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Remove lappend_cell...() family of List functions.

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It seems worth getting rid of these functions because they require the
caller to retain a ListCell pointer into a List that it's modifying,
which is a dangerous practice with the new List implementation.
(The only other List-modifying function that takes a ListCell pointer
as input is list_delete_cell, which nowadays is preferentially used
via the constrained API foreach_delete_current.)

There was only one remaining caller of these functions after commit
2f5b8eb5a, and that was some fairly ugly GEQO code that can be much
more clearly expressed using a list-index variable and list_insert_nth.
Hence, rewrite that code, and remove the functions.

Discussion: https://postgr.es/m/26193.1563228600@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2019-07-16 13:12:24 -04:00
parent 2f5b8eb5a2
commit c245776906
3 changed files with 6 additions and 62 deletions
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47
src/backend/nodes/list.c
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@@ -438,53 +438,6 @@ list_insert_nth_oid(List *list, int pos, Oid datum)
return list;
}
/*
* Add a new cell to the list, in the position after 'prev_cell'. The
* data in the cell is left undefined, and must be filled in by the
* caller. 'list' is assumed to be non-NIL, and 'prev_cell' is assumed
* to be non-NULL and a member of 'list'. Returns address of new cell.
*
* Caution: prev_cell might no longer point into the list after this!
*/
static ListCell *
add_new_cell_after(List *list, ListCell *prev_cell)
{
/* insert_new_cell will assert that this is in-range: */
int pos = prev_cell - list->elements;
return insert_new_cell(list, pos + 1);
}
/*
* Add a new cell to the specified list (which must be non-NIL);
* it will be placed after the list cell 'prev' (which must be
* non-NULL and a member of 'list'). The data placed in the new cell
* is 'datum'.
*/
void
lappend_cell(List *list, ListCell *prev, void *datum)
{
Assert(IsPointerList(list));
lfirst(add_new_cell_after(list, prev)) = datum;
check_list_invariants(list);
}
void
lappend_cell_int(List *list, ListCell *prev, int datum)
{
Assert(IsIntegerList(list));
lfirst_int(add_new_cell_after(list, prev)) = datum;
check_list_invariants(list);
}
void
lappend_cell_oid(List *list, ListCell *prev, Oid datum)
{
Assert(IsOidList(list));
lfirst_oid(add_new_cell_after(list, prev)) = datum;
check_list_invariants(list);
}
/*
* Prepend a new element to the list. A pointer to the modified list
* is returned. Note that this function may or may not destructively