10.1/sql/item_sum.h:1089: virtual Field* Item_sum_field::get_tmp_table_field(): Assertion `0' failed.

160228 23:21:27 [ERROR] mysqld got signal 6 ;

#7  0x00007f31f89261d2 in __assert_fail () from /lib64/libc.so.6

#8  0x000055a9aba0d999 in Item_sum_field::get_tmp_table_field (this=0x7f31ef0569f8) at /src/10.1/sql/item_sum.h:1089

#9  0x000055a9ab782ba1 in remove_duplicates (join=0x7f31ef055f18, table=0x7f31ef0b0088, fields=..., having=0x0) at /src/10.1/sql/sql_select.cc:21493

#10 0x000055a9ab754af5 in JOIN::exec_inner (this=0x7f31ef053e20) at /src/10.1/sql/sql_select.cc:2998

#11 0x000055a9ab752d13 in JOIN::exec (this=0x7f31ef053e20) at /src/10.1/sql/sql_select.cc:2518

#12 0x000055a9ab7562c6 in mysql_select (thd=0x7f31f47c9230, rref_pointer_array=0x7f31f47cd5c0, tables=0x7f31ef0531e0, wild_num=0, fields=..., conds=0x0, og_num=1, order=0x0, group=0x7f31ef053cf0, having=0x0, proc_param=0x0, select_options=2147748609, result=0x7f31ef053e00, unit=0x7f31f47ccc48, select_lex=0x7f31f47cd348) at /src/10.1/sql/sql_select.cc:3451

#13 0x000055a9ab74bd6b in handle_select (thd=0x7f31f47c9230, lex=0x7f31f47ccb80, result=0x7f31ef053e00, setup_tables_done_option=0) at /src/10.1/sql/sql_select.cc:384

#14 0x000055a9ab71c096 in execute_sqlcom_select (thd=0x7f31f47c9230, all_tables=0x7f31ef0531e0) at /src/10.1/sql/sql_parse.cc:5936

#15 0x000055a9ab711e72 in mysql_execute_command (thd=0x7f31f47c9230) at /src/10.1/sql/sql_parse.cc:2962

#16 0x000055a9ab71f6de in mysql_parse (thd=0x7f31f47c9230, rawbuf=0x7f31ef052ec8 "SELECT DISTINCT VAR_POP(1) FROM t1 GROUP BY @a := 's'", length=53, parser_state=0x7f31fabf45e0) at /src/10.1/sql/sql_parse.cc:7336

#17 0x000055a9ab70e0d9 in dispatch_command (command=COM_QUERY, thd=0x7f31f47c9230, packet=0x7f31f39c9231 "SELECT DISTINCT VAR_POP(1) FROM t1 GROUP BY @a := 's'", packet_length=53) at /src/10.1/sql/sql_parse.cc:1488

#18 0x000055a9ab70ce0b in do_command (thd=0x7f31f47c9230) at /src/10.1/sql/sql_parse.cc:1109

#19 0x000055a9ab842bc0 in do_handle_one_connection (thd_arg=0x7f31f47c9230) at /src/10.1/sql/sql_connect.cc:1349

#20 0x000055a9ab842924 in handle_one_connection (arg=0x7f31f47c9230) at /src/10.1/sql/sql_connect.cc:1261

#21 0x000055a9abf4aafa in pfs_spawn_thread (arg=0x7f31f33b0bf0) at /src/10.1/storage/perfschema/pfs.cc:1860

#22 0x00007f31fa86f0a4 in start_thread () from /lib64/libpthread.so.0

#23 0x00007f31f89dd04d in clone () from /lib64/libc.so.6

commit 7091b7852d27e6c8a1875b2acc0d1adbfb29984f

Author: Alexander Barkov <bar@mariadb.org>

Date:   Thu Oct 8 19:19:21 2015 +0400

    MDEV-8918 Wrong result for CAST(AVG(bigint_column) AS SIGNED)

    - Moving Item_xxx_field declarations after Item_sum_xxx declarations,

      so Item_xxx_field constructors can be defined directly in item_sum.h

      rather than item_sum.cc. This removes some duplicate code, e.g.

      initialization of the following members at constructor time:

      name, decimals, max_length, unsigned_flag, field, maybe_null.

    - Adding Item_sum_field as a common parent for Item_avg_field and

      Item_variance_field

    - Deriving Item_sum_field directly from Item rather that Item_result_field,

      as Item_sum_field descendants do not need anything from Item_result_field.

    - Removing hybrid infrastructure from Item_avg_field,

      adding Item_avg_field_decimal and Item_avg_field_double instead,

      as desired result type is already known at constructor time

      (not only at fix_fields time). This simplifies the code.

    - Changing Item_avg_field_decimal::val_int() to call val_int_from_decimal()

      instead of doing { return (longlong) rint(val_real()); }

      This is the fix itself.