0

我们有这个 MySQL SP，它使用动态 SQL。似乎它在负载下表现不佳。

有可能这个 SP 在负载下变慢是因为它使用动态 SQL 吗？动态 SQL 会导致 MySql 中的性能问题（例如，因为它没有被引擎缓存）吗？

请注意，此 SP 是从其他几个 SP 调用的。它使用临时表将结果传递给父 SP。

CREATE PROCEDURE `CreateAreas`(
    _areas varchar(21844),
    _comparisonGroup varchar(21844),
    _parentArea varchar(21844),
    _areaType varchar(21844)
)
BEGIN

    -- create temporary table "areas"
    -- fill with area ids

    create temporary table areas (
        id int not null,
        code varchar(30),
        name varchar(100),
        shortName varchar(100),
        levelid int not null,
        sortOrder int not null,
        key (id)
    );

    -- assumes that only one of the 3 options is valid, areas, comparison group, bounded comparison group

    if (_areas is not null) then

        set @sql = concat('insert into areas (id, code, name, shortName, levelid, sortOrder) select id, Code, Name, ShortName, LevelID, 0 from GeoArea where Code in (''', replace(_areas, ',', ''','''), ''')');
        prepare stmt from @sql;
        execute stmt;
        deallocate prepare stmt;

    elseif (_comparisonGroup is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        insert into areas (id, code, name, shortName, levelid, sortOrder)
        select GeoAreaID, GeoArea.Code, GeoArea.Name, GeoArea.ShortName, GeoArea.LevelID, SortOrder
        from ComparisonGroupGeoAreaLink
        INNER JOIN
        GeoArea
        ON GeoArea.ID = GeoAreaID
        where ComparisonGroupID = (select id from ComparisonGroup where Identifier = _comparisonGroup)
        and IsMember = 1;

    elseif (_parentArea is not null and _areaType is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        insert into areas (id, code, name, shortName, levelid, sortOrder)
    select a.ID, a.Code, a.Name, a.ShortName, a.LevelID, 0
        from (select id from GeoArea where Code = _parentArea) as t
        INNER JOIN
        GeoAreaLinkCache c
        ON
        c.ParentAreaID = t.id
        inner join GeoArea a
        on c.ChildAreaID = a.ID
        INNER JOIN
        (select id from GeoAreaLevel where Identifier = _areaType) as l
        ON
        a.LevelID = l.id;        

    elseif (_areaType is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        set @sql = concat('insert into areas (id, code, name, shortName, levelid, sortOrder)
        select a.ID, a.Code, a.Name, a.ShortName, a.LevelID, 0
        from 
        (select id from GeoAreaLevel where Identifier in (''', replace(_areaType, ',', ''','''), ''')) l
        INNER JOIN
        GeoArea a
        ON
        a.LevelID = l.id');
        prepare stmt from @sql;
        execute stmt;
        deallocate prepare stmt;


    end if;                 

END
4

3 回答 3

1

动态 SQL 似乎不是瓶颈。

我已经将临时表更改为 MEMORY 引擎，它确实起到了作用，并产生了惊人的差异。解决方案建议在

https://dba.stackexchange.com/questions/52825/can-mysql-nested-sp-be-a-bottleneck/52863?noredirect=1#52863

create temporary table areas (
    id int not null,
    code varchar(30),
    name varchar(100),
    shortName varchar(100),
    levelid int not null,
    sortOrder int not null,
    key (id)
) ENGINE=MEMORY;
于 2013-11-06T15:46:44.983 回答
1

是的。存储过程的一个优点是它们可以被解析，查询计划可以被缓存，等等。

动态 SQL（或即席查询）没有这样的优势。

也就是说，您的性能瓶颈不太可能来自动态 SQL，更有可能来自缺少索引、插入/删除过多等。

于 2013-11-06T08:47:37.407 回答
0

尝试从插入中删除子查询（未测试）。可能值得尝试对这些查询（好吧，选择部分）进行解释，并将它们与原始 SP 的解释进行比较。

CREATE PROCEDURE `CreateAreas`(
    _areas varchar(21844),
    _comparisonGroup varchar(21844),
    _parentArea varchar(21844),
    _areaType varchar(21844)
)
BEGIN

    -- create temporary table "areas"
    -- fill with area ids

    create temporary table areas (
        id int not null,
        code varchar(30),
        name varchar(100),
        shortName varchar(100),
        levelid int not null,
        sortOrder int not null,
        key (id)
    );

    -- assumes that only one of the 3 options is valid, areas, comparison group, bounded comparison group

    if (_areas is not null) then

        set @sql = concat('insert into areas (id, code, name, shortName, levelid, sortOrder) 
                            select id, Code, Name, ShortName, LevelID, 0 
                            from GeoArea 
                            where Code in (''', replace(_areas, ',', ''','''), ''')');
        prepare stmt from @sql;
        execute stmt;
        deallocate prepare stmt;

    elseif (_comparisonGroup is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        insert into areas (id, code, name, shortName, levelid, sortOrder)
        select GeoAreaID, GeoArea.Code, GeoArea.Name, GeoArea.ShortName, GeoArea.LevelID, SortOrder
        from ComparisonGroupGeoAreaLink
        INNER JOIN GeoArea
        ON GeoArea.ID = GeoAreaID
        INNER JOIN ComparisonGroup
        ON ComparisonGroupID = ComparisonGroup.id
        WHERE ComparisonGroup.Identifier = _comparisonGroup
        AND IsMember = 1;

    elseif (_parentArea is not null and _areaType is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        insert into areas (id, code, name, shortName, levelid, sortOrder)
    select a.ID, a.Code, a.Name, a.ShortName, a.LevelID, 0
        from GeoArea t
        INNER JOIN GeoAreaLinkCache c
        ON c.ParentAreaID = t.id
        inner join GeoArea a
        on c.ChildAreaID = a.ID
        INNER JOIN GeoAreaLevel l
        ON a.LevelID = l.id
        where l.Identifier = _areaType
        AND Code = _parentArea;        

    elseif (_areaType is not null) then

        -- might not be the most efficient way, but is consistent with the approach above, and we do not expect the list to be long
        set @sql = concat('insert into areas (id, code, name, shortName, levelid, sortOrder)
        select a.ID, a.Code, a.Name, a.ShortName, a.LevelID, 0
        from GeoAreaLevel l
        INNER JOIN GeoArea a
        ON a.LevelID = l.id
        where l.Identifier in (''', replace(_areaType, ',', ''','''), ''')');
        prepare stmt from @sql;
        execute stmt;
        deallocate prepare stmt;


    end if;                 

END
于 2013-11-06T09:59:25.353 回答