Re: very slow largeobject transfers through JDBC

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
>>>>
>>>