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Re: To know what a macro does

From: Werner Echezuria <wercool(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org, kleptog(at)svana(dot)org
Subject: Re: To know what a macro does
Date: 2009-04-27 15:19:33
Message-ID: 2485a25e0904270819yb52263t3bc061e614580da0@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2009/4/28 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>

> Well, you've omitted showing us the code where the problem is likely to
> be, but I am kinda thinking that you've shot yourself in the foot by
> trying to represent your special ordering clause as a simple constant.
> The planner is quite smart enough to throw away "order by constant"
> as a no-op.  By the time you get down to the pathkey logic it's just
> going to be ignoring that clause entirely; and if you try to brute-force
> it you're more than likely going to break something.
>

Well, I know I'm breaking something, because when I execute "\d" in psql,
the server hangs out.

When I performs the order by clause, I call a function in
transformSelectStmt on analyze.c (This is parse->hasGrMemb, that I call in
grouping_planner  ) :

qry->hasGrMemb = hassSortByGrMemb(stmt->sortClause);

|****************************************************************************************************|

Then the function is this (on parse_clause.c):

//To know if the query has an ORDER BY grmemb
bool
hassSortByGrMemb(List *orderlist){

    ListCell   *olitem;
    bool        result;

    result=false;
    foreach(olitem, orderlist)
    {
        SortBy       *sortby = lfirst(olitem);
        char       *namegrmemb = strVal(linitial(((ColumnRef *)
sortby->node)->fields));

        if (strcmp(namegrmemb, "grmemb")==0)
            result=true;
    }

    return result;

}


> Rather than kluging up any of this code, I wonder whether you couldn't
> represent your fuzzy sorting requirement as ORDER BY some_function(...)
> and put all the smarts into that function.
>
> Well, the project force me to include all the source in the core. That is
why I wanna know if there's any chance that I could sort the final
resultSlot?.

regards

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