Adding upstream version 15.5.upstream/15.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1676 insertions, 0 deletions

diff --git a/src/backend/nodes/list.c b/src/backend/nodes/list.c
new file mode 100644
index 0000000..90f93e8
--- /dev/null
+++ b/src/backend/nodes/list.c
@@ -0,0 +1,1676 @@
+/*-------------------------------------------------------------------------
+ *
+ * list.c
+ *	  implementation for PostgreSQL generic list package
+ *
+ * See comments in pg_list.h.
+ *
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/nodes/list.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "nodes/pg_list.h"
+#include "port/pg_bitutils.h"
+#include "utils/memdebug.h"
+#include "utils/memutils.h"
+
+
+/*
+ * The previous List implementation, since it used a separate palloc chunk
+ * for each cons cell, had the property that adding or deleting list cells
+ * did not move the storage of other existing cells in the list.  Quite a
+ * bit of existing code depended on that, by retaining ListCell pointers
+ * across such operations on a list.  There is no such guarantee in this
+ * implementation, so instead we have debugging support that is meant to
+ * help flush out now-broken assumptions.  Defining DEBUG_LIST_MEMORY_USAGE
+ * while building this file causes the List operations to forcibly move
+ * all cells in a list whenever a cell is added or deleted.  In combination
+ * with MEMORY_CONTEXT_CHECKING and/or Valgrind, this can usually expose
+ * broken code.  It's a bit expensive though, as there's many more palloc
+ * cycles and a lot more data-copying than in a default build.
+ *
+ * By default, we enable this when building for Valgrind.
+ */
+#ifdef USE_VALGRIND
+#define DEBUG_LIST_MEMORY_USAGE
+#endif
+
+/* Overhead for the fixed part of a List header, measured in ListCells */
+#define LIST_HEADER_OVERHEAD  \
+	((int) ((offsetof(List, initial_elements) - 1) / sizeof(ListCell) + 1))
+
+/*
+ * Macros to simplify writing assertions about the type of a list; a
+ * NIL list is considered to be an empty list of any type.
+ */
+#define IsPointerList(l)		((l) == NIL || IsA((l), List))
+#define IsIntegerList(l)		((l) == NIL || IsA((l), IntList))
+#define IsOidList(l)			((l) == NIL || IsA((l), OidList))
+
+#ifdef USE_ASSERT_CHECKING
+/*
+ * Check that the specified List is valid (so far as we can tell).
+ */
+static void
+check_list_invariants(const List *list)
+{
+	if (list == NIL)
+		return;
+
+	Assert(list->length > 0);
+	Assert(list->length <= list->max_length);
+	Assert(list->elements != NULL);
+
+	Assert(list->type == T_List ||
+		   list->type == T_IntList ||
+		   list->type == T_OidList);
+}
+#else
+#define check_list_invariants(l)  ((void) 0)
+#endif							/* USE_ASSERT_CHECKING */
+
+/*
+ * Return a freshly allocated List with room for at least min_size cells.
+ *
+ * Since empty non-NIL lists are invalid, new_list() sets the initial length
+ * to min_size, effectively marking that number of cells as valid; the caller
+ * is responsible for filling in their data.
+ */
+static List *
+new_list(NodeTag type, int min_size)
+{
+	List	   *newlist;
+	int			max_size;
+
+	Assert(min_size > 0);
+
+	/*
+	 * We allocate all the requested cells, and possibly some more, as part of
+	 * the same palloc request as the List header.  This is a big win for the
+	 * typical case of short fixed-length lists.  It can lose if we allocate a
+	 * moderately long list and then it gets extended; we'll be wasting more
+	 * initial_elements[] space than if we'd made the header small.  However,
+	 * rounding up the request as we do in the normal code path provides some
+	 * defense against small extensions.
+	 */
+
+#ifndef DEBUG_LIST_MEMORY_USAGE
+
+	/*
+	 * Normally, we set up a list with some extra cells, to allow it to grow
+	 * without a repalloc.  Prefer cell counts chosen to make the total
+	 * allocation a power-of-2, since palloc would round it up to that anyway.
+	 * (That stops being true for very large allocations, but very long lists
+	 * are infrequent, so it doesn't seem worth special logic for such cases.)
+	 *
+	 * The minimum allocation is 8 ListCell units, providing either 4 or 5
+	 * available ListCells depending on the machine's word width.  Counting
+	 * palloc's overhead, this uses the same amount of space as a one-cell
+	 * list did in the old implementation, and less space for any longer list.
+	 *
+	 * We needn't worry about integer overflow; no caller passes min_size
+	 * that's more than twice the size of an existing list, so the size limits
+	 * within palloc will ensure that we don't overflow here.
+	 */
+	max_size = pg_nextpower2_32(Max(8, min_size + LIST_HEADER_OVERHEAD));
+	max_size -= LIST_HEADER_OVERHEAD;
+#else
+
+	/*
+	 * For debugging, don't allow any extra space.  This forces any cell
+	 * addition to go through enlarge_list() and thus move the existing data.
+	 */
+	max_size = min_size;
+#endif
+
+	newlist = (List *) palloc(offsetof(List, initial_elements) +
+							  max_size * sizeof(ListCell));
+	newlist->type = type;
+	newlist->length = min_size;
+	newlist->max_length = max_size;
+	newlist->elements = newlist->initial_elements;
+
+	return newlist;
+}
+
+/*
+ * Enlarge an existing non-NIL List to have room for at least min_size cells.
+ *
+ * This does *not* update list->length, as some callers would find that
+ * inconvenient.  (list->length had better be the correct number of existing
+ * valid cells, though.)
+ */
+static void
+enlarge_list(List *list, int min_size)
+{
+	int			new_max_len;
+
+	Assert(min_size > list->max_length);	/* else we shouldn't be here */
+
+#ifndef DEBUG_LIST_MEMORY_USAGE
+
+	/*
+	 * As above, we prefer power-of-two total allocations; but here we need
+	 * not account for list header overhead.
+	 */
+
+	/* clamp the minimum value to 16, a semi-arbitrary small power of 2 */
+	new_max_len = pg_nextpower2_32(Max(16, min_size));
+
+#else
+	/* As above, don't allocate anything extra */
+	new_max_len = min_size;
+#endif
+
+	if (list->elements == list->initial_elements)
+	{
+		/*
+		 * Replace original in-line allocation with a separate palloc block.
+		 * Ensure it is in the same memory context as the List header.  (The
+		 * previous List implementation did not offer any guarantees about
+		 * keeping all list cells in the same context, but it seems reasonable
+		 * to create such a guarantee now.)
+		 */
+		list->elements = (ListCell *)
+			MemoryContextAlloc(GetMemoryChunkContext(list),
+							   new_max_len * sizeof(ListCell));
+		memcpy(list->elements, list->initial_elements,
+			   list->length * sizeof(ListCell));
+
+		/*
+		 * We must not move the list header, so it's unsafe to try to reclaim
+		 * the initial_elements[] space via repalloc.  In debugging builds,
+		 * however, we can clear that space and/or mark it inaccessible.
+		 * (wipe_mem includes VALGRIND_MAKE_MEM_NOACCESS.)
+		 */
+#ifdef CLOBBER_FREED_MEMORY
+		wipe_mem(list->initial_elements,
+				 list->max_length * sizeof(ListCell));
+#else
+		VALGRIND_MAKE_MEM_NOACCESS(list->initial_elements,
+								   list->max_length * sizeof(ListCell));
+#endif
+	}
+	else
+	{
+#ifndef DEBUG_LIST_MEMORY_USAGE
+		/* Normally, let repalloc deal with enlargement */
+		list->elements = (ListCell *) repalloc(list->elements,
+											   new_max_len * sizeof(ListCell));
+#else
+		/*
+		 * repalloc() might enlarge the space in-place, which we don't want
+		 * for debugging purposes, so forcibly move the data somewhere else.
+		 */
+		ListCell   *newelements;
+
+		newelements = (ListCell *)
+			MemoryContextAlloc(GetMemoryChunkContext(list),
+							   new_max_len * sizeof(ListCell));
+		memcpy(newelements, list->elements,
+			   list->length * sizeof(ListCell));
+		pfree(list->elements);
+		list->elements = newelements;
+#endif
+	}
+
+	list->max_length = new_max_len;
+}
+
+/*
+ * Convenience functions to construct short Lists from given values.
+ * (These are normally invoked via the list_makeN macros.)
+ */
+List *
+list_make1_impl(NodeTag t, ListCell datum1)
+{
+	List	   *list = new_list(t, 1);
+
+	list->elements[0] = datum1;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_make2_impl(NodeTag t, ListCell datum1, ListCell datum2)
+{
+	List	   *list = new_list(t, 2);
+
+	list->elements[0] = datum1;
+	list->elements[1] = datum2;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_make3_impl(NodeTag t, ListCell datum1, ListCell datum2,
+				ListCell datum3)
+{
+	List	   *list = new_list(t, 3);
+
+	list->elements[0] = datum1;
+	list->elements[1] = datum2;
+	list->elements[2] = datum3;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_make4_impl(NodeTag t, ListCell datum1, ListCell datum2,
+				ListCell datum3, ListCell datum4)
+{
+	List	   *list = new_list(t, 4);
+
+	list->elements[0] = datum1;
+	list->elements[1] = datum2;
+	list->elements[2] = datum3;
+	list->elements[3] = datum4;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_make5_impl(NodeTag t, ListCell datum1, ListCell datum2,
+				ListCell datum3, ListCell datum4, ListCell datum5)
+{
+	List	   *list = new_list(t, 5);
+
+	list->elements[0] = datum1;
+	list->elements[1] = datum2;
+	list->elements[2] = datum3;
+	list->elements[3] = datum4;
+	list->elements[4] = datum5;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Make room for a new head cell in the given (non-NIL) list.
+ *
+ * The data in the new head cell is undefined; the caller should be
+ * sure to fill it in
+ */
+static void
+new_head_cell(List *list)
+{
+	/* Enlarge array if necessary */
+	if (list->length >= list->max_length)
+		enlarge_list(list, list->length + 1);
+	/* Now shove the existing data over */
+	memmove(&list->elements[1], &list->elements[0],
+			list->length * sizeof(ListCell));
+	list->length++;
+}
+
+/*
+ * Make room for a new tail cell in the given (non-NIL) list.
+ *
+ * The data in the new tail cell is undefined; the caller should be
+ * sure to fill it in
+ */
+static void
+new_tail_cell(List *list)
+{
+	/* Enlarge array if necessary */
+	if (list->length >= list->max_length)
+		enlarge_list(list, list->length + 1);
+	list->length++;
+}
+
+/*
+ * Append a pointer to the list. A pointer to the modified list is
+ * returned. Note that this function may or may not destructively
+ * modify the list; callers should always use this function's return
+ * value, rather than continuing to use the pointer passed as the
+ * first argument.
+ */
+List *
+lappend(List *list, void *datum)
+{
+	Assert(IsPointerList(list));
+
+	if (list == NIL)
+		list = new_list(T_List, 1);
+	else
+		new_tail_cell(list);
+
+	llast(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Append an integer to the specified list. See lappend()
+ */
+List *
+lappend_int(List *list, int datum)
+{
+	Assert(IsIntegerList(list));
+
+	if (list == NIL)
+		list = new_list(T_IntList, 1);
+	else
+		new_tail_cell(list);
+
+	llast_int(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Append an OID to the specified list. See lappend()
+ */
+List *
+lappend_oid(List *list, Oid datum)
+{
+	Assert(IsOidList(list));
+
+	if (list == NIL)
+		list = new_list(T_OidList, 1);
+	else
+		new_tail_cell(list);
+
+	llast_oid(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Make room for a new cell at position 'pos' (measured from 0).
+ * The data in the cell is left undefined, and must be filled in by the
+ * caller. 'list' is assumed to be non-NIL, and 'pos' must be a valid
+ * list position, ie, 0 <= pos <= list's length.
+ * Returns address of the new cell.
+ */
+static ListCell *
+insert_new_cell(List *list, int pos)
+{
+	Assert(pos >= 0 && pos <= list->length);
+
+	/* Enlarge array if necessary */
+	if (list->length >= list->max_length)
+		enlarge_list(list, list->length + 1);
+	/* Now shove the existing data over */
+	if (pos < list->length)
+		memmove(&list->elements[pos + 1], &list->elements[pos],
+				(list->length - pos) * sizeof(ListCell));
+	list->length++;
+
+	return &list->elements[pos];
+}
+
+/*
+ * Insert the given datum at position 'pos' (measured from 0) in the list.
+ * 'pos' must be valid, ie, 0 <= pos <= list's length.
+ *
+ * Note that this takes time proportional to the distance to the end of the
+ * list, since the following entries must be moved.
+ */
+List *
+list_insert_nth(List *list, int pos, void *datum)
+{
+	if (list == NIL)
+	{
+		Assert(pos == 0);
+		return list_make1(datum);
+	}
+	Assert(IsPointerList(list));
+	lfirst(insert_new_cell(list, pos)) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_insert_nth_int(List *list, int pos, int datum)
+{
+	if (list == NIL)
+	{
+		Assert(pos == 0);
+		return list_make1_int(datum);
+	}
+	Assert(IsIntegerList(list));
+	lfirst_int(insert_new_cell(list, pos)) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+List *
+list_insert_nth_oid(List *list, int pos, Oid datum)
+{
+	if (list == NIL)
+	{
+		Assert(pos == 0);
+		return list_make1_oid(datum);
+	}
+	Assert(IsOidList(list));
+	lfirst_oid(insert_new_cell(list, pos)) = datum;
+	check_list_invariants(list);
+	return 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
+ * modify the list; callers should always use this function's return
+ * value, rather than continuing to use the pointer passed as the
+ * second argument.
+ *
+ * Note that this takes time proportional to the length of the list,
+ * since the existing entries must be moved.
+ *
+ * Caution: before Postgres 8.0, the original List was unmodified and
+ * could be considered to retain its separate identity.  This is no longer
+ * the case.
+ */
+List *
+lcons(void *datum, List *list)
+{
+	Assert(IsPointerList(list));
+
+	if (list == NIL)
+		list = new_list(T_List, 1);
+	else
+		new_head_cell(list);
+
+	linitial(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Prepend an integer to the list. See lcons()
+ */
+List *
+lcons_int(int datum, List *list)
+{
+	Assert(IsIntegerList(list));
+
+	if (list == NIL)
+		list = new_list(T_IntList, 1);
+	else
+		new_head_cell(list);
+
+	linitial_int(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Prepend an OID to the list. See lcons()
+ */
+List *
+lcons_oid(Oid datum, List *list)
+{
+	Assert(IsOidList(list));
+
+	if (list == NIL)
+		list = new_list(T_OidList, 1);
+	else
+		new_head_cell(list);
+
+	linitial_oid(list) = datum;
+	check_list_invariants(list);
+	return list;
+}
+
+/*
+ * Concatenate list2 to the end of list1, and return list1.
+ *
+ * This is equivalent to lappend'ing each element of list2, in order, to list1.
+ * list1 is destructively changed, list2 is not.  (However, in the case of
+ * pointer lists, list1 and list2 will point to the same structures.)
+ *
+ * Callers should be sure to use the return value as the new pointer to the
+ * concatenated list: the 'list1' input pointer may or may not be the same
+ * as the returned pointer.
+ *
+ * Note that this takes at least time proportional to the length of list2.
+ * It'd typically be the case that we have to enlarge list1's storage,
+ * probably adding time proportional to the length of list1.
+ */
+List *
+list_concat(List *list1, const List *list2)
+{
+	int			new_len;
+
+	if (list1 == NIL)
+		return list_copy(list2);
+	if (list2 == NIL)
+		return list1;
+
+	Assert(list1->type == list2->type);
+
+	new_len = list1->length + list2->length;
+	/* Enlarge array if necessary */
+	if (new_len > list1->max_length)
+		enlarge_list(list1, new_len);
+
+	/* Even if list1 == list2, using memcpy should be safe here */
+	memcpy(&list1->elements[list1->length], &list2->elements[0],
+		   list2->length * sizeof(ListCell));
+	list1->length = new_len;
+
+	check_list_invariants(list1);
+	return list1;
+}
+
+/*
+ * Form a new list by concatenating the elements of list1 and list2.
+ *
+ * Neither input list is modified.  (However, if they are pointer lists,
+ * the output list will point to the same structures.)
+ *
+ * This is equivalent to, but more efficient than,
+ * list_concat(list_copy(list1), list2).
+ * Note that some pre-v13 code might list_copy list2 as well, but that's
+ * pointless now.
+ */
+List *
+list_concat_copy(const List *list1, const List *list2)
+{
+	List	   *result;
+	int			new_len;
+
+	if (list1 == NIL)
+		return list_copy(list2);
+	if (list2 == NIL)
+		return list_copy(list1);
+
+	Assert(list1->type == list2->type);
+
+	new_len = list1->length + list2->length;
+	result = new_list(list1->type, new_len);
+	memcpy(result->elements, list1->elements,
+		   list1->length * sizeof(ListCell));
+	memcpy(result->elements + list1->length, list2->elements,
+		   list2->length * sizeof(ListCell));
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * Truncate 'list' to contain no more than 'new_size' elements. This
+ * modifies the list in-place! Despite this, callers should use the
+ * pointer returned by this function to refer to the newly truncated
+ * list -- it may or may not be the same as the pointer that was
+ * passed.
+ *
+ * Note that any cells removed by list_truncate() are NOT pfree'd.
+ */
+List *
+list_truncate(List *list, int new_size)
+{
+	if (new_size <= 0)
+		return NIL;				/* truncate to zero length */
+
+	/* If asked to effectively extend the list, do nothing */
+	if (new_size < list_length(list))
+		list->length = new_size;
+
+	/*
+	 * Note: unlike the individual-list-cell deletion functions, we don't move
+	 * the list cells to new storage, even in DEBUG_LIST_MEMORY_USAGE mode.
+	 * This is because none of them can move in this operation, so just like
+	 * in the old cons-cell-based implementation, this function doesn't
+	 * invalidate any pointers to cells of the list.  This is also the reason
+	 * for not wiping the memory of the deleted cells: the old code didn't
+	 * free them either.  Perhaps later we'll tighten this up.
+	 */
+
+	return list;
+}
+
+/*
+ * Return true iff 'datum' is a member of the list. Equality is
+ * determined via equal(), so callers should ensure that they pass a
+ * Node as 'datum'.
+ *
+ * This does a simple linear search --- avoid using it on long lists.
+ */
+bool
+list_member(const List *list, const void *datum)
+{
+	const ListCell *cell;
+
+	Assert(IsPointerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (equal(lfirst(cell), datum))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Return true iff 'datum' is a member of the list. Equality is
+ * determined by using simple pointer comparison.
+ */
+bool
+list_member_ptr(const List *list, const void *datum)
+{
+	const ListCell *cell;
+
+	Assert(IsPointerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst(cell) == datum)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Return true iff the integer 'datum' is a member of the list.
+ */
+bool
+list_member_int(const List *list, int datum)
+{
+	const ListCell *cell;
+
+	Assert(IsIntegerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst_int(cell) == datum)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Return true iff the OID 'datum' is a member of the list.
+ */
+bool
+list_member_oid(const List *list, Oid datum)
+{
+	const ListCell *cell;
+
+	Assert(IsOidList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst_oid(cell) == datum)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Delete the n'th cell (counting from 0) in list.
+ *
+ * The List is pfree'd if this was the last member.
+ *
+ * Note that this takes time proportional to the distance to the end of the
+ * list, since the following entries must be moved.
+ */
+List *
+list_delete_nth_cell(List *list, int n)
+{
+	check_list_invariants(list);
+
+	Assert(n >= 0 && n < list->length);
+
+	/*
+	 * If we're about to delete the last node from the list, free the whole
+	 * list instead and return NIL, which is the only valid representation of
+	 * a zero-length list.
+	 */
+	if (list->length == 1)
+	{
+		list_free(list);
+		return NIL;
+	}
+
+	/*
+	 * Otherwise, we normally just collapse out the removed element.  But for
+	 * debugging purposes, move the whole list contents someplace else.
+	 *
+	 * (Note that we *must* keep the contents in the same memory context.)
+	 */
+#ifndef DEBUG_LIST_MEMORY_USAGE
+	memmove(&list->elements[n], &list->elements[n + 1],
+			(list->length - 1 - n) * sizeof(ListCell));
+	list->length--;
+#else
+	{
+		ListCell   *newelems;
+		int			newmaxlen = list->length - 1;
+
+		newelems = (ListCell *)
+			MemoryContextAlloc(GetMemoryChunkContext(list),
+							   newmaxlen * sizeof(ListCell));
+		memcpy(newelems, list->elements, n * sizeof(ListCell));
+		memcpy(&newelems[n], &list->elements[n + 1],
+			   (list->length - 1 - n) * sizeof(ListCell));
+		if (list->elements != list->initial_elements)
+			pfree(list->elements);
+		else
+		{
+			/*
+			 * As in enlarge_list(), clear the initial_elements[] space and/or
+			 * mark it inaccessible.
+			 */
+#ifdef CLOBBER_FREED_MEMORY
+			wipe_mem(list->initial_elements,
+					 list->max_length * sizeof(ListCell));
+#else
+			VALGRIND_MAKE_MEM_NOACCESS(list->initial_elements,
+									   list->max_length * sizeof(ListCell));
+#endif
+		}
+		list->elements = newelems;
+		list->max_length = newmaxlen;
+		list->length--;
+		check_list_invariants(list);
+	}
+#endif
+
+	return list;
+}
+
+/*
+ * Delete 'cell' from 'list'.
+ *
+ * The List is pfree'd if this was the last member.  However, we do not
+ * touch any data the cell might've been pointing to.
+ *
+ * Note that this takes time proportional to the distance to the end of the
+ * list, since the following entries must be moved.
+ */
+List *
+list_delete_cell(List *list, ListCell *cell)
+{
+	return list_delete_nth_cell(list, cell - list->elements);
+}
+
+/*
+ * Delete the first cell in list that matches datum, if any.
+ * Equality is determined via equal().
+ *
+ * This does a simple linear search --- avoid using it on long lists.
+ */
+List *
+list_delete(List *list, void *datum)
+{
+	ListCell   *cell;
+
+	Assert(IsPointerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (equal(lfirst(cell), datum))
+			return list_delete_cell(list, cell);
+	}
+
+	/* Didn't find a match: return the list unmodified */
+	return list;
+}
+
+/* As above, but use simple pointer equality */
+List *
+list_delete_ptr(List *list, void *datum)
+{
+	ListCell   *cell;
+
+	Assert(IsPointerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst(cell) == datum)
+			return list_delete_cell(list, cell);
+	}
+
+	/* Didn't find a match: return the list unmodified */
+	return list;
+}
+
+/* As above, but for integers */
+List *
+list_delete_int(List *list, int datum)
+{
+	ListCell   *cell;
+
+	Assert(IsIntegerList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst_int(cell) == datum)
+			return list_delete_cell(list, cell);
+	}
+
+	/* Didn't find a match: return the list unmodified */
+	return list;
+}
+
+/* As above, but for OIDs */
+List *
+list_delete_oid(List *list, Oid datum)
+{
+	ListCell   *cell;
+
+	Assert(IsOidList(list));
+	check_list_invariants(list);
+
+	foreach(cell, list)
+	{
+		if (lfirst_oid(cell) == datum)
+			return list_delete_cell(list, cell);
+	}
+
+	/* Didn't find a match: return the list unmodified */
+	return list;
+}
+
+/*
+ * Delete the first element of the list.
+ *
+ * This is useful to replace the Lisp-y code "list = lnext(list);" in cases
+ * where the intent is to alter the list rather than just traverse it.
+ * Beware that the list is modified, whereas the Lisp-y coding leaves
+ * the original list head intact in case there's another pointer to it.
+ *
+ * Note that this takes time proportional to the length of the list,
+ * since the remaining entries must be moved.  Consider reversing the
+ * list order so that you can use list_delete_last() instead.  However,
+ * if that causes you to replace lappend() with lcons(), you haven't
+ * improved matters.  (In short, you can make an efficient stack from
+ * a List, but not an efficient FIFO queue.)
+ */
+List *
+list_delete_first(List *list)
+{
+	check_list_invariants(list);
+
+	if (list == NIL)
+		return NIL;				/* would an error be better? */
+
+	return list_delete_nth_cell(list, 0);
+}
+
+/*
+ * Delete the last element of the list.
+ */
+List *
+list_delete_last(List *list)
+{
+	check_list_invariants(list);
+
+	if (list == NIL)
+		return NIL;				/* would an error be better? */
+
+	/* list_truncate won't free list if it goes to empty, but this should */
+	if (list_length(list) <= 1)
+	{
+		list_free(list);
+		return NIL;
+	}
+
+	return list_truncate(list, list_length(list) - 1);
+}
+
+/*
+ * Delete the first N cells of the list.
+ *
+ * The List is pfree'd if the request causes all cells to be deleted.
+ *
+ * Note that this takes time proportional to the distance to the end of the
+ * list, since the following entries must be moved.
+ */
+List *
+list_delete_first_n(List *list, int n)
+{
+	check_list_invariants(list);
+
+	/* No-op request? */
+	if (n <= 0)
+		return list;
+
+	/* Delete whole list? */
+	if (n >= list_length(list))
+	{
+		list_free(list);
+		return NIL;
+	}
+
+	/*
+	 * Otherwise, we normally just collapse out the removed elements.  But for
+	 * debugging purposes, move the whole list contents someplace else.
+	 *
+	 * (Note that we *must* keep the contents in the same memory context.)
+	 */
+#ifndef DEBUG_LIST_MEMORY_USAGE
+	memmove(&list->elements[0], &list->elements[n],
+			(list->length - n) * sizeof(ListCell));
+	list->length -= n;
+#else
+	{
+		ListCell   *newelems;
+		int			newmaxlen = list->length - n;
+
+		newelems = (ListCell *)
+			MemoryContextAlloc(GetMemoryChunkContext(list),
+							   newmaxlen * sizeof(ListCell));
+		memcpy(newelems, &list->elements[n], newmaxlen * sizeof(ListCell));
+		if (list->elements != list->initial_elements)
+			pfree(list->elements);
+		else
+		{
+			/*
+			 * As in enlarge_list(), clear the initial_elements[] space and/or
+			 * mark it inaccessible.
+			 */
+#ifdef CLOBBER_FREED_MEMORY
+			wipe_mem(list->initial_elements,
+					 list->max_length * sizeof(ListCell));
+#else
+			VALGRIND_MAKE_MEM_NOACCESS(list->initial_elements,
+									   list->max_length * sizeof(ListCell));
+#endif
+		}
+		list->elements = newelems;
+		list->max_length = newmaxlen;
+		list->length = newmaxlen;
+		check_list_invariants(list);
+	}
+#endif
+
+	return list;
+}
+
+/*
+ * Generate the union of two lists. This is calculated by copying
+ * list1 via list_copy(), then adding to it all the members of list2
+ * that aren't already in list1.
+ *
+ * Whether an element is already a member of the list is determined
+ * via equal().
+ *
+ * The returned list is newly-allocated, although the content of the
+ * cells is the same (i.e. any pointed-to objects are not copied).
+ *
+ * NB: this function will NOT remove any duplicates that are present
+ * in list1 (so it only performs a "union" if list1 is known unique to
+ * start with).  Also, if you are about to write "x = list_union(x, y)"
+ * you probably want to use list_concat_unique() instead to avoid wasting
+ * the storage of the old x list.
+ *
+ * Note that this takes time proportional to the product of the list
+ * lengths, so beware of using it on long lists.  (We could probably
+ * improve that, but really you should be using some other data structure
+ * if this'd be a performance bottleneck.)
+ */
+List *
+list_union(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	result = list_copy(list1);
+	foreach(cell, list2)
+	{
+		if (!list_member(result, lfirst(cell)))
+			result = lappend(result, lfirst(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_union() determines duplicates via simple
+ * pointer comparison.
+ */
+List *
+list_union_ptr(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	result = list_copy(list1);
+	foreach(cell, list2)
+	{
+		if (!list_member_ptr(result, lfirst(cell)))
+			result = lappend(result, lfirst(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_union() operates upon lists of integers.
+ */
+List *
+list_union_int(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	Assert(IsIntegerList(list1));
+	Assert(IsIntegerList(list2));
+
+	result = list_copy(list1);
+	foreach(cell, list2)
+	{
+		if (!list_member_int(result, lfirst_int(cell)))
+			result = lappend_int(result, lfirst_int(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_union() operates upon lists of OIDs.
+ */
+List *
+list_union_oid(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	Assert(IsOidList(list1));
+	Assert(IsOidList(list2));
+
+	result = list_copy(list1);
+	foreach(cell, list2)
+	{
+		if (!list_member_oid(result, lfirst_oid(cell)))
+			result = lappend_oid(result, lfirst_oid(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * Return a list that contains all the cells that are in both list1 and
+ * list2.  The returned list is freshly allocated via palloc(), but the
+ * cells themselves point to the same objects as the cells of the
+ * input lists.
+ *
+ * Duplicate entries in list1 will not be suppressed, so it's only a true
+ * "intersection" if list1 is known unique beforehand.
+ *
+ * This variant works on lists of pointers, and determines list
+ * membership via equal().  Note that the list1 member will be pointed
+ * to in the result.
+ *
+ * Note that this takes time proportional to the product of the list
+ * lengths, so beware of using it on long lists.  (We could probably
+ * improve that, but really you should be using some other data structure
+ * if this'd be a performance bottleneck.)
+ */
+List *
+list_intersection(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	if (list1 == NIL || list2 == NIL)
+		return NIL;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	result = NIL;
+	foreach(cell, list1)
+	{
+		if (list_member(list2, lfirst(cell)))
+			result = lappend(result, lfirst(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * As list_intersection but operates on lists of integers.
+ */
+List *
+list_intersection_int(const List *list1, const List *list2)
+{
+	List	   *result;
+	const ListCell *cell;
+
+	if (list1 == NIL || list2 == NIL)
+		return NIL;
+
+	Assert(IsIntegerList(list1));
+	Assert(IsIntegerList(list2));
+
+	result = NIL;
+	foreach(cell, list1)
+	{
+		if (list_member_int(list2, lfirst_int(cell)))
+			result = lappend_int(result, lfirst_int(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * Return a list that contains all the cells in list1 that are not in
+ * list2. The returned list is freshly allocated via palloc(), but the
+ * cells themselves point to the same objects as the cells of the
+ * input lists.
+ *
+ * This variant works on lists of pointers, and determines list
+ * membership via equal()
+ *
+ * Note that this takes time proportional to the product of the list
+ * lengths, so beware of using it on long lists.  (We could probably
+ * improve that, but really you should be using some other data structure
+ * if this'd be a performance bottleneck.)
+ */
+List *
+list_difference(const List *list1, const List *list2)
+{
+	const ListCell *cell;
+	List	   *result = NIL;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	if (list2 == NIL)
+		return list_copy(list1);
+
+	foreach(cell, list1)
+	{
+		if (!list_member(list2, lfirst(cell)))
+			result = lappend(result, lfirst(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_difference() determines list membership via
+ * simple pointer equality.
+ */
+List *
+list_difference_ptr(const List *list1, const List *list2)
+{
+	const ListCell *cell;
+	List	   *result = NIL;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	if (list2 == NIL)
+		return list_copy(list1);
+
+	foreach(cell, list1)
+	{
+		if (!list_member_ptr(list2, lfirst(cell)))
+			result = lappend(result, lfirst(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_difference() operates upon lists of integers.
+ */
+List *
+list_difference_int(const List *list1, const List *list2)
+{
+	const ListCell *cell;
+	List	   *result = NIL;
+
+	Assert(IsIntegerList(list1));
+	Assert(IsIntegerList(list2));
+
+	if (list2 == NIL)
+		return list_copy(list1);
+
+	foreach(cell, list1)
+	{
+		if (!list_member_int(list2, lfirst_int(cell)))
+			result = lappend_int(result, lfirst_int(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * This variant of list_difference() operates upon lists of OIDs.
+ */
+List *
+list_difference_oid(const List *list1, const List *list2)
+{
+	const ListCell *cell;
+	List	   *result = NIL;
+
+	Assert(IsOidList(list1));
+	Assert(IsOidList(list2));
+
+	if (list2 == NIL)
+		return list_copy(list1);
+
+	foreach(cell, list1)
+	{
+		if (!list_member_oid(list2, lfirst_oid(cell)))
+			result = lappend_oid(result, lfirst_oid(cell));
+	}
+
+	check_list_invariants(result);
+	return result;
+}
+
+/*
+ * Append datum to list, but only if it isn't already in the list.
+ *
+ * Whether an element is already a member of the list is determined
+ * via equal().
+ *
+ * This does a simple linear search --- avoid using it on long lists.
+ */
+List *
+list_append_unique(List *list, void *datum)
+{
+	if (list_member(list, datum))
+		return list;
+	else
+		return lappend(list, datum);
+}
+
+/*
+ * This variant of list_append_unique() determines list membership via
+ * simple pointer equality.
+ */
+List *
+list_append_unique_ptr(List *list, void *datum)
+{
+	if (list_member_ptr(list, datum))
+		return list;
+	else
+		return lappend(list, datum);
+}
+
+/*
+ * This variant of list_append_unique() operates upon lists of integers.
+ */
+List *
+list_append_unique_int(List *list, int datum)
+{
+	if (list_member_int(list, datum))
+		return list;
+	else
+		return lappend_int(list, datum);
+}
+
+/*
+ * This variant of list_append_unique() operates upon lists of OIDs.
+ */
+List *
+list_append_unique_oid(List *list, Oid datum)
+{
+	if (list_member_oid(list, datum))
+		return list;
+	else
+		return lappend_oid(list, datum);
+}
+
+/*
+ * Append to list1 each member of list2 that isn't already in list1.
+ *
+ * Whether an element is already a member of the list is determined
+ * via equal().
+ *
+ * This is almost the same functionality as list_union(), but list1 is
+ * modified in-place rather than being copied. However, callers of this
+ * function may have strict ordering expectations -- i.e. that the relative
+ * order of those list2 elements that are not duplicates is preserved.
+ *
+ * Note that this takes time proportional to the product of the list
+ * lengths, so beware of using it on long lists.  (We could probably
+ * improve that, but really you should be using some other data structure
+ * if this'd be a performance bottleneck.)
+ */
+List *
+list_concat_unique(List *list1, const List *list2)
+{
+	ListCell   *cell;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	foreach(cell, list2)
+	{
+		if (!list_member(list1, lfirst(cell)))
+			list1 = lappend(list1, lfirst(cell));
+	}
+
+	check_list_invariants(list1);
+	return list1;
+}
+
+/*
+ * This variant of list_concat_unique() determines list membership via
+ * simple pointer equality.
+ */
+List *
+list_concat_unique_ptr(List *list1, const List *list2)
+{
+	ListCell   *cell;
+
+	Assert(IsPointerList(list1));
+	Assert(IsPointerList(list2));
+
+	foreach(cell, list2)
+	{
+		if (!list_member_ptr(list1, lfirst(cell)))
+			list1 = lappend(list1, lfirst(cell));
+	}
+
+	check_list_invariants(list1);
+	return list1;
+}
+
+/*
+ * This variant of list_concat_unique() operates upon lists of integers.
+ */
+List *
+list_concat_unique_int(List *list1, const List *list2)
+{
+	ListCell   *cell;
+
+	Assert(IsIntegerList(list1));
+	Assert(IsIntegerList(list2));
+
+	foreach(cell, list2)
+	{
+		if (!list_member_int(list1, lfirst_int(cell)))
+			list1 = lappend_int(list1, lfirst_int(cell));
+	}
+
+	check_list_invariants(list1);
+	return list1;
+}
+
+/*
+ * This variant of list_concat_unique() operates upon lists of OIDs.
+ */
+List *
+list_concat_unique_oid(List *list1, const List *list2)
+{
+	ListCell   *cell;
+
+	Assert(IsOidList(list1));
+	Assert(IsOidList(list2));
+
+	foreach(cell, list2)
+	{
+		if (!list_member_oid(list1, lfirst_oid(cell)))
+			list1 = lappend_oid(list1, lfirst_oid(cell));
+	}
+
+	check_list_invariants(list1);
+	return list1;
+}
+
+/*
+ * Remove adjacent duplicates in a list of OIDs.
+ *
+ * It is caller's responsibility to have sorted the list to bring duplicates
+ * together, perhaps via list_sort(list, list_oid_cmp).
+ *
+ * Note that this takes time proportional to the length of the list.
+ */
+void
+list_deduplicate_oid(List *list)
+{
+	int			len;
+
+	Assert(IsOidList(list));
+	len = list_length(list);
+	if (len > 1)
+	{
+		ListCell   *elements = list->elements;
+		int			i = 0;
+
+		for (int j = 1; j < len; j++)
+		{
+			if (elements[i].oid_value != elements[j].oid_value)
+				elements[++i].oid_value = elements[j].oid_value;
+		}
+		list->length = i + 1;
+	}
+	check_list_invariants(list);
+}
+
+/*
+ * Free all storage in a list, and optionally the pointed-to elements
+ */
+static void
+list_free_private(List *list, bool deep)
+{
+	if (list == NIL)
+		return;					/* nothing to do */
+
+	check_list_invariants(list);
+
+	if (deep)
+	{
+		for (int i = 0; i < list->length; i++)
+			pfree(lfirst(&list->elements[i]));
+	}
+	if (list->elements != list->initial_elements)
+		pfree(list->elements);
+	pfree(list);
+}
+
+/*
+ * Free all the cells of the list, as well as the list itself. Any
+ * objects that are pointed-to by the cells of the list are NOT
+ * free'd.
+ *
+ * On return, the argument to this function has been freed, so the
+ * caller would be wise to set it to NIL for safety's sake.
+ */
+void
+list_free(List *list)
+{
+	list_free_private(list, false);
+}
+
+/*
+ * Free all the cells of the list, the list itself, and all the
+ * objects pointed-to by the cells of the list (each element in the
+ * list must contain a pointer to a palloc()'d region of memory!)
+ *
+ * On return, the argument to this function has been freed, so the
+ * caller would be wise to set it to NIL for safety's sake.
+ */
+void
+list_free_deep(List *list)
+{
+	/*
+	 * A "deep" free operation only makes sense on a list of pointers.
+	 */
+	Assert(IsPointerList(list));
+	list_free_private(list, true);
+}
+
+/*
+ * Return a shallow copy of the specified list.
+ */
+List *
+list_copy(const List *oldlist)
+{
+	List	   *newlist;
+
+	if (oldlist == NIL)
+		return NIL;
+
+	newlist = new_list(oldlist->type, oldlist->length);
+	memcpy(newlist->elements, oldlist->elements,
+		   newlist->length * sizeof(ListCell));
+
+	check_list_invariants(newlist);
+	return newlist;
+}
+
+/*
+ * Return a shallow copy of the specified list containing only the first 'len'
+ * elements.  If oldlist is shorter than 'len' then we copy the entire list.
+ */
+List *
+list_copy_head(const List *oldlist, int len)
+{
+	List	   *newlist;
+
+	if (oldlist == NIL || len <= 0)
+		return NIL;
+
+	len = Min(oldlist->length, len);
+
+	newlist = new_list(oldlist->type, len);
+	memcpy(newlist->elements, oldlist->elements, len * sizeof(ListCell));
+
+	check_list_invariants(newlist);
+	return newlist;
+}
+
+/*
+ * Return a shallow copy of the specified list, without the first N elements.
+ */
+List *
+list_copy_tail(const List *oldlist, int nskip)
+{
+	List	   *newlist;
+
+	if (nskip < 0)
+		nskip = 0;				/* would it be better to elog? */
+
+	if (oldlist == NIL || nskip >= oldlist->length)
+		return NIL;
+
+	newlist = new_list(oldlist->type, oldlist->length - nskip);
+	memcpy(newlist->elements, &oldlist->elements[nskip],
+		   newlist->length * sizeof(ListCell));
+
+	check_list_invariants(newlist);
+	return newlist;
+}
+
+/*
+ * Return a deep copy of the specified list.
+ *
+ * The list elements are copied via copyObject(), so that this function's
+ * idea of a "deep" copy is considerably deeper than what list_free_deep()
+ * means by the same word.
+ */
+List *
+list_copy_deep(const List *oldlist)
+{
+	List	   *newlist;
+
+	if (oldlist == NIL)
+		return NIL;
+
+	/* This is only sensible for pointer Lists */
+	Assert(IsA(oldlist, List));
+
+	newlist = new_list(oldlist->type, oldlist->length);
+	for (int i = 0; i < newlist->length; i++)
+		lfirst(&newlist->elements[i]) =
+			copyObjectImpl(lfirst(&oldlist->elements[i]));
+
+	check_list_invariants(newlist);
+	return newlist;
+}
+
+/*
+ * Sort a list according to the specified comparator function.
+ *
+ * The list is sorted in-place.
+ *
+ * The comparator function is declared to receive arguments of type
+ * const ListCell *; this allows it to use lfirst() and variants
+ * without casting its arguments.  Otherwise it behaves the same as
+ * the comparator function for standard qsort().
+ *
+ * Like qsort(), this provides no guarantees about sort stability
+ * for equal keys.
+ *
+ * This is based on qsort(), so it likewise has O(N log N) runtime.
+ */
+void
+list_sort(List *list, list_sort_comparator cmp)
+{
+	typedef int (*qsort_comparator) (const void *a, const void *b);
+	int			len;
+
+	check_list_invariants(list);
+
+	/* Nothing to do if there's less than two elements */
+	len = list_length(list);
+	if (len > 1)
+		qsort(list->elements, len, sizeof(ListCell), (qsort_comparator) cmp);
+}
+
+/*
+ * list_sort comparator for sorting a list into ascending int order.
+ */
+int
+list_int_cmp(const ListCell *p1, const ListCell *p2)
+{
+	int			v1 = lfirst_int(p1);
+	int			v2 = lfirst_int(p2);
+
+	if (v1 < v2)
+		return -1;
+	if (v1 > v2)
+		return 1;
+	return 0;
+}
+
+/*
+ * list_sort comparator for sorting a list into ascending OID order.
+ */
+int
+list_oid_cmp(const ListCell *p1, const ListCell *p2)
+{
+	Oid			v1 = lfirst_oid(p1);
+	Oid			v2 = lfirst_oid(p2);
+
+	if (v1 < v2)
+		return -1;
+	if (v1 > v2)
+		return 1;
+	return 0;
+}