/*
* __REC_SEARCH -- Search a btree for a key.
*
* Parameters:
* t: tree to search
* recno: key to find
* op: search operation
*
* Returns:
* EPG for matching record, if any, or the EPG for the location of the
* key, if it were inserted into the tree.
*
* 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 *
__rec_search(BTREE *t, recno_t recno, enum SRCHOP op)
{
indx_t idx;
PAGE *h;
EPGNO *parent;
RINTERNAL *r;
pgno_t pg;
indx_t top;
recno_t total;
int sverrno;
BT_CLR(t);
for (pg = P_ROOT, total = 0;;) {
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
goto err;
if (h->flags & P_RLEAF) {
t->bt_cur.page = h;
t->bt_cur.index = recno - total;
return (&t->bt_cur);
}
for (idx = 0, top = NEXTINDEX(h);;) {
r = GETRINTERNAL(h, idx);
if (++idx == top || total + r->nrecs > recno)
break;
total += r->nrecs;
}
BT_PUSH(t, pg, idx - 1);
pg = r->pgno;
switch (op) {
case SDELETE:
--GETRINTERNAL(h, (idx - 1))->nrecs;
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
break;
case SINSERT:
++GETRINTERNAL(h, (idx - 1))->nrecs;
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
break;
case SEARCH:
mpool_put(t->bt_mp, h, 0);
break;
}
}
/* Try and recover the tree. */
err: sverrno = errno;
if (op != SEARCH)
while ((parent = BT_POP(t)) != NULL) {
if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
break;
if (op == SINSERT)
--GETRINTERNAL(h, parent->index)->nrecs;
else
++GETRINTERNAL(h, parent->index)->nrecs;
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
}
errno = sverrno;
return (NULL);
}
/*
* __bt_stkacq --
* Acquire a stack so we can delete a cursor entry.
*
* Parameters:
* t: tree
* hp: pointer to current, pinned PAGE pointer
* c: pointer to the cursor
*
* Returns:
* 0 on success, 1 on failure
*/
static int
__bt_stkacq(BTREE *t, PAGE **hp, CURSOR *c)
{
BINTERNAL *bi;
EPG *e;
EPGNO *parent;
PAGE *h;
indx_t idx;
pgno_t pgno;
recno_t nextpg, prevpg;
int exact, level;
/*
* Find the first occurrence of the key in the tree. Toss the
* currently locked page so we don't hit an already-locked page.
*/
h = *hp;
mpool_put(t->bt_mp, h, 0);
if ((e = __bt_search(t, &c->key, &exact)) == NULL)
return (1);
h = e->page;
/* See if we got it in one shot. */
if (h->pgno == c->pg.pgno)
goto ret;
/*
* Move right, looking for the page. At each move we have to move
* up the stack until we don't have to move to the next page. If
* we have to change pages at an internal level, we have to fix the
* stack back up.
*/
while (h->pgno != c->pg.pgno) {
if ((nextpg = h->nextpg) == P_INVALID)
break;
mpool_put(t->bt_mp, h, 0);
/* Move up the stack. */
for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
/* Get the parent page. */
if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
return (1);
/* Move to the next index. */
if (parent->index != NEXTINDEX(h) - 1) {
idx = parent->index + 1;
BT_PUSH(t, h->pgno, idx);
break;
}
mpool_put(t->bt_mp, h, 0);
}
/* Restore the stack. */
while (level--) {
/* Push the next level down onto the stack. */
bi = GETBINTERNAL(h, idx);
pgno = bi->pgno;
BT_PUSH(t, pgno, 0);
/* Lose the currently pinned page. */
mpool_put(t->bt_mp, h, 0);
/* Get the next level down. */
if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
return (1);
idx = 0;
}
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, nextpg, 0)) == NULL)
return (1);
}
if (h->pgno == c->pg.pgno)
goto ret;
/* Reacquire the original stack. */
mpool_put(t->bt_mp, h, 0);
if ((e = __bt_search(t, &c->key, &exact)) == NULL)
return (1);
h = e->page;
/*
* Move left, looking for the page. At each move we have to move
* up the stack until we don't have to change pages to move to the
* next page. If we have to change pages at an internal level, we
* have to fix the stack back up.
*/
while (h->pgno != c->pg.pgno) {
if ((prevpg = h->prevpg) == P_INVALID)
break;
mpool_put(t->bt_mp, h, 0);
/* Move up the stack. */
for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
/* Get the parent page. */
if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
return (1);
/* Move to the next index. */
if (parent->index != 0) {
idx = parent->index - 1;
BT_PUSH(t, h->pgno, idx);
break;
}
mpool_put(t->bt_mp, h, 0);
}
/* Restore the stack. */
while (level--) {
/* Push the next level down onto the stack. */
bi = GETBINTERNAL(h, idx);
pgno = bi->pgno;
/* Lose the currently pinned page. */
mpool_put(t->bt_mp, h, 0);
/* Get the next level down. */
if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
return (1);
idx = NEXTINDEX(h) - 1;
BT_PUSH(t, pgno, idx);
}
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, prevpg, 0)) == NULL)
return (1);
}
ret: mpool_put(t->bt_mp, h, 0);
return ((*hp = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL);
}
/*
* __bt_pdelete --
* Delete a single page from the tree.
*
* Parameters:
* t: tree
* h: leaf page
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side-effects:
* mpool_put's the page
*/
static int
__bt_pdelete(BTREE *t, PAGE *h)
{
BINTERNAL *bi;
PAGE *pg;
EPGNO *parent;
indx_t cnt, idx, *ip, offset;
u_int32_t nksize;
char *from;
/*
* Walk the parent page stack -- a LIFO stack of the pages that were
* traversed when we searched for the page where the delete occurred.
* Each stack entry is a page number and a page index offset. The
* offset is for the page traversed on the search. We've just deleted
* a page, so we have to delete the key from the parent page.
*
* If the delete from the parent page makes it empty, this process may
* continue all the way up the tree. We stop if we reach the root page
* (which is never deleted, it's just not worth the effort) or if the
* delete does not empty the page.
*/
while ((parent = BT_POP(t)) != NULL) {
/* Get the parent page. */
if ((pg = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
return (RET_ERROR);
idx = parent->index;
bi = GETBINTERNAL(pg, idx);
/* Free any overflow pages. */
if (bi->flags & P_BIGKEY &&
__ovfl_delete(t, bi->bytes) == RET_ERROR) {
mpool_put(t->bt_mp, pg, 0);
return (RET_ERROR);
}
/*
* Free the parent if it has only the one key and it's not the
* root page. If it's the rootpage, turn it back into an empty
* leaf page.
*/
if (NEXTINDEX(pg) == 1) {
if (pg->pgno == P_ROOT) {
pg->lower = BTDATAOFF;
pg->upper = t->bt_psize;
pg->flags = P_BLEAF;
} else {
if (__bt_relink(t, pg) || __bt_free(t, pg))
return (RET_ERROR);
continue;
}
} else {
/* Pack remaining key items at the end of the page. */
nksize = NBINTERNAL(bi->ksize);
from = (char *)pg + pg->upper;
memmove(from + nksize, from, (char *)bi - from);
pg->upper += nksize;
/* Adjust indices' offsets, shift the indices down. */
offset = pg->linp[idx];
for (cnt = idx, ip = &pg->linp[0]; cnt--; ++ip)
if (ip[0] < offset)
ip[0] += nksize;
for (cnt = NEXTINDEX(pg) - idx; --cnt; ++ip)
ip[0] = ip[1] < offset ? ip[1] + nksize : ip[1];
pg->lower -= sizeof(indx_t);
}
mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
break;
}
/* Free the leaf page, as long as it wasn't the root. */
if (h->pgno == P_ROOT) {
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
return (RET_SUCCESS);
}
return (__bt_relink(t, h) || __bt_free(t, h));
}
/*
* __BT_SPLIT -- Split the tree.
*
* Parameters:
* t: tree
* sp: page to split
* key: key to insert
* data: data to insert
* flags: BIGKEY/BIGDATA flags
* ilen: insert length
* skip: index to leave open
*
* Returns:
* RET_ERROR, RET_SUCCESS
*/
int
__bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags,
size_t ilen, u_int32_t argskip)
{
BINTERNAL *bi;
BLEAF *bl, *tbl;
DBT a, b;
EPGNO *parent;
PAGE *h, *l, *r, *lchild, *rchild;
indx_t nxtindex;
u_int16_t skip;
u_int32_t n, nbytes, nksize;
int parentsplit;
char *dest;
/*
* Split the page into two pages, l and r. The split routines return
* a pointer to the page into which the key should be inserted and with
* skip set to the offset which should be used. Additionally, l and r
* are pinned.
*/
skip = argskip;
h = sp->pgno == P_ROOT ?
bt_root(t, sp, &l, &r, &skip, ilen) :
bt_page(t, sp, &l, &r, &skip, ilen);
if (h == NULL)
return (RET_ERROR);
/*
* Insert the new key/data pair into the leaf page. (Key inserts
* always cause a leaf page to split first.)
*/
h->linp[skip] = h->upper -= ilen;
dest = (char *)h + h->upper;
if (F_ISSET(t, R_RECNO))
WR_RLEAF(dest, data, flags)
else
WR_BLEAF(dest, key, data, flags)
/* If the root page was split, make it look right. */
if (sp->pgno == P_ROOT &&
(F_ISSET(t, R_RECNO) ?
bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
goto err2;
/*
* Now we walk the parent page stack -- a LIFO stack of the pages that
* were traversed when we searched for the page that split. Each stack
* entry is a page number and a page index offset. The offset is for
* the page traversed on the search. We've just split a page, so we
* have to insert a new key into the parent page.
*
* If the insert into the parent page causes it to split, may have to
* continue splitting all the way up the tree. We stop if the root
* splits or the page inserted into didn't have to split to hold the
* new key. Some algorithms replace the key for the old page as well
* as the new page. We don't, as there's no reason to believe that the
* first key on the old page is any better than the key we have, and,
* in the case of a key being placed at index 0 causing the split, the
* key is unavailable.
*
* There are a maximum of 5 pages pinned at any time. We keep the left
* and right pages pinned while working on the parent. The 5 are the
* two children, left parent and right parent (when the parent splits)
* and the root page or the overflow key page when calling bt_preserve.
* This code must make sure that all pins are released other than the
* root page or overflow page which is unlocked elsewhere.
*/
while ((parent = BT_POP(t)) != NULL) {
lchild = l;
rchild = r;
/* Get the parent page. */
if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
goto err2;
/*
* The new key goes ONE AFTER the index, because the split
* was to the right.
*/
skip = parent->index + 1;
/*
* Calculate the space needed on the parent page.
*
* Prefix trees: space hack when inserting into BINTERNAL
* pages. Retain only what's needed to distinguish between
* the new entry and the LAST entry on the page to its left.
* If the keys compare equal, retain the entire key. Note,
* we don't touch overflow keys, and the entire key must be
* retained for the next-to-left most key on the leftmost
* page of each level, or the search will fail. Applicable
* ONLY to internal pages that have leaf pages as children.
* Further reduction of the key between pairs of internal
* pages loses too much information.
*/
switch (rchild->flags & P_TYPE) {
case P_BINTERNAL:
bi = GETBINTERNAL(rchild, 0);
nbytes = NBINTERNAL(bi->ksize);
break;
case P_BLEAF:
bl = GETBLEAF(rchild, 0);
nbytes = NBINTERNAL(bl->ksize);
if (t->bt_pfx && !(bl->flags & P_BIGKEY) &&
(h->prevpg != P_INVALID || skip > 1)) {
tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1);
a.size = tbl->ksize;
a.data = tbl->bytes;
b.size = bl->ksize;
b.data = bl->bytes;
nksize = t->bt_pfx(&a, &b);
n = NBINTERNAL(nksize);
if (n < nbytes) {
#ifdef STATISTICS
bt_pfxsaved += nbytes - n;
#endif
nbytes = n;
} else
nksize = 0;
} else
nksize = 0;
break;
case P_RINTERNAL:
case P_RLEAF:
nbytes = NRINTERNAL;
break;
default:
abort();
}
/* Split the parent page if necessary or shift the indices. */
if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t)) {
sp = h;
h = h->pgno == P_ROOT ?
bt_root(t, h, &l, &r, &skip, nbytes) :
bt_page(t, h, &l, &r, &skip, nbytes);
if (h == NULL)
goto err1;
parentsplit = 1;
} else {
if (skip < (nxtindex = NEXTINDEX(h)))
memmove(h->linp + skip + 1, h->linp + skip,
(nxtindex - skip) * sizeof(indx_t));
h->lower += sizeof(indx_t);
parentsplit = 0;
}
/* Insert the key into the parent page. */
switch (rchild->flags & P_TYPE) {
case P_BINTERNAL:
h->linp[skip] = h->upper -= nbytes;
dest = (char *)h + h->linp[skip];
memmove(dest, bi, nbytes);
((BINTERNAL *)dest)->pgno = rchild->pgno;
break;
case P_BLEAF:
h->linp[skip] = h->upper -= nbytes;
dest = (char *)h + h->linp[skip];
WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
rchild->pgno, bl->flags & P_BIGKEY);
memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
if (bl->flags & P_BIGKEY) {
pgno_t pgno;
memcpy(&pgno, bl->bytes, sizeof(pgno));
if (bt_preserve(t, pgno) == RET_ERROR)
goto err1;
}
break;
case P_RINTERNAL:
/*
* Update the left page count. If split
* added at index 0, fix the correct page.
*/
if (skip > 0)
dest = (char *)h + h->linp[skip - 1];
else
dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
((RINTERNAL *)dest)->nrecs = rec_total(lchild);
((RINTERNAL *)dest)->pgno = lchild->pgno;
/* Update the right page count. */
h->linp[skip] = h->upper -= nbytes;
dest = (char *)h + h->linp[skip];
((RINTERNAL *)dest)->nrecs = rec_total(rchild);
((RINTERNAL *)dest)->pgno = rchild->pgno;
break;
case P_RLEAF:
/*
* Update the left page count. If split
* added at index 0, fix the correct page.
*/
if (skip > 0)
dest = (char *)h + h->linp[skip - 1];
else
dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild);
((RINTERNAL *)dest)->pgno = lchild->pgno;
/* Update the right page count. */
h->linp[skip] = h->upper -= nbytes;
dest = (char *)h + h->linp[skip];
((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild);
((RINTERNAL *)dest)->pgno = rchild->pgno;
break;
default:
abort();
}
/* Unpin the held pages. */
if (!parentsplit) {
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
break;
}
/* If the root page was split, make it look right. */
if (sp->pgno == P_ROOT &&
(F_ISSET(t, R_RECNO) ?
bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
goto err1;
mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
}
/* Unpin the held pages. */
mpool_put(t->bt_mp, l, MPOOL_DIRTY);
mpool_put(t->bt_mp, r, MPOOL_DIRTY);
/* Clear any pages left on the stack. */
return (RET_SUCCESS);
/*
* If something fails in the above loop we were already walking back
* up the tree and the tree is now inconsistent. Nothing much we can
* do about it but release any memory we're holding.
*/
err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
err2: mpool_put(t->bt_mp, l, 0);
mpool_put(t->bt_mp, r, 0);
__dbpanic(t->bt_dbp);
return (RET_ERROR);
}