/*
* __cursor_var_append_prev --
* Return the previous variable-length entry on the append list.
*/
static inline int
__cursor_var_append_prev(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_ITEM *val;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
val = &cbt->iface.value;
if (newpage) {
cbt->ins = WT_SKIP_LAST(cbt->ins_head);
goto new_page;
}
for (;;) {
WT_RET(__cursor_skip_prev(cbt));
new_page: if (cbt->ins == NULL)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, WT_INSERT_RECNO(cbt->ins));
if ((upd = __wt_txn_read(session, cbt->ins->upd)) == NULL)
continue;
if (WT_UPDATE_DELETED_ISSET(upd)) {
if (__wt_txn_visible_all(session, upd->txnid))
++cbt->page_deleted_count;
continue;
}
val->data = WT_UPDATE_DATA(upd);
val->size = upd->size;
return (0);
}
/* NOTREACHED */
}
/*
* __cursor_var_append_prev --
* Return the previous variable-length entry on the append list.
*/
static inline int
__cursor_var_append_prev(WT_CURSOR_BTREE *cbt, int newpage)
{
WT_ITEM *val;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
val = &cbt->iface.value;
if (newpage) {
cbt->ins = WT_SKIP_LAST(cbt->ins_head);
goto new_page;
}
for (;;) {
WT_RET(__cursor_skip_prev(cbt));
new_page: if (cbt->ins == NULL)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, WT_INSERT_RECNO(cbt->ins));
if ((upd = __wt_txn_read(session, cbt->ins->upd)) == NULL ||
WT_UPDATE_DELETED_ISSET(upd))
continue;
val->data = WT_UPDATE_DATA(upd);
val->size = upd->size;
break;
}
return (0);
}
/*
* __cursor_fix_append_prev --
* Return the previous fixed-length entry on the append list.
*/
static inline int
__cursor_fix_append_prev(WT_CURSOR_BTREE *cbt, int newpage)
{
WT_ITEM *val;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
val = &cbt->iface.value;
if (newpage) {
if ((cbt->ins = WT_SKIP_LAST(cbt->ins_head)) == NULL)
return (WT_NOTFOUND);
cbt->recno = WT_INSERT_RECNO(cbt->ins);
} else {
if (cbt->recno == WT_INSERT_RECNO(cbt->ins)) {
__cursor_skip_prev(cbt);
if (cbt->ins == NULL)
return (WT_NOTFOUND);
}
--cbt->recno;
}
/*
* Column store appends are inherently non-transactional.
*
* Even a non-visible update by a concurrent or aborted transaction
* changes the effective end of the data. The effect is subtle because
* of the blurring between deleted and empty values, but ideally we
* would skip all uncommitted changes at the end of the data.
*/
cbt->iface.recno = cbt->recno;
if (cbt->recno > WT_INSERT_RECNO(cbt->ins) ||
(upd = __wt_txn_read(session, cbt->ins->upd)) == NULL) {
cbt->v = 0;
val->data = &cbt->v;
} else
val->data = WT_UPDATE_DATA(upd);
val->size = 1;
return (0);
}
/*
* __cursor_row_prev --
* Move to the previous row-store item.
*/
static inline int
__cursor_row_prev(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_INSERT *ins;
WT_ITEM *key, *val;
WT_PAGE *page;
WT_ROW *rip;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
page = cbt->ref->page;
key = &cbt->iface.key;
val = &cbt->iface.value;
/*
* For row-store pages, we need a single item that tells us the part
* of the page we're walking (otherwise switching from next to prev
* and vice-versa is just too complicated), so we map the WT_ROW and
* WT_INSERT_HEAD insert array slots into a single name space: slot 1
* is the "smallest key insert list", slot 2 is WT_ROW[0], slot 3 is
* WT_INSERT_HEAD[0], and so on. This means WT_INSERT lists are
* odd-numbered slots, and WT_ROW array slots are even-numbered slots.
*
* New page configuration.
*/
if (newpage) {
/*
* If we haven't instantiated keys on this page, do so, else it
* is a very, very slow traversal.
*/
if (!F_ISSET_ATOMIC(page, WT_PAGE_BUILD_KEYS))
WT_RET(__wt_row_leaf_keys(session, page));
if (page->pg_row_entries == 0)
cbt->ins_head = WT_ROW_INSERT_SMALLEST(page);
else
cbt->ins_head =
WT_ROW_INSERT_SLOT(page, page->pg_row_entries - 1);
cbt->ins = WT_SKIP_LAST(cbt->ins_head);
cbt->row_iteration_slot = page->pg_row_entries * 2 + 1;
goto new_insert;
}
/* Move to the previous entry and return the item. */
for (;;) {
/*
* Continue traversing any insert list. Maintain the reference
* to the current insert element in case we switch to a cursor
* next movement.
*/
if (cbt->ins != NULL)
WT_RET(__cursor_skip_prev(cbt));
new_insert: if ((ins = cbt->ins) != NULL) {
if ((upd = __wt_txn_read(session, ins->upd)) == NULL)
continue;
if (WT_UPDATE_DELETED_ISSET(upd)) {
if (__wt_txn_visible_all(session, upd->txnid))
++cbt->page_deleted_count;
continue;
}
key->data = WT_INSERT_KEY(ins);
key->size = WT_INSERT_KEY_SIZE(ins);
val->data = WT_UPDATE_DATA(upd);
val->size = upd->size;
return (0);
}
/* Check for the beginning of the page. */
if (cbt->row_iteration_slot == 1)
return (WT_NOTFOUND);
--cbt->row_iteration_slot;
/*
* Odd-numbered slots configure as WT_INSERT_HEAD entries,
* even-numbered slots configure as WT_ROW entries.
*/
if (cbt->row_iteration_slot & 0x01) {
cbt->ins_head = cbt->row_iteration_slot == 1 ?
WT_ROW_INSERT_SMALLEST(page) :
WT_ROW_INSERT_SLOT(
page, cbt->row_iteration_slot / 2 - 1);
cbt->ins = WT_SKIP_LAST(cbt->ins_head);
goto new_insert;
}
cbt->ins_head = NULL;
cbt->ins = NULL;
cbt->slot = cbt->row_iteration_slot / 2 - 1;
rip = &page->pg_row_d[cbt->slot];
upd = __wt_txn_read(session, WT_ROW_UPDATE(page, rip));
if (upd != NULL && WT_UPDATE_DELETED_ISSET(upd)) {
if (__wt_txn_visible_all(session, upd->txnid))
++cbt->page_deleted_count;
continue;
}
return (__cursor_row_slot_return(cbt, rip, upd));
}
/* NOTREACHED */
}
/*
* __cursor_fix_append_prev --
* Return the previous fixed-length entry on the append list.
*/
static inline int
__cursor_fix_append_prev(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_ITEM *val;
WT_PAGE *page;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
page = cbt->ref->page;
val = &cbt->iface.value;
if (newpage) {
if ((cbt->ins = WT_SKIP_LAST(cbt->ins_head)) == NULL)
return (WT_NOTFOUND);
} else {
/*
* Handle the special case of leading implicit records, that is,
* there aren't any records in the tree not on the append list,
* and the first record on the append list isn't record 1.
*
* The "right" place to handle this is probably in our caller.
* The high-level cursor-previous routine would:
* -- call this routine to walk the append list
* -- call the routine to walk the standard page items
* -- call the tree walk routine looking for a previous page
* Each of them returns WT_NOTFOUND, at which point our caller
* checks the cursor record number, and if it's larger than 1,
* returns the implicit records. Instead, I'm trying to detect
* the case here, mostly because I don't want to put that code
* into our caller. Anyway, if this code breaks for any reason,
* that's the way I'd go.
*
* If we're not pointing to a WT_INSERT entry, or we can't find
* a WT_INSERT record that precedes our record name-space, check
* if there are any records on the page. If there aren't, then
* we're in the magic zone, keep going until we get to a record
* number of 1.
*/
if (cbt->ins != NULL &&
cbt->recno <= WT_INSERT_RECNO(cbt->ins))
WT_RET(__cursor_skip_prev(cbt));
if (cbt->ins == NULL &&
(cbt->recno == 1 || __col_fix_last_recno(page) != 0))
return (WT_NOTFOUND);
}
/*
* This code looks different from the cursor-next code. The append
* list appears on the last page of the tree and contains the last
* records in the tree. If we're iterating through the tree, starting
* at the last record in the tree, by definition we're starting a new
* iteration and we set the record number to the last record found in
* the tree. Otherwise, decrement the record.
*/
if (newpage)
__cursor_set_recno(cbt, WT_INSERT_RECNO(cbt->ins));
else
__cursor_set_recno(cbt, cbt->recno - 1);
/*
* Fixed-width column store appends are inherently non-transactional.
* Even a non-visible update by a concurrent or aborted transaction
* changes the effective end of the data. The effect is subtle because
* of the blurring between deleted and empty values, but ideally we
* would skip all uncommitted changes at the end of the data. This
* doesn't apply to variable-width column stores because the implicitly
* created records written by reconciliation are deleted and so can be
* never seen by a read.
*/
if (cbt->ins == NULL ||
cbt->recno > WT_INSERT_RECNO(cbt->ins) ||
(upd = __wt_txn_read(session, cbt->ins->upd)) == NULL) {
cbt->v = 0;
val->data = &cbt->v;
} else
val->data = WT_UPDATE_DATA(upd);
val->size = 1;
return (0);
}
/*
* __cursor_fix_append_prev --
* Return the previous fixed-length entry on the append list.
*/
static inline int
__cursor_fix_append_prev(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
if (newpage) {
if ((cbt->ins = WT_SKIP_LAST(cbt->ins_head)) == NULL)
return (WT_NOTFOUND);
} else {
/* Move to the previous record in the append list, if any. */
if (cbt->ins != NULL &&
cbt->recno <= WT_INSERT_RECNO(cbt->ins))
WT_RET(__cursor_skip_prev(cbt));
/*
* Handle the special case of leading implicit records, that is,
* there aren't any records in the page not on the append list,
* and the append list's first record isn't the first record on
* the page. (Although implemented as a test of the page values,
* this is really a test for a tree where the first inserted
* record wasn't record 1, any other page with only an append
* list will have a first page record number matching the first
* record in the append list.)
*
* The "right" place to handle this is probably in our caller.
* The high-level cursor-previous routine would:
* -- call this routine to walk the append list
* -- call the routine to walk the standard page items
* -- call the tree walk routine looking for a previous page
* Each of them returns WT_NOTFOUND, at which point our caller
* checks the cursor record number, and if it's larger than 1,
* returns the implicit records. Instead, I'm trying to detect
* the case here, mostly because I don't want to put that code
* into our caller. Anyway, if this code breaks for any reason,
* that's the way I'd go.
*
* If we're not pointing to a WT_INSERT entry (we didn't find a
* WT_INSERT record preceding our record name-space), check if
* we've reached the beginning of this page, a possibility if a
* page had a large number of items appended, and then split.
* If not, check if there are any records on the page. If there
* aren't, then we're in the magic zone, keep going until we get
* to a record number matching the first record on the page.
*/
if (cbt->ins == NULL &&
(cbt->recno == cbt->ref->ref_recno ||
__col_fix_last_recno(cbt->ref) != 0))
return (WT_NOTFOUND);
}
/*
* This code looks different from the cursor-next code. The append list
* may be preceded by other rows. If we're iterating through the tree,
* starting at the last record in the tree, by definition we're starting
* a new iteration and we set the record number to the last record found
* on the page. Otherwise, decrement the record.
*/
if (newpage)
__cursor_set_recno(cbt, WT_INSERT_RECNO(cbt->ins));
else
__cursor_set_recno(cbt, cbt->recno - 1);
/*
* Fixed-width column store appends are inherently non-transactional.
* Even a non-visible update by a concurrent or aborted transaction
* changes the effective end of the data. The effect is subtle because
* of the blurring between deleted and empty values, but ideally we
* would skip all uncommitted changes at the end of the data. This
* doesn't apply to variable-width column stores because the implicitly
* created records written by reconciliation are deleted and so can be
* never seen by a read.
*/
if (cbt->ins == NULL ||
cbt->recno > WT_INSERT_RECNO(cbt->ins) ||
(upd = __wt_txn_read(session, cbt->ins->upd)) == NULL) {
cbt->v = 0;
cbt->iface.value.data = &cbt->v;
} else
cbt->iface.value.data = upd->data;
cbt->iface.value.size = 1;
return (0);
}
