Hi, all
I’ve discussed with @Timo @Jark about the time function evaluation further. We
reach a consensus that we’d better address the time function
evaluation(function value materialization) in this FLIP as well.
We’re fine with introducing an option table.exec.time-function-evaluation to
control the materialize time point of time function value. The time function
includes
LOCALTIME
LOCALTIMESTAMP
CURRENT_DATE
CURRENT_TIME
CURRENT_TIMESTAMP
NOW()
The default value of table.exec.time-function-evaluation is 'per-record', which
means Flink evaluates the function value per record, we recommend users config
this option value for their streaming pipe lines.
Another valid option value is ’query-start’, which means Flink evaluates the
function value at the query start, we recommend users config this option value
for their batch pipelines.
In the future, more valid evaluation option value like ‘auto' may be supported
if there’re new requirements, e.g： support ‘auto’ option which evaluates time
function value per-record in streaming mode and evaluates
time function value at query start in batch mode.
Alternative1:
Introduce function like CURRENT_TIMESTAMP2/CURRENT_TIMESTAMP_NOW which
evaluates function value at query start. This may confuse users a bit that we
provide two similar functions but with different return value.
Alternative2:
Do not introduce any configuration/function, control the function
evaluation by pipeline execution mode. This may produce different result when
user use their streaming pipeline sql to run a batch pipeline(e.g
backfilling), and user also
can not control these function behavior.
How do you think ?
Thanks,
Leonard
> 在 2021年2月1日，18:23，Timo Walther <twal...@apache.org> 写道：
>
> Parts of the FLIP can already be implemented without a completed voting, e.g.
> there is no doubt that we should support TIME(9).
>
> However, I don't see a benefit of reworking the time functions to rework them
> again later. If we lock the time on query-start the implementation of the
> previsouly mentioned functions will be completely different.
>
> Regards,
> Timo
>
>
> On 01.02.21 02:37, Kurt Young wrote:
>> I also prefer to not expand this FLIP further, but we could open a
>> discussion thread
>> right after this FLIP being accepted and start coding & reviewing. Make
>> technique
>> discussion and coding more pipelined will improve efficiency.
>> Best,
>> Kurt
>> On Sat, Jan 30, 2021 at 3:47 PM Leonard Xu <xbjt...@gmail.com> wrote:
>>> Hi, Timo
>>>
>>>> I do think that this topic must be part of the FLIP as well. Esp. if the
>>> FLIP has the title "time function behavior" and this is clearly a
>>> behavioral aspect. We are performing a heavy refactoring of the SQL query
>>> semantics in Flink here which will affect a lot of users. We cannot rework
>>> the time functions a third time after this.
>>>> I checked a couple of other vendors. It seems that they all lock the
>>> timestamp when the query is started. And as you said, in this case both
>>> mature (Oracle) and less mature systems (Hive, MySQL) have the same
>>> behavior.
>>>
>>> FLIP-162> “These problems come from the fact that lots of time-related
>>> functions like PROCTIME(), NOW(), CURRENT_DATE, CURRENT_TIME and
>>> CURRENT_TIMESTAMP are returning time values based on UTC+0 time zone."
>>> The motivation of FLIP-162 is to correct the wrong time-related function
>>> value which caused by timezone. And after our discussed before, we found
>>> it's related to the function return type compared to SQL standard and other
>>> vendors and thus we proposed make the function return type also consistent.
>>> This is the exact meaning of the FLIP title and that the FLIP plans to do.
>>>
>>> But for the function materialization mechanism, we didn't consider yet as
>>> a part of our plan because we need to fix the timezone and function type
>>> issues no matter we modify the function materialization mechanism in the
>>> future or not.
>>> So I think it's not belong to this FLIP scope.
>>>
>>> It will have been a great work if we can fix current FLIP's 7 proposals
>>> well, we don't want to expand the scope again Eps it's not part of our
>>> plan.
>>>
>>> What do you think? @Timo
>>>
>>> And what’s others' thoughts? @Jark @Kurt
>>>
>>> Best,
>>> Leonard
>>>
>>>
>>>
>>>
>>>> Flink should not differ. I fear that we have to adopt this behavior as
>>> well to call us standard compliant. Otherwise it will also not be possible
>>> to have Hive compatibility with proper semantics. It could lead to
>>> unintended behavior.
>>>>
>>>> I see two options for this topic:
>>>>
>>>> 1) Clearly distinguish between query-start and processing time
>>>>
>>>> MySQL offers NOW() and SYSDATE() to distinguish the two semantics. We
>>> could run all the previously discussed functions that have a meaning in
>>> other systems in query-start time and use a different name for processing
>>> time. `SYS_TIMESTAMP`, `SYS_DATE`, `SYS_TIME`, `SYS_LOCALTIMESTAMP`,
>>> `SYS_LOCALDATE`, `SYS_LOCALTIME`?
>>>>
>>>> 2) Introduce a config option
>>>>
>>>> We are non-compliant by default and allow typical batch behavior if
>>> needed via a config option. But batch/stream unification should not mean
>>> that we disable certain unification aspects by default.
>>>>
>>>> What do you think?
>>>>
>>>> Regards,
>>>> Timo
>>>>
>>>> On 28.01.21 16:51, Leonard Xu wrote:
>>>>> Hi, Timo
>>>>>> I'm sorry that I need to open another discussion thread befoe voting
>>> but I think we should also discuss this in this FLIP before it pops up at a
>>> later stage.
>>>>>>
>>>>>> How do we want our time functions to behave in long running queries?
>>>>> It’s okay to open this thread. Although I don’t want to consider the
>>> function value materialization in this FLIP scope, I could try explain
>>> something.
>>>>>> See also:
>>>>>>
>>> https://stackoverflow.com/questions/5522656/sql-now-in-long-running-query
>>>>>>
>>>>>> I think this was never discussed thoroughly. Actually
>>> CURRENT_TIMESTAMP/NOW/LOCALTIMESTAMP should have slightly different
>>> semantics than PROCTIME(). What it is our current behavior? Are we
>>> materializing those time values during planning?
>>>>> Currently CURRENT_TIMESTAMP/NOW/LOCALTIMESTAMP keeps same behavior in
>>> both Batch and Stream world, the function value is materialized for per
>>> record not the query start(plan phase).
>>>>> For PROCTIME(), it also keeps same behavior in both Batch and Stream
>>> world, in fact we just supported PROCTIME() in Batch last week[1].
>>>>> In one word, we keep same semantics/behavior for Batch and Stream.
>>>>>> Esp. long running batch queries might suffer from inconsistencies
>>> here. When a timestamp is produced by one operator using CURRENT_TIMESTAMP
>>> and a different one might filter relating to CURRENT_TIMESTAMP.
>>>>> It’s a good question, and I've found some users have asked simillar
>>> questions in user/user-zh mail-list, given a fact that many Batch systems
>>> like Hive/Presto using the value of query start, but it’s not suitable for
>>> Stream engine, for example user will use CURRENT_TIMESTAMP to define event
>>> time.
>>>>> As a unified Batch/Stream SQL engine, keep same semantics/behavior is
>>> important, and I agree the Batch user case should also be considered.
>>>>> But I think this should be discussed in another topic like 'the
>>> unification of Batch/Stream' which is beyond the scope of this FLIP.
>>>>> This FLIP aims to correct the wrong return type/return value of current
>>> time functions.
>>>>> Best,
>>>>> Leonard
>>>>> [1] https://issues.apache.org/jira/browse/FLINK-17868 <
>>> https://issues.apache.org/jira/browse/FLINK-17868> <
>>> https://issues.apache.org/jira/browse/FLINK-17868 <
>>> https://issues.apache.org/jira/browse/FLINK-17868>>
>>>>>> Regards,
>>>>>> Timo
>>>>>>
>>>>>>
>>>>>> On 28.01.21 13:46, Leonard Xu wrote:
>>>>>>> Hi, Jark
>>>>>>>> I have a minor suggestion:
>>>>>>>> I think we will still suggest users use TIMESTAMP even if we have
>>> TIMESTAMP_NTZ. Then it seems
>>>>>>>> introducing TIMESTAMP_NTZ doesn't help much for users, but
>>> introduces more learning costs.
>>>>>>> I think your suggestion makes sense, we should suggest users use
>>> TIMESTAMP for TIMESTAMP WITHOUT TIME ZONE as we did now, updated as
>>> following:
>>>>>>> original type name :
>>> shortcut type name :
>>>>>>> TIMESTAMP / TIMESTAMP WITHOUT TIME ZONE <=> TIMESTAMP
>>>>>>> TIMESTAMP WITH LOCAL TIME ZONE <=>
>>> TIMESTAMP_LTZ
>>>>>>> TIMESTAMP WITH TIME ZONE <=>
>>> TIMESTAMP_TZ (supports them in the future)
>>>>>>> Best,
>>>>>>> Leonard
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, 28 Jan 2021 at 18:52, Leonard Xu <xbjt...@gmail.com <mailto:
>>> xbjt...@gmail.com> <mailto:xbjt...@gmail.com <mailto:xbjt...@gmail.com>>>
>>> wrote:
>>>>>>>>
>>>>>>>>> Thanks all for sharing your opinions.
>>>>>>>>>
>>>>>>>>> Looks like we’ve reached a consensus about the topic.
>>>>>>>>>
>>>>>>>>> @Timo:
>>>>>>>>>> 1) Are we on the same page that LOCALTIMESTAMP returns TIMESTAMP
>>> and not
>>>>>>>>> TIMESTAMP_LTZ? Maybe we should quickly list also
>>> LOCALTIME/LOCALDATE and
>>>>>>>>> LOCALTIMESTAMP for completeness.
>>>>>>>>> Yes, LOCALTIMESTAMP returns TIMESTAMP, LOCALTIME returns TIME, the
>>>>>>>>> behavior of them is clear so I just listed them in the excel[1] of
>>> this
>>>>>>>>> FLIP references.
>>>>>>>>>
>>>>>>>>>> 2) Shall we add aliases for the timestamp types as part of this
>>> FLIP? I
>>>>>>>>> see Snowflake supports TIMESTAMP_LTZ , TIMESTAMP_NTZ , TIMESTAMP_TZ
>>> [1]. I
>>>>>>>>> think the discussion was quite cumbersome with the full string of
>>>>>>>>> `TIMESTAMP WITH LOCAL TIME ZONE`. With this FLIP we are making this
>>> type
>>>>>>>>> even more prominent. And important concepts should have a short name
>>>>>>>>> because they are used frequently. According to the FLIP, we are
>>> introducing
>>>>>>>>> the abbriviation already in function names like `TO_TIMESTAMP_LTZ`.
>>>>>>>>> `TIMESTAMP_LTZ` could be treated similar to `STRING` for
>>>>>>>>> `VARCHAR(MAX_INT)`, the serializable string representation would
>>> not change.
>>>>>>>>>
>>>>>>>>> @Timo @Jark
>>>>>>>>> Nice idea, I also suffered from the long name during the
>>> discussions, the
>>>>>>>>> abbreviation will not only help us, but also makes it more
>>> convenient for
>>>>>>>>> users. I list the abbreviation name mapping to support:
>>>>>>>>> TIMESTAMP WITHOUT TIME ZONE <=> TIMESTAMP_NTZ (which
>>> synonyms
>>>>>>>>> TIMESTAMP)
>>>>>>>>> TIMESTAMP WITH LOCAL TIME ZONE <=> TIMESTAMP_LTZ
>>>>>>>>> TIMESTAMP WITH TIME ZONE <=> TIMESTAMP_TZ
>>> (supports
>>>>>>>>> them in the future)
>>>>>>>>>> 3) I'm fine with supporting all conversion classes like
>>>>>>>>> java.time.LocalDateTime, java.sql.Timestamp that TimestampType
>>> supported
>>>>>>>>> for LocalZonedTimestampType. But we agree that Instant stays the
>>> default
>>>>>>>>> conversion class right? The default extraction defined in [2] will
>>> not
>>>>>>>>> change, correct?
>>>>>>>>> Yes, Instant stays the default conversion class. The default
>>>>>>>>>
>>>>>>>>>> 4) I would remove the comment "Flink supports TIME-related types
>>> with
>>>>>>>>> precision well", because unfortunately this is still not correct.
>>> We still
>>>>>>>>> have issues with TIME(9), it would be great if someone can finally
>>> fix that
>>>>>>>>> though. Maybe the implementation of this FLIP would be a good time
>>> to fix
>>>>>>>>> this issue.
>>>>>>>>> You’re right, TIME(9) is not supported yet, I'll take account of
>>> TIME(9)
>>>>>>>>> to the scope of this FLIP.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I’ve updated this FLIP[2] according your suggestions @Jark @Timo
>>>>>>>>> I’ll start the vote soon if there’re no objections.
>>>>>>>>>
>>>>>>>>> Best,
>>>>>>>>> Leonard
>>>>>>>>>
>>>>>>>>> [1]
>>>>>>>>>
>>> https://docs.google.com/spreadsheets/d/1T178krh9xG-WbVpN7mRVJ8bzFnaSJx3l-eg1EWZe_X4/edit?usp=sharing
>>>>>>>>> <
>>>>>>>>>
>>> https://docs.google.com/spreadsheets/d/1T178krh9xG-WbVpN7mRVJ8bzFnaSJx3l-eg1EWZe_X4/edit?usp=sharing
>>> <
>>> https://docs.google.com/spreadsheets/d/1T178krh9xG-WbVpN7mRVJ8bzFnaSJx3l-eg1EWZe_X4/edit?usp=sharing
>>>>
>>>>>>>>>>
>>>>>>>>> [2]
>>>>>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-162%3A+Consistent+Flink+SQL+time+function+behavior
>>> <
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-162%3A+Consistent+Flink+SQL+time+function+behavior
>>>>
>>>>>>>>> <
>>>>>>>>>
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-162:+Consistent+Flink+SQL+time+function+behavior
>>> <
>>> https://cwiki.apache.org/confluence/display/FLINK/FLIP-162:+Consistent+Flink+SQL+time+function+behavior
>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 28.01.21 03:18, Jark Wu wrote:
>>>>>>>>>>> Thanks Leonard for the further investigation.
>>>>>>>>>>> I think we all agree we should correct the return value of
>>>>>>>>>>> CURRENT_TIMESTAMP.
>>>>>>>>>>> Regarding the return type of CURRENT_TIMESTAMP, I also agree
>>>>>>>>> TIMESTAMP_LTZ
>>>>>>>>>>> would be more worldwide useful. This may need more effort, but if
>>> this
>>>>>>>>> is
>>>>>>>>>>> the right direction, we should do it.
>>>>>>>>>>> Regarding the CURRENT_TIME, if CURRENT_TIMESTAMP returns
>>>>>>>>>>> TIMESTAMP_LTZ, then I think CURRENT_TIME shouldn't return TIME_TZ.
>>>>>>>>>>> Otherwise, CURRENT_TIME will be quite special and strange.
>>>>>>>>>>> Thus I think it has to return TIME type. Given that we already
>>> have
>>>>>>>>>>> CURRENT_DATE which returns
>>>>>>>>>>> DATE WITHOUT TIME ZONE, I think it's fine to return TIME WITHOUT
>>> TIME
>>>>>>>>> ZONE
>>>>>>>>>>> for CURRENT_TIME.
>>>>>>>>>>> In a word, the updated FLIP looks good to me. I especially like
>>> the
>>>>>>>>>>> proposed new function TO_TIMESTAMP_LTZ(numeric, [,scale]).
>>>>>>>>>>> This will be very convenient to define rowtime on a long value
>>> which is
>>>>>>>>> a
>>>>>>>>>>> very common case and has been complained a lot in mailing list.
>>>>>>>>>>> Best,
>>>>>>>>>>> Jark
>>>>>>>>>>> On Mon, 25 Jan 2021 at 21:12, Kurt Young <ykt...@gmail.com>
>>> wrote:
>>>>>>>>>>>> Thanks Leonard for the detailed response and also the bad case
>>> about
>>>>>>>>> option
>>>>>>>>>>>> 1, these all
>>>>>>>>>>>> make sense to me.
>>>>>>>>>>>>
>>>>>>>>>>>> Also nice catch about conversion support of
>>> LocalZonedTimestampType, I
>>>>>>>>>>>> think it actually
>>>>>>>>>>>> makes sense to support java.sql.Timestamp as well as
>>>>>>>>>>>> java.time.LocalDateTime. It also has
>>>>>>>>>>>> a slight benefit that we might have a chance to run the udf
>>> which took
>>>>>>>>> them
>>>>>>>>>>>> as input parameter
>>>>>>>>>>>> after we change the return type.
>>>>>>>>>>>>
>>>>>>>>>>>> Regarding to the return type of CURRENT_TIME, I also think
>>> timezone
>>>>>>>>>>>> information is not useful.
>>>>>>>>>>>> To not expand this FLIP further, I'm lean to keep it as it is.
>>>>>>>>>>>>
>>>>>>>>>>>> Best,
>>>>>>>>>>>> Kurt
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On Mon, Jan 25, 2021 at 8:50 PM Leonard Xu <xbjt...@gmail.com>
>>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Hi, All
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks for your comments. I think all of the thread have agreed
>>> that:
>>>>>>>>>>>>> (1) The return values of
>>>>>>>>> CURRENT_TIME/CURRENT_TIMESTAMP/NOW()/PROCTIME()
>>>>>>>>>>>>> are wrong.
>>>>>>>>>>>>> (2) The LOCALTIME/LOCALTIMESTAMP and
>>> CURRENT_TIME/CURRENT_TIMESTAMP
>>>>>>>>>>>> should
>>>>>>>>>>>>> be different whether from SQL standard’s perspective or mature
>>>>>>>>> systems.
>>>>>>>>>>>>> (3) The semantics of three TIMESTAMP types in Flink SQL follows
>>> the
>>>>>>>>> SQL
>>>>>>>>>>>>> standard and also keeps the same with other 'good' vendors.
>>>>>>>>>>>>> TIMESTAMP => A literal in
>>>>>>>>>>>>> ‘yyyy-MM-dd HH:mm:ss’ format to describe a time, does not
>>> contain
>>>>>>>>>>>> timezone
>>>>>>>>>>>>> info, can not represent an absolute time point.
>>>>>>>>>>>>> TIMESTAMP WITH LOCAL ZONE => Records the elapsed time from
>>>>>>>>> absolute
>>>>>>>>>>>>> time point origin, can represent an absolute time point,
>>> requires
>>>>>>>>> local
>>>>>>>>>>>>> time zone when expressed with ‘yyyy-MM-dd HH:mm:ss’ format.
>>>>>>>>>>>>> TIMESTAMP WITH TIME ZONE => Consists of time zone info
>>> and a
>>>>>>>>>>>>> literal in ‘yyyy-MM-dd HH:mm:ss’ format to describe time, can
>>>>>>>>> represent
>>>>>>>>>>>> an
>>>>>>>>>>>>> absolute time point.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> Currently we've two ways to correct
>>>>>>>>>>>>> CURRENT_TIME/CURRENT_TIMESTAMP/NOW()/PROCTIME().
>>>>>>>>>>>>>
>>>>>>>>>>>>> option (1): As the FLIP proposed, change the return value from
>>> UTC
>>>>>>>>>>>>> timezone to local timezone.
>>>>>>>>>>>>> Pros: (1) The change looks smaller to users and
>>> developers
>>>>>>>>> (2)
>>>>>>>>>>>>> There're many SQL engines adopted this way
>>>>>>>>>>>>> Cons: (1) connector devs may confuse the underlying
>>> value of
>>>>>>>>>>>>> TimestampData which needs to change according to data type (2)
>>> I
>>>>>>>>> thought
>>>>>>>>>>>>> about this weekend. Unfortunately I found a bad case:
>>>>>>>>>>>>>
>>>>>>>>>>>>> The proposal is fine if we only use it in FLINK SQL world, but
>>> we
>>>>>>>>> need to
>>>>>>>>>>>>> consider the conversion between Table/DataStream, assume a
>>> record
>>>>>>>>>>>> produced
>>>>>>>>>>>>> in UTC+0 timezone with TIMESTAMP '1970-01-01 08:00:44' and the
>>> Flink
>>>>>>>>> SQL
>>>>>>>>>>>>> processes the data with session time zone 'UTC+8', if the sql
>>> program
>>>>>>>>>>>> need
>>>>>>>>>>>>> to convert the Table to DataStream, then we need to calculate
>>> the
>>>>>>>>>>>> timestamp
>>>>>>>>>>>>> in StreamRecord with session time zone (UTC+8), then we will
>>> get 44 in
>>>>>>>>>>>>> DataStream program, but it is wrong because the expected value
>>> should
>>>>>>>>> be
>>>>>>>>>>>> (8
>>>>>>>>>>>>> * 60 * 60 + 44). The corner case tell us that the
>>> ROWTIME/PROCTIME in
>>>>>>>>>>>> Flink
>>>>>>>>>>>>> are based on UTC+0, when correct the PROCTIME() function, the
>>> better
>>>>>>>>> way
>>>>>>>>>>>> is
>>>>>>>>>>>>> to use TIMESTAMP WITH LOCAL TIME ZONE which keeps same long
>>> value with
>>>>>>>>>>>> time
>>>>>>>>>>>>> based on UTC+0 and can be expressed with local timezone.
>>>>>>>>>>>>>
>>>>>>>>>>>>> option (2) : As we considered in the FLIP as well as @Timo
>>> suggested,
>>>>>>>>>>>>> change the return type to TIMESTAMP WITH LOCAL TIME ZONE, the
>>>>>>>>> expressed
>>>>>>>>>>>>> value depends on the local time zone.
>>>>>>>>>>>>> Pros: (1) Make Flink SQL more close to SQL standard (2)
>>> Can
>>>>>>>>> deal
>>>>>>>>>>>>> the conversion between Table/DataStream well
>>>>>>>>>>>>> Cons: (1) We need to discuss the return value/type of
>>>>>>>>>>>> CURRENT_TIME
>>>>>>>>>>>>> function (2) The change is bigger to users, we need to support
>>>>>>>>> TIMESTAMP
>>>>>>>>>>>>> WITH LOCAL TIME ZONE in connectors/formats as well as custom
>>>>>>>>> connectors.
>>>>>>>>>>>>> (3)The TIMESTAMP WITH LOCAL TIME ZONE support
>>> is
>>>>>>>>> weak
>>>>>>>>>>>>> in Flink, thus we need some improvement，but the workload does
>>> not
>>>>>>>>> matter
>>>>>>>>>>>>> as long as we are doing the right thing ^_^
>>>>>>>>>>>>>
>>>>>>>>>>>>> Due to the above bad case for option (1). I think option 2
>>> should be
>>>>>>>>>>>>> adopted,
>>>>>>>>>>>>> But we also need to consider some problems:
>>>>>>>>>>>>> (1) More conversion classes like LocalDateTime, sql.Timestamp
>>> should
>>>>>>>>> be
>>>>>>>>>>>>> supported for LocalZonedTimestampType to resolve the UDF
>>> compatibility
>>>>>>>>>>>> issue
>>>>>>>>>>>>> (2) The timezone offset for window size of one day should still
>>> be
>>>>>>>>>>>>> considered
>>>>>>>>>>>>> (3) All connectors/formats should supports TIMESTAMP WITH LOCAL
>>> TIME
>>>>>>>>> ZONE
>>>>>>>>>>>>> well and we also should record in document
>>>>>>>>>>>>> I’ll update these sections of FLIP-162.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> We also need to discuss the CURRENT_TIME function. I know the
>>> standard
>>>>>>>>>>>> way
>>>>>>>>>>>>> is using TIME WITH TIME ZONE(there's no TIME WITH LOCAL TIME
>>> ZONE),
>>>>>>>>> but
>>>>>>>>>>>> we
>>>>>>>>>>>>> don't support this type yet and I don't see strong motivation to
>>>>>>>>> support
>>>>>>>>>>>> it
>>>>>>>>>>>>> so far.
>>>>>>>>>>>>> Compared to CURRENT_TIMESTAMP, the CURRENT_TIME can not
>>> represent an
>>>>>>>>>>>>> absolute time point which should be considered as a string
>>> consisting
>>>>>>>>> of
>>>>>>>>>>>> a
>>>>>>>>>>>>> time with 'HH:mm:ss' format and time zone info. We have several
>>>>>>>>> options
>>>>>>>>>>>>> for this:
>>>>>>>>>>>>> (1) We can forbid CURRENT_TIME as @Timo proposed to make all
>>> Flink SQL
>>>>>>>>>>>>> functions follow the standard well, in this way, we need to
>>> offer
>>>>>>>>> some
>>>>>>>>>>>>> guidance for user upgrading Flink versions.
>>>>>>>>>>>>> (2) We can also support it from a user's perspective who has
>>> used
>>>>>>>>>>>>> CURRENT_DATE/CURRENT_TIME/CURRENT_TIMESTAMP, btw，Snowflake also
>>>>>>>>> returns
>>>>>>>>>>>>> TIME type.
>>>>>>>>>>>>> (3) Returns TIMESTAMP WITH LOCAL TIME ZONE to make it equal to
>>>>>>>>>>>>> CURRENT_TIMESTAMP as Calcite did.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I can image (1) which we don't want to left a bad smell in
>>> Flink SQL,
>>>>>>>>>>>> and
>>>>>>>>>>>>> I also accept (2) because I think users do not consider time
>>> zone
>>>>>>>>> issues
>>>>>>>>>>>>> when they use CURRENT_DATE/CURRENT_TIME, and the timezone info
>>> in
>>>>>>>>> time is
>>>>>>>>>>>>> not very useful.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I don’t have a strong opinion for them. What do others think?
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> I hope I've addressed your concerns. @Timo @Kurt
>>>>>>>>>>>>>
>>>>>>>>>>>>> Best，
>>>>>>>>>>>>> Leonard
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Most of the mature systems have a clear difference between
>>>>>>>>>>>>> CURRENT_TIMESTAMP and LOCALTIMESTAMP. I wouldn't take Spark or
>>> Hive
>>>>>>>>> as a
>>>>>>>>>>>>> good example. Snowflake decided for TIMESTAMP WITH LOCAL TIME
>>> ZONE.
>>>>>>>>> As I
>>>>>>>>>>>>> mentioned in the last comment, I could also imagine this
>>> behavior for
>>>>>>>>>>>>> Flink. But in any case, there should be some time zone
>>> information
>>>>>>>>>>>>> considered in order to cast to all other types.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The function CURRENT_DATE/CURRENT_TIME is supporting in SQL
>>>>>>>>>>>>> standard, but
>>>>>>>>>>>>>>>>> LOCALDATE not, I don’t think it’s a good idea that dropping
>>>>>>>>>>>>> functions which
>>>>>>>>>>>>>>>>> SQL standard supported and introducing a replacement which
>>> SQL
>>>>>>>>>>>>> standard not
>>>>>>>>>>>>>>>>> reminded.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> We can still add those functions in the future. But since we
>>> don't
>>>>>>>>>>>> offer
>>>>>>>>>>>>> a TIME WITH TIME ZONE, it is better to not support this
>>> function at
>>>>>>>>> all
>>>>>>>>>>>> for
>>>>>>>>>>>>> now. And by the way, this is exactly the behavior that also
>>> Microsoft
>>>>>>>>> SQL
>>>>>>>>>>>>> Server does: it also just supports CURRENT_TIMESTAMP (but it
>>> returns
>>>>>>>>>>>>> TIMESTAMP without a zone which completes the confusion).
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> I also agree returning TIMESTAMP WITH LOCAL TIME ZONE for
>>>>>>>>> PROCTIME
>>>>>>>>>>>>> has
>>>>>>>>>>>>>>>>> more clear semantics, but I realized that user didn’t care
>>> the
>>>>>>>>> type
>>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>> more about the expressed value they saw, and change the
>>> type from
>>>>>>>>>>>>> TIMESTAMP
>>>>>>>>>>>>>>>>> to TIMESTAMP WITH LOCAL TIME ZONE brings huge refactor that
>>> we
>>>>>>>>> need
>>>>>>>>>>>>>>>>> consider all places where the TIMESTAMP type used
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> From a UDF perspective, I think nothing will change. The new
>>> type
>>>>>>>>>>>> system
>>>>>>>>>>>>> and type inference were designed to support all these cases.
>>> There is
>>>>>>>>> a
>>>>>>>>>>>>> reason why Java has adopted Joda time, because it is hard to
>>> come up
>>>>>>>>>>>> with a
>>>>>>>>>>>>> good time library. That's why also we and the other Hadoop
>>> ecosystem
>>>>>>>>>>>> folks
>>>>>>>>>>>>> have decided for 3 different kinds of LocalDateTime,
>>> ZonedDateTime,
>>>>>>>>> and
>>>>>>>>>>>>> Instance. It makes the library more complex, but time is a
>>> complex
>>>>>>>>> topic.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I also doubt that many users work with only one time zone.
>>> Take the
>>>>>>>>> US
>>>>>>>>>>>>> as an example, a country with 3 different timezones. Somebody
>>> working
>>>>>>>>>>>> with
>>>>>>>>>>>>> US data cannot properly see the data points with just LOCAL
>>> TIME ZONE.
>>>>>>>>>>>> But
>>>>>>>>>>>>> on the other hand, a lot of event data is stored using a UTC
>>>>>>>>> timestamp.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Before jumping into technique details, let's take a step
>>> back to
>>>>>>>>>>>>> discuss
>>>>>>>>>>>>>>>> user experience.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> The first important question is what kind of date and time
>>> will
>>>>>>>>>>>> Flink
>>>>>>>>>>>>>>>> display when users call
>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP and maybe also PROCTIME (if we think they
>>> are
>>>>>>>>>>>>> similar).
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Should it always display the date and time in UTC or in the
>>> user's
>>>>>>>>>>>>> time
>>>>>>>>>>>>>>>> zone?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> @Kurt: I think we all agree that the current behavior with just
>>>>>>>>> showing
>>>>>>>>>>>>> UTC is wrong. Also, we all agree that when calling
>>> CURRENT_TIMESTAMP
>>>>>>>>> or
>>>>>>>>>>>>> PROCTIME a user would like to see the time in it's current time
>>> zone.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> As you said, "my wall clock time".
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> However, the question is what is the data type of what you
>>> "see". If
>>>>>>>>>>>> you
>>>>>>>>>>>>> pass this record on to a different system, operator, or
>>> different
>>>>>>>>>>>> cluster,
>>>>>>>>>>>>> should the "my" get lost or materialized into the record?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> TIMESTAMP -> completely lost and could cause confusion in a
>>> different
>>>>>>>>>>>>> system
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> TIMESTAMP WITH LOCAL TIME ZONE -> at least the UTC is correct,
>>> so you
>>>>>>>>>>>>> can provide a new local time zone
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> TIMESTAMP WITH TIME ZONE -> also "your" location is persisted
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Regards,
>>>>>>>>>>>>>> Timo
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 22.01.21 09:38, Kurt Young wrote:
>>>>>>>>>>>>>>> Forgot one more thing. Continue with displaying in UTC. As a
>>> user,
>>>>>>>>> if
>>>>>>>>>>>>> Flink
>>>>>>>>>>>>>>> want to display the timestamp
>>>>>>>>>>>>>>> in UTC, why don't we offer something like UTC_TIMESTAMP?
>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>> Kurt
>>>>>>>>>>>>>>> On Fri, Jan 22, 2021 at 4:33 PM Kurt Young <ykt...@gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>>>>>>>> Before jumping into technique details, let's take a step
>>> back to
>>>>>>>>>>>>> discuss
>>>>>>>>>>>>>>>> user experience.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> The first important question is what kind of date and time
>>> will
>>>>>>>>> Flink
>>>>>>>>>>>>>>>> display when users call
>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP and maybe also PROCTIME (if we think they
>>> are
>>>>>>>>>>>>> similar).
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Should it always display the date and time in UTC or in the
>>> user's
>>>>>>>>>>>> time
>>>>>>>>>>>>>>>> zone? I think this part is the
>>>>>>>>>>>>>>>> reason that surprised lots of users. If we forget about the
>>> type
>>>>>>>>> and
>>>>>>>>>>>>>>>> internal representation of these
>>>>>>>>>>>>>>>> two methods, as a user, my instinct tells me that these two
>>> methods
>>>>>>>>>>>>> should
>>>>>>>>>>>>>>>> display my wall clock time.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Display time in UTC? I'm not sure, why I should care about
>>> UTC
>>>>>>>>> time?
>>>>>>>>>>>> I
>>>>>>>>>>>>>>>> want to get my current timestamp.
>>>>>>>>>>>>>>>> For those users who have never gone abroad, they might not
>>> even be
>>>>>>>>>>>>> able to
>>>>>>>>>>>>>>>> realize that this is affected
>>>>>>>>>>>>>>>> by the time zone.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>> Kurt
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Fri, Jan 22, 2021 at 12:25 PM Leonard Xu <
>>> xbjt...@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Thanks @Timo for the detailed reply, let's go on this topic
>>> on
>>>>>>>>> this
>>>>>>>>>>>>>>>>> discussion, I've merged all mails to this discussion.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> LOCALDATE / LOCALTIME / LOCALTIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --> uses session time zone, returns DATE/TIME/TIMESTAMP
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> CURRENT_DATE/CURRENT_TIME/CURRENT_TIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --> uses session time zone, returns DATE/TIME/TIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I'm very sceptical about this behavior. Almost all mature
>>> systems
>>>>>>>>>>>>>>>>> (Oracle, Postgres) and new high quality systems (Presto,
>>>>>>>>> Snowflake)
>>>>>>>>>>>>> use a
>>>>>>>>>>>>>>>>> data type with some degree of time zone information
>>> encoded. In a
>>>>>>>>>>>>>>>>> globalized world with businesses spanning different
>>> regions, I
>>>>>>>>> think
>>>>>>>>>>>>> we
>>>>>>>>>>>>>>>>> should do this as well. There should be a difference between
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP and LOCALTIMESTAMP. And users should be
>>> able to
>>>>>>>>>>>>> choose
>>>>>>>>>>>>>>>>> which behavior they prefer for their pipeline.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> I know that the two series should be different at first
>>> glance,
>>>>>>>>> but
>>>>>>>>>>>>>>>>> different SQL engines can have their own explanations，for
>>> example,
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP and LOCALTIMESTAMP are synonyms in
>>> Snowflake[1]
>>>>>>>>>>>> and
>>>>>>>>>>>>> has
>>>>>>>>>>>>>>>>> no difference, and Spark only supports the later one and
>>> doesn’t
>>>>>>>>>>>>> support
>>>>>>>>>>>>>>>>> LOCALTIME/LOCALTIMESTAMP[2].
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If we would design this from scatch, I would suggest the
>>>>>>>>> following:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - drop CURRENT_DATE / CURRENT_TIME and let users pick
>>> LOCALDATE /
>>>>>>>>>>>>>>>>> LOCALTIME for materialized timestamp parts
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The function CURRENT_DATE/CURRENT_TIME is supporting in SQL
>>>>>>>>>>>> standard,
>>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>> LOCALDATE not, I don’t think it’s a good idea that dropping
>>>>>>>>>>>> functions
>>>>>>>>>>>>> which
>>>>>>>>>>>>>>>>> SQL standard supported and introducing a replacement which
>>> SQL
>>>>>>>>>>>>> standard not
>>>>>>>>>>>>>>>>> reminded.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - CURRENT_TIMESTAMP should return a TIMESTAMP WITH TIME
>>> ZONE to
>>>>>>>>>>>>>>>>> materialize all session time information into every record.
>>> It it
>>>>>>>>>>>> the
>>>>>>>>>>>>> most
>>>>>>>>>>>>>>>>> generic data type and allows to cast to all other timestamp
>>> data
>>>>>>>>>>>>> types.
>>>>>>>>>>>>>>>>> This generic ability can be used for filter predicates as
>>> well
>>>>>>>>>>>> either
>>>>>>>>>>>>>>>>> through implicit or explicit casting.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> TIMESTAMP WITH TIME ZONE indeed contains more information to
>>>>>>>>>>>> describe
>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>> time point, but the type TIMESTAMP can cast to all other
>>>>>>>>> timestamp
>>>>>>>>>>>>> data
>>>>>>>>>>>>>>>>> types combining with session time zone as well, and it also
>>> can be
>>>>>>>>>>>>> used for
>>>>>>>>>>>>>>>>> filter predicates. For type casting between BIGINT and
>>> TIMESTAMP,
>>>>>>>>> I
>>>>>>>>>>>>> think
>>>>>>>>>>>>>>>>> the function way using TO_TIMEMTAMP()/FROM_UNIXTIMESTAMP()
>>> is more
>>>>>>>>>>>>> clear.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> PROCTIME/ROWTIME should be time functions based on a long
>>> value.
>>>>>>>>>>>> Both
>>>>>>>>>>>>>>>>> System.currentMillis() and our watermark system work on long
>>>>>>>>> values.
>>>>>>>>>>>>> Those
>>>>>>>>>>>>>>>>> should return TIMESTAMP WITH LOCAL TIME ZONE because the
>>> main
>>>>>>>>>>>>> calculation
>>>>>>>>>>>>>>>>> should always happen based on UTC.
>>>>>>>>>>>>>>>>>> We discussed it in a different thread, but we should allow
>>>>>>>>> PROCTIME
>>>>>>>>>>>>>>>>> globally. People need a way to create instances of
>>> TIMESTAMP WITH
>>>>>>>>>>>>> LOCAL
>>>>>>>>>>>>>>>>> TIME ZONE. This is not considered in the current design doc.
>>>>>>>>>>>>>>>>>> Many pipelines contain UTC timestamps and thus it should
>>> be easy
>>>>>>>>> to
>>>>>>>>>>>>>>>>> create one.
>>>>>>>>>>>>>>>>>> Also, both CURRENT_TIMESTAMP and LOCALTIMESTAMP can work
>>> with
>>>>>>>>> this
>>>>>>>>>>>>> type
>>>>>>>>>>>>>>>>> because we should remember that TIMESTAMP WITH LOCAL TIME
>>> ZONE
>>>>>>>>>>>>> accepts all
>>>>>>>>>>>>>>>>> timestamp data types as casting target [1]. We could allow
>>>>>>>>> TIMESTAMP
>>>>>>>>>>>>> WITH
>>>>>>>>>>>>>>>>> TIME ZONE in the future for ROWTIME.
>>>>>>>>>>>>>>>>>> In any case, windows should simply adapt their behavior to
>>> the
>>>>>>>>>>>> passed
>>>>>>>>>>>>>>>>> timestamp type. And with TIMESTAMP WITH LOCAL TIME ZONE a
>>> day is
>>>>>>>>>>>>> defined by
>>>>>>>>>>>>>>>>> considering the current session time zone.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> I also agree returning TIMESTAMP WITH LOCAL TIME ZONE for
>>>>>>>>> PROCTIME
>>>>>>>>>>>>> has
>>>>>>>>>>>>>>>>> more clear semantics, but I realized that user didn’t care
>>> the
>>>>>>>>> type
>>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>> more about the expressed value they saw, and change the
>>> type from
>>>>>>>>>>>>> TIMESTAMP
>>>>>>>>>>>>>>>>> to TIMESTAMP WITH LOCAL TIME ZONE brings huge refactor that
>>> we
>>>>>>>>> need
>>>>>>>>>>>>>>>>> consider all places where the TIMESTAMP type used, and many
>>>>>>>>> builtin
>>>>>>>>>>>>>>>>> functions and UDFs doest not support TIMESTAMP WITH LOCAL
>>> TIME
>>>>>>>>> ZONE
>>>>>>>>>>>>> type.
>>>>>>>>>>>>>>>>> That means both user and Flink devs need to refactor the
>>> code(UDF,
>>>>>>>>>>>>> builtin
>>>>>>>>>>>>>>>>> functions, sql pipeline), to be honest, I didn’t see strong
>>>>>>>>>>>>> motivation that
>>>>>>>>>>>>>>>>> we have to do the pretty big refactor from user’s
>>> perspective and
>>>>>>>>>>>>>>>>> developer’s perspective.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> In one word, both your suggestion and my proposal can
>>> resolve
>>>>>>>>> almost
>>>>>>>>>>>>> all
>>>>>>>>>>>>>>>>> user problems，the divergence is whether we need to spend
>>> pretty
>>>>>>>>>>>>> energy just
>>>>>>>>>>>>>>>>> to get a bit more accurate semantics? I think we need a
>>>>>>>>> tradeoff.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>> Leonard
>>>>>>>>>>>>>>>>> [1]
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>
>>> https://trino.io/docs/current/functions/datetime.html#current_timestamp
>>>>>>>>>>>> <
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>
>>> https://trino.io/docs/current/functions/datetime.html#current_timestamp>
>>>>>>>>>>>>>>>>> [2] https://issues.apache.org/jira/browse/SPARK-30374 <
>>>>>>>>>>>>>>>>> https://issues.apache.org/jira/browse/SPARK-30374>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2021-01-22，00:53，Timo Walther <twal...@apache.org> ：
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Hi Leonard,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> thanks for working on this topic. I agree that time
>>> handling is
>>>>>>>>> not
>>>>>>>>>>>>>>>>> easy in Flink at the moment. We added new time data types
>>> (and
>>>>>>>>> some
>>>>>>>>>>>>> are
>>>>>>>>>>>>>>>>> still not supported which even further complicates things
>>> like
>>>>>>>>>>>>> TIME(9)). We
>>>>>>>>>>>>>>>>> should definitely improve this situation for users.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> This is a pretty opinionated topic and it seems that the
>>> SQL
>>>>>>>>>>>> standard
>>>>>>>>>>>>>>>>> is not really deciding this but is at least supporting. So
>>> let me
>>>>>>>>>>>>> express
>>>>>>>>>>>>>>>>> my opinion for the most important functions:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> LOCALDATE / LOCALTIME / LOCALTIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --> uses session time zone, returns DATE/TIME/TIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I think those are the most obvious ones because the LOCAL
>>>>>>>>> indicates
>>>>>>>>>>>>>>>>> that the locality should be materialized into the result
>>> and any
>>>>>>>>>>>> time
>>>>>>>>>>>>> zone
>>>>>>>>>>>>>>>>> information (coming from session config or data) is not
>>> important
>>>>>>>>>>>>>>>>> afterwards.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> CURRENT_DATE/CURRENT_TIME/CURRENT_TIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --> uses session time zone, returns DATE/TIME/TIMESTAMP
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I'm very sceptical about this behavior. Almost all mature
>>> systems
>>>>>>>>>>>>>>>>> (Oracle, Postgres) and new high quality systems (Presto,
>>>>>>>>> Snowflake)
>>>>>>>>>>>>> use a
>>>>>>>>>>>>>>>>> data type with some degree of time zone information
>>> encoded. In a
>>>>>>>>>>>>>>>>> globalized world with businesses spanning different
>>> regions, I
>>>>>>>>> think
>>>>>>>>>>>>> we
>>>>>>>>>>>>>>>>> should do this as well. There should be a difference between
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP and LOCALTIMESTAMP. And users should be
>>> able to
>>>>>>>>>>>>> choose
>>>>>>>>>>>>>>>>> which behavior they prefer for their pipeline.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If we would design this from scatch, I would suggest the
>>>>>>>>> following:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - drop CURRENT_DATE / CURRENT_TIME and let users pick
>>> LOCALDATE /
>>>>>>>>>>>>>>>>> LOCALTIME for materialized timestamp parts
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> - CURRENT_TIMESTAMP should return a TIMESTAMP WITH TIME
>>> ZONE to
>>>>>>>>>>>>>>>>> materialize all session time information into every record.
>>> It it
>>>>>>>>>>>> the
>>>>>>>>>>>>> most
>>>>>>>>>>>>>>>>> generic data type and allows to cast to all other timestamp
>>> data
>>>>>>>>>>>>> types.
>>>>>>>>>>>>>>>>> This generic ability can be used for filter predicates as
>>> well
>>>>>>>>>>>> either
>>>>>>>>>>>>>>>>> through implicit or explicit casting.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> PROCTIME/ROWTIME should be time functions based on a long
>>> value.
>>>>>>>>>>>> Both
>>>>>>>>>>>>>>>>> System.currentMillis() and our watermark system work on long
>>>>>>>>> values.
>>>>>>>>>>>>> Those
>>>>>>>>>>>>>>>>> should return TIMESTAMP WITH LOCAL TIME ZONE because the
>>> main
>>>>>>>>>>>>> calculation
>>>>>>>>>>>>>>>>> should always happen based on UTC. We discussed it in a
>>> different
>>>>>>>>>>>>> thread,
>>>>>>>>>>>>>>>>> but we should allow PROCTIME globally. People need a way to
>>> create
>>>>>>>>>>>>>>>>> instances of TIMESTAMP WITH LOCAL TIME ZONE. This is not
>>>>>>>>> considered
>>>>>>>>>>>>> in the
>>>>>>>>>>>>>>>>> current design doc. Many pipelines contain UTC timestamps
>>> and thus
>>>>>>>>>>>> it
>>>>>>>>>>>>>>>>> should be easy to create one. Also, both CURRENT_TIMESTAMP
>>> and
>>>>>>>>>>>>>>>>> LOCALTIMESTAMP can work with this type because we should
>>> remember
>>>>>>>>>>>> that
>>>>>>>>>>>>>>>>> TIMESTAMP WITH LOCAL TIME ZONE accepts all timestamp data
>>> types as
>>>>>>>>>>>>> casting
>>>>>>>>>>>>>>>>> target [1]. We could allow TIMESTAMP WITH TIME ZONE in the
>>> future
>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>> ROWTIME.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> In any case, windows should simply adapt their behavior to
>>> the
>>>>>>>>>>>> passed
>>>>>>>>>>>>>>>>> timestamp type. And with TIMESTAMP WITH LOCAL TIME ZONE a
>>> day is
>>>>>>>>>>>>> defined by
>>>>>>>>>>>>>>>>> considering the current session time zone.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If we would like to design this with less effort required,
>>> we
>>>>>>>>> could
>>>>>>>>>>>>>>>>> think about returning TIMESTAMP WITH LOCAL TIME ZONE also
>>> for
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I will try to involve more people into this discussion.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>> Timo
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> [1]
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/Data-Types.html#GUID-E7CA339A-2093-4FE4-A36E-1D09593591D3
>>>>>>>>>>>>>>>>> <
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/Data-Types.html#GUID-E7CA339A-2093-4FE4-A36E-1D09593591D3
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2021-01-21，22:32，Leonard Xu <xbjt...@gmail.com> ：
>>>>>>>>>>>>>>>>>>> Before the changes, as I am writing this reply, the local
>>> time
>>>>>>>>>>>> here
>>>>>>>>>>>>> is
>>>>>>>>>>>>>>>>> 2021-01-21 12:03:35 (Beijing time, UTC+8).
>>>>>>>>>>>>>>>>>>> And I tried these 5 functions in sql client, and got:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Flink SQL> select now(), PROCTIME(), CURRENT_TIMESTAMP,
>>>>>>>>>>>>> CURRENT_DATE,
>>>>>>>>>>>>>>>>> CURRENT_TIME;
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> | EXPR$0 | EXPR$1 |
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP | CURRENT_DATE | CURRENT_TIME |
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> | 2021-01-21T04:03:35.228 | 2021-01-21T04:03:35.228 |
>>>>>>>>>>>>>>>>> 2021-01-21T04:03:35.228 | 2021-01-21 | 04:03:35.228 |
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> After the changes, the expected behavior will change to:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Flink SQL> select now(), PROCTIME(), CURRENT_TIMESTAMP,
>>>>>>>>>>>>> CURRENT_DATE,
>>>>>>>>>>>>>>>>> CURRENT_TIME;
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> | EXPR$0 | EXPR$1 |
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP | CURRENT_DATE | CURRENT_TIME |
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> | 2021-01-21T12:03:35.228 | 2021-01-21T12:03:35.228 |
>>>>>>>>>>>>>>>>> 2021-01-21T12:03:35.228 | 2021-01-21 | 12:03:35.228 |
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>>> The return type of now(), proctime() and
>>> CURRENT_TIMESTAMP still
>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>> TIMESTAMP;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> To Kurt, thanks for the intuitive case, it really clear,
>>> you’re
>>>>>>>>>>>>> wright
>>>>>>>>>>>>>>>>> that I want to propose to change the return value of these
>>>>>>>>>>>> functions.
>>>>>>>>>>>>> It’s
>>>>>>>>>>>>>>>>> the most important part of the topic from user's
>>> perspective.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> I think this definitely deserves a FLIP.
>>>>>>>>>>>>>>>>>> To Jark, nice suggestion, I prepared a FLIP for this
>>> topic, and
>>>>>>>>>>>> will
>>>>>>>>>>>>>>>>> start the FLIP discussion soon.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> If use the default Flink SQL, the window time
>>> range of
>>>>>>>>> the
>>>>>>>>>>>>>>>>>>>> statistics is incorrect, then the statistical results
>>> will
>>>>>>>>>>>>> naturally
>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>> incorrect.
>>>>>>>>>>>>>>>>>> To zhisheng, sorry to hear that this problem influenced
>>> your
>>>>>>>>>>>>> production
>>>>>>>>>>>>>>>>> jobs, Could you share your SQL pattern? we can have more
>>> inputs
>>>>>>>>>>>> and
>>>>>>>>>>>>> try
>>>>>>>>>>>>>>>>> to resolve them.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>> Leonard
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2021-01-21，14:19，Jark Wu <imj...@gmail.com> ：
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Great examples to understand the problem and the proposed
>>>>>>>>> changes,
>>>>>>>>>>>>>>>>> @Kurt!
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks Leonard for investigating this problem.
>>>>>>>>>>>>>>>>>> The time-zone problems around time functions and windows
>>> have
>>>>>>>>>>>>> bothered a
>>>>>>>>>>>>>>>>>> lot of users. It's time to fix them!
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> The return value changes sound reasonable to me, and
>>> keeping the
>>>>>>>>>>>>> return
>>>>>>>>>>>>>>>>>> type unchanged will minimize the surprise to the users.
>>>>>>>>>>>>>>>>>> Besides that, I think it would be better to mention how
>>> this
>>>>>>>>>>>> affects
>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>> window behaviors, and the interoperability with DataStream.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I think this definitely deserves a FLIP.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> ====================================================
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Hi zhisheng,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Do you have examples to illustrate which case will get the
>>> wrong
>>>>>>>>>>>>> window
>>>>>>>>>>>>>>>>>> boundaries?
>>>>>>>>>>>>>>>>>> That will help to verify whether the proposed changes can
>>> solve
>>>>>>>>>>>> your
>>>>>>>>>>>>>>>>>> problem.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>> Jark
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2021-01-21，12:54，zhisheng <173855...@qq.com> ：
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks to Leonard Xu for discussing this tricky topic. At
>>>>>>>>> present,
>>>>>>>>>>>>>>>>> there are many Flink jobs in our production environment
>>> that are
>>>>>>>>>>>> used
>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>> count day-level reports (eg: count PV/UV ).
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If use the default Flink SQL, the window time range
>>> of the
>>>>>>>>>>>>>>>>> statistics is incorrect, then the statistical results will
>>>>>>>>> naturally
>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>> incorrect.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> The user needs to deal with the time zone manually in
>>> order to
>>>>>>>>>>>> solve
>>>>>>>>>>>>>>>>> the problem.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If Flink itself can solve these time zone issues, then I
>>> think it
>>>>>>>>>>>>> will
>>>>>>>>>>>>>>>>> be user-friendly.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thank you
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Best!;
>>>>>>>>>>>>>>>>>> zhisheng
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2021-01-21，12:11，Kurt Young <ykt...@gmail.com> ：
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> cc this to user & user-zh mailing list because this will
>>> affect
>>>>>>>>>>>> lots
>>>>>>>>>>>>> of
>>>>>>>>>>>>>>>>> users, and also quite a lot of users
>>>>>>>>>>>>>>>>>> were asking questions around this topic.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Let me try to understand this from user's perspective.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Your proposal will affect five functions, which are:
>>>>>>>>>>>>>>>>>> PROCTIME()
>>>>>>>>>>>>>>>>>> NOW()
>>>>>>>>>>>>>>>>>> CURRENT_DATE
>>>>>>>>>>>>>>>>>> CURRENT_TIME
>>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP
>>>>>>>>>>>>>>>>>> Before the changes, as I am writing this reply, the local
>>> time
>>>>>>>>> here
>>>>>>>>>>>>> is
>>>>>>>>>>>>>>>>> 2021-01-21 12:03:35 (Beijing time, UTC+8).
>>>>>>>>>>>>>>>>>> And I tried these 5 functions in sql client, and got:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Flink SQL> select now(), PROCTIME(), CURRENT_TIMESTAMP,
>>>>>>>>>>>> CURRENT_DATE,
>>>>>>>>>>>>>>>>> CURRENT_TIME;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> | EXPR$0 | EXPR$1 |
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP | CURRENT_DATE | CURRENT_TIME |
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> | 2021-01-21T04:03:35.228 | 2021-01-21T04:03:35.228 |
>>>>>>>>>>>>>>>>> 2021-01-21T04:03:35.228 | 2021-01-21 | 04:03:35.228 |
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> After the changes, the expected behavior will change to:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Flink SQL> select now(), PROCTIME(), CURRENT_TIMESTAMP,
>>>>>>>>>>>> CURRENT_DATE,
>>>>>>>>>>>>>>>>> CURRENT_TIME;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> | EXPR$0 | EXPR$1 |
>>>>>>>>>>>>>>>>> CURRENT_TIMESTAMP | CURRENT_DATE | CURRENT_TIME |
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> | 2021-01-21T12:03:35.228 | 2021-01-21T12:03:35.228 |
>>>>>>>>>>>>>>>>> 2021-01-21T12:03:35.228 | 2021-01-21 | 12:03:35.228 |
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>>> +-------------------------+-------------------------+-------------------------+--------------+--------------+
>>>>>>>>>>>>>>>>>> The return type of now(), proctime() and CURRENT_TIMESTAMP
>>> still
>>>>>>>>> be
>>>>>>>>>>>>>>>>> TIMESTAMP;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>>>> Kurt
>>>
>>>
>
