Hi Timo,
Thanks for your comments. After the offline discussion, I have updated the FLIP
with the following change.
1. Update the end to end process
a. The Table.cache method should only wrap the origin query operation with
CacheOperation.
b. The planner will add the CacheSink or replace subtree with CacheSource
while translating the QueryOperation to rel node. The CacheSink and CacheSource
are treated as regular sinks and sources while the planner optimizes and
translates the rel nodes.
c. The StreamGraphGenerator will recognize the CacheSink and CacheSource
and generate the StreamGraph accordingly. When it sees the CacheSink, it will
remove the CacheSink and set the cache flag in the StreamNode. When it sees the
CacheSource, it will include the ClusterPartitionDescriptor in the StreamNode.
d. The JobGraph generator will not modify the graph. It only set the result
partition type of the intermediate result to BLOCKING_PERSISTENT if it sees a
StreamNode with the cache flag set or passes the ClusterPartitionDescriptor
from the StreamNode to the JobVertex if the StreamNode has the
ClusterPartitionDescriptor.
e. The ClusterPartitionDescriptor will be included in the JobResult and
sent back to the client.
2. The metadata of the cached table will be stored in the CatalogManager
instead of the TableEnvironment
3. The Table.cache method returns a CachedTable, which is a subclass of Table.
4. Add a paragraph to explain that the cache table will not work in Per-Job
Mode cluster.
5. Add SQL integration and Cache Eviction in the future work section.
As of the @Public and @PublicEvolving interface, I think it should be covered
in the public interface section, i.e., Table and TableEnvironment. Other than
those, all the changes should only affect the internal class.
Please let me know if you have any further comments.
Best,
Xuannan
On Aug 10, 2020, 9:32 PM +0800, Timo Walther <twal...@apache.org>, wrote:
> Hi Xuannan,
>
> sorry for joining the discussion so late. I agree that this is a very
> nice and useful feature. However, the impact it has to many components
> in the stack requires more discussion in my opinion.
>
> 1) Separation of concerns:
> The current design seems to mix different layers. We should make sure
> that all layers do what they are supposed to do:
>
> 1a) The FLIP states: "The cache() method returns a new Table object with
> a flag set."
>
> The `Table` object is just a thin API class that wraps a
> `QueryOperation`. Other than that the `Table` object should not contain
> futher state. The tree of `QueryOperation` should be an immutable,
> independent data structure that can be passed around and will eventually
> be passed to the `Planner`.
>
> The mentioned `CacheSink` should be added by the optimizer. It is not
> the responsibility of the API do perform optimizer-like tasks. A call to
> `t1.cache()` should simply wrap the original operation into something
> like `CacheOperation(t1.getQueryOperation)`. A `CacheOperation` could
> still extend from `QueryOperation` and assign a unique string identifier
> already. A specialized `StreamTransformation` would be necessary during
> translation.
>
> 1b) The FLIP states: "The default table service stores the metadata in
> the client (e.g. TableEnvironment)"
>
> `TableEnvironment` is not a client. Similar to `Table`, it is an API
> class that just delegates to other session components. Currently, the
> table environment has (again) to many responsibilities that should
> better be split into other components. The table's `Executor` is the
> client that performs the cluster communication. But in general it also
> just delegates to `org.apache.flink.core.execution.PipelineExecutor`.
> IMO the `PipelineExecutor` is a better fit for a back-and-forth
> communication to determine existing cluster partitions and modify the
> job graph. Or even further down the stack, because as far as I know,
> `PipelineExecutor` works with `StreamGraph`.
>
> `flink-table-api-java` has no dependency to `flink-runtime`. This has
> been done on purpose.
>
> 2) API
> I still see the rejected option 2 a good fit to expose this feature.
>
> A `Table.cache(): CachedTable` with `CachedTable.invalidate(): void` and
> maybe `CachedTable.getId(): String` makes the feature and its operations
> very explicit. It also avoids following up questions such as:
>
> Will `invalidateCache()` be transitively propagated in
> `t1.cache().join(t2.cache()).invalidateCache()`?
>
> Or as the FLIP states:
>
> `Table t3 = t1.select(...) // cache will NOT be used.`
> but
> `t1.invalidateCache() // cache will be released`
>
> This sounds a bit contradicting to me. Because sometimes the
> `t1.cache()` has implications on t1 and sometimes not.
>
> 3) Big picture
>
> After reading the FLIP, I still don't understand how a user can
> configure or control the table service. Will we offer options through
> `TableConfig` or `TableEnvironment` or is this configuration done via
> ConfigOptions for lower layers?
>
> 4) SQL integration
>
> As I mentioned earlier, we should think about a SQL integration as well.
> Otherwise we need to redesign the Java API to align it with SQL later.
> SQL has also a bigger user base than Table API. Let's assume we
> introduce a new keyword and combine the caching with regular CREATE VIEW
> syntax such as:
> `CREATE CACHED TEMPORARY VIEW MyTable AS SELECT *`
> This would align well with:
> `tEnv.registerTemporaryView("MyTable", table.cache())`
>
> What do you think?
>
> 4) TableEnvironment.close()
>
> Will `TableEnvironment` implement `AutoCloseable`?
>
>
> In summary, I think the FLIP should go into more details how this effort
> affects each layer. Because a lot of the interfaces are `@Public` or
> `@PublicEvolving`. And the FLIP still leaves a lot of questions how this
> high level concept ends up in JobGraph.
>
> Regards,
> Timo
>
>
>
> On 30.07.20 09:00, Xuannan Su wrote:
> > Hi folks,
> >
> > It seems that all the raised concerns so far have been resolved. I plan to
> > start a voting thread for FLIP-36 early next week if there are no comments.
> >
> > Thanks,
> > Xuannan
> > On Jul 28, 2020, 7:42 PM +0800, Xuannan Su <suxuanna...@gmail.com>, wrote:
> > > Hi Kurt,
> > >
> > > Thanks for the comments.
> > >
> > > You are right that the FLIP lacks a proper discussion about the impact of
> > > the optimizer. I have added the section to talk about how the cache table
> > > works with the optimizer. I hope this could resolve your concern. Please
> > > let me know if you have any further comments.
> > >
> > > Best,
> > > Xuannan
> > > On Jul 22, 2020, 4:36 PM +0800, Kurt Young <ykt...@gmail.com>, wrote:
> > > > Thanks for the reply, I have one more comment about the optimizer
> > > > affection. Even if you are
> > > > trying to make the cached table be as orthogonal to the optimizer as
> > > > possible by introducing
> > > > a special sink, it is still not clear why this approach is safe. Maybe
> > > > you
> > > > can add some process
> > > > introduction from API to JobGraph, otherwise I can't make sure everyone
> > > > reviewing the design
> > > > doc will have the same imagination about this. And I'm also quite sure
> > > > some
> > > > of the existing
> > > > mechanism will be affected by this special sink, e.g. multi sink
> > > > optimization.
> > > >
> > > > Best,
> > > > Kurt
> > > >
> > > >
> > > > On Wed, Jul 22, 2020 at 2:31 PM Xuannan Su <suxuanna...@gmail.com>
> > > > wrote:
> > > >
> > > > > Hi Kurt,
> > > > >
> > > > > Thanks for the comments.
> > > > >
> > > > > 1. How do you identify the CachedTable?
> > > > > For the current design proposed in FLIP-36, we are using the first
> > > > > approach you mentioned, where the key of the map is the Cached Table
> > > > > java
> > > > > object. I think it is fine not to be able to identify another table
> > > > > representing the same DAG and not using the cached intermediate result
> > > > > because we want to make the caching table explicit. As mentioned in
> > > > > the
> > > > > FLIP, the cache API will return a Table object. And the user has to
> > > > > use the
> > > > > returned Table object to make use of the cached table. The rationale
> > > > > is
> > > > > that if the user builds the same DAG from scratch with some
> > > > > TableEnvironment instead of using the cached table object, the user
> > > > > probably doesn't want to use the cache.
> > > > >
> > > > > 2. How does the CachedTable affect the optimizer?
> > > > > We try to make the logic dealing with the cached table be as
> > > > > orthogonal to
> > > > > the optimizer as possible. That's why we introduce a special sink
> > > > > when we
> > > > > are going to cache a table and a special source when we are going to
> > > > > use a
> > > > > cached table. This way, we can let the optimizer does it works, and
> > > > > the
> > > > > logic of modifying the job graph can happen in the job graph
> > > > > generator. We
> > > > > can recognize the cached node with the special sink and source.
> > > > >
> > > > > 3. What's the effect of calling TableEnvironment.close()?
> > > > > We introduce the close method to prevent leaking of the cached table
> > > > > when
> > > > > the user is done with the table environment. Therefore, it makes more
> > > > > sense
> > > > > that the table environment, including all of its functionality,
> > > > > should not
> > > > > be used after closing. Otherwise, we should rename the close method to
> > > > > clearAllCache or something similar.
> > > > >
> > > > > And thanks for pointing out the use of not existing API used in the
> > > > > given
> > > > > examples. I have updated the examples in the FLIP accordingly.
> > > > >
> > > > > Best,
> > > > > Xuannan
> > > > > On Jul 16, 2020, 4:15 PM +0800, Kurt Young <ykt...@gmail.com>, wrote:
> > > > > > Hi Xuanna,
> > > > > >
> > > > > > Thanks for the detailed design doc, it described clearly how the API
> > > > > looks
> > > > > > and how to interact with Flink runtime.
> > > > > > However, the part which relates to SQL's optimizer is kind of
> > > > > > blurry. To
> > > > > be
> > > > > > more precise, I have following questions:
> > > > > >
> > > > > > 1. How do you identify the CachedTable? I can imagine there would
> > > > > > be map
> > > > > > representing the cache, how do you
> > > > > > compare the keys of the map? One approach is they will be compared
> > > > > > by
> > > > > java
> > > > > > objects, which is simple but has
> > > > > > limited scope. For example, users created another table using some
> > > > > > interfaces of TableEnvironment, and the table
> > > > > > is exactly the same as the cached one, you won't be able to
> > > > > > identify it.
> > > > > > Another choice is calculating the "signature" or
> > > > > > "diest" of the cached table, which involves string representation
> > > > > > of the
> > > > > > whole sub tree represented by the cached table.
> > > > > > I don't think Flink currently provides such a mechanism around Table
> > > > > > though.
> > > > > >
> > > > > > 2. How does the CachedTable affect the optimizer? Specifically,
> > > > > > will you
> > > > > > have a dedicated QueryOperation for it, will you have
> > > > > > a dedicated logical & physical RelNode for it? And I also don't see
> > > > > > a
> > > > > > description about how to work with current optimize phases,
> > > > > > from Operation to Calcite rel node, and then to Flink's logical and
> > > > > > physical node, which will be at last translated to Flink's exec
> > > > > > node.
> > > > > > There also exists other optimizations such as dead lock breaker, as
> > > > > > well
> > > > > as
> > > > > > sub plan reuse inside the optimizer, I'm not sure whether
> > > > > > the logic dealing with cached tables can be orthogonal to all of
> > > > > > these.
> > > > > > Hence I expect you could have a more detailed description here.
> > > > > >
> > > > > > 3. What's the effect of calling TableEnvironment.close()? You
> > > > > > already
> > > > > > explained this would drop all caches this table env has,
> > > > > > could you also explain where other functionality still works for
> > > > > > this
> > > > > table
> > > > > > env? Like can use still create/drop tables/databases/function
> > > > > > through this table env? What happens to the catalog and all
> > > > > > temporary
> > > > > > objects of this table env?
> > > > > >
> > > > > > One minor comment: I noticed you used some not existing API in the
> > > > > examples
> > > > > > you gave, like table.collect(), which is a little
> > > > > > misleading.
> > > > > >
> > > > > > Best,
> > > > > > Kurt
> > > > > >
> > > > > >
> > > > > > On Thu, Jul 9, 2020 at 4:00 PM Xuannan Su <suxuanna...@gmail.com>
> > > > > > wrote:
> > > > > >
> > > > > > > Hi folks,
> > > > > > >
> > > > > > > I'd like to revive the discussion about FLIP-36 Support
> > > > > > > Interactive
> > > > > > > Programming in Flink Table API
> > > > > > >
> > > > > > >
> > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-36%3A+Support+Interactive+Programming+in+Flink
> > > > > > >
> > > > > > > The FLIP proposes to add support for interactive programming in
> > > > > > > Flink
> > > > > > > Table API. Specifically, it let users cache the intermediate
> > > > > > > results(tables) and use them in the later jobs to avoid
> > > > > > > recomputing the
> > > > > > > intermediate result(tables).
> > > > > > >
> > > > > > > I am looking forward to any opinions and suggestions from the
> > > > > community.
> > > > > > >
> > > > > > > Best,
> > > > > > > Xuannan
> > > > > > > On May 7, 2020, 5:40 PM +0800, Xuannan Su <suxuanna...@gmail.com>,
> > > > > wrote:
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > There are some feedbacks from @Timo and @Kurt in the voting
> > > > > > > > thread
> > > > > for
> > > > > > > FLIP-36 and I want to share my thoughts here.
> > > > > > > >
> > > > > > > > 1. How would the FLIP-36 look like after FLIP-84?
> > > > > > > > I don't think FLIP-84 will affect FLIP-36 from the public API
> > > > > > > perspective. Users can call .cache on a table object and the
> > > > > > > cached
> > > > > table
> > > > > > > will be generated whenever the table job is triggered to execute,
> > > > > either by
> > > > > > > Table#executeInsert or StatementSet#execute. I think that FLIP-36
> > > > > should
> > > > > > > aware of the changes made by FLIP-84, but it shouldn't be a
> > > > > > > problem.
> > > > > At the
> > > > > > > end of the day, FLIP-36 only requires the ability to add a sink
> > > > > > > to a
> > > > > node,
> > > > > > > submit a table job with multiple sinks, and replace the cached
> > > > > > > table
> > > > > with a
> > > > > > > source.
> > > > > > > >
> > > > > > > > 2. How can we support cache in a multi-statement SQL file?
> > > > > > > > The most intuitive way to support cache in a multi-statement SQL
> > > > > file is
> > > > > > > by using a view, where the view is corresponding to a cached
> > > > > > > table.
> > > > > > > >
> > > > > > > > 3. Unifying the cached table and materialized views
> > > > > > > > It is true that the cached table and the materialized view are
> > > > > similar
> > > > > > > in some way. However, I think the materialized view is a more
> > > > > > > complex
> > > > > > > concept. First, a materialized view requires some kind of a
> > > > > > > refresh
> > > > > > > mechanism to synchronize with the table. Secondly, the life cycle
> > > > > > > of a
> > > > > > > materialized view is longer. The materialized view should be
> > > > > > > accessible
> > > > > > > even after the application exits and should be accessible by
> > > > > > > another
> > > > > > > application, while the cached table is only accessible in the
> > > > > application
> > > > > > > where it is created. The cached table is introduced to avoid
> > > > > recomputation
> > > > > > > of an intermediate table to support interactive programming in
> > > > > > > Flink
> > > > > Table
> > > > > > > API. And I think the materialized view needs more discussion and
> > > > > certainly
> > > > > > > deserves a whole new FLIP.
> > > > > > > >
> > > > > > > > Please let me know your thought.
> > > > > > > >
> > > > > > > > Best,
> > > > > > > > Xuannan
> > > > > > > >
> > > > > > > On Wed, Apr 29, 2020 at 3:53 PM Xuannan Su <suxuanna...@gmail.com>
> > > > > wrote:
> > > > > > > > Hi folks,
> > > > > > > >
> > > > > > > > The FLIP-36 is updated according to the discussion with Becket.
> > > > > > > > In
> > > > > the
> > > > > > > meantime, any comments are very welcome.
> > > > > > > >
> > > > > > > > If there are no further comments, I would like to start the
> > > > > > > > voting
> > > > > > > > thread by tomorrow.
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Xuannan
> > > > > > > >
> > > > > > > >
> > > > > > > > > On Sun, Apr 26, 2020 at 9:34 AM Xuannan Su
> > > > > > > > > <suxuanna...@gmail.com>
> > > > > > > wrote:
> > > > > > > > > > Hi Becket,
> > > > > > > > > >
> > > > > > > > > > You are right. It makes sense to treat retry of job 2 as an
> > > > > ordinary
> > > > > > > job. And the config does introduce some unnecessary confusion.
> > > > > > > Thank
> > > > > you
> > > > > > > for you comment. I will update the FLIP.
> > > > > > > > > >
> > > > > > > > > > Best,
> > > > > > > > > > Xuannan
> > > > > > > > > >
> > > > > > > > > > > On Sat, Apr 25, 2020 at 7:44 AM Becket Qin <
> > > > > becket....@gmail.com>
> > > > > > > wrote:
> > > > > > > > > > > > Hi Xuannan,
> > > > > > > > > > > >
> > > > > > > > > > > > If user submits Job 1 and generated a cached
> > > > > > > > > > > > intermediate
> > > > > > > result. And later
> > > > > > > > > > > > on, user submitted job 2 which should ideally use the
> > > > > > > intermediate result.
> > > > > > > > > > > > In that case, if job 2 failed due to missing the
> > > > > > > > > > > > intermediate
> > > > > > > result, Job 2
> > > > > > > > > > > > should be retried with its full DAG. After that when
> > > > > > > > > > > > Job 2
> > > > > runs,
> > > > > > > it will
> > > > > > > > > > > > also re-generate the cache. However, once job 2 has fell
> > > > > back to
> > > > > > > the
> > > > > > > > > > > > original DAG, should it just be treated as an ordinary
> > > > > > > > > > > > job
> > > > > that
> > > > > > > follow the
> > > > > > > > > > > > recovery strategy? Having a separate configuration
> > > > > > > > > > > > seems a
> > > > > little
> > > > > > > > > > > > confusing. In another word, re-generating the cache is
> > > > > > > > > > > > just a
> > > > > > > byproduct of
> > > > > > > > > > > > running the full DAG of job 2, but is not the main
> > > > > > > > > > > > purpose.
> > > > > It
> > > > > > > is just like
> > > > > > > > > > > > when job 1 runs to generate cache, it does not have a
> > > > > separate
> > > > > > > config of
> > > > > > > > > > > > retry to make sure the cache is generated. If it fails,
> > > > > > > > > > > > it
> > > > > just
> > > > > > > fail like
> > > > > > > > > > > > an ordinary job.
> > > > > > > > > > > >
> > > > > > > > > > > > What do you think?
> > > > > > > > > > > >
> > > > > > > > > > > > Thanks,
> > > > > > > > > > > >
> > > > > > > > > > > > Jiangjie (Becket) Qin
> > > > > > > > > > > >
> > > > > > > > > > > > On Fri, Apr 24, 2020 at 5:00 PM Xuannan Su <
> > > > > > > suxuanna...@gmail.com> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > > Hi Becket,
> > > > > > > > > > > > >
> > > > > > > > > > > > > The intermediate result will indeed be automatically
> > > > > > > re-generated by
> > > > > > > > > > > > > resubmitting the original DAG. And that job could
> > > > > > > > > > > > > fail as
> > > > > > > well. In that
> > > > > > > > > > > > > case, we need to decide if we should resubmit the
> > > > > > > > > > > > > original
> > > > > DAG
> > > > > > > to
> > > > > > > > > > > > > re-generate the intermediate result or give up and
> > > > > > > > > > > > > throw an
> > > > > > > exception to
> > > > > > > > > > > > > the user. And the config is to indicate how many
> > > > > > > > > > > > > resubmit
> > > > > > > should happen
> > > > > > > > > > > > > before giving up.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Thanks,
> > > > > > > > > > > > > Xuannan
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Fri, Apr 24, 2020 at 4:19 PM Becket Qin <
> > > > > > > becket....@gmail.com> wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi Xuannan,
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I am not entirely sure if I understand the cases you
> > > > > > > mentioned. The
> > > > > > > > > > > > > users
> > > > > > > > > > > > > > > can use the cached table object returned by the
> > > > > .cache()
> > > > > > > method in
> > > > > > > > > > > > > other
> > > > > > > > > > > > > > > job and it should read the intermediate result.
> > > > > > > > > > > > > > > The
> > > > > > > intermediate result
> > > > > > > > > > > > > > can
> > > > > > > > > > > > > > > gone in the following three cases: 1. the user
> > > > > explicitly
> > > > > > > call the
> > > > > > > > > > > > > > > invalidateCache() method 2. the TableEnvironment
> > > > > > > > > > > > > > > is
> > > > > closed
> > > > > > > 3. failure
> > > > > > > > > > > > > > > happens on the TM. When that happens, the
> > > > > > > > > > > > > > > intermeidate
> > > > > > > result will not
> > > > > > > > > > > > > be
> > > > > > > > > > > > > > > available unless it is re-generated.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > What confused me was that why do we need to have a
> > > > > > > *cache.retries.max
> > > > > > > > > > > > > > *config?
> > > > > > > > > > > > > > Shouldn't the missing intermediate result always be
> > > > > > > automatically
> > > > > > > > > > > > > > re-generated if it is gone?
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Thanks,
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Jiangjie (Becket) Qin
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > On Fri, Apr 24, 2020 at 3:59 PM Xuannan Su <
> > > > > > > suxuanna...@gmail.com>
> > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Hi Becket,
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Thanks for the comments.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > On Fri, Apr 24, 2020 at 9:12 AM Becket Qin <
> > > > > > > becket....@gmail.com>
> > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Hi Xuannan,
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Thanks for picking up the FLIP. It looks good
> > > > > > > > > > > > > > > > to me
> > > > > > > overall. Some
> > > > > > > > > > > > > quick
> > > > > > > > > > > > > > > > comments / questions below:
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > 1. Do we also need changes in the Java API?
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Yes, the public interface of Table and
> > > > > > > > > > > > > > > TableEnvironment
> > > > > > > should be made
> > > > > > > > > > > > > in
> > > > > > > > > > > > > > > the Java API.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > 2. What are the cases that users may want to
> > > > > > > > > > > > > > > > retry
> > > > > > > reading the
> > > > > > > > > > > > > > > intermediate
> > > > > > > > > > > > > > > > result? It seems that once the intermediate
> > > > > > > > > > > > > > > > result
> > > > > has
> > > > > > > gone, it will
> > > > > > > > > > > > > > not
> > > > > > > > > > > > > > > be
> > > > > > > > > > > > > > > > available later without being generated again,
> > > > > > > > > > > > > > > > right?
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > I am not entirely sure if I understand the cases
> > > > > > > > > > > > > > > you
> > > > > > > mentioned. The
> > > > > > > > > > > > > > users
> > > > > > > > > > > > > > > can use the cached table object returned by the
> > > > > .cache()
> > > > > > > method in
> > > > > > > > > > > > > other
> > > > > > > > > > > > > > > job and it should read the intermediate result.
> > > > > > > > > > > > > > > The
> > > > > > > intermediate result
> > > > > > > > > > > > > > can
> > > > > > > > > > > > > > > gone in the following three cases: 1. the user
> > > > > explicitly
> > > > > > > call the
> > > > > > > > > > > > > > > invalidateCache() method 2. the TableEnvironment
> > > > > > > > > > > > > > > is
> > > > > closed
> > > > > > > 3. failure
> > > > > > > > > > > > > > > happens on the TM. When that happens, the
> > > > > > > > > > > > > > > intermeidate
> > > > > > > result will not
> > > > > > > > > > > > > be
> > > > > > > > > > > > > > > available unless it is re-generated.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > 3. In the "semantic of cache() method" section,
> > > > > > > > > > > > > > > the
> > > > > > > description "The
> > > > > > > > > > > > > > > > semantic of the *cache() *method is a little
> > > > > different
> > > > > > > depending on
> > > > > > > > > > > > > > > whether
> > > > > > > > > > > > > > > > auto caching is enabled or not." seems not
> > > > > > > > > > > > > > > > explained.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > This line is actually outdated and should be
> > > > > > > > > > > > > > > removed,
> > > > > as
> > > > > > > we are not
> > > > > > > > > > > > > > adding
> > > > > > > > > > > > > > > the auto caching functionality in this FLIP. Auto
> > > > > caching
> > > > > > > will be added
> > > > > > > > > > > > > > in
> > > > > > > > > > > > > > > the future, and the semantic of cache() when auto
> > > > > caching
> > > > > > > is enabled
> > > > > > > > > > > > > will
> > > > > > > > > > > > > > > be discussed in detail by a new FLIP. I will
> > > > > > > > > > > > > > > remove the
> > > > > > > descriptor to
> > > > > > > > > > > > > > avoid
> > > > > > > > > > > > > > > further confusion.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Thanks,
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Jiangjie (Becket) Qin
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > On Wed, Apr 22, 2020 at 4:00 PM Xuannan Su <
> > > > > > > suxuanna...@gmail.com>
> > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Hi folks,
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > I'd like to start the discussion about FLIP-36
> > > > > Support
> > > > > > > Interactive
> > > > > > > > > > > > > > > > > Programming in Flink Table API
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > >
> > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-36%3A+Support+Interactive+Programming+in+Flink
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > The FLIP proposes to add support for
> > > > > > > > > > > > > > > > > interactive
> > > > > > > programming in
> > > > > > > > > > > > > Flink
> > > > > > > > > > > > > > > > Table
> > > > > > > > > > > > > > > > > API. Specifically, it let users cache the
> > > > > intermediate
> > > > > > > > > > > > > > results(tables)
> > > > > > > > > > > > > > > > and
> > > > > > > > > > > > > > > > > use them in the later jobs.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Even though the FLIP has been discussed in the
> > > > > > > past[1], the FLIP
> > > > > > > > > > > > > > hasn't
> > > > > > > > > > > > > > > > > formally passed the vote yet. And some of the
> > > > > design
> > > > > > > and
> > > > > > > > > > > > > > implementation
> > > > > > > > > > > > > > > > > detail have to change to incorporates the
> > > > > > > > > > > > > > > > > cluster
> > > > > > > partition
> > > > > > > > > > > > > proposed
> > > > > > > > > > > > > > in
> > > > > > > > > > > > > > > > > FLIP-67[2].
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Looking forward to your feedback.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Thanks,
> > > > > > > > > > > > > > > > > Xuannan
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > [1]
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > >
> > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-67%3A+Cluster+partitions+lifecycle
> > > > > > > > > > > > > > > > > [2]
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > >
> > > > > https://lists.apache.org/thread.html/b372fd7b962b9f37e4dace3bc8828f6e2a2b855e56984e58bc4a413f@%3Cdev.flink.apache.org%3E
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