/*
* __bt_search --
* Search a btree for a key.
*
* Parameters:
* t: tree to search
* key: key to find
* exactp: pointer to exact match flag
*
* Returns:
* The EPG for matching record, if any, or the EPG for the location
* of the key, if it were inserted into the tree, is entered into
* the bt_cur field of the tree. A pointer to the field is returned.
*/
EPG *
__bt_search(BTREE *t, const DBT *key, int *exactp)
{
PAGE *h;
indx_t base, idx, lim;
pgno_t pg;
int cmp;
BT_CLR(t);
for (pg = P_ROOT;;) {
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (NULL);
/* Do a binary search on the current page. */
t->bt_cur.page = h;
for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
t->bt_cur.index = idx = base + (lim >> 1);
if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
if (h->flags & P_BLEAF) {
*exactp = 1;
return (&t->bt_cur);
}
goto next;
}
if (cmp > 0) {
base = idx + 1;
--lim;
}
}
/*
* If it's a leaf page, we're almost done. If no duplicates
* are allowed, or we have an exact match, we're done. Else,
* it's possible that there were matching keys on this page,
* which later deleted, and we're on a page with no matches
* while there are matches on other pages. If at the start or
* end of a page, check the adjacent page.
*/
if (h->flags & P_BLEAF) {
if (!F_ISSET(t, B_NODUPS)) {
if (base == 0 &&
h->prevpg != P_INVALID &&
__bt_sprev(t, h, key, exactp))
return (&t->bt_cur);
if (base == NEXTINDEX(h) &&
h->nextpg != P_INVALID &&
__bt_snext(t, h, key, exactp))
return (&t->bt_cur);
}
*exactp = 0;
t->bt_cur.index = base;
return (&t->bt_cur);
}
/*
* No match found. Base is the smallest index greater than
* key and may be zero or a last + 1 index. If it's non-zero,
* decrement by one, and record the internal page which should
* be a parent page for the key. If a split later occurs, the
* inserted page will be to the right of the saved page.
*/
idx = base ? base - 1 : base;
next: BT_PUSH(t, h->pgno, idx);
pg = GETBINTERNAL(h, idx)->pgno;
mpool_put(t->bt_mp, h, 0);
}
}
/*
* __bt_search --
* Search a btree for a key.
*
* Parameters:
* t: tree to search
* key: key to find
* exactp: pointer to exact match flag
*
* Returns:
* The EPG for matching record, if any, or the EPG for the location
* of the key, if it were inserted into the tree, is entered into
* the bt_cur field of the tree. A pointer to the field is returned.
*/
EPG *
__bt_search_st(BTREE *t,const DBT *key,int *exactp)
{
/*
* 1.Read from root of the btree in NTT
* 2.reconstruct the node
*/
PAGE *h=NULL; /* h is a logical B-Tree node, either a disk mode node or a virtual node in memory construct by log */
indx_t base, index, lim;
pgno_t pg; //node id of the page
int cmp;
BT_CLR(t); /* @mx it initializes t->bt_sp */
err_debug(("Searh Btree"));
for (pg = P_ROOT;;) {
err_debug(("~^"));
err_debug(("Read Node %ud",pg));
h = read_node(t,pg);
//__bt_dpage(h);
err_debug(("~$End Read"));
if(h==NULL)
return (NULL);
/* ??? not so clear about the binary search */
/* Do a binary search on the current page. */
t->bt_cur.page = h;
for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
t->bt_cur.index = index = base + (lim >> 1);
if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
if (h->flags & P_BLEAF) {
*exactp = 1;
err_debug(("End Search"));
return (&t->bt_cur);
}
goto next;
}
if (cmp > 0) {
base = index + 1;
--lim;
}
}
/*
* If it's a leaf page, we're almost done. If no duplicates
* are allowed, or we have an exact match, we're done. Else,
* it's possible that there were matching keys on this page,
* which later deleted, and we're on a page with no matches
* while there are matches on other pages. If at the start or
* end of a page, check the adjacent page.
*
* TODO: what about this condition for log mode ?
*/
if (h->flags & P_BLEAF) {
#if 0
if (!F_ISSET(t, B_NODUPS)) {
if (base == 0 &&
h->prevpg != P_INVALID &&
__bt_sprev(t, h, key, exactp))
err_debug(("End Search"));
return (&t->bt_cur);
if (base == NEXTINDEX(h) &&
h->nextpg != P_INVALID &&
__bt_snext(t, h, key, exactp))
err_debug(("End Search\n"));
return (&t->bt_cur);
}
#endif
*exactp = 0;
t->bt_cur.index = base;
err_debug(("End Search"));
return (&t->bt_cur);
}
/*
* No match found. Base is the smallest index greater than
* key and may be zero or a last + 1 index. If it's non-zero,
* decrement by one, and record the internal page which should
* be a parent page for the key. If a split later occurs, the
* inserted page will be to the right of the saved page.
*/
index = base ? base - 1 : base;
next: BT_PUSH(t, pg, index);
pg = GETBINTERNAL(h, index)->pgno;
Mpool_put(t->bt_mp, h, 0);
}
}
