On 29 syys, 21:51, Shai Berger <s...@platonix.com> wrote:
> On Sunday 23 September 2012, Anssi Kääriäinen wrote:> On 22 syys, 23:34, Shai
> Berger <s...@platonix.com> wrote:
> > There isn't much time to do feature additions. It is possible to get
> > the feature into 1.5, but you should not expect it to happen. As for
> > the feature itself, I am not yet sure if it is a good idea or not. The
> > basic problem is granularity: wouldn't you want to do this per query,
> > or even per expression basis?
>
> No, I don't; the issue is cross-database compatibility. We have raw SQL
> statements calculating some expressions, and then use the returned values in
> calculations in Python -- adding and muliplying them with floats. This worked
> fine with MySql and the 3rd-party SQL Server backends, but blew up on Oracle
> because Decimals and floats don't mix very well:
The problem seems to be that on Oracle, 1.1 is NUMERIC, and that is
something which _is_ a decimal in Python. We should not change that.
To me it seems the answer is to use to_binary_float/to_binary_double
in raw SQL queries. For example:
cur = connection.cursor()
cur.execute("select count(*) from tests_place")
print cur.fetchone()[0]
vals = None
def do_query():
global vals
cur.execute("select 1.1 from tests_place")
vals = [val[0] for val in cur.fetchall()]
t = Timer('do_query()', 'from __main__ import do_query')
print t.timeit(number=20)
print type(vals[0])
OUT:
2000
0.719314813614
<class 'decimal.Decimal'>
Replace the query with "select to_binary_double(1.1) from
tests_place":
OUT:
2000
0.337587118149
<type 'float'>
Based on the above I am -1 on having a flag that interprets NUMBER
fields as floats. There is already an Oracle data type to use for
this.
I tested the pull request 393 (the speedup to ._rowfactory). Above
test case, and the decimal case runs in around one second, the float
case in 0.1 seconds. So, there is a regressions for decimals. On the
other hand floats are way faster. Will investigate...
As for new features for 1.5: there is roughly a day before feature
freeze. Getting any new ticket into 1.5 is really unlikely at this
point, existing pull requests have priority.
- Anssi
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