從視圖中選擇*比直接通過MySQL 5.7執行視圖create語句慢10倍以上

Question

我創建了一個視圖作為多個表的聯接以隱藏復雜性。

現在，當我select * from view執行select * from view時，它花費了直接執行select語句（定義視圖）的執行時間的10倍以上（大約70毫秒vs 900毫秒）。

在MySQL 5.7.23服務器上會發生此行為。

我比較了兩個查詢的執行計划，唯一的區別（如預期的那樣）是派生表：

這是視圖的正常行為還是我該如何解決？

PS：按要求創建視圖語句（混淆的名稱）：

create view vrs as select
rs."id" as "id",
l."language" as "language",
rss."t" as "discriminator",
rss."type" as "type",
coalesce(lt3."text", concat('!',s3."textkey",'(',l."language",')')) as "typeText",
rss."model" as "model",
coalesce(lt2."text", concat('!',s2."textkey",'(',l."language",')')) as "modelText",
rs."name"  as "name",
rs."reqCATGroup" as "CATGroup",
rs."devID" as "devID",
case s."builtIn"
    when 0 then s."displayName"
    else (select lt1."text"
        from loctext lt1
        where lt1."language"=l."language"
        and lt1."textkey"=s."displayName")
end as "sName",
s."id" as "sId",
s."postcode" as "sPostcode",
s."place" as "sPlace",
s."street" as "sStreet",
s."streetNumber" as "sStreetNumber",
s."tId" as "tId",
t."tName" as "tName",
rss."CCVMajor" as "CCVMajor",
rss."CCVMinor" as "CCVMinor",
rss."CCVPatch" as "CCVPatch",
rss."CCHV" as "CCHV",
coalesce(lHw."text", concat('!',sHw."textkey",'(',l."language",')')) as "CCHVText",
rss."MCVMajor" as "MCVMajor",
rss."MCVMinor" as "MCVMinor",
rss."MCVPatch" as "MCVPatch",
rss."level",
coalesce(lLevel."text", concat('!', sLevel."textkey", '(', l."language", ')')) as "levelText",
rss."event",
coalesce(lEvent."text", concat('!', sEvent."textkey", '(', l."language", ')')) as "eventText",
rss."isBusy" as "isBusy",
rss."tsLastComIn" as "tsLastCom",
rss."tsBT" AS "tsBT",
b1."ordinal" as "isSending",
coalesce(ltSend."text", concat('!',b1."textkey",'(',l."language",')')) as "isSendingText",
b2."ordinal" as "isReceiving",
coalesce(ltReceive."text", concat('!',b2."textkey",'(',l."language",')')) as "isReceivingText",
rs."historyCreateDevTs",
rs."historyCreateDevUserId",
rs."historyCreateDevUserLoginName",
rs."historyModifyDevLinkTs",
rs."historyModifyDevLinkUserId",
rs."historyModifyDevLinkUserLoginName",
rs."monitorStartTs",
rs."monitorEndTs"
from synch rss
cross join loclanguages l
join cfgrs rs on rs."id" = rss."id"
join cfgs s on s."id" = rs."sId"
join cfgt t on t."id" = s."tId"
left join locmodel s2 on s2."ordinal" = rss."model"
left join loctext lt2 on lt2."textkey" = s2."textkey" and lt2."language" = l."language"
left join loctype s3 on s3."ordinal" = rss."type"
left join loctext lt3 on lt3."textkey" = s3."textkey" and lt3."language" = l."language"
left join locbooleanrange b1 on rs."sending"+1 = b1."ordinal"
left join loctext ltSend on ltSend."textkey" = b1."textkey" and ltSend."language" = l."language"
left join locbooleanrange b2 on rs."receiving"+1 = b2."ordinal"
left join loctext ltReceive on ltReceive."textkey" = b2."textkey" and ltReceive."language" = l."language"
left join loceventlevel sLevel on sLevel."ordinal" = rss."level"
left join loctext lLevel on lLevel."textkey" = sLevel."textkey" and lLevel."language" = l."language"
left join locevent sEvent on sEvent."ordinal" = rss."event" and sEvent."type" = rss."type"
left join loctext lEvent on lEvent."textkey" = sEvent."textkey" and lEvent."language" = l."language"
left join loccchv sHw on sHw."ordinal" = rss."CCHV"
left join loctext lHw on lHw."textkey" = sHw."textkey" and lHw."language" = l."language"
where rs."deleted" = 0
;

PPS：完整的執行計划如下所示：

直接致電：

視圖：

Answer 1

該鏈接適用於MySQL 8.0，但是當我上次遇到MySQL 5.6、5.7中的Views的性能問題並進行挖掘時，我得到了相同的答案：使用Views時，您基本上不能利用索引。

https://dev.mysql.com/doc/refman/8.0/en/view-restrictions.html

我個人發現，由於上述限制，特別是由於性能下降，MySQL中的視圖總體上沒有用。

讀者-如果以某種方式可以在MySQL中執行View，那么我肯定在某個地方錯過了重要備忘錄。 如果是這種情況，請糾正我。