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Fix some latent bugs in dllist.c (carelessness about setting

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all fields that should be set).  Add a MoveToFront primitive to speed up
one of the hotspots in SearchSysCache.
This commit is contained in:
Tom Lane
1999-05-31 23:48:04 +00:00
parent 2a44383a2d
commit 185b427284
3 changed files with 73 additions and 40 deletions
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96
src/backend/lib/dllist.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/lib/dllist.c,v 1.12 1999/02/13 23:15:34 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/lib/dllist.c,v 1.13 1999/05/31 23:48:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -30,7 +30,9 @@ DLNewList(void)
return l;
}
/* free up a list and all the nodes in it */
/* free up a list and all the nodes in it --- but *not* whatever the nodes
* might point to!
*/
void
DLFreeList(Dllist *l)
{
@ -85,7 +87,7 @@ DLGetTail(Dllist *l)
return l ? l->dll_tail : 0;
}
/* get the value stored in the first element */
/* get the value stored in the last element */
#ifdef NOT_USED
void *
DLGetTailVal(Dllist *l)
@ -112,20 +114,26 @@ DLGetSucc(Dlelem *e) /* get successor */
void
DLRemove(Dlelem *e)
{
Dllist *l;
Dllist *l = e->dle_list;
if (e->dle_prev)
e->dle_prev->dle_next = e->dle_next;
else /* must be the head element */
{
Assert(e == l->dll_head);
l->dll_head = e->dle_next;
}
if (e->dle_next)
e->dle_next->dle_prev = e->dle_prev;
else /* must be the tail element */
{
Assert(e == l->dll_tail);
l->dll_tail = e->dle_prev;
}
/* check to see if we're removing the head or tail */
l = e->dle_list;
if (e == l->dll_head)
DLRemHead(l);
if (e == l->dll_tail)
DLRemTail(l);
e->dle_next = 0;
e->dle_prev = 0;
e->dle_list = 0;
}
void
@ -134,15 +142,13 @@ DLAddHead(Dllist *l, Dlelem *e)
e->dle_list = l;
if (l->dll_head)
{
l->dll_head->dle_prev = e;
e->dle_next = l->dll_head;
}
e->dle_next = l->dll_head;
e->dle_prev = 0;
l->dll_head = e;
if (l->dll_tail == 0) /* if this is first element added */
l->dll_tail = l->dll_head;
l->dll_tail = e;
}
void
@ -151,31 +157,28 @@ DLAddTail(Dllist *l, Dlelem *e)
e->dle_list = l;
if (l->dll_tail)
{
l->dll_tail->dle_next = e;
e->dle_prev = l->dll_tail;
}
e->dle_prev = l->dll_tail;
e->dle_next = 0;
l->dll_tail = e;
if (l->dll_head == 0) /* if this is first element added */
l->dll_head = l->dll_tail;
l->dll_head = e;
}
Dlelem *
DLRemHead(Dllist *l)
{
/* remove and return the head */
Dlelem *result;
Dlelem *result = l->dll_head;
if (l->dll_head == 0)
return 0;
if (result == 0)
return result;
result = l->dll_head;
if (l->dll_head->dle_next)
l->dll_head->dle_next->dle_prev = 0;
if (result->dle_next)
result->dle_next->dle_prev = 0;
l->dll_head = l->dll_head->dle_next;
l->dll_head = result->dle_next;
result->dle_next = 0;
result->dle_list = 0;
@ -190,15 +193,15 @@ Dlelem *
DLRemTail(Dllist *l)
{
/* remove and return the tail */
Dlelem *result;
Dlelem *result = l->dll_tail;
if (l->dll_tail == 0)
return 0;
if (result == 0)
return result;
result = l->dll_tail;
if (l->dll_tail->dle_prev)
l->dll_tail->dle_prev->dle_next = 0;
l->dll_tail = l->dll_tail->dle_prev;
if (result->dle_prev)
result->dle_prev->dle_next = 0;
l->dll_tail = result->dle_prev;
result->dle_prev = 0;
result->dle_list = 0;
@ -208,3 +211,30 @@ DLRemTail(Dllist *l)
return result;
}
/* Same as DLRemove followed by DLAddHead, but faster */
void
DLMoveToFront(Dlelem *e)
{
Dllist *l = e->dle_list;
if (l->dll_head == e)
return; /* Fast path if already at front */
Assert(e->dle_prev != 0); /* since it's not the head */
e->dle_prev->dle_next = e->dle_next;
if (e->dle_next)
e->dle_next->dle_prev = e->dle_prev;
else /* must be the tail element */
{
Assert(e == l->dll_tail);
l->dll_tail = e->dle_prev;
}
l->dll_head->dle_prev = e;
e->dle_next = l->dll_head;
e->dle_prev = 0;
l->dll_head = e;
/* We need not check dll_tail, since there must have been > 1 entry */
}