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/*-
* Copyright (c) 2014-2018 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
/*
* __key_return --
* Change the cursor to reference an internal return key.
*/
static inline int
__key_return(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt)
{
WT_CURSOR *cursor;
WT_ITEM *tmp;
WT_PAGE *page;
WT_ROW *rip;
page = cbt->ref->page;
cursor = &cbt->iface;
if (page->type == WT_PAGE_ROW_LEAF) {
rip = &page->pg_row[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);
return (0);
}
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;
return (0);
}
return (__wt_row_leaf_key(
session, page, rip, &cursor->key, false));
}
/*
* WT_PAGE_COL_FIX, 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;
return (0);
}
/*
* __value_return --
* Change the cursor to reference an internal original-page return value.
*/
static inline int
__value_return(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt)
{
WT_BTREE *btree;
WT_CELL *cell;
WT_CELL_UNPACK unpack;
WT_CURSOR *cursor;
WT_PAGE *page;
WT_ROW *rip;
uint8_t v;
btree = S2BT(session);
page = cbt->ref->page;
cursor = &cbt->iface;
if (page->type == WT_PAGE_ROW_LEAF) {
rip = &page->pg_row[cbt->slot];
/* 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. */
__wt_row_leaf_value_cell(page, rip, NULL, &unpack);
return (__wt_page_cell_data_ref(
session, page, &unpack, &cursor->value));
}
if (page->type == WT_PAGE_COL_VAR) {
/* Take the value from the original page cell. */
cell = WT_COL_PTR(page, &page->pg_var[cbt->slot]);
__wt_cell_unpack(page, cell, &unpack);
return (__wt_page_cell_data_ref(
session, page, &unpack, &cursor->value));
}
/* WT_PAGE_COL_FIX: Take the value from the original page. */
v = __bit_getv_recno(cbt->ref, cursor->recno, btree->bitcnt);
return (__wt_buf_set(session, &cursor->value, &v, 1));
}
/*
* When threads race modifying a record, we can end up with more than the usual
* maximum number of modifications in an update list. We'd prefer not to
* allocate memory in a return path, so add a few additional slots to the array
* we use to build up a list of modify records to apply.
*/
#define WT_MODIFY_ARRAY_SIZE (WT_MAX_MODIFY_UPDATE + 10)
/*
* __wt_value_return_upd --
* Change the cursor to reference an internal update structure return
* value.
*/
int
__wt_value_return_upd(WT_SESSION_IMPL *session,
WT_CURSOR_BTREE *cbt, WT_UPDATE *upd, bool ignore_visibility)
{
WT_CURSOR *cursor;
WT_DECL_RET;
WT_UPDATE **listp, *list[WT_MODIFY_ARRAY_SIZE];
size_t allocated_bytes;
u_int i;
bool skipped_birthmark;
cursor = &cbt->iface;
allocated_bytes = 0;
/*
* We're passed a "standard" or "modified" update that's visible to us.
* Our caller should have already checked for deleted items (we're too
* far down the call stack to return not-found).
*
* Fast path if it's a standard item, assert our caller's behavior.
*/
if (upd->type == WT_UPDATE_STANDARD) {
cursor->value.data = upd->data;
cursor->value.size = upd->size;
return (0);
}
WT_ASSERT(session, upd->type == WT_UPDATE_MODIFY);
/*
* Find a complete update that's visible to us, tracking modifications
* that are visible to us.
*/
for (i = 0, listp = list, skipped_birthmark = false;
upd != NULL;
upd = upd->next) {
if (upd->txnid == WT_TXN_ABORTED)
continue;
if (!ignore_visibility && !__wt_txn_upd_visible(session, upd)) {
if (upd->type == WT_UPDATE_BIRTHMARK)
skipped_birthmark = true;
continue;
}
if (upd->type == WT_UPDATE_BIRTHMARK) {
upd = NULL;
break;
}
if (WT_UPDATE_DATA_VALUE(upd))
break;
if (upd->type == WT_UPDATE_MODIFY) {
/*
* Update lists are expected to be short, but it's not
* guaranteed. There's sufficient room on the stack to
* avoid memory allocation in normal cases, but we have
* to handle the edge cases too.
*/
if (i >= WT_MODIFY_ARRAY_SIZE) {
if (i == WT_MODIFY_ARRAY_SIZE)
listp = NULL;
WT_ERR(__wt_realloc_def(
session, &allocated_bytes, i + 1, &listp));
if (i == WT_MODIFY_ARRAY_SIZE)
memcpy(listp, list, sizeof(list));
}
listp[i++] = upd;
}
}
/*
* If there's no visible update and we skipped a birthmark, the base
* item is an empty item (in other words, birthmarks we can't read act
* as tombstones).
* If there's no visible update and we didn't skip a birthmark, the base
* item is the on-page item, which must be globally visible.
* If there's a visible update and it's a tombstone, the base item is an
* empty item.
* If there's a visible update and it's not a tombstone, the base item
* is the on-page item.
*/
if (upd == NULL) {
if (skipped_birthmark)
WT_ERR(__wt_buf_set(session, &cursor->value, "", 0));
else {
/*
* Callers of this function set the cursor slot to an
* impossible value to check we don't try and return
* on-page values when the update list should have been
* sufficient (which happens, for example, if an update
* list was truncated, deleting some standard update
* required by a previous modify update). Assert the
* case.
*/
WT_ASSERT(session, cbt->slot != UINT32_MAX);
WT_ERR(__value_return(session, cbt));
}
} else if (upd->type == WT_UPDATE_TOMBSTONE)
WT_ERR(__wt_buf_set(session, &cursor->value, "", 0));
else
WT_ERR(__wt_buf_set(session,
&cursor->value, upd->data, upd->size));
/*
* Once we have a base item, roll forward through any visible modify
* updates.
*/
while (i > 0)
WT_ERR(__wt_modify_apply(session, cursor, listp[--i]->data));
err: if (allocated_bytes != 0)
__wt_free(session, listp);
return (ret);
}
/*
* __wt_key_return --
* Change the cursor to reference an internal return key.
*/
int
__wt_key_return(WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt)
{
WT_CURSOR *cursor;
cursor = &cbt->iface;
/*
* We may already have an internal key and the cursor may not be set up
* to get another copy, so we have to leave it alone. Consider a cursor
* search followed by an update: the update doesn't repeat the search,
* it simply updates the currently referenced key's value. We will end
* up here with the correct internal key, but we can't "return" the key
* again even if we wanted to do the additional work, the cursor isn't
* set up for that because we didn't just complete a search.
*/
F_CLR(cursor, WT_CURSTD_KEY_EXT);
if (!F_ISSET(cursor, WT_CURSTD_KEY_INT)) {
WT_RET(__key_return(session, cbt));
F_SET(cursor, WT_CURSTD_KEY_INT);
}
return (0);
}
/*
* __wt_value_return --
* Change the cursor to reference an internal return value.
*/
int
__wt_value_return(
WT_SESSION_IMPL *session, WT_CURSOR_BTREE *cbt, WT_UPDATE *upd)
{
WT_CURSOR *cursor;
cursor = &cbt->iface;
F_CLR(cursor, WT_CURSTD_VALUE_EXT);
if (upd == NULL)
WT_RET(__value_return(session, cbt));
else
WT_RET(__wt_value_return_upd(session, cbt, upd, false));
F_SET(cursor, WT_CURSTD_VALUE_INT);
return (0);
}
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