2022-07-29 mysql/stonedb慢SQL-Q17-分析

摘要:

对Q17慢SQL进行分析

SQL分析:

SQL:

/stonedb57/install/bin/mysql -D tpch -e " 
        select
            sum(l_extendedprice) / 7.0 as avg_yearly
        from
            lineitem,
            part
        where
            p_partkey = l_partkey
            and p_brand = 'Brand#23'
            and p_container = 'MED BOX'
            and l_quantity < (
                select
                    0.2 * avg(l_quantity)
                from
                    lineitem
                where
                    l_partkey = p_partkey
            );
    "

explain分析:

*************************** 1. row ***************************
           id: 1
  select_type: PRIMARY
        table: lineitem
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 59986052
     filtered: 100.00
        Extra: NULL
*************************** 2. row ***************************
           id: 1
  select_type: PRIMARY
        table: part
   partitions: NULL
         type: eq_ref
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: tpch.lineitem.l_partkey
         rows: 1
     filtered: 5.00
        Extra: Using where with pushed condition ((`tpch`.`part`.`p_brand` = 'Brand#23') and (`tpch`.`part`.`p_container` = 'MED BOX'))(t0) Pckrows: 16, susp. 16 (0 empty 0 full). Conditions: 2
*************************** 3. row ***************************
           id: 2
  select_type: DEPENDENT SUBQUERY
        table: lineitem
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 59986052
     filtered: 10.00
        Extra: Using where

id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	PRIMARY	lineitem		ALL					59986052	100
1	PRIMARY	part		eq_ref	PRIMARY	PRIMARY	4	tpch.lineitem.l_partkey	1	5	Using where with pushed condition ((`tpch`.`part`.`p_brand` = 'Brand#23') and (`tpch`.`part`.`p_container` = 'MED BOX'))(t0) Pckrows: 16, susp. 16 (0 empty 0 full). Conditions: 2
2	DEPENDENT SUBQUERY	lineitem		ALL					59986052	10	Using where

热力图:

拆分SQL后分析:

外层表查询:

time /stonedb57/install/bin/mysql -D tpch -e " 
         select
            l_extendedprice
        from
            lineitem,
            part
        where
            p_partkey = l_partkey\G
    "

*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: lineitem
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 59986052
     filtered: 100.00
        Extra: NULL
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: part
   partitions: NULL
         type: eq_ref
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: tpch.lineitem.l_partkey
         rows: 1
     filtered: 100.00
        Extra: NULL

内层查询:

time /stonedb57/install/bin/mysql -D tpch -e " 
        explain select
            0.2 * avg(l_quantity)
        from
            lineitem \G
    "

*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: lineitem
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 59986052
     filtered: 100.00
        Extra: NULL