Hi Caizhi, thanks for starting this discussion. There is a FLIP-71 [1] to describe the whole story of view.
Sql-cli now implements a wrong way, and a separate way, which should be deprecated and unified to TableEnvironment. > Shall we make it clear and support create table / create temporary table / create view / create temporary view statements? I think there are clear definitions for "create view" (permanent) and "create temporary view" (temporary). > If yes, shall we need to support them just in SQL client or in SQL parser, or in some other places? We should support in a unify way for TableEnvironment.sqlUpdate, and SQL-CLI just pass to this method. > Shall catalog manager support creating both permanent and temporary views? Actually, it already supports these things, has done in FLIP-64 [2]. If you are interested, consider moving forward with the design and implementation of FLIP-71. What do you think? [1] https://cwiki.apache.org/confluence/display/FLINK/FLIP-71+-+E2E+View+support+in+FLINK+SQL [2] https://cwiki.apache.org/confluence/display/FLINK/FLIP-64%3A+Support+for+Temporary+Objects+in+Table+module <https://cwiki.apache.org/confluence/display/FLINK/FLIP-64%3A+Support+for+Temporary+Objects+in+Table+module?src=contextnavpagetreemode> Best, Jingsong Lee On Fri, Feb 21, 2020 at 11:21 AM Caizhi Weng <tsreape...@gmail.com> wrote: > Hi dear Flink developers, > > I'm quite confused by the "create view" statement in SQL client. > > From traditional database we expect that a view behaves just like a table > except that it will be computed when used. We also expect that a view > should be created under a database just like a table. > > But when I create a view in SQL client and switch to another database by > the "use" statement, the view is still there. It seems that this view is > created in all databases under the same catalog. > > I look into the source code and discover that the view I created is > actually a temporary view. In > > https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/common.html > it > is stated that > > > On the other hand, temporary tables are always stored in memory and only > > exist for the duration of the Flink session they are created within. > These > > tables are not visible to other sessions. They are not bound to any > catalog > > or database but can be created in the namespace of one. Temporary tables > > are not dropped if their corresponding database is removed. > > So this seems to be the desired behavior. > > What seems really strange is that in SQL client, by using the "create > table" statement I'll get a permanent table, while by using the "create > view" statement I'll get a temporary view, which is sort of inconsistent. > > So I would like to discuss that > > 1. Shall we make it clear and support create table / create temporary > table / create view / create temporary view statements? > 2. If yes, shall we need to support them just in SQL client or in SQL > parser, or in some other places? > 3. Shall catalog manager support creating both permanent and temporary > views? > > Thanks. > -- Best, Jingsong Lee
