Hi Mingliang, Thanks for bringing this up >From one side, yes some engines use SHOW syntax and I would rather +0.5 here.
>From another side both SHOW and SET are very limited commands. Maybe it would make sense to look at information_schema (mentioned in SQL 92[1]) and most databases already support it (Postgres[2], MySQL[3], CockRoach[4]). Hive does not support it yet however there are some activities in that direction[5]. This approach will allow to query from these tables (not only properties, also functions, databases and all other data available via SHOW command) as from any other Flink tables. [1] https://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt [2] https://www.postgresql.org/docs/current/information-schema.html [3] https://dev.mysql.com/doc/refman/8.0/en/information-schema.html [4] https://www.cockroachlabs.com/docs/stable/information-schema.html [5] https://issues.apache.org/jira/browse/HIVE-1010 On Wed, Dec 21, 2022 at 12:09 PM yuxia <luoyu...@alumni.sjtu.edu.cn> wrote: > HI, Mingliang. > Thanks for bringing this up. +1 to add this support. > I think use syntax "SET 'key'" to show a signle variable is weird, but use > it may be more convinent and more unified since we have used "SET" to show > all variable. > Considering many hive/spark users may be used to it, seems use "SET > 'key'" is also acceptable. > But I have no much strong preference, use some other thing like "SHOW" > statement also sounds good to me. > > Best regards, > Yuxia > > ----- 原始邮件 ----- > 发件人: "Martijn Visser" <martijnvis...@apache.org> > 收件人: "dev" <dev@flink.apache.org> > 发送时间: 星期三, 2022年 12 月 21日 下午 5:44:15 > 主题: Re: [Discuss] SQL Client syntax to show a configuration > > Hi Mingliang, > > Thanks for opening a discussion thread on this topic, much appreciated. If > there is no standard SQL for this, then we should have a discussion on this > topic indeed. > > I'm not a fan of using "SET" to show a value. For me, "SET" implies that > you are setting a value. I prefer "SHOW" since that clearly identifies that > you want to display a value. Curious what others think on this topic. > > Best regards, > > Martijn > > On Wed, Dec 21, 2022 at 9:48 AM Mingliang Liu <lium...@apache.org> wrote: > > > Hi all, > > > > Currently in SQL Client we can use the "SET 'key'='value'" command to > set a > > value to a config property key for the session. We can also list all > config > > properties by just calling "SET". It would be convenient to show the > value > > of a specific config property given its key(s). Without this, users will > > need to eyeball the very one config from all config properties which may > > need scrolling the screen. > > > > I do not find a standard SQL syntax for this. > > - Some use the syntax "SET 'key'" to show the value, for e.g. Spark SQL > and > > Hive. > > - Some use the "SHOW" keyword to show session properties, for > > e.g. CockroachDB. Trino and MySqL support a key pattern in the "SHOW > > SESSION" statement. > > > > I filed FLINK-30459 to track this. I also attached initial PR #21535 that > > uses the "SET 'key'" syntax. I chose that because I previously used this > > syntax. It seems simpler to just use one keyword to interact with > > session configs. When using Hive dialect, Flink SQL also supports that. > > However, it's not straightforward enough and one probably needs to check > > the doc first. > > > > As Martijn suggested, before improving the code, it's better to get it > > discussed here first. So, is it a good idea to add this support? Which > > syntax is preferred by our community, and are there other better ways of > > supporting this? > > > > Thanks, > > > -- Best regards, Sergey
