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From Shawn Li <shawnli...@gmail.com>
Subject Re: "upsert select" with "limit" clause
Date Thu, 13 Dec 2018 02:05:59 GMT
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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