From: | Daniele Varrazzo <daniele(dot)varrazzo(at)gmail(dot)com> |
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To: | Federico Di Gregorio <federico(dot)digregorio(at)dndg(dot)it> |
Cc: | psycopg(at)postgresql(dot)org |
Subject: | Re: Proposal: efficient iter on named cursors |
Date: | 2011-02-17 11:12:12 |
Message-ID: | AANLkTimiLhbme59jpbr+frx7YNW0MJpMgv-WZ1eyVprA@mail.gmail.com |
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Lists: | psycopg |
On Thu, Feb 17, 2011 at 11:09 AM, Federico Di Gregorio
<federico(dot)digregorio(at)dndg(dot)it> wrote:
> On 17/02/11 11:57, Daniele Varrazzo wrote:
>>> I think the original implementation was right because "foreach ..."
>>> > doesn't mean fetch one record at a time. IMHO,
>>> >
>>> > 1) .fetchone() should _always_ fetch one record
>>> > 2) iter(cursor) should fetch as many records as we feel right
>> Yes, this is what I think too. It is consistent with what happens with
>> iter(file) vs. file.readline(). The only hitch is that the DBAPI asks
>> for a default of 1 for arraysize.
>>
>>
>>> > But we can do a little trick here and make iter(cursor) respect
>>> > .arraysize if arraysize was explicitly set so that if one really wants
>>> > to fetch one record at a time can just set .arraysize to 1.
>>> >
>>> > Good or bad?
>> Quite tricky as arraysize is currently a simple property. Even if we
>> could do it with some property trickery, it would be surprising if
>> "print cur.arraysize" would return 1 and iter(cur) was efficient;
>> then, after "cur.arraysize = 1", iter(cur) would switch to fetch one
>> record at time, while "print cur.arraysize" would still report 1. I
>> feel it violates the principle of least astonishment, as much as being
>> difficult for the user to predict what the library would do.
>
> Then we need a different property: itersize?
While I don't like the multiplication of attributes and extensions,
this sounds like the cleaner option.
-- Daniele
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