/*btree cursor移向下一个记录，仅仅在append list上移动*/
static inline int __cursor_fix_append_next(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;
/*新载入的page,判断ins_head是否为空，如果为空表示没有append的记录*/
if (newpage){
if ((cbt->ins = WT_SKIP_FIRST(cbt->ins_head)) == NULL)
return (WT_NOTFOUND);
}
else{
/*已经到append list的最后一条记录了，后面没有记录*/
if (cbt->recno >= WT_INSERT_RECNO(cbt->ins) && (cbt->ins = WT_SKIP_NEXT(cbt->ins)) == NULL)
return (WT_NOTFOUND);
}
/*
* This code looks different from the cursor-previous code. The append
* list appears on the last page of the tree, but it may be preceded by
* other rows, which means the cursor's recno will be set to a value and
* we simply want to increment it. If the cursor's recno is NOT set,
* we're starting our iteration in a tree that has only appended items.
* In that case, recno will be 0 and happily enough the increment will
* set it to 1, which is correct.
*/
__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.
*
* The problem is that we don't know at this point whether there may be
* multiple uncommitted changes at the end of the data, and it would be
* expensive to check every time we hit an aborted update. If an
* insert is aborted, we simply return zero (empty), regardless of
* whether we are at the end of the data.
*/
if (cbt->recno < WT_INSERT_RECNO(cbt->ins) || (upd = __wt_txn_read(session, cbt->ins->upd)) == NULL){ /*没有可见的记录值，直接返回0*/
cbt->v = 0;
val->data = &cbt->v;
}
else
val->data = WT_UPDATE_DATA(upd);
val->size = 1;
return 0;
}
/*
* __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_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_next --
* Return the next variable-length entry on the append list.
*/
static inline int
__cursor_var_append_next(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
if (newpage) {
cbt->ins = WT_SKIP_FIRST(cbt->ins_head);
goto new_page;
}
for (;;) {
cbt->ins = WT_SKIP_NEXT(cbt->ins);
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 (upd->type == WT_UPDATE_DELETED) {
if (__wt_txn_upd_visible_all(session, upd))
++cbt->page_deleted_count;
continue;
}
return (__wt_value_return(session, cbt, 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, 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_fix_prev --
* Move to the previous, fixed-length column-store item.
*/
static inline int
__cursor_fix_prev(WT_CURSOR_BTREE *cbt, int newpage)
{
WT_BTREE *btree;
WT_ITEM *val;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
btree = session->btree;
val = &cbt->iface.value;
/* Initialize for each new page. */
if (newpage) {
cbt->last_standard_recno = __col_last_recno(cbt->page);
if (cbt->last_standard_recno == 0)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->last_standard_recno);
goto new_page;
}
/* Move to the previous entry and return the item. */
for (;;) {
if (cbt->recno == cbt->page->u.col_fix.recno)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->recno - 1);
new_page: /* Check any insert list for a matching record. */
cbt->ins_head = WT_COL_UPDATE_SINGLE(cbt->page);
cbt->ins = __col_insert_search(
cbt->ins_head, cbt->ins_stack, cbt->next_stack, cbt->recno);
if (cbt->ins != NULL &&
cbt->recno != WT_INSERT_RECNO(cbt->ins))
cbt->ins = NULL;
upd = cbt->ins == NULL ?
NULL : __wt_txn_read(session, cbt->ins->upd);
if (upd != NULL) {
val->data = WT_UPDATE_DATA(upd);
val->size = 1;
return (0);
}
cbt->v = __bit_getv_recno(cbt->page, cbt->recno, btree->bitcnt);
val->data = &cbt->v;
val->size = 1;
return (0);
}
/* NOTREACHED */
}
/*btree cursor移向下一个记录(fix col方式存储)，在btree树空间上移动*/
static inline int __cursor_fix_next(WT_CURSOR_BTREE* cbt, int newpage)
{
WT_BTREE *btree;
WT_ITEM *val;
WT_PAGE *page;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
btree = S2BT(session);
page = cbt->ref->page;
val = &cbt->iface.value;
/*切换到新的page上做next操作*/
if (newpage){
cbt->last_standard_recno = __col_fix_last_recno(page);
if (cbt->last_standard_recno == 0)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, page->pg_fix_recno);
goto new_page;
}
/*记录序号超出最后一个序号，到末尾了*/
if (cbt->recno >= cbt->last_standard_recno)
return WT_NOTFOUND;
__cursor_set_recno(cbt, cbt->recno + 1);
new_page:
/*获得第一个修改列表*/
cbt->ins_head = WT_COL_UPDATE_SINGLE(page);
/*定位recno所在的修改条目*/
cbt->ins = __col_insert_search(cbt->ins_head, cbt->ins_stack, cbt->next_stack, cbt->recno);
if (cbt->ins != NULL && cbt->recno != WT_INSERT_RECNO(cbt->ins)) /*不正确的修改定位，将ins设置为NULL表示定位失败*/
cbt->ins = NULL;
/*做事务隔离读取记录版本*/
upd = cbt->ins == NULL ? NULL : __wt_txn_read(session, cbt->ins->upd);
if (upd == NULL){
cbt->v = __bit_getv_recno(page, cbt->recno, btree->bitcnt); /*V赋值*/
val->data = &cbt->v;
}
else
val->data = WT_UPDATE_DATA(upd);
val->size = 1;
return 0;
}
/*
* __txn_op_log --
* Log an operation for the current transaction.
*/
static int
__txn_op_log(WT_SESSION_IMPL *session,
WT_ITEM *logrec, WT_TXN_OP *op, WT_CURSOR_BTREE *cbt)
{
WT_DECL_RET;
WT_ITEM key, value;
WT_UPDATE *upd;
uint64_t recno;
WT_CLEAR(key);
upd = op->u.upd;
value.data = WT_UPDATE_DATA(upd);
value.size = upd->size;
/*
* Log the operation. It must be one of the following:
* 1) column store remove;
* 2) column store insert/update;
* 3) row store remove; or
* 4) row store insert/update.
*/
if (cbt->btree->type == BTREE_ROW) {
WT_ERR(__wt_cursor_row_leaf_key(cbt, &key));
if (WT_UPDATE_DELETED_ISSET(upd))
WT_ERR(__wt_logop_row_remove_pack(session, logrec,
op->fileid, &key));
else
WT_ERR(__wt_logop_row_put_pack(session, logrec,
op->fileid, &key, &value));
} else {
recno = WT_INSERT_RECNO(cbt->ins);
WT_ASSERT(session, recno != WT_RECNO_OOB);
if (WT_UPDATE_DELETED_ISSET(upd))
WT_ERR(__wt_logop_col_remove_pack(session, logrec,
op->fileid, recno));
else
WT_ERR(__wt_logop_col_put_pack(session, logrec,
op->fileid, recno, &value));
}
err: __wt_buf_free(session, &key);
return (ret);
}
/*
* __cursor_fix_next --
* Move to the next, fixed-length column-store item.
*/
static inline int
__cursor_fix_next(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_BTREE *btree;
WT_PAGE *page;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
session = (WT_SESSION_IMPL *)cbt->iface.session;
btree = S2BT(session);
page = cbt->ref->page;
/* Initialize for each new page. */
if (newpage) {
cbt->last_standard_recno = __col_fix_last_recno(cbt->ref);
if (cbt->last_standard_recno == 0)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->ref->ref_recno);
goto new_page;
}
/* Move to the next entry and return the item. */
if (cbt->recno >= cbt->last_standard_recno)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->recno + 1);
new_page:
/* Check any insert list for a matching record. */
cbt->ins_head = WT_COL_UPDATE_SINGLE(page);
cbt->ins = __col_insert_search(
cbt->ins_head, cbt->ins_stack, cbt->next_stack, cbt->recno);
if (cbt->ins != NULL && cbt->recno != WT_INSERT_RECNO(cbt->ins))
cbt->ins = NULL;
upd = cbt->ins == NULL ? NULL : __wt_txn_read(session, cbt->ins->upd);
if (upd == NULL) {
cbt->v = __bit_getv_recno(cbt->ref, cbt->recno, btree->bitcnt);
cbt->iface.value.data = &cbt->v;
} else
cbt->iface.value.data = upd->data;
cbt->iface.value.size = 1;
return (0);
}
/*
* __col_insert_alloc --
* Column-store insert: allocate a WT_INSERT structure and fill it in.
*/
static int
__col_insert_alloc(WT_SESSION_IMPL *session,
uint64_t recno, u_int skipdepth, WT_INSERT **insp, size_t *ins_sizep)
{
WT_INSERT *ins;
size_t ins_size;
/*
* Allocate the WT_INSERT structure and skiplist pointers, then copy
* the record number into place.
*/
ins_size = sizeof(WT_INSERT) + skipdepth * sizeof(WT_INSERT *);
WT_RET(__wt_calloc(session, 1, ins_size, &ins));
WT_INSERT_RECNO(ins) = recno;
*insp = ins;
*ins_sizep = ins_size;
return (0);
}
/*在append list上移动variable-length类型的btree cursor*/
static inline int __cursor_var_append_next(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_FIRST(cbt->ins_head);
goto new_page;
}
for (;;){
cbt->ins = WT_SKIP_NEXT(cbt->ins);
new_page:
if (cbt->ins == NULL)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, WT_INSERT_RECNO(cbt->ins));
/*事务隔离读，对本事务不可见，继续向前*/
if ((upd = __wt_txn_read(session, cbt->ins->upd)) == NULL)
continue;
/*删除集合，不做指向这条记录，继续向下移动*/
if (WT_UPDATE_DELETED_ISSET(upd)) {
++cbt->page_deleted_count;
continue;
}
/*赋值value*/
val->data = WT_UPDATE_DATA(upd);
val->size = upd->size;
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_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);
}
/*移向下条variable-length column-store 记录*/
static inline int __cursor_var_next(WT_CURSOR_BTREE* cbt, int newpage)
{
WT_CELL *cell;
WT_CELL_UNPACK unpack;
WT_COL *cip;
WT_ITEM *val;
WT_INSERT *ins;
WT_PAGE *page;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
uint64_t rle, rle_start;
session = (WT_SESSION_IMPL *)cbt->iface.session;
page = cbt->ref->page;
val = &cbt->iface.value;
rle_start = 0; /* -Werror=maybe-uninitialized */
if (newpage){
cbt->last_standard_recno = __col_var_last_recno(page);
if (cbt->last_standard_recno == 0)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, page->pg_var_recno);
goto new_page;
}
for (;;){
if (cbt->recno >= cbt->last_standard_recno)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->recno + 1);
new_page:
/*定位到recno对应的WT_COL slot*/
if ((cip = __col_var_search(page, cbt->recno, &rle_start)) == NULL)
return (WT_NOTFOUND);
cbt->slot = WT_COL_SLOT(page, cip);
/*读取内容值*/
cbt->ins_head = WT_COL_UPDATE_SLOT(page, cbt->slot);
cbt->ins = __col_insert_search_match(cbt->ins_head, cbt->recno);
upd = cbt->ins == NULL ? NULL : __wt_txn_read(session, cbt->ins->upd);
if (upd != NULL) {
if (WT_UPDATE_DELETED_ISSET(upd)) {
++cbt->page_deleted_count;
continue;
}
val->data = WT_UPDATE_DATA(upd);
val->size = upd->size;
return (0);
}
/*
* If we're at the same slot as the last reference and there's
* no matching insert list item, re-use the return information
* (so encoded items with large repeat counts aren't repeatedly
* decoded). Otherwise, unpack the cell and build the return
* information.
* upd == NULL, 记录可能被删除放入到了insert列表中，slot可能被重用了，那么需要进行cell unpack取值
*/
if (cbt->cip_saved != cip) {
if ((cell = WT_COL_PTR(page, cip)) == NULL)
continue;
__wt_cell_unpack(cell, &unpack);
if (unpack.type == WT_CELL_DEL) {
if ((rle = __wt_cell_rle(&unpack)) == 1)
continue;
/*定位到修改列表中的记录*/
ins = __col_insert_search_gt(cbt->ins_head, cbt->recno);
cbt->recno = rle_start + rle;
if (ins != NULL && WT_INSERT_RECNO(ins) < cbt->recno)
cbt->recno = WT_INSERT_RECNO(ins);
/* Adjust for the outer loop increment. */
--cbt->recno;
continue;
}
/*取出cell中的值到tmp中*/
WT_RET(__wt_page_cell_data_ref(session, page, &unpack, &cbt->tmp));
cbt->cip_saved = cip;
}
val->data = cbt->tmp.data;
val->size = cbt->tmp.size;
return 0;
}
}
/*
* __wt_col_modify --
* Column-store delete, insert, and update.
*/
int
__wt_col_modify(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt,
uint64_t recno, const WT_ITEM *value,
WT_UPDATE *upd_arg, u_int modify_type, bool exclusive)
{
static const WT_ITEM col_fix_remove = { "", 1, NULL, 0, 0 };
WT_BTREE *btree;
WT_DECL_RET;
WT_INSERT *ins;
WT_INSERT_HEAD *ins_head, **ins_headp;
WT_PAGE *page;
WT_PAGE_MODIFY *mod;
WT_UPDATE *old_upd, *upd;
size_t ins_size, upd_size;
u_int i, skipdepth;
bool append, logged;
btree = cbt->btree;
ins = NULL;
page = cbt->ref->page;
upd = upd_arg;
append = logged = false;
if (upd_arg == NULL) {
if (modify_type == WT_UPDATE_RESERVE ||
modify_type == WT_UPDATE_TOMBSTONE) {
/*
* Fixed-size column-store doesn't have on-page deleted
* values, it's a nul byte.
*/
if (modify_type == WT_UPDATE_TOMBSTONE &&
btree->type == BTREE_COL_FIX) {
modify_type = WT_UPDATE_STANDARD;
value = &col_fix_remove;
}
}
/*
* There's a chance the application specified a record past the
* last record on the page. If that's the case and we're
* inserting a new WT_INSERT/WT_UPDATE pair, it goes on the
* append list, not the update list. Also, an out-of-band recno
* implies an append operation, we're allocating a new row.
* Ignore any information obtained from the search.
*/
WT_ASSERT(session, recno != WT_RECNO_OOB || cbt->compare != 0);
if (cbt->compare != 0 &&
(recno == WT_RECNO_OOB ||
recno > (btree->type == BTREE_COL_VAR ?
__col_var_last_recno(cbt->ref) :
__col_fix_last_recno(cbt->ref)))) {
append = true;
cbt->ins = NULL;
cbt->ins_head = NULL;
}
}
/* We're going to modify the page, we should have loaded history. */
WT_ASSERT(session, cbt->ref->state != WT_REF_LIMBO);
/* If we don't yet have a modify structure, we'll need one. */
WT_RET(__wt_page_modify_init(session, page));
mod = page->modify;
/*
* If modifying a record not previously modified, but which is in the
* same update slot as a previously modified record, cursor.ins will
* not be set because there's no list of update records for this recno,
* but cursor.ins_head will be set to point to the correct update slot.
* Acquire the necessary insert information, then create a new update
* entry and link it into the existing list. We get here if a page has
* a single cell representing multiple records (the records have the
* same value), and then a record in the cell is updated or removed,
* creating the update list for the cell, and then a cursor iterates
* into that same cell to update/remove a different record. We find the
* correct slot in the update array, but we don't find an update list
* (because it doesn't exist), and don't have the information we need
* to do the insert. Normally, we wouldn't care (we could fail and do
* a search for the record which would configure everything for the
* insert), but range truncation does this pattern for every record in
* the cell, and the performance is terrible. For that reason, catch it
* here.
*/
if (cbt->ins == NULL && cbt->ins_head != NULL) {
cbt->ins = __col_insert_search(
cbt->ins_head, cbt->ins_stack, cbt->next_stack, recno);
if (cbt->ins != NULL) {
if (WT_INSERT_RECNO(cbt->ins) == recno)
cbt->compare = 0;
else {
/*
* The test below is for cursor.compare set to 0
* and cursor.ins set: cursor.compare wasn't set
* by the search we just did, and has an unknown
* value. Clear cursor.ins to avoid the test.
*/
cbt->ins = NULL;
}
}
}
/*
* Delete, insert or update a column-store entry.
*
* If modifying a previously modified record, cursor.ins will be set to
* point to the correct update list. Create a new update entry and link
* it into the existing list.
*
* Else, allocate an insert array as necessary, build an insert/update
* structure pair, and link it into place.
*/
if (cbt->compare == 0 && cbt->ins != NULL) {
/*
* If we are restoring updates that couldn't be evicted, the
* key must not exist on the new page.
*/
WT_ASSERT(session, upd_arg == NULL);
/* Make sure the update can proceed. */
WT_ERR(__wt_txn_update_check(session, old_upd = cbt->ins->upd));
/* Allocate a WT_UPDATE structure and transaction ID. */
WT_ERR(__wt_update_alloc(session,
value, &upd, &upd_size, modify_type));
WT_ERR(__wt_txn_modify(session, upd));
logged = true;
/* Avoid a data copy in WT_CURSOR.update. */
cbt->modify_update = upd;
/*
* Point the new WT_UPDATE item to the next element in the list.
* If we get it right, the serialization function lock acts as
* our memory barrier to flush this write.
*/
upd->next = old_upd;
/* Serialize the update. */
WT_ERR(__wt_update_serial(
session, page, &cbt->ins->upd, &upd, upd_size, false));
} else {
/* Allocate the append/update list reference as necessary. */
if (append) {
WT_PAGE_ALLOC_AND_SWAP(session,
page, mod->mod_col_append, ins_headp, 1);
ins_headp = &mod->mod_col_append[0];
} else if (page->type == WT_PAGE_COL_FIX) {
WT_PAGE_ALLOC_AND_SWAP(session,
page, mod->mod_col_update, ins_headp, 1);
ins_headp = &mod->mod_col_update[0];
} else {
WT_PAGE_ALLOC_AND_SWAP(session, page,
mod->mod_col_update, ins_headp, page->entries);
ins_headp = &mod->mod_col_update[cbt->slot];
}
/* Allocate the WT_INSERT_HEAD structure as necessary. */
WT_PAGE_ALLOC_AND_SWAP(session, page, *ins_headp, ins_head, 1);
ins_head = *ins_headp;
/* Choose a skiplist depth for this insert. */
skipdepth = __wt_skip_choose_depth(session);
/*
* Allocate a WT_INSERT/WT_UPDATE pair and transaction ID, and
* update the cursor to reference it (the WT_INSERT_HEAD might
* be allocated, the WT_INSERT was allocated).
*/
WT_ERR(__col_insert_alloc(
session, recno, skipdepth, &ins, &ins_size));
cbt->ins_head = ins_head;
cbt->ins = ins;
/*
* Check for insert split and checkpoint races in column-store:
* it's easy (as opposed to in row-store) and a difficult bug to
* otherwise diagnose.
*/
WT_ASSERT(session, mod->mod_col_split_recno == WT_RECNO_OOB ||
(recno != WT_RECNO_OOB &&
mod->mod_col_split_recno > recno));
if (upd_arg == NULL) {
WT_ERR(__wt_update_alloc(session,
value, &upd, &upd_size, modify_type));
WT_ERR(__wt_txn_modify(session, upd));
logged = true;
/* Avoid a data copy in WT_CURSOR.update. */
cbt->modify_update = upd;
} else
upd_size = __wt_update_list_memsize(upd);
ins->upd = upd;
ins_size += upd_size;
/*
* If there was no insert list during the search, or there was
* no search because the record number has not been allocated
* yet, the cursor's information cannot be correct, search
* couldn't have initialized it.
*
* Otherwise, point the new WT_INSERT item's skiplist to the
* next elements in the insert list (which we will check are
* still valid inside the serialization function).
*
* The serial mutex acts as our memory barrier to flush these
* writes before inserting them into the list.
*/
if (cbt->ins_stack[0] == NULL || recno == WT_RECNO_OOB)
for (i = 0; i < skipdepth; i++) {
cbt->ins_stack[i] = &ins_head->head[i];
ins->next[i] = cbt->next_stack[i] = NULL;
}
else
for (i = 0; i < skipdepth; i++)
ins->next[i] = cbt->next_stack[i];
/* Append or insert the WT_INSERT structure. */
if (append)
WT_ERR(__wt_col_append_serial(
session, page, cbt->ins_head, cbt->ins_stack,
&ins, ins_size, &cbt->recno, skipdepth, exclusive));
else
WT_ERR(__wt_insert_serial(
session, page, cbt->ins_head, cbt->ins_stack,
&ins, ins_size, skipdepth, exclusive));
}
/* If the update was successful, add it to the in-memory log. */
if (logged && modify_type != WT_UPDATE_RESERVE) {
WT_ERR(__wt_txn_log_op(session, cbt));
/*
* In case of append, the recno (key) for the value is assigned
* now. Set the recno in the transaction operation to be used
* incase this transaction is prepared to retrieve the update
* corresponding to this operation.
*/
__wt_txn_op_set_recno(session, cbt->recno);
}
if (0) {
err: /*
* Remove the update from the current transaction, so we don't
* try to modify it on rollback.
*/
if (logged)
__wt_txn_unmodify(session);
__wt_free(session, ins);
if (upd_arg == NULL)
__wt_free(session, upd);
}
return (ret);
}
/*
* __cursor_var_prev --
* Move to the previous, variable-length column-store item.
*/
static inline int
__cursor_var_prev(WT_CURSOR_BTREE *cbt, bool newpage)
{
WT_CELL *cell;
WT_CELL_UNPACK unpack;
WT_COL *cip;
WT_INSERT *ins;
WT_ITEM *val;
WT_PAGE *page;
WT_SESSION_IMPL *session;
WT_UPDATE *upd;
uint64_t rle_start;
session = (WT_SESSION_IMPL *)cbt->iface.session;
page = cbt->ref->page;
val = &cbt->iface.value;
rle_start = 0; /* -Werror=maybe-uninitialized */
/* Initialize for each new page. */
if (newpage) {
cbt->last_standard_recno = __col_var_last_recno(page);
if (cbt->last_standard_recno == 0)
return (WT_NOTFOUND);
__cursor_set_recno(cbt, cbt->last_standard_recno);
goto new_page;
}
/* Move to the previous entry and return the item. */
for (;;) {
__cursor_set_recno(cbt, cbt->recno - 1);
new_page: if (cbt->recno < page->pg_var_recno)
return (WT_NOTFOUND);
/* Find the matching WT_COL slot. */
if ((cip =
__col_var_search(page, cbt->recno, &rle_start)) == NULL)
return (WT_NOTFOUND);
cbt->slot = WT_COL_SLOT(page, cip);
/* Check any insert list for a matching record. */
cbt->ins_head = WT_COL_UPDATE_SLOT(page, cbt->slot);
cbt->ins = __col_insert_search_match(cbt->ins_head, cbt->recno);
upd = cbt->ins == NULL ?
NULL : __wt_txn_read(session, cbt->ins->upd);
if (upd != NULL) {
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);
}
/*
* If we're at the same slot as the last reference and there's
* no matching insert list item, re-use the return information
* (so encoded items with large repeat counts aren't repeatedly
* decoded). Otherwise, unpack the cell and build the return
* information.
*/
if (cbt->cip_saved != cip) {
if ((cell = WT_COL_PTR(page, cip)) == NULL)
continue;
__wt_cell_unpack(cell, &unpack);
if (unpack.type == WT_CELL_DEL) {
if (__wt_cell_rle(&unpack) == 1)
continue;
/*
* There can be huge gaps in the variable-length
* column-store name space appearing as deleted
* records. If more than one deleted record, do
* the work of finding the next record to return
* instead of looping through the records.
*
* First, find the largest record in the update
* list that's smaller than the current record.
*/
ins = __col_insert_search_lt(
cbt->ins_head, cbt->recno);
/*
* Second, for records with RLEs greater than 1,
* the above call to __col_var_search located
* this record in the page's list of repeating
* records, and returned the starting record.
* The starting record - 1 is the record to
* which we could skip, if there was no larger
* record in the update list.
*/
cbt->recno = rle_start - 1;
if (ins != NULL &&
WT_INSERT_RECNO(ins) > cbt->recno)
cbt->recno = WT_INSERT_RECNO(ins);
/* Adjust for the outer loop decrement. */
++cbt->recno;
continue;
}
WT_RET(__wt_page_cell_data_ref(
session, page, &unpack, cbt->tmp));
cbt->cip_saved = cip;
}
val->data = cbt->tmp->data;
val->size = cbt->tmp->size;
return (0);
}
/* NOTREACHED */
}
/*
* __txn_op_log --
* Log an operation for the current transaction.
*/
static int
__txn_op_log(WT_SESSION_IMPL *session,
WT_ITEM *logrec, WT_TXN_OP *op, WT_CURSOR_BTREE *cbt)
{
WT_CURSOR *cursor;
WT_ITEM value;
WT_UPDATE *upd;
uint64_t recno;
cursor = &cbt->iface;
upd = op->u.upd;
value.data = upd->data;
value.size = upd->size;
/*
* Log the row- or column-store insert, modify, remove or update. Our
* caller doesn't log reserve operations, we shouldn't see them here.
*/
if (cbt->btree->type == BTREE_ROW) {
#ifdef HAVE_DIAGNOSTIC
__txn_op_log_row_key_check(session, cbt);
#endif
switch (upd->type) {
case WT_UPDATE_DELETED:
WT_RET(__wt_logop_row_remove_pack(
session, logrec, op->fileid, &cursor->key));
break;
case WT_UPDATE_MODIFIED:
WT_RET(__wt_logop_row_modify_pack(
session, logrec, op->fileid, &cursor->key, &value));
break;
case WT_UPDATE_STANDARD:
WT_RET(__wt_logop_row_put_pack(
session, logrec, op->fileid, &cursor->key, &value));
break;
WT_ILLEGAL_VALUE(session);
}
} else {
recno = WT_INSERT_RECNO(cbt->ins);
WT_ASSERT(session, recno != WT_RECNO_OOB);
switch (upd->type) {
case WT_UPDATE_DELETED:
WT_RET(__wt_logop_col_remove_pack(
session, logrec, op->fileid, recno));
break;
case WT_UPDATE_MODIFIED:
WT_RET(__wt_logop_col_modify_pack(
session, logrec, op->fileid, recno, &value));
break;
case WT_UPDATE_STANDARD:
WT_RET(__wt_logop_col_put_pack(
session, logrec, op->fileid, recno, &value));
break;
WT_ILLEGAL_VALUE(session);
}
}
return (0);
}
/*
* __wt_col_append_serial_func --
* Server function to append an WT_INSERT entry to the tree.
*/
int
__wt_col_append_serial_func(WT_SESSION_IMPL *session, void *args)
{
WT_BTREE *btree;
WT_INSERT *ins, *new_ins, ***ins_stack, **next_stack;
WT_INSERT_HEAD *inshead, **insheadp, **new_inslist, *new_inshead;
WT_PAGE *page;
uint64_t recno;
uint32_t write_gen;
u_int i, skipdepth;
btree = S2BT(session);
__wt_col_append_unpack(args,
&page, &write_gen, &insheadp, &ins_stack, &next_stack,
&new_inslist, &new_inshead, &new_ins, &skipdepth);
/* Check the page's write-generation. */
WT_RET(__wt_page_write_gen_check(session, page, write_gen));
if ((inshead = *insheadp) == NULL)
inshead = new_inshead;
/*
* If the application specified a record number, there's a race: the
* application may have searched for the record, not found it, then
* called into the append code, and another thread might have added
* the record. Fortunately, we're in the right place because if the
* record didn't exist at some point, it can only have been created
* on this list. Search for the record, if specified.
*/
if ((recno = WT_INSERT_RECNO(new_ins)) == 0)
recno = WT_INSERT_RECNO(new_ins) = ++btree->last_recno;
ins = __col_insert_search(inshead, ins_stack, next_stack, recno);
/* If we find the record number, there's been a race. */
if (ins != NULL && WT_INSERT_RECNO(ins) == recno)
WT_RET(WT_RESTART);
/*
* Publish: First, point the new WT_INSERT item's skiplist references
* to the next elements in the insert list, then flush memory. Second,
* update the skiplist elements that reference the new WT_INSERT item,
* this ensures the list is never inconsistent.
*/
for (i = 0; i < skipdepth; i++)
new_ins->next[i] = *ins_stack[i];
WT_WRITE_BARRIER();
for (i = 0; i < skipdepth; i++) {
if (inshead->tail[i] == NULL ||
ins_stack[i] == &inshead->tail[i]->next[i])
inshead->tail[i] = new_ins;
*ins_stack[i] = new_ins;
}
__wt_col_append_new_ins_taken(args);
/*
* If the insert head does not yet have an insert list, our caller
* passed us one.
*
* NOTE: it is important to do this after the item has been added to
* the list. Code can assume that if the list is set, it is non-empty.
*/
if (*insheadp == NULL) {
WT_PUBLISH(*insheadp, new_inshead);
__wt_col_append_new_inshead_taken(args);
}
/*
* If the page does not yet have an insert array, our caller passed
* us one.
*
* NOTE: it is important to do this after publishing the list entry.
* Code can assume that if the array is set, it is non-empty.
*/
if (page->modify->append == NULL) {
page->modify->append = new_inslist;
__wt_col_append_new_inslist_taken(args);
}
/*
* If we don't find the record, check to see if we extended the file,
* and update the last record number.
*/
if (recno > btree->last_recno)
btree->last_recno = recno;
__wt_page_and_tree_modify_set(session, page);
return (0);
}
/*
* __wt_col_modify --
* Column-store delete, insert, and update.
*/
int
__wt_col_modify(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt, int op)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_INSERT *ins, *ins_copy;
WT_INSERT_HEAD **inshead, *new_inshead, **new_inslist;
WT_ITEM *value, _value;
WT_PAGE *page;
WT_UPDATE *old_upd, *upd, *upd_obsolete;
size_t ins_size, new_inshead_size, new_inslist_size, upd_size;
uint64_t recno;
u_int skipdepth;
int i, logged;
btree = cbt->btree;
page = cbt->page;
recno = cbt->iface.recno;
logged = 0;
WT_ASSERT(session, op != 1);
switch (op) {
case 2: /* Remove */
if (btree->type == BTREE_COL_FIX) {
value = &_value;
value->data = "";
value->size = 1;
} else
value = NULL;
break;
case 3: /* Insert/Update */
default:
value = &cbt->iface.value;
/*
* There's some chance the application specified a record past
* the last record on the page. If that's the case, and we're
* inserting a new WT_INSERT/WT_UPDATE pair, it goes on the
* append list, not the update list.
*/
if (recno == 0 || recno > __col_last_recno(page))
op = 1;
break;
}
/* If we don't yet have a modify structure, we'll need one. */
WT_RET(__wt_page_modify_init(session, page));
ins = NULL;
new_inshead = NULL;
new_inslist = NULL;
upd = NULL;
/*
* Delete, insert or update a column-store entry.
*
* If modifying a previously modified record, create a new WT_UPDATE
* entry and have a serialized function link it into an existing
* WT_INSERT entry's WT_UPDATE list.
*
* Else, allocate an insert array as necessary, build a WT_INSERT and
* WT_UPDATE structure pair, and call a serialized function to insert
* the WT_INSERT structure.
*/
if (cbt->compare == 0 && cbt->ins != NULL) {
/* Make sure the update can proceed. */
WT_ERR(
__wt_update_check(session, page, old_upd = cbt->ins->upd));
/* Allocate the WT_UPDATE structure and transaction ID. */
WT_ERR(__wt_update_alloc(session, value, &upd, &upd_size));
WT_ERR(__wt_txn_modify(session, &upd->txnid));
logged = 1;
/* Serialize the update. */
WT_ERR(__wt_update_serial(session, page,
cbt->write_gen, &cbt->ins->upd, old_upd,
NULL, 0, &upd, upd_size, &upd_obsolete));
/* Discard any obsolete WT_UPDATE structures. */
if (upd_obsolete != NULL)
__wt_update_obsolete_free(session, page, upd_obsolete);
} else {
/* Make sure the update can proceed. */
WT_ERR(__wt_update_check(session, page, NULL));
/* There may be no insert list, allocate as necessary. */
new_inshead_size = new_inslist_size = 0;
if (op == 1) {
if (page->modify->append == NULL) {
new_inslist_size = 1 * sizeof(WT_INSERT_HEAD *);
WT_ERR(
__wt_calloc_def(session, 1, &new_inslist));
inshead = &new_inslist[0];
} else
inshead = &page->modify->append[0];
cbt->ins_head = *inshead;
} else if (page->type == WT_PAGE_COL_FIX) {
if (page->modify->update == NULL) {
new_inslist_size = 1 * sizeof(WT_INSERT_HEAD *);
WT_ERR(
__wt_calloc_def(session, 1, &new_inslist));
inshead = &new_inslist[0];
} else
inshead = &page->modify->update[0];
} else {
if (page->modify->update == NULL) {
new_inslist_size =
page->entries * sizeof(WT_INSERT_HEAD *);
WT_ERR(__wt_calloc_def(
session, page->entries, &new_inslist));
inshead = &new_inslist[cbt->slot];
} else
inshead = &page->modify->update[cbt->slot];
}
/* There may be no WT_INSERT list, allocate as necessary. */
if (*inshead == NULL) {
new_inshead_size = sizeof(WT_INSERT_HEAD);
WT_ERR(__wt_calloc_def(session, 1, &new_inshead));
for (i = 0; i < WT_SKIP_MAXDEPTH; i++) {
cbt->ins_stack[i] = &new_inshead->head[i];
cbt->next_stack[i] = NULL;
}
cbt->ins_head = new_inshead;
}
/* Choose a skiplist depth for this insert. */
skipdepth = __wt_skip_choose_depth();
/*
* Allocate a WT_INSERT/WT_UPDATE pair and transaction ID, and
* update the cursor to reference it.
*/
WT_ERR(__col_insert_alloc(
session, recno, skipdepth, &ins, &ins_size));
WT_ERR(__wt_update_alloc(session, value, &upd, &upd_size));
WT_ERR(__wt_txn_modify(session, &upd->txnid));
logged = 1;
ins->upd = upd;
ins_size += upd_size;
cbt->ins = ins;
/* Insert or append the WT_INSERT structure. */
if (op == 1) {
/*
* The serialized function clears ins: take a copy of
* the pointer so we can look up the record number.
*/
ins_copy = ins;
WT_ERR(__wt_col_append_serial(session,
page, cbt->write_gen, inshead,
cbt->ins_stack, cbt->next_stack,
&new_inslist, new_inslist_size,
&new_inshead, new_inshead_size,
&ins, ins_size, skipdepth));
/* Put the new recno into the cursor. */
cbt->recno = WT_INSERT_RECNO(ins_copy);
} else
WT_ERR(__wt_insert_serial(session,
page, cbt->write_gen, inshead,
cbt->ins_stack, cbt->next_stack,
&new_inslist, new_inslist_size,
&new_inshead, new_inshead_size,
&ins, ins_size, skipdepth));
}
if (0) {
err: /*
* Remove the update from the current transaction, so we don't
* try to modify it on rollback.
*/
if (logged)
__wt_txn_unmodify(session);
__wt_free(session, ins);
__wt_free(session, upd);
}
__wt_free(session, new_inslist);
__wt_free(session, new_inshead);
return (ret);
}
/*
* __cursor_skip_prev --
* Move back one position in a skip list stack (aka "finger").
*/
static inline int
__cursor_skip_prev(WT_CURSOR_BTREE *cbt)
{
WT_INSERT *current, *ins;
WT_ITEM key;
WT_SESSION_IMPL *session;
int i;
session = (WT_SESSION_IMPL *)cbt->iface.session;
restart:
/*
* If the search stack does not point at the current item, fill it in
* with a search.
*/
while ((current = cbt->ins) != PREV_INS(cbt, 0)) {
if (cbt->btree->type == BTREE_ROW) {
key.data = WT_INSERT_KEY(current);
key.size = WT_INSERT_KEY_SIZE(current);
WT_RET(__wt_search_insert(session, cbt, &key));
} else
cbt->ins = __col_insert_search(cbt->ins_head,
cbt->ins_stack, cbt->next_stack,
WT_INSERT_RECNO(current));
}
/*
* Find the first node up the search stack that does not move.
*
* The depth of the current item must be at least this level, since we
* see it in that many levels of the stack.
*
* !!! Watch these loops carefully: they all rely on the value of i,
* and the exit conditions to end up with the right values are
* non-trivial.
*/
ins = NULL; /* -Wconditional-uninitialized */
for (i = 0; i < WT_SKIP_MAXDEPTH - 1; i++)
if ((ins = PREV_INS(cbt, i + 1)) != current)
break;
/*
* Find a starting point for the new search. That is either at the
* non-moving node if we found a valid node, or the beginning of the
* next list down that is not the current node.
*
* Since it is the beginning of a list, and we know the current node is
* has a skip depth at least this high, any node we find must sort
* before the current node.
*/
if (ins == NULL || ins == current)
for (; i >= 0; i--) {
cbt->ins_stack[i] = NULL;
cbt->next_stack[i] = NULL;
ins = cbt->ins_head->head[i];
if (ins != NULL && ins != current)
break;
}
/* Walk any remaining levels until just before the current node. */
while (i >= 0) {
/*
* If we get to the end of a list without finding the current
* item, we must have raced with an insert. Restart the search.
*/
if (ins == NULL) {
cbt->ins_stack[0] = NULL;
cbt->next_stack[0] = NULL;
goto restart;
}
if (ins->next[i] != current) /* Stay at this level */
ins = ins->next[i];
else { /* Drop down a level */
cbt->ins_stack[i] = &ins->next[i];
cbt->next_stack[i] = ins->next[i];
--i;
}
}
/* If we found a previous node, the next one must be current. */
if (cbt->ins_stack[0] != NULL && *cbt->ins_stack[0] != current)
goto restart;
cbt->ins = PREV_INS(cbt, 0);
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);
}