int __wt_kv_return(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt, WT_UPDATE *upd)
{
WT_BTREE *btree;
WT_CELL *cell;
WT_CELL_UNPACK unpack;
WT_CURSOR *cursor;
WT_PAGE *page;
WT_ROW *rip;
uint8_t v;
switch (page->type){
case WT_PAGE_COL_FIX:
cursor->recno = cbt->recno;
/*cursor对应的是一个upd,直接返回value*/
if (upd != NULL){
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return 0;
}
v = __bit_getv_recno(page, cbt->iface.recno, btree->bitcnt);
return __wt_buf_set(session, &cursor->value, &v, 1);
case WT_PAGE_COL_VAR:
cursor->recno = cbt->recno;
if (upd != NULL) {
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return (0);
}
/*获得对应的cell,并通过cell得到K/V值*/
cell = WT_COL_PTR(page, &page->pg_var_d[cbt->slot]);
break;
case WT_PAGE_ROW_LEAF:
rip = &page->pg_row_d[cbt->slot];
if (cbt->ins != NULL){ /*插入的k/v对*/
cursor->key.data = WT_INSERT_KEY(cbt->ins);
cursor->key.size = WT_INSERT_KEY_SIZE(cbt->ins);
}
else if (cbt->compare == 0){/*比较器定位到了对应的k/v对*/
cursor->key.data = cbt->search_key.data;
cursor->key.size = cbt->search_key.size;
}
else
WT_RET(__wt_row_leaf_key(session, page, rip, &cursor->key, 0)); /*设置key的值*/
/*值是在append/update list当中，从当中取*/
if (upd != NULL) {
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return (0);
}
/*可以直接通过rip指针获得value,K/V是存储在cell空间之内*/
if (__wt_row_leaf_value(page, rip, &cursor->value))
return 0;
/*不是连续存储的，需要通过解析cell来定位到value*/
if (cell = __wt_row_leaf_value_cell(page, rip, NULL) == NULL){
cursor->value.size = 0;
return 0;
}
break;
WT_ILLEGAL_VALUE(session);
}
/*通过cell解析到对应的value值, ovfl item*/
__wt_cell_unpack(cell, &unpack);
WT_RET(__wt_page_cell_data_ref(session, page, &unpack, &cursor->value));
return 0;
}
/*
* __wt_kv_return --
* Return a page referenced key/value pair to the application.
*/
int
__wt_kv_return(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt, WT_UPDATE *upd)
{
WT_BTREE *btree;
WT_CELL *cell;
WT_CELL_UNPACK unpack;
WT_CURSOR *cursor;
WT_ITEM *tmp;
WT_PAGE *page;
WT_ROW *rip;
uint8_t v;
btree = S2BT(session);
page = cbt->ref->page;
cursor = &cbt->iface;
switch (page->type) {
case WT_PAGE_COL_FIX:
/*
* The interface cursor's record has usually been set, but that
* isn't universally true, specifically, cursor.search_near may
* call here without first setting the interface cursor.
*/
cursor->recno = cbt->recno;
/* If the cursor references a WT_UPDATE item, return it. */
if (upd != NULL) {
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return (0);
}
/* Take the value from the original page. */
v = __bit_getv_recno(page, cbt->iface.recno, btree->bitcnt);
return (__wt_buf_set(session, &cursor->value, &v, 1));
case WT_PAGE_COL_VAR:
/*
* The interface cursor's record has usually been set, but that
* isn't universally true, specifically, cursor.search_near may
* call here without first setting the interface cursor.
*/
cursor->recno = cbt->recno;
/* If the cursor references a WT_UPDATE item, return it. */
if (upd != NULL) {
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return (0);
}
/* Take the value from the original page cell. */
cell = WT_COL_PTR(page, &page->pg_var_d[cbt->slot]);
break;
case WT_PAGE_ROW_LEAF:
rip = &page->pg_row_d[cbt->slot];
/*
* If the cursor references a WT_INSERT item, take its key.
* Else, if we have an exact match, we copied the key in the
* search function, take it from there.
* If we don't have an exact match, take the key from the
* original page.
*/
if (cbt->ins != NULL) {
cursor->key.data = WT_INSERT_KEY(cbt->ins);
cursor->key.size = WT_INSERT_KEY_SIZE(cbt->ins);
} else if (cbt->compare == 0) {
/*
* If not in an insert list and there's an exact match,
* the row-store search function built the key we want
* to return in the cursor's temporary buffer. Swap the
* cursor's search-key and temporary buffers so we can
* return it (it's unsafe to return the temporary buffer
* itself because our caller might do another search in
* this table using the key we return, and we'd corrupt
* the search key during any subsequent search that used
* the temporary buffer.
*/
tmp = cbt->row_key;
cbt->row_key = cbt->tmp;
cbt->tmp = tmp;
cursor->key.data = cbt->row_key->data;
cursor->key.size = cbt->row_key->size;
} else
WT_RET(__wt_row_leaf_key(
session, page, rip, &cursor->key, false));
/* If the cursor references a WT_UPDATE item, return it. */
if (upd != NULL) {
cursor->value.data = WT_UPDATE_DATA(upd);
cursor->value.size = upd->size;
return (0);
}
/* Simple values have their location encoded in the WT_ROW. */
if (__wt_row_leaf_value(page, rip, &cursor->value))
return (0);
/*
* Take the value from the original page cell (which may be
* empty).
*/
if ((cell =
__wt_row_leaf_value_cell(page, rip, NULL)) == NULL) {
cursor->value.size = 0;
return (0);
}
break;
WT_ILLEGAL_VALUE(session);
}
/* The value is an on-page cell, unpack and expand it as necessary. */
__wt_cell_unpack(cell, &unpack);
WT_RET(__wt_page_cell_data_ref(session, page, &unpack, &cursor->value));
return (0);
}
