Re: [Haskelldb-users] Request for code review: Patch removing "distinct" option, adds "unique" function

[Bjorn B. <bri...@cs...>]

Hi Justin,

this looks good. I haven't run the testsuite yet, since it still =20
requires hs-plugins. I really should get around to fixing that. Hope =20
seems to run fine with it.

I'll be happy to push this to the main repo. Would it be possible for =20=

you to send me an updated patch with only the necessary changes? Some =20=

of the changes in the patch seem to only affect whitespace. I prefer =20
to keep patches minimal.

/Bj=F6rn


On Dec 11, 2007, at 21:53 , Justin Bailey wrote:

> All,
>
> Attached you'll find a patch that removes the mandatory "DISTINCT"
> clause from select statements. Instead, if a query has the "unqiue"
> function applied, a 'group by' statement will appear in the select,
> grouping by all non-aggregate columns. This works properly with
> optimization so unused columns do not appear in the group-by. Note
> this patch replaces my previous one - I think this approach is a lot
> better and works in more situations.
>
> One change I'm unsure of is that "unique" is NOT default behavior
> anymore. I think a select statement with a "distinct" on all columns
> is very surprising so I like the change. Others may disagree.
>
> A summary of significant changes:
>
>     M ./src/Database/HaskellDB/PrimQuery.hs -3 +7
> * Added "Group" value to PrimQuery. This value holds an association
> list and a query. The association list is the columns/expressions that
> will be grouped; the query is the query to which Group was applied. In
> SQL, grouping can happen on expressions, which is why an Assoc list is
> used instead of a simple list of column names.
>
>
>     M ./src/Database/HaskellDB/Query.hs -9 +30
> * Added the 'unique' function, which causes the Group value to be
> added to the query. All currently projected columns are examined and
> non-aggregates are added to the Group value. This allows those columns
> to be later generated in a "group by" statement.
>
>     M ./src/Database/HaskellDB/Sql/Generate.hs +3
> * Added 'sqlGroup' field to SqlGenerator value. Used to process =20
> Group values.
>
>     M ./src/Database/HaskellDB/Sql.hs -12 +16
> * Changed the 'groupby' field from a list of SqlExpr to a list of
> (SqlColumn, SqlExpr) pairs. Not really needed right now, but will
> allow 'GROUP BY' to be as expressive as the 'column list' available to
> SELECT.
>
>     M ./src/Database/HaskellDB/Sql/Default.hs -8 +12
> * Added 'defaultSqlGroup' converts the Assoc list from the Group value
> to a list of (SqlColumn, SqlExpr) pairs and stores them in the groupby
> field.
> * Note that defaultSqlSelect did NOT have to change - it already
> handled grouping for non-aggregate expressions properly.
>
>     M ./src/Database/HaskellDB/Sql/Print.hs -3 +9
>     M ./src/Database/HaskellDB.hs -1 +1
>     M ./src/Database/HaskellDB/Optimize.hs -7 +16
> * Various small changes to support new values and changed structures.
>
> I welcome feedback on this patch. I'm happy to clarify anything or
> provide examples.
>
> Justin<JGBAILEY.12112007.patch.txt>