[Haskell-cafe] Announce: HDBI-1.3 and friends
s9gf4ult at gmail.com
Wed Oct 16 16:16:11 UTC 2013
I understand why do you point on this feature. I see that Oracle supports
such feature natively, stored procedures can return multiple results and
native API support working with result sets. This specific feature can be
added exclusively for Oracle driver. While the `Connection` is just a
typeclass you can define any functions you need in the driver. For example
hdbi-postgresql driver exports function `pgAffectedRows` which return the
count of rows affected by executed statement. SQLite have no such function,
thats why this is not in `Connection` typeclass. The same is posible for
i.e. `OracleStatement` type: you can just implement additional functions in
the driver and export them. Note, this is not true for HDBC because the
`Statement` is data in HDBC but not typeclass.
2013/10/16 Gauthier Segay <gauthier.segay at gmail.com>
> I got it Alexey, thanks.
> I wasn't aware that this feature is not widespread in RDBMS, indeed
> postgresql and sqlite are not exposing it; so this would require some
> added complexity in those drivers without added benefits since it
> would be equivalent to sending separate statements.
> On Wed, Oct 16, 2013 at 5:50 PM, Alexey Uimanov <s9gf4ult at gmail.com>
> > Now I understand what you want, but it looks like something strange. Why
> > dont just execute many statements and accumulate them in some container
> > after that fetch results of this statements ? For me It looks like
> > foreign in HDBI especially because I did not see any support of such
> > in native database interfaces not in Postgresql nor in SQlite.
> > 2013/10/16 Gauthier Segay <gauthier.segay at gmail.com>
> >> no the use case is to issue a bunch of disparate select statements,
> >> i.e. retrieving data from several tables in a single roundtrip.
> >> select 1,2,3
> >> select 'a', 'b'
> >> In this case, I'd like to call the API in this manner (or something
> >> better):
> >> -- statement is prepared
> >> rows1 <- fetchAllRows statement
> >> _ <- nextResults statement
> >> rows2 <- fetchAllRows statement
> >> -- continue
> >> right now, with hdbc-odbc (nextResults doesn't exist though so I don't
> >> call it) rows2 will be an empty list, I'd expect it to be[(SqlText
> >> "a"), (SqlText "b")]
> >> I assume in the case of odbc, the related C function is SQLMoreResults
> >> http://msdn.microsoft.com/en-us/library/ms714673%28v=vs.85%29.aspx
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