It seems this FLIP's name is somewhat misleading. From my understanding, this FLIP is trying to address the dynamic parameter issue, and table hints is the way we wan to choose. I think we should be focus on "what's the right way to solve dynamic property" instead of discussing "whether table hints can affect query semantics".
For now, there are two proposed ways to achieve dynamic property: 1. FLIP-110: create temporary table xx like xx with (xxx) 2. use custom "from t with (xxx)" syntax 3. "Borrow" the table hints to have a special PROPERTIES hint. The first one didn't break anything, but the only problem i see is a little more verbose than the table hint approach. I can imagine when someone using SQL CLI to have a sql experience, it's quite often that he will modify the table property, some use cases i can think of: 1. the source contains some corrupted data, i want to turn on the "ignore-error" flag for certain formats. 2. I have a kafka table and want to see some sample data from the beginning, so i change the offset to "earliest", and then I want to observe the latest data which keeps coming in. I would write another query to select from the latest table. 3. I want to my jdbc sink flush data more eagerly then i can observe the data from database side. Most of such use cases are quite ad-hoc. If every time I want to have a different experience, i need to create a temporary table and then also modify my query, it doesn't feel smooth. Embed such dynamic property into query would have better user experience. Both 2 & 3 can make this happen. The cons of #2 is breaking SQL compliant, and for #3, it only breaks some unwritten rules, but we can have an explanation on that. And I really doubt whether user would complain about this when they actually have flexible and good experience using this. My tendency would be #3 > #1 > #2, what do you think? Best, Kurt On Thu, Mar 12, 2020 at 1:11 PM Danny Chan <yuzhao....@gmail.com> wrote: > Thanks Aljoscha ~ > > I agree for most of the query hints, they are optional as an optimizer > instruction, especially for the traditional RDBMS. > > But, just like BenChao said, Flink as a computation engine has many > different kind of data sources, thus, dynamic parameters like start_offest > can only bind to each table scope, we can not set a session config like > KSQL because they are all about Kafka: > > SET ‘auto.offset.reset’=‘earliest’; > > Thus the most flexible way to set up these dynamic params is to bind to > the table scope in the query when we want to override something, so we have > these solutions above (with pros and cons from my side): > > • 1. Select * from t(offset=123) (from Timo) > > Pros: > - Easy to add > - Parameters are part of the main query > Cons: > - Not SQL compliant > > > • 2. Select * from t /*+ PROPERTIES(offset=123) */ (from me) > > Pros: > - Easy to add > - SQL compliant because it is nested in the comments > > Cons: > - Parameters are not part of the main query > - Cryptic syntax for new users > > The biggest problem for hints way may be the “if hints must be optional”, > actually we have though about 1 for a while but aborted because it breaks > the SQL standard too much. And we replace it with 2, because the hints > syntax do not break SQL standard(nested in comments). > > What if we have the special /*+ PROPERTIES */ hint that allows override > some properties of table dynamically, it does not break anything, at lease > for current Flink use cases. > > Planner hints are optional just because they are naturally enforcers of > the planner, most of them aim to instruct the optimizer, but, the table > hints is a little different, table hints can specify the table meta like > index column, and it is very convenient to specify table properties. > > Or shall we not call /*+ PROPERTIES(offset=123) */ table hint, we can > call it table dynamic parameters. > > Best, > Danny Chan > 在 2020年3月11日 +0800 PM9:20，Aljoscha Krettek <aljos...@apache.org>，写道： > > Hi, > > > > I don't understand this discussion. Hints, as I understand them, should > > work like this: > > > > - hints are *optional* advice for the optimizer to try and help it to > > find a good execution strategy > > - hints should not change query semantics, i.e. they should not change > > connector properties executing a query with taking into account the > > hints *must* produce the same result as executing the query without > > taking into account the hints > > > > From these simple requirements you can derive a solution that makes > > sense. I don't have a strong preference for the syntax but we should > > strive to be in line with prior work. > > > > Best, > > Aljoscha > > > > On 11.03.20 11:53, Danny Chan wrote: > > > Thanks Timo for summarize the 3 options ~ > > > > > > I agree with Kurt that option2 is too complicated to use because: > > > > > > • As a Kafka topic consumer, the user must define both the virtual > column for start offset and he must apply a special filter predicate after > each query > > > • And for the internal implementation, the metadata column push down > is another hard topic, each kind of message queue may have its offset > attribute, we need to consider the expression type for different kind; the > source also need to recognize the constant column as a config option(which > is weird because usually what we pushed down is a table column) > > > > > > For option 1 and option3, I think there is no difference, option1 is > also a hint syntax which is introduced in Sybase and referenced then > deprecated by MS-SQL in 199X years because of the ambitiousness. Personally > I prefer /*+ */ style table hint than WITH keyword for these reasons: > > > > > > • We do not break the standard SQL, the hints are nested in SQL > comments > > > • We do not need to introduce additional WITH keyword which may appear > in a query if we use that because a table can be referenced in all kinds of > SQL contexts: INSERT/DELETE/FROM/JOIN …. That would make our sql query > break too much of the SQL from standard > > > • We would have uniform syntax for hints as query hint, one syntax > fits all and more easy to use > > > > > > > > > And here is the reason why we choose a uniform Oracle style query > hint syntax which is addressed by Julian Hyde when we design the syntax > from the Calcite community: > > > > > > I don’t much like the MSSQL-style syntax for table hints. It adds a > new use of the WITH keyword that is unrelated to the use of WITH for > common-table expressions. > > > > > > A historical note. Microsoft SQL Server inherited its hint syntax from > Sybase a very long time ago. (See “Transact SQL Programming”[1], page 632, > “Optimizer hints”. The book was written in 1999, and covers Microsoft SQL > Server 6.5 / 7.0 and Sybase Adaptive Server 11.5, but the syntax very > likely predates Sybase 4.3, from which Microsoft SQL Server was forked in > 1993.) > > > > > > Microsoft later added the WITH keyword to make it less ambiguous, and > has now deprecated the syntax that does not use WITH. > > > > > > They are forced to keep the syntax for backwards compatibility but > that doesn’t mean that we should shoulder their burden. > > > > > > I think formatted comments are the right container for hints because > it allows us to change the hint syntax without changing the SQL parser, and > makes clear that we are at liberty to ignore hints entirely. > > > > > > Julian > > > > > > [1] https://www.amazon.com/s?k=9781565924017 < > https://www.amazon.com/s?k=9781565924017> > > > > > > Best, > > > Danny Chan > > > 在 2020年3月11日 +0800 PM4:03，Timo Walther <twal...@apache.org>，写道： > > > > Hi Danny, > > > > > > > > it is true that our DDL is not standard compliant by using the WITH > > > > clause. Nevertheless, we aim for not diverging too much and the LIKE > > > > clause is an example of that. It will solve things like overwriting > > > > WATERMARKs, add additional/modifying properties and inherit schema. > > > > > > > > Bowen is right that Flink's DDL is mixing 3 types definition > together. > > > > We are not the first ones that try to solve this. There is also the > SQL > > > > MED standard [1] that tried to tackle this problem. I think it was > not > > > > considered when designing the current DDL. > > > > > > > > Currently, I see 3 options for handling Kafka offsets. I will give > some > > > > examples and look forward to feedback here: > > > > > > > > *Option 1* Runtime and semantic parms as part of the query > > > > > > > > `SELECT * FROM MyTable('offset'=123)` > > > > > > > > Pros: > > > > - Easy to add > > > > - Parameters are part of the main query > > > > - No complicated hinting syntax > > > > > > > > Cons: > > > > - Not SQL compliant > > > > > > > > *Option 2* Use metadata in query > > > > > > > > `CREATE TABLE MyTable (id INT, offset AS SYSTEM_METADATA('offset'))` > > > > > > > > `SELECT * FROM MyTable WHERE offset > TIMESTAMP '2012-12-12 > 12:34:22'` > > > > > > > > Pros: > > > > - SQL compliant in the query > > > > - Access of metadata in the DDL which is required anyway > > > > - Regular pushdown rules apply > > > > > > > > Cons: > > > > - Users need to add an additional comlumn in the DDL > > > > > > > > *Option 3*: Use hints for properties > > > > > > > > ` > > > > SELECT * > > > > FROM MyTable /*+ PROPERTIES('offset'=123) */ > > > > ` > > > > > > > > Pros: > > > > - Easy to add > > > > > > > > Cons: > > > > - Parameters are not part of the main query > > > > - Cryptic syntax for new users > > > > - Not standard compliant. > > > > > > > > If we go with this option, I would suggest to make it available in a > > > > separate map and don't mix it with statically defined properties. > Such > > > > that the factory can decide which properties have the right to be > > > > overwritten by the hints: > > > > TableSourceFactory.Context.getQueryHints(): ReadableConfig > > > > > > > > Regards, > > > > Timo > > > > > > > > [1] https://en.wikipedia.org/wiki/SQL/MED > > > > > > > > Currently I see 3 options as a > > > > > > > > > > > > On 11.03.20 07:21, Danny Chan wrote: > > > > > Thanks Bowen ~ > > > > > > > > > > I agree we should somehow categorize our connector parameters. > > > > > > > > > > For type1, I’m already preparing a solution like the Confluent > schema registry + Avro schema inference thing, so this may not be a problem > in the near future. > > > > > > > > > > For type3, I have some questions: > > > > > > > > > > > "SELECT * FROM mykafka WHERE offset > 12pm yesterday” > > > > > > > > > > Where does the offset column come from, a virtual column from the > table schema, you said that > > > > > > > > > > > They change > > > > > almost every time a query starts and have nothing to do with > metadata, thus > > > > > should not be part of table definition/DDL > > > > > > > > > > But why you can reference it in the query, I’m confused for that, > can you elaborate a little ? > > > > > > > > > > Best, > > > > > Danny Chan > > > > > 在 2020年3月11日 +0800 PM12:52，Bowen Li <bowenl...@gmail.com>，写道： > > > > > > Thanks Danny for kicking off the effort > > > > > > > > > > > > The root cause of too much manual work is Flink DDL has mixed 3 > types of > > > > > > params together and doesn't handle each of them very well. Below > are how I > > > > > > categorize them and corresponding solutions in my mind: > > > > > > > > > > > > - type 1: Metadata of external data, like external endpoint/url, > > > > > > username/pwd, schemas, formats. > > > > > > > > > > > > Such metadata are mostly already accessible in external system > as long as > > > > > > endpoints and credentials are provided. Flink can get it thru > catalogs, but > > > > > > we haven't had many catalogs yet and thus Flink just hasn't been > able to > > > > > > leverage that. So the solution should be building more catalogs. > Such > > > > > > params should be part of a Flink table DDL/definition, and not > overridable > > > > > > in any means. > > > > > > > > > > > > > > > > > > - type 2: Runtime params, like jdbc connector's fetch size, > elasticsearch > > > > > > connector's bulk flush size. > > > > > > > > > > > > Such params don't affect query results, but affect how results > are produced > > > > > > (eg. fast or slow, aka performance) - they are essentially > execution and > > > > > > implementation details. They change often in exploration or > development > > > > > > stages, but not quite frequently in well-defined long-running > pipelines. > > > > > > They should always have default values and can be missing in > query. They > > > > > > can be part of a table DDL/definition, but should also be > replaceable in a > > > > > > query - *this is what table "hints" in FLIP-113 should cover*. > > > > > > > > > > > > > > > > > > - type 3: Semantic params, like kafka connector's start offset. > > > > > > > > > > > > Such params affect query results - the semantics. They'd better > be as > > > > > > filter conditions in WHERE clause that can be pushed down. They > change > > > > > > almost every time a query starts and have nothing to do with > metadata, thus > > > > > > should not be part of table definition/DDL, nor be persisted in > catalogs. > > > > > > If they will, users should create views to keep such params > around (note > > > > > > this is different from variable substitution). > > > > > > > > > > > > > > > > > > Take Flink-Kafka as an example. Once we get these params right, > here're the > > > > > > steps users need to do to develop and run a Flink job: > > > > > > - configure a Flink ConfluentSchemaRegistry with url, username, > and password > > > > > > - run "SELECT * FROM mykafka WHERE offset > 12pm yesterday" > (simplified > > > > > > timestamp) in SQL CLI, Flink automatically retrieves all > metadata of > > > > > > schema, file format, etc and start the job > > > > > > - users want to make the job read Kafka topic faster, so it goes > as "SELECT > > > > > > * FROM mykafka /* faster_read_key=value*/ WHERE offset > 12pm > yesterday" > > > > > > - done and satisfied, users submit it to production > > > > > > > > > > > > > > > > > > Regarding "CREATE TABLE t LIKE with (k1=v1, k2=v2), I think it's > a > > > > > > nice-to-have feature, but not a strategically critical, > long-term solution, > > > > > > because > > > > > > 1) It may seem promising at the current stage to solve the > > > > > > too-much-manual-work problem, but that's only because Flink > hasn't > > > > > > leveraged catalogs well and handled the 3 types of params above > properly. > > > > > > Once we get the params types right, the LIKE syntax won't be that > > > > > > important, and will be just an easier way to create tables > without retyping > > > > > > long fields like username and pwd. > > > > > > 2) Note that only some rare type of catalog can store k-v > property pair, so > > > > > > table created this way often cannot be persisted. In the > foreseeable > > > > > > future, such catalog will only be HiveCatalog, and not everyone > has a Hive > > > > > > metastore. To be honest, without persistence, recreating tables > every time > > > > > > this way is still a lot of keyboard typing. > > > > > > > > > > > > Cheers, > > > > > > Bowen > > > > > > > > > > > > On Tue, Mar 10, 2020 at 8:07 PM Kurt Young <ykt...@gmail.com> > wrote: > > > > > > > > > > > > > If a specific connector want to have such parameter and read > if out of > > > > > > > configuration, then that's fine. > > > > > > > If we are talking about a configuration for all kinds of > sources, I would > > > > > > > be super careful about that. > > > > > > > It's true it can solve maybe 80% cases, but it will also make > the left 20% > > > > > > > feels weird. > > > > > > > > > > > > > > Best, > > > > > > > Kurt > > > > > > > > > > > > > > > > > > > > > On Wed, Mar 11, 2020 at 11:00 AM Jark Wu <imj...@gmail.com> > wrote: > > > > > > > > > > > > > > > Hi Kurt, > > > > > > > > > > > > > > > > #3 Regarding to global offset: > > > > > > > > I'm not saying to use the global configuration to override > connector > > > > > > > > properties by the planner. > > > > > > > > But the connector should take this configuration and > translate into their > > > > > > > > client API. > > > > > > > > AFAIK, almost all the message queues support eariliest and > latest and a > > > > > > > > timestamp value as start point. > > > > > > > > So we can support 3 options for this configuration: > "eariliest", "latest" > > > > > > > > and a timestamp string value. > > > > > > > > Of course, this can't solve 100% cases, but I guess can > sovle 80% or 90% > > > > > > > > cases. > > > > > > > > And the remaining cases can be resolved by LIKE syntax which > I guess is > > > > > > > not > > > > > > > > very common cases. > > > > > > > > > > > > > > > > Best, > > > > > > > > Jark > > > > > > > > > > > > > > > > > > > > > > > > On Wed, 11 Mar 2020 at 10:33, Kurt Young <ykt...@gmail.com> > wrote: > > > > > > > > > > > > > > > > > Good to have such lovely discussions. I also want to share > some of my > > > > > > > > > opinions. > > > > > > > > > > > > > > > > > > #1 Regarding to error handling: I also think ignore > invalid hints would > > > > > > > > be > > > > > > > > > dangerous, maybe > > > > > > > > > the simplest solution is just throw an exception. > > > > > > > > > > > > > > > > > > #2 Regarding to property replacement: I don't think we > should > > > > > > > constraint > > > > > > > > > ourself to > > > > > > > > > the meaning of the word "hint", and forbidden it modifying > any > > > > > > > properties > > > > > > > > > which can effect > > > > > > > > > query results. IMO `PROPERTIES` is one of the table hints, > and a > > > > > > > powerful > > > > > > > > > one. It can > > > > > > > > > modify properties located in DDL's WITH block. But I also > see the harm > > > > > > > > that > > > > > > > > > if we make it > > > > > > > > > too flexible like change the kafka topic name with a hint. > Such use > > > > > > > case > > > > > > > > is > > > > > > > > > not common and > > > > > > > > > sounds very dangerous to me. I would propose we have a map > of hintable > > > > > > > > > properties for each > > > > > > > > > connector, and should validate all passed in properties > are actually > > > > > > > > > hintable. And combining with > > > > > > > > > #1 error handling, we can throw an exception once received > invalid > > > > > > > > > property. > > > > > > > > > > > > > > > > > > #3 Regarding to global offset: I'm not sure it's feasible. > Different > > > > > > > > > connectors will have totally > > > > > > > > > different properties to represent offset, some might be > timestamps, > > > > > > > some > > > > > > > > > might be string literals > > > > > > > > > like "earliest", and others might be just integers. > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > Kurt > > > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, Mar 10, 2020 at 11:46 PM Jark Wu <imj...@gmail.com> > wrote: > > > > > > > > > > > > > > > > > > > Hi everyone, > > > > > > > > > > > > > > > > > > > > I want to jump in the discussion about the "dynamic > start offset" > > > > > > > > > problem. > > > > > > > > > > First of all, I share the same concern with Timo and > Fabian, that the > > > > > > > > > > "start offset" affects the query semantics, i.e. the > query result. > > > > > > > > > > But "hints" is just used for optimization which should > affect the > > > > > > > > result? > > > > > > > > > > > > > > > > > > > > I think the "dynamic start offset" is an very important > usability > > > > > > > > problem > > > > > > > > > > which will be faced by many streaming platforms. > > > > > > > > > > I also agree "CREATE TEMPORARY TABLE Temp (LIKE t) WITH > > > > > > > > > > ('connector.startup-timestamp-millis' = > '1578538374471')" is verbose, > > > > > > > > > what > > > > > > > > > > if we have 10 tables to join? > > > > > > > > > > > > > > > > > > > > However, what I want to propose (should be another > thread) is a > > > > > > > global > > > > > > > > > > configuration to reset start offsets of all the source > connectors > > > > > > > > > > in the query session, e.g. "table.sources.start-offset". > This is > > > > > > > > possible > > > > > > > > > > now because `TableSourceFactory.Context` has > `getConfiguration` > > > > > > > > > > method to get the session configuration, and use it to > create an > > > > > > > > adapted > > > > > > > > > > TableSource. > > > > > > > > > > Then we can also expose to SQL CLI via SET command, e.g. > `SET > > > > > > > > > > 'table.sources.start-offset'='earliest';`, which is > pretty simple and > > > > > > > > > > straightforward. > > > > > > > > > > > > > > > > > > > > This is very similar to KSQL's `SET > 'auto.offset.reset'='earliest'` > > > > > > > > which > > > > > > > > > > is very helpful IMO. > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > Jark > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, 10 Mar 2020 at 22:29, Timo Walther < > twal...@apache.org> > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > Hi Danny, > > > > > > > > > > > > > > > > > > > > > > compared to the hints, FLIP-110 is fully compliant to > the SQL > > > > > > > > standard. > > > > > > > > > > > > > > > > > > > > > > I don't think that `CREATE TEMPORARY TABLE Temp (LIKE > t) WITH > > > > > > > (k=v)` > > > > > > > > is > > > > > > > > > > > too verbose or awkward for the power of basically > changing the > > > > > > > entire > > > > > > > > > > > connector. Usually, this statement would just precede > the query in > > > > > > > a > > > > > > > > > > > multiline file. So it can be change "in-place" like > the hints you > > > > > > > > > > proposed. > > > > > > > > > > > > > > > > > > > > > > Many companies have a well-defined set of tables that > should be > > > > > > > used. > > > > > > > > > It > > > > > > > > > > > would be dangerous if users can change the path or > topic in a hint. > > > > > > > > The > > > > > > > > > > > catalog/catalog manager should be the entity that > controls which > > > > > > > > tables > > > > > > > > > > > exist and how they can be accessed. > > > > > > > > > > > > > > > > > > > > > > > what’s the problem there if we user the table hints > to support > > > > > > > > > “start > > > > > > > > > > > offset”? > > > > > > > > > > > > > > > > > > > > > > IMHO it violates the meaning of a hint. According to > the > > > > > > > dictionary, > > > > > > > > a > > > > > > > > > > > hint is "a statement that expresses indirectly what > one prefers not > > > > > > > > to > > > > > > > > > > > say explicitly". But offsets are a property that are > very explicit. > > > > > > > > > > > > > > > > > > > > > > If we go with the hint approach, it should be > expressible in the > > > > > > > > > > > TableSourceFactory which properties are supported for > hinting. Or > > > > > > > do > > > > > > > > > you > > > > > > > > > > > plan to offer those hints in a separate Map<String, > String> that > > > > > > > > cannot > > > > > > > > > > > overwrite existing properties? I think this would be a > different > > > > > > > > > story... > > > > > > > > > > > > > > > > > > > > > > Regards, > > > > > > > > > > > Timo > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 10.03.20 10:34, Danny Chan wrote: > > > > > > > > > > > > Thanks Timo ~ > > > > > > > > > > > > > > > > > > > > > > > > Personally I would say that offset > 0 and start > offset = 10 does > > > > > > > > not > > > > > > > > > > > have the same semantic, so from the SQL aspect, we can > not > > > > > > > implement > > > > > > > > a > > > > > > > > > > > “starting offset” hint for query with such a syntax. > > > > > > > > > > > > > > > > > > > > > > > > And the CREATE TABLE LIKE syntax is a DDL which is > just verbose > > > > > > > for > > > > > > > > > > > defining such dynamic parameters even if it could do > that, shall we > > > > > > > > > force > > > > > > > > > > > users to define a temporal table for each query with > dynamic > > > > > > > params, > > > > > > > > I > > > > > > > > > > > would say it’s an awkward solution. > > > > > > > > > > > > > > > > > > > > > > > > "Hints should give "hints" but not affect the actual > produced > > > > > > > > > result.” > > > > > > > > > > > You mentioned that multiple times and could we give a > reason, > > > > > > > what’s > > > > > > > > > the > > > > > > > > > > > problem there if we user the table hints to support > “start offset” > > > > > > > ? > > > > > > > > > From > > > > > > > > > > > my side I saw some benefits for that: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > • It’s very convent to set up these parameters, the > syntax is > > > > > > > very > > > > > > > > > much > > > > > > > > > > > like the DDL definition > > > > > > > > > > > > • It’s scope is very clear, right on the table it > attathed > > > > > > > > > > > > • It does not affect the table schema, which means > in order to > > > > > > > > > specify > > > > > > > > > > > the offset, there is no need to define an offset > column which is > > > > > > > > weird > > > > > > > > > > > actually, offset should never be a column, it’s more > like a > > > > > > > metadata > > > > > > > > > or a > > > > > > > > > > > start option. > > > > > > > > > > > > > > > > > > > > > > > > So in total, FLIP-110 uses the offset more like a > Hive partition > > > > > > > > > prune, > > > > > > > > > > > we can do that if we have an offset column, but most > of the case we > > > > > > > > do > > > > > > > > > > not > > > > > > > > > > > define that, so there is actually no conflict or > overlap. > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > Danny Chan > > > > > > > > > > > > 在 2020年3月10日 +0800 PM4:28，Timo Walther < > twal...@apache.org>，写道： > > > > > > > > > > > > > Hi Danny, > > > > > > > > > > > > > > > > > > > > > > > > > > shouldn't FLIP-110[1] solve most of the problems > we have around > > > > > > > > > > defining > > > > > > > > > > > > > table properties more dynamically without manual > schema work? > > > > > > > Also > > > > > > > > > > > > > offset definition is easier with such a syntax. > They must not be > > > > > > > > > > defined > > > > > > > > > > > > > in catalog but could be temporary tables that > extend from the > > > > > > > > > original > > > > > > > > > > > > > table. > > > > > > > > > > > > > > > > > > > > > > > > > > In general, we should aim to keep the syntax > concise and don't > > > > > > > > > provide > > > > > > > > > > > > > too many ways of doing the same thing. Hints > should give "hints" > > > > > > > > but > > > > > > > > > > not > > > > > > > > > > > > > affect the actual produced result. > > > > > > > > > > > > > > > > > > > > > > > > > > Some connector properties might also change the > plan or schema > > > > > > > in > > > > > > > > > the > > > > > > > > > > > > > future. E.g. they might also define whether a > table source > > > > > > > > supports > > > > > > > > > > > > > certain push-downs (e.g. predicate push-down). > > > > > > > > > > > > > > > > > > > > > > > > > > Dawid is currently working a draft that might > makes it possible > > > > > > > to > > > > > > > > > > > > > expose a Kafka offset via the schema such that > `SELECT * FROM > > > > > > > > Topic > > > > > > > > > > > > > WHERE offset > 10` would become possible and could > be pushed > > > > > > > down. > > > > > > > > > But > > > > > > > > > > > > > this is of course, not planned initially. > > > > > > > > > > > > > > > > > > > > > > > > > > Regards, > > > > > > > > > > > > > Timo > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-110%3A+Support+LIKE+clause+in+CREATE+TABLE > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 10.03.20 08:34, Danny Chan wrote: > > > > > > > > > > > > > > Thanks Wenlong ~ > > > > > > > > > > > > > > > > > > > > > > > > > > > > For PROPERTIES Hint Error handling > > > > > > > > > > > > > > > > > > > > > > > > > > > > Actually we have no way to figure out whether a > error prone > > > > > > > hint > > > > > > > > > is a > > > > > > > > > > > PROPERTIES hint, for example, if use writes a hint like > > > > > > > ‘PROPERTIAS’, > > > > > > > > > we > > > > > > > > > > do > > > > > > > > > > > not know if this hint is a PROPERTIES hint, what we > know is that > > > > > > > the > > > > > > > > > hint > > > > > > > > > > > name was not registered in our Flink. > > > > > > > > > > > > > > > > > > > > > > > > > > > > If the user writes the hint name correctly (i.e. > PROPERTIES), > > > > > > > we > > > > > > > > > did > > > > > > > > > > > can enforce the validation of the hint options though > the pluggable > > > > > > > > > > > HintOptionChecker. > > > > > > > > > > > > > > > > > > > > > > > > > > > > For PROPERTIES Hint Option Format > > > > > > > > > > > > > > > > > > > > > > > > > > > > For a key value style hint option, the key can > be either a > > > > > > > simple > > > > > > > > > > > identifier or a string literal, which means that it’s > compatible > > > > > > > with > > > > > > > > > our > > > > > > > > > > > DDL syntax. We support simple identifier because many > other hints > > > > > > > do > > > > > > > > > not > > > > > > > > > > > have the component complex keys like the table > properties, and we > > > > > > > > want > > > > > > > > > to > > > > > > > > > > > unify the parse block. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > Danny Chan > > > > > > > > > > > > > > 在 2020年3月10日 +0800 PM3:19，wenlong.lwl < > wenlong88....@gmail.com > > > > > > > > > > ，写道： > > > > > > > > > > > > > > > Hi Danny, thanks for the proposal. +1 for > adding table hints, > > > > > > > it > > > > > > > > > is > > > > > > > > > > > really > > > > > > > > > > > > > > > a necessary feature for flink sql to integrate > with a catalog. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > For error handling, I think it would be more > natural to throw > > > > > > > an > > > > > > > > > > > > > > > exception when error table hint provided, > because the > > > > > > > properties > > > > > > > > > in > > > > > > > > > > > hint > > > > > > > > > > > > > > > will be merged and used to find the table > factory which would > > > > > > > > > cause > > > > > > > > > > an > > > > > > > > > > > > > > > exception when error properties provided, > right? On the other > > > > > > > > > hand, > > > > > > > > > > > unlike > > > > > > > > > > > > > > > other hints which just affect the way to > execute the query, > > > > > > > the > > > > > > > > > > > property > > > > > > > > > > > > > > > table hint actually affects the result of the > query, we should > > > > > > > > > never > > > > > > > > > > > ignore > > > > > > > > > > > > > > > the given property hints. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > For the format of property hints, currently, > in sql client, we > > > > > > > > > > accept > > > > > > > > > > > > > > > properties in format of string only in DDL: > > > > > > > > > > 'connector.type'='kafka', > > > > > > > > > > > I > > > > > > > > > > > > > > > think the format of properties in hint should > be the same as > > > > > > > the > > > > > > > > > > > format we > > > > > > > > > > > > > > > defined in ddl. What do you think? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Bests, > > > > > > > > > > > > > > > Wenlong Lyu > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, 10 Mar 2020 at 14:22, Danny Chan < > > > > > > > yuzhao....@gmail.com> > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > To Weike: About the Error Handing > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > To be consistent with other SQL vendors, the > default is to > > > > > > > log > > > > > > > > > > > warnings > > > > > > > > > > > > > > > > and if there is any error (invalid hint name > or options), the > > > > > > > > > hint > > > > > > > > > > > is just > > > > > > > > > > > > > > > > ignored. I have already addressed in the > wiki. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > To Timo: About the PROPERTIES Table Hint > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > • The properties hints is also optional, > user can pass in an > > > > > > > > > option > > > > > > > > > > > to > > > > > > > > > > > > > > > > override the table properties but this does > not mean it is > > > > > > > > > > required. > > > > > > > > > > > > > > > > • They should not include semantics: does > the properties > > > > > > > belong > > > > > > > > > to > > > > > > > > > > > > > > > > semantic ? I don't think so, the plan does > not change right ? > > > > > > > > The > > > > > > > > > > > result > > > > > > > > > > > > > > > > set may be affected, but there are already > some hints do so, > > > > > > > > for > > > > > > > > > > > example, > > > > > > > > > > > > > > > > MS-SQL MAXRECURSION and SNAPSHOT hint [1] > > > > > > > > > > > > > > > > • `SELECT * FROM t(k=v, k=v)`: this grammar > breaks the SQL > > > > > > > > > standard > > > > > > > > > > > > > > > > compared to the hints way(which is included > in comments) > > > > > > > > > > > > > > > > • I actually didn't found any vendors to > support such > > > > > > > grammar, > > > > > > > > > and > > > > > > > > > > > there > > > > > > > > > > > > > > > > is no way to override table level properties > dynamically. For > > > > > > > > > > normal > > > > > > > > > > > RDBMS, > > > > > > > > > > > > > > > > I think there are no requests for such > dynamic parameters > > > > > > > > because > > > > > > > > > > > all the > > > > > > > > > > > > > > > > table have the same storage and computation > and they are > > > > > > > almost > > > > > > > > > all > > > > > > > > > > > batch > > > > > > > > > > > > > > > > tables. > > > > > > > > > > > > > > > > • While Flink as a computation engine has > many connectors, > > > > > > > > > > > especially for > > > > > > > > > > > > > > > > some message queue like Kafka, we would have > a start_offset > > > > > > > > which > > > > > > > > > > is > > > > > > > > > > > > > > > > different each time we start the query, such > parameters can > > > > > > > not > > > > > > > > > be > > > > > > > > > > > > > > > > persisted to catalog, because it’s not > static, this is > > > > > > > actually > > > > > > > > > the > > > > > > > > > > > > > > > > background we propose the table hints to > indicate such > > > > > > > > properties > > > > > > > > > > > > > > > > dynamically. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > To Jark and Jinsong: I have removed the > query hints part and > > > > > > > > > change > > > > > > > > > > > the > > > > > > > > > > > > > > > > title. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://docs.microsoft.com/en-us/sql/t-sql/queries/hints-transact-sql-query?view=sql-server-ver15 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > > > Danny Chan > > > > > > > > > > > > > > > > 在 2020年3月9日 +0800 PM5:46，Timo Walther < > twal...@apache.org > > > > > > > > ，写道： > > > > > > > > > > > > > > > > > Hi Danny, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > thanks for the proposal. I agree with Jark > and Jingsong. > > > > > > > > Planner > > > > > > > > > > > hints > > > > > > > > > > > > > > > > > and table hints are orthogonal topics that > should be > > > > > > > discussed > > > > > > > > > > > > > > > > separately. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I share Jingsong's opinion that we should > not use planner > > > > > > > > hints > > > > > > > > > > for > > > > > > > > > > > > > > > > > passing connector properties. Planner > hints should be > > > > > > > optional > > > > > > > > > at > > > > > > > > > > > any > > > > > > > > > > > > > > > > > time. They should not include semantics > but only affect > > > > > > > > > execution > > > > > > > > > > > time. > > > > > > > > > > > > > > > > > Connector properties are an important part > of the query > > > > > > > > itself. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Have you thought about options such as > `SELECT * FROM t(k=v, > > > > > > > > > > k=v)`? > > > > > > > > > > > How > > > > > > > > > > > > > > > > > are other vendors deal with this problem? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Regards, > > > > > > > > > > > > > > > > > Timo > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 09.03.20 10:37, Jingsong Li wrote: > > > > > > > > > > > > > > > > > > Hi Danny, +1 for table hints, thanks for > driving. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I took a look to FLIP, most of content > are talking about > > > > > > > > query > > > > > > > > > > > hints. > > > > > > > > > > > > > > > > It is > > > > > > > > > > > > > > > > > > hard to discussion and voting. So +1 to > split it as Jark > > > > > > > > said. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Another thing is configuration that > suitable to config with > > > > > > > > > table > > > > > > > > > > > > > > > > hints: > > > > > > > > > > > > > > > > > > "connector.path" and "connector.topic", > Are they really > > > > > > > > > suitable > > > > > > > > > > > for > > > > > > > > > > > > > > > > table > > > > > > > > > > > > > > > > > > hints? Looks weird to me. Because I > think these properties > > > > > > > > are > > > > > > > > > > the > > > > > > > > > > > > > > > > core of > > > > > > > > > > > > > > > > > > table. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > > > > > Jingsong Lee > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Mar 9, 2020 at 5:30 PM Jark Wu < > imj...@gmail.com> > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks Danny for starting the > discussion. > > > > > > > > > > > > > > > > > > > +1 for this feature. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > If we just focus on the table hints > not the query hints in > > > > > > > > > this > > > > > > > > > > > > > > > > release, > > > > > > > > > > > > > > > > > > > could you split the FLIP into two > FLIPs? > > > > > > > > > > > > > > > > > > > Because it's hard to vote on partial > part of a FLIP. You > > > > > > > can > > > > > > > > > > keep > > > > > > > > > > > > > > > > the table > > > > > > > > > > > > > > > > > > > hints proposal in FLIP-113 and move > query hints into > > > > > > > another > > > > > > > > > > FLIP. > > > > > > > > > > > > > > > > > > > So that we can focuse on the table > hints in the FLIP. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > Jark > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, 9 Mar 2020 at 17:14, DONG, > Weike < > > > > > > > > > > kyled...@connect.hku.hk > > > > > > > > > > > > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Danny, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > This is a nice feature, +1. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > One thing I am interested in but not > mentioned in the > > > > > > > > > proposal > > > > > > > > > > is > > > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > > > > > error > > > > > > > > > > > > > > > > > > > > handling, as it is quite common for > users to write > > > > > > > > > > inappropriate > > > > > > > > > > > > > > > > hints in > > > > > > > > > > > > > > > > > > > > SQL code, if illegal or "bad" hints > are given, would the > > > > > > > > > system > > > > > > > > > > > > > > > > simply > > > > > > > > > > > > > > > > > > > > ignore them or throw exceptions? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks : ) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > > > > > > > Weike > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Mar 9, 2020 at 5:02 PM Danny > Chan < > > > > > > > > > > yuzhao....@gmail.com> > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Note: > > > > > > > > > > > > > > > > > > > > > we only plan to support table > hints in Flink release > > > > > > > 1.11, > > > > > > > > > so > > > > > > > > > > > > > > > > please > > > > > > > > > > > > > > > > > > > > focus > > > > > > > > > > > > > > > > > > > > > mainly on the table hints part and > just ignore the > > > > > > > planner > > > > > > > > > > > > > > > > hints, sorry > > > > > > > > > > > > > > > > > > > > for > > > > > > > > > > > > > > > > > > > > > that mistake ~ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > > > > > > > > Danny Chan > > > > > > > > > > > > > > > > > > > > > 在 2020年3月9日 +0800 PM4:36，Danny > Chan < > > > > > > > yuzhao....@gmail.com > > > > > > > > > > > ，写道： > > > > > > > > > > > > > > > > > > > > > > Hi, fellows ~ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I would like to propose the > supports for SQL hints for > > > > > > > > our > > > > > > > > > > > > > > > > Flink SQL. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > We would support hints syntax as > following: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > select /*+ NO_HASH_JOIN, > RESOURCE(mem='128mb', > > > > > > > > > > > > > > > > parallelism='24') */ > > > > > > > > > > > > > > > > > > > > > > from > > > > > > > > > > > > > > > > > > > > > > emp /*+ INDEX(idx1, idx2) */ > > > > > > > > > > > > > > > > > > > > > > join > > > > > > > > > > > > > > > > > > > > > > dept /*+ PROPERTIES(k1='v1', > k2='v2') */ > > > > > > > > > > > > > > > > > > > > > > on > > > > > > > > > > > > > > > > > > > > > > emp.deptno = dept.deptno > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Basically we would support both > query hints(after the > > > > > > > > > SELECT > > > > > > > > > > > > > > > > keyword) > > > > > > > > > > > > > > > > > > > > > and table hints(after the > referenced table name), for > > > > > > > > 1.11, > > > > > > > > > we > > > > > > > > > > > > > > > > plan to > > > > > > > > > > > > > > > > > > > > only > > > > > > > > > > > > > > > > > > > > > support table hints with a hint > probably named > > > > > > > PROPERTIES: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > table_name /*+ > PROPERTIES(k1='v1', k2='v2') *+/ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I am looking forward to your > comments. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > You can access the FLIP here: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-113%3A+SQL+and+Planner+Hints > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > > > > > > > > > Danny Chan > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
