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From: Bram Van Steenlandt <bram@diomedia.be>
To: pgsql-performance@postgresql.org
Subject: Re: large object write performance
Date: Thu, 08 Oct 2015 14:29:28 +0200
Message-ID: <561661A8.90301@diomedia.be> (raw)
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Op 08-10-15 om 14:10 schreef Graeme B. Bell:
>> On 08 Oct 2015, at 13:50, Bram Van Steenlandt <bram@diomedia.be> wrote:
>>>> 1. The part is "fobj = lobject(db.db,0,"r",0,fpath)", I don't think there is anything there
> Re: lobject
>
> http://initd.org/psycopg/docs/usage.html#large-objects
>
> "Psycopg large object support *efficient* import/export with file system files using the lo_import() and lo_export() libpq functions.”
>
> See *
I was under the impression they meant that the lobject was using 
lo_import and lo_export.
I can't seem to find how to use lo_import en export, I searched google 
and came to the conclusion the lobject was the way to go.
 >>> x.lo_import()
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
AttributeError: 'psycopg2._psycopg.connection' object has no attribute 
'lo_import'

 >>> from psycopg2.extensions import lo_importTraceback (most recent 
call last):
   File "<stdin>", line 1, in <module>
ImportError: cannot import name lo_import

Also:
http://initd.org/psycopg/docs/connection.html

|lobject|([/oid/[, /mode/[, /new_oid/[, /new_file/[, /lobject_factory/]]]]])

    Return a new database large object as a |lobject|
    <http://initd.org/psycopg/docs/extensions.html#psycopg2.extensions.lobject;
    instance.

    See Access to PostgreSQL large objects
    <http://initd.org/psycopg/docs/usage.html#large-objects; for an
    overview.

    Parameters: 	

      * *oid* – The OID of the object to read or write. 0 to create a
        new large object and and have its OID assigned automatically.
      * *mode* – Access mode to the object, see below.
      * *new_oid* – Create a new object using the specified OID. The
        function raises |OperationalError|
        <http://initd.org/psycopg/docs/module.html#psycopg2.OperationalError;
        if the OID is already in use. Default is 0, meaning assign a new
        one automatically.
      * *new_file* – The name of a file to be imported in the the
        database (using the |lo_import()|
        <http://www.postgresql.org/docs/current/static/lo-interfaces.html#LO-IMPORT;
        function)
      * *lobject_factory* – Subclass of |lobject|
        <http://initd.org/psycopg/docs/extensions.html#psycopg2.extensions.lobject;
        to be instantiated.


>
> lobject seems to default to string handling in Python
> That’s going to be slow.
> Try using lo_import / export?
>
> Graeme Bell
>

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