Attached is a patch that avoids a needless copy of the result tuple in
nodeMaterial, in the case that we don't have a previously-materialized
tuple to return. We can just return the TTS produced by executing our
child node, rather than returning a copy of it.
I didn't bother pulling the MinimalTuple out of "outerslot" and stuffing
it back into the nodeMaterial's result slot, as AFAICS that is not
necessary. Although I suppose you could make a cleanliness argument that
that would be worth doing instead.
(This is 8.4 material...)
-Neil
Index: source/src/backend/executor/nodeMaterial.c
===================================================================
RCS file: /home/neilc/postgres/cvs_root/pgsql/src/backend/executor/nodeMaterial.c,v
retrieving revision 1.59
diff -p -c -r1.59 nodeMaterial.c
*** source/src/backend/executor/nodeMaterial.c 21 May 2007 17:57:33 -0000 1.59
--- source/src/backend/executor/nodeMaterial.c 16 Oct 2007 04:00:46 -0000
*************** ExecMaterial(MaterialState *node)
*** 98,103 ****
--- 98,105 ----
eof_tuplestore = true;
}
+ ExecClearTuple(slot);
+
/*
* If necessary, try to fetch another row from the subplan.
*
*************** ExecMaterial(MaterialState *node)
*** 124,147 ****
}
/*
! * Append returned tuple to tuplestore. NOTE: because the tuplestore
! * is certainly in EOF state, its read position will move forward over
! * the added tuple. This is what we want.
*/
if (tuplestorestate)
tuplestore_puttupleslot(tuplestorestate, outerslot);
! /*
! * And return a copy of the tuple. (XXX couldn't we just return the
! * outerslot?)
! */
! return ExecCopySlot(slot, outerslot);
}
! /*
! * Nothing left ...
! */
! return ExecClearTuple(slot);
}
/* ----------------------------------------------------------------
--- 126,143 ----
}
/*
! * Append a copy of the returned tuple to tuplestore. NOTE: because
! * the tuplestore is certainly in EOF state, its read position will
! * move forward over the added tuple. This is what we want.
*/
if (tuplestorestate)
tuplestore_puttupleslot(tuplestorestate, outerslot);
! return outerslot;
}
! /* Nothing left, return empty slot */
! return slot;
}
/* ----------------------------------------------------------------
---------------------------(end of broadcast)---------------------------
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