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From Shawn Li <shawnli...@gmail.com>
Subject Re: "upsert select" with "limit" clause
Date Tue, 18 Dec 2018 01:43:42 GMT
Hi Vincent,

Thanks for explaining. That makes much more sense now and it explains the
high memory usage when without "limit" clause. Because it upserts much
quickly when using "upsert select" without "limit", the memory usage in
client machine is much higher than "upsert select" with "limit" .

So back to the other question. Can you explain what is underlying Phoenix
implementation for "upsert select limit"? Why it is slower than without
"limit" when insert a huge number (2m rows) like ""upsert into table2
select * from table1 limit 2,000,000;". This is much slower than inserting
the whole table (upsert into table2 select * from table1;).

Thanks,
Xiang


On Mon, Dec 17, 2018 at 1:56 PM Vincent Poon <vincentpoon@apache.org> wrote:

> Shawn,
> Your query *upsert into table2 select * from table1;  *would not be run
> on the server - the source and target table are different.  It would have
> to be something like:
> *upsert into table1 select * from table1;*
>
> If you want to run server-side upsert select on a target table that is
> different from the source table, you need to set
> "phoenix.client.enable.server.upsert.select" to true on your client.
> The are some other restrictions: the table can't have any global indexes,
> and the statement can't have a join or where subquery.  We need to update
> the documentation with this information.
>
> The reason there are all these hurdles is because it's generally not
> recommended to do server-side upsert select across different tables,
> because that means you're doing cross-regionserver RPCs (e.g. read data
> from a region of sourcetable, and write to a region of targettable on a
> different regionserver), potentially tying up handlers in an unpredictable
> way.
>
> On Sun, Dec 16, 2018 at 7:12 PM Shawn Li <shawnlijob@gmail.com> wrote:
>
>> Hi Jaanai,
>>
>> According to Phoenix website, " If auto commit is on, and both a) the
>> target table matches the source table, and b) the select performs no
>> aggregation, then the population of the target table will be done
>> completely on the server-side (with constraint violations logged, but
>> otherwise ignored). Otherwise, data is buffered on the client and, if auto
>> commit is on, committed in row batches as specified by the UpsertBatchSize
>> connection property (or the phoenix.mutate.upsertBatchSize HBase config
>> property which defaults to 10000 rows)"
>>
>> And our sql statement is just: *upsert into table2 select * from table1;
>> *which should match the first case, all operations should be in server
>> site. But the memory usage on the client machine is higher than "upsert
>> select limit" clause. And the memory usage is check by run 'top'  command
>> under Linux. So we are sure it is caused by "select upsert" in Phoenix and
>> not others, and can't explain why there is so high memory usage on
>> client/gateway machine when all operations are supposed to happen on the
>> serve side.
>>
>> Thanks,
>> Shawn
>>
>> On Thu, Dec 13, 2018 at 3:15 AM Jaanai Zhang <cloud.poster@gmail.com>
>> wrote:
>>
>>> Shawn,
>>>
>>> The UPSERT SELECT will run in a coprocessor on if it hasn't limit
>>> clause, only query 1 table, the query is doing aggregation, no sequences
>>> and auto commit is on. Please check your SQL ... and you can also check
>>> whether some resources have not been released.
>>>
>>> ----------------------------------------
>>>    Jaanai Zhang
>>>    Best regards!
>>>
>>>
>>>
>>> Shawn Li <shawnlijob@gmail.com> 于2018年12月13日周四 下午12:10写道:
>>>
>>>> Hi Jaanai,
>>>>
>>>> Thanks for putting your thought. The behavior you describe is correct
>>>> on the Hbase region sever side. The memory usage for blockcache and
>>>> memstore will be high under such high throughput. But our phoenix client
is
>>>> on a gateway machine (no hbase region server sitting on it or any Hbase
>>>> service on it), so not sure how to explain such high memory usage for
>>>> upsert select without "limit" clause. The high memory usage behavior like
>>>> all select results send to client machine, cached in client machine's
>>>> memory, and then insert back to target table, which is not like the
>>>> behavior that should happen, all of this should be done on the server side
>>>> as the table schema is exactly the same. By the way, this happens on both
>>>> Phoenix 4.7 and Phoenix 4.14.
>>>>
>>>>
>>>> Thanks,
>>>> Shawn
>>>>
>>>> On Wed, Dec 12, 2018 at 10:26 PM Jaanai Zhang <cloud.poster@gmail.com>
>>>> wrote:
>>>>
>>>>> Shawn,
>>>>>
>>>>>
>>>>> For the upsert without limit,  which will read the source table and
>>>>> write the target tables on the server side.  I think the higher memory
>>>>> usage is caused by using scan cache and memstore under the higher
>>>>> throughput.
>>>>>
>>>>> ----------------------------------------
>>>>>    Jaanai Zhang
>>>>>    Best regards!
>>>>>
>>>>>
>>>>>
>>>>> Shawn Li <shawnlijob@gmail.com> 于2018年12月13日周四 上午10:13写道:
>>>>>
>>>>>> Hi Vincent,
>>>>>>
>>>>>> So you describe limit will sent result to client side and then write
>>>>>> to server, this might explain why upsert with limit is slower than
without
>>>>>> limit. But looks like it can't explain the memory usage? The memory
usage
>>>>>> on client machine is 8gb (without "limit") vs 2gb (with limit), sometime
>>>>>> upsert without "limit" can even reach 20gb for big table.
>>>>>>
>>>>>> Thanks,
>>>>>> Shawn
>>>>>>
>>>>>> On Wed, Dec 12, 2018 at 6:34 PM Vincent Poon <vincentpoon@apache.org>
>>>>>> wrote:
>>>>>>
>>>>>>> I think it's done client-side if you have LIMIT.  If you have
e.g.
>>>>>>> LIMIT 1000 , it would be incorrect for each regionserver to upsert
100, if
>>>>>>> you have more than one regionserver.  So instead results are
sent back to
>>>>>>> the client, where the LIMIT is applied and then written back
to the server
>>>>>>> in the UPSERT.
>>>>>>>
>>>>>>> On Wed, Dec 12, 2018 at 1:18 PM Shawn Li <shawnlijob@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi Vincent,
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> The table creation statement is similar to below. We have
about 200
>>>>>>>> fields. Table is mutable and don’t have any index on the
table.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> CREATE TABLE IF NOT EXISTS us_population (
>>>>>>>>
>>>>>>>>       state CHAR(2) NOT NULL,
>>>>>>>>
>>>>>>>>       city VARCHAR,
>>>>>>>>
>>>>>>>>       population BIGINT,
>>>>>>>>
>>>>>>>>       …
>>>>>>>>
>>>>>>>>       CONSTRAINT my_pk PRIMARY KEY (state));
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Shawn
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wed, Dec 12, 2018, 13:42 Vincent Poon <vincentpoon@apache.org
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> For #2, can you provide the table definition and the
statement
>>>>>>>>> used?  e.g. Is the table immutable, or does it have indexes?
>>>>>>>>>
>>>>>>>>> On Tue, Dec 11, 2018 at 6:08 PM Shawn/Xiang Li <
>>>>>>>>> shawnlijob@gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 1.       Want to check what is underlying running
for limit
>>>>>>>>>> clause used in the following Upsert statement (is
it involving any
>>>>>>>>>> coprocessor working behind?):
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> *                                  upsert into table2
select *
>>>>>>>>>> from table1 limit 3000000; * (table 1 and table 2
have same
>>>>>>>>>> schema)
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>               The above statement is running a lot
slower than
>>>>>>>>>> without “limit”  clause as shown in following,
even the above statement
>>>>>>>>>> upsert less data:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> *                                upsert into table2
select * from
>>>>>>>>>> table1;*
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 2.       We also observe memory usable is pretty
high without
>>>>>>>>>> the limit clause (8gb vs 2gb), sometimes for big
table it can reach 20gb
>>>>>>>>>> without using limit clause.  According to phoenix
website description for
>>>>>>>>>> upsert select “If auto commit is on, and both a)
the target table matches
>>>>>>>>>> the source table, and b) the select performs no aggregation,
then the
>>>>>>>>>> population of the target table will be done completely
on the server-side
>>>>>>>>>> (with constraint violations logged, but otherwise
ignored).”
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>                My question is If everything is done
on
>>>>>>>>>> server-side, how come we have such high memory usage
on the client machine?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> Shawn
>>>>>>>>>>
>>>>>>>>>

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