Re: very slow largeobject transfers through JDBC

Not sure why reading from a socket is taking 1ms ?

Dave Cramer

davec(at)postgresintl(dot)com
www.postgresintl.com

On Mon, 3 Sep 2018 at 09:39, Mate Varga <m(at)matevarga(dot)net> wrote:

> Hi,
>
> https://imgur.com/a/ovsJPRv -- I've uploaded the profiling info (as an
> image, sorry). It seems this is a JDBC-level problem. I understand that the
> absolute timing is not meaningful at all because you don't know how large
> the resultset is, but I can tell that this is only a few thousands rows +
> few thousand largeobjects, each largeobject is around 1 kByte. (Yes I know
> this is not a proper use of LOBs -- it's a legacy db structure that's hard
> to change.)
>
> Thanks.
> Mate
>
> On Mon, Sep 3, 2018 at 11:52 AM Mate Varga <m(at)matevarga(dot)net> wrote:
>
>> Hey,
>>
>> we'll try to test this with pure JDBC versus hibernate. Thanks!
>>
>>
>> On Mon, Sep 3, 2018 at 11:48 AM Dave Cramer <pg(at)fastcrypt(dot)com> wrote:
>>
>>>
>>>
>>> On Mon, 3 Sep 2018 at 03:55, Mate Varga <m(at)matevarga(dot)net> wrote:
>>>
>>>> Basically there's a class with a byte[] field, the class is mapped to
>>>> table T and the byte field is annotated with @Lob so it goes to the
>>>> pg_largeobject table.
>>>>
>>>
>>> Ah, so hibernate is in the mix. I wonder if that is causing some
>>> challenges ?
>>>
>>>
>>>> The DB is on separate host but relatively close to the app, and I can
>>>> reproduce the problem locally as well. One interesting bit is that turning
>>>> of SSL between the app and PSQL speeds up things by at least 50%.
>>>>
>>>> Ah, one addition -- the binary objects are encrypted, so their entropy
>>>> is very high.
>>>>
>>>> Any chance you could write a simple non-hibernate test code to time the
>>> code ?
>>>
>>> Dave Cramer
>>>
>>> dave(dot)cramer(at)crunchydata(dot)ca
>>> www.crunchydata.ca
>>>
>>>
>>>
>>>> Mate
>>>>
>>>> On Sun, Sep 2, 2018 at 12:55 AM Dave Cramer <pg(at)fastcrypt(dot)com> wrote:
>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Fri, 31 Aug 2018 at 10:15, Mate Varga <m(at)matevarga(dot)net> wrote:
>>>>>
>>>>>> I see -- we could try that, though we're mostly using an ORM
>>>>>> (Hibernate) to do this. Thanks!
>>>>>>
>>>>>> On Fri, Aug 31, 2018 at 3:57 PM Dmitry Igrishin <dmitigr(at)gmail(dot)com>
>>>>>> wrote:
>>>>>>
>>>>>>> пт, 31 авг. 2018 г. в 16:35, Mate Varga <m(at)matevarga(dot)net>:
>>>>>>> >
>>>>>>> > Hi,
>>>>>>> >
>>>>>>> > we're fetching binary data from pg_largeobject table. The data is
>>>>>>> not very large, but we ended up storing it there. If I'm copying the data
>>>>>>> to a file from the psql console, then it takes X time (e.g. a second),
>>>>>>> fetching it through the JDBC driver takes at least 10x more. We don't see
>>>>>>> this difference between JDBC and 'native' performance for anything except
>>>>>>> largeobjects (and bytea columns, for the record).
>>>>>>> >
>>>>>>> > Does anyone have any advice about whether this can be tuned or
>>>>>>> what the cause is?
>>>>>>> I don't know what a reason of that, but I think it's reasonable and
>>>>>>> quite simple to call lo_import()/lo_export() via JNI.
>>>>>>>
>>>>>>
>>>>> Can't imagine that's any faster. The driver simply implements the
>>>>> protocol
>>>>>
>>>>> Do you have any code to share ? Any other information ?
>>>>>
>>>>> Is the JDBC connection significantly further away network wise ?
>>>>>
>>>>>
>>>>> Dave Cramer
>>>>>
>>>>> davec(at)postgresintl(dot)com
>>>>> www.postgresintl.com
>>>>>
>>>>