Re: POC, WIP: OR-clause support for indexes

On Mon, Oct 7, 2024 at 10:06 PM jian he <jian(dot)universality(at)gmail(dot)com> wrote:
>
> assume v40 is the latest version.

make_bitmap_paths_for_or_group
{
/*
* First, try to match the whole group to the one index.
*/
orargs = list_make1(ri);
indlist = build_paths_for_OR(root, rel,
orargs,
other_clauses);
if (indlist != NIL)
{
bitmapqual = choose_bitmap_and(root, rel, indlist);
jointcost = bitmapqual->total_cost;
jointlist = list_make1(bitmapqual);
}
/*
* Also try to match all containing clauses 'one-by-one.
*/
foreach(lc, args)
{
orargs = list_make1(lfirst(lc));
indlist = build_paths_for_OR(root, rel,
orargs,
other_clauses);
if (indlist == NIL)
{
splitlist = NIL;
break;
}
bitmapqual = choose_bitmap_and(root, rel, indlist);
}

if other_clauses is not NIL, then "try to match all containing clauses
'one-by-one"
the foreach loop "foreach(lc, args)" will apply other_clauses in
build_paths_for_OR every time.
then splitcost will obviously be higher than jointcost.

if other_clauses is NIL.
"foreach(lc, args)" will have list_length(args) startup cost.
So overall, it looks like jointcost will alway less than splitcost,
the only corner case would be both are zero.

anyway, in make_bitmap_paths_for_or_group,
above line "Pick the best option." I added:

if (splitcost <= jointcost && splitcost != 0 && jointcost != 0)
elog(INFO, "%s:%d splitcost <= jointcost and both is not
zero", __FILE_NAME__, __LINE__);
and the regress tests passed.
That means we don't need to iterate "((BoolExpr *)
ri->orclause)->args" in make_bitmap_paths_for_or_group
?