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Add support for index-only scans in GiST.

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This adds a new GiST opclass method, 'fetch', which is used to reconstruct
the original Datum from the value stored in the index. Also, the 'canreturn'
index AM interface function gains a new 'attno' argument. That makes it
possible to use index-only scans on a multi-column index where some of the
opclasses support index-only scans but some do not.

This patch adds support in the box and point opclasses. Other opclasses
can added later as follow-on patches (btree_gist would be particularly
interesting).

Anastasia Lubennikova, with additional fixes and modifications by me.
This commit is contained in:
Heikki Linnakangas
2015-03-26 19:12:00 +02:00
parent 8fa393a6d7
commit d04c8ed904
24 changed files with 575 additions and 73 deletions
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37
src/backend/access/gist/gistproc.c
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@ -151,6 +151,16 @@ gist_box_decompress(PG_FUNCTION_ARGS)
PG_RETURN_POINTER(PG_GETARG_POINTER(0));
}
/*
* GiST Fetch method for boxes
* do not do anything --- we just return the stored box as is.
*/
Datum
gist_box_fetch(PG_FUNCTION_ARGS)
{
PG_RETURN_POINTER(PG_GETARG_POINTER(0));
}
/*
* The GiST Penalty method for boxes (also used for points)
*
@ -1186,6 +1196,33 @@ gist_point_compress(PG_FUNCTION_ARGS)
PG_RETURN_POINTER(entry);
}
/*
* GiST Fetch method for point
*
* Get point coordinates from its bounding box coordinates and form new
* gistentry.
*/
Datum
gist_point_fetch(PG_FUNCTION_ARGS)
{
GISTENTRY *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
BOX *in = DatumGetBoxP(entry->key);
Point *r;
GISTENTRY *retval;
retval = palloc(sizeof(GISTENTRY));
r = (Point *) palloc(sizeof(Point));
r->x = in->high.x;
r->y = in->high.y;
gistentryinit(*retval, PointerGetDatum(r),
entry->rel, entry->page,
entry->offset, FALSE);
PG_RETURN_POINTER(retval);
}
#define point_point_distance(p1,p2) \
DatumGetFloat8(DirectFunctionCall2(point_distance, \
PointPGetDatum(p1), PointPGetDatum(p2)))