commit 98b0d40af27051ded465a5ca81fac8e3110cc2c1

Author:	Manuel Ung <mung@fb.com>  Tue Mar 19 16:44:54 2019

Committer:	Facebook Github Bot <facebook-github-bot@users.noreply.github.com>  Fri Apr  5 22:13:46 2019

Fix error handling in group by plans

Summary:

For certain GROUP BY plans, the QUICK_RANGE_SELECT class is used to iterate through all possible prefixes that form a group. The current iteration process calls read_range_first with both a start and end range, and then iterates until we've moved past the end range. However, the storage engine may choose to honour the end range (because of index condition pushdown, rocksdb iterator bounds, or rocksdb prefix seek mode) and return HA_ERR_KEY_NOT_FOUND or HA_ERR_END_OF_FILE instead. Instead of moving onto the next range, this causes the QUICK_RANGE_SELECT::get_next_prefix to return early without actually advancing onto the next prefix. This can cause an infinite loop in QUICK_GROUP_MIN_MAX_SELECT::get_next, or QUICK_GROUP_MIN_MAX_SELECT::get_next to return HA_ERR_END_OF_FILE too early.

The fix is to detect if HA_ERR_KEY_NOT_FOUND or HA_ERR_END_OF_FILE is returned, and continue onto the next range instead of returning early.

Reviewed By: hermanlee

Differential Revision: D14521084

fbshipit-source-id: 6963b17081f

create table t2 (

  a1 char(64), 

  a2 char(64) not null, 

  b char(16), 

  c char(16), 

  d char(16), 

  dummy char(248) default ' '

) engine=RocksDB;

create index idx_t2_0 on t2 (a1);

create index idx_t2_1 on t2 (a1,a2,b,c);

create index idx_t2_2 on t2 (a1,a2,b);

select

  a1,a2,b,max(c),min(c) 

from 

  t1 

where 

  (a2 = 'a' or a2 = 'b') and (b = 'b') 

group by a1;

                  "group_index_range": {

                    "potential_group_range_indexes": [

                      {

                        "index": "idx_t1_0",

                        "usable": false,

                        "cause": "not_covering"

                      },

                      {

                        "index": "idx_t1_1",

                        "covering": true,

                        "usable": false,

                        "cause": "nonconst_equality_gap_attribute"

                      },

                      {

                        "index": "idx_t1_2",

                        "usable": false,

                        "cause": "not_covering"

                      }

                    ]

commit 60a92a79a3b7fde3c6efe91799e344b977c8e5c3

Author: Manuel Ung <mung@fb.com>

Date:   Thu Apr 19 23:06:27 2018 -0700

    Enhance group-by loose index scan

    Summary:

    This enhances the current group by plan so that every "gap attribute" is allowed to have a disjunction of equality predicates. The predicates from different attributes must still be conjunctive to each other though, and this is all enforced in check_key_infix.

mysql>  select version();

+------------------+

| version()        |

+------------------+

| 5.6.35-debug-log |

+------------------+

1 row in set (0.00 sec)

mysql> select a1,a2,b,max(c),min(c) from t2 use index() where (a2 = 'a' or a2 = 'b') and (b = 'b') group by a1;

+------+----+------+--------+--------+

| a1   | a2 | b    | max(c) | min(c) |

+------+----+------+--------+--------+

| a    | a  | b    | p122   | e112   |

| b    | a  | b    | p222   | e212   |

| c    | a  | b    | p322   | e312   |

| d    | a  | b    | p422   | e412   |

| e    | a  | b    | NULL   | NULL   |

+------+----+------+--------+--------+

5 rows in set (0.01 sec)

mysql>  select a1,a2,b,max(c),min(c) from t2  where (a2 = 'a' or a2 = 'b') and (b = 'b') group by a1;

+------+----+------+--------+--------+

| a1   | a2 | b    | max(c) | min(c) |

+------+----+------+--------+--------+

| a    | b  | b    | p122   | e112   |

| b    | b  | b    | p222   | e212   |

| c    | b  | b    | p322   | e312   |

| d    | b  | b    | p422   | e412   |

+------+----+------+--------+--------+

4 rows in set (0.00 sec)