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|
/*-
* Copyright (c) 2014-present MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
/*
* __wt_ref_is_root --
* Return if the page reference is for the root page.
*/
static inline bool
__wt_ref_is_root(WT_REF *ref)
{
return (ref->home == NULL);
}
/*
* __wt_ref_cas_state_int --
* Try to do a compare and swap, if successful update the ref history in diagnostic mode.
*/
static inline bool
__wt_ref_cas_state_int(WT_SESSION_IMPL *session, WT_REF *ref, uint8_t old_state, uint8_t new_state,
const char *func, int line)
{
bool cas_result;
/* Parameters that are used in a macro for diagnostic builds */
WT_UNUSED(session);
WT_UNUSED(func);
WT_UNUSED(line);
cas_result = __wt_atomic_casv8(&ref->state, old_state, new_state);
#ifdef HAVE_DIAGNOSTIC
/*
* The history update here has potential to race; if the state gets updated again after the CAS
* above but before the history has been updated.
*/
if (cas_result)
WT_REF_SAVE_STATE(ref, new_state, func, line);
#endif
return (cas_result);
}
/*
* __wt_btree_disable_bulk --
* Disable bulk loads into a tree.
*/
static inline void
__wt_btree_disable_bulk(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
btree = S2BT(session);
/*
* Once a tree (other than the LSM primary) is no longer empty, eviction should pay attention to
* it, and it's no longer possible to bulk-load into it.
*/
if (!btree->original)
return;
if (btree->lsm_primary) {
btree->original = 0; /* Make the next test faster. */
return;
}
/*
* We use a compare-and-swap here to avoid races among the first inserts into a tree. Eviction
* is disabled when an empty tree is opened, and it must only be enabled once.
*/
if (__wt_atomic_cas8(&btree->original, 1, 0)) {
btree->evict_disabled_open = false;
__wt_evict_file_exclusive_off(session);
}
}
/*
* __wt_page_is_empty --
* Return if the page is empty.
*/
static inline bool
__wt_page_is_empty(WT_PAGE *page)
{
/*
* Be cautious modifying this function: it's reading fields set by checkpoint reconciliation,
* and we're not blocking checkpoints (although we must block eviction as it might clear and
* free these structures).
*/
return (page->modify != NULL && page->modify->rec_result == WT_PM_REC_EMPTY);
}
/*
* __wt_page_evict_clean --
* Return if the page can be evicted without dirtying the tree.
*/
static inline bool
__wt_page_evict_clean(WT_PAGE *page)
{
/*
* Be cautious modifying this function: it's reading fields set by checkpoint reconciliation,
* and we're not blocking checkpoints (although we must block eviction as it might clear and
* free these structures).
*/
return (page->modify == NULL ||
(page->modify->page_state == WT_PAGE_CLEAN && page->modify->rec_result == 0));
}
/*
* __wt_page_is_modified --
* Return if the page is dirty.
*/
static inline bool
__wt_page_is_modified(WT_PAGE *page)
{
/*
* Be cautious modifying this function: it's reading fields set by checkpoint reconciliation,
* and we're not blocking checkpoints (although we must block eviction as it might clear and
* free these structures).
*/
return (page->modify != NULL && page->modify->page_state != WT_PAGE_CLEAN);
}
/*
* __wt_btree_block_free --
* Helper function to free a block from the current tree.
*/
static inline int
__wt_btree_block_free(WT_SESSION_IMPL *session, const uint8_t *addr, size_t addr_size)
{
WT_BM *bm;
WT_BTREE *btree;
btree = S2BT(session);
bm = btree->bm;
return (bm->free(bm, session, addr, addr_size));
}
/*
* __wt_btree_bytes_inuse --
* Return the number of bytes in use.
*/
static inline uint64_t
__wt_btree_bytes_inuse(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
WT_CACHE *cache;
btree = S2BT(session);
cache = S2C(session)->cache;
return (__wt_cache_bytes_plus_overhead(cache, btree->bytes_inmem));
}
/*
* __wt_btree_bytes_evictable --
* Return the number of bytes that can be evicted (i.e. bytes apart from the pinned root page).
*/
static inline uint64_t
__wt_btree_bytes_evictable(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
WT_CACHE *cache;
WT_PAGE *root_page;
uint64_t bytes_inmem, bytes_root;
btree = S2BT(session);
cache = S2C(session)->cache;
root_page = btree->root.page;
bytes_inmem = btree->bytes_inmem;
bytes_root = root_page == NULL ? 0 : root_page->memory_footprint;
return (bytes_inmem <= bytes_root ?
0 :
__wt_cache_bytes_plus_overhead(cache, bytes_inmem - bytes_root));
}
/*
* __wt_btree_dirty_inuse --
* Return the number of dirty bytes in use.
*/
static inline uint64_t
__wt_btree_dirty_inuse(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
WT_CACHE *cache;
btree = S2BT(session);
cache = S2C(session)->cache;
return (
__wt_cache_bytes_plus_overhead(cache, btree->bytes_dirty_intl + btree->bytes_dirty_leaf));
}
/*
* __wt_btree_dirty_leaf_inuse --
* Return the number of bytes in use by dirty leaf pages.
*/
static inline uint64_t
__wt_btree_dirty_leaf_inuse(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
WT_CACHE *cache;
btree = S2BT(session);
cache = S2C(session)->cache;
return (__wt_cache_bytes_plus_overhead(cache, btree->bytes_dirty_leaf));
}
/*
* __wt_btree_bytes_updates --
* Return the number of bytes in use by dirty leaf pages.
*/
static inline uint64_t
__wt_btree_bytes_updates(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
WT_CACHE *cache;
btree = S2BT(session);
cache = S2C(session)->cache;
return (__wt_cache_bytes_plus_overhead(cache, btree->bytes_updates));
}
/*
* __wt_cache_page_inmem_incr --
* Increment a page's memory footprint in the cache.
*/
static inline void
__wt_cache_page_inmem_incr(WT_SESSION_IMPL *session, WT_PAGE *page, size_t size)
{
WT_BTREE *btree;
WT_CACHE *cache;
WT_ASSERT(session, size < WT_EXABYTE);
btree = S2BT(session);
cache = S2C(session)->cache;
if (size == 0)
return;
/*
* Always increase the size in sequence of cache, btree, and page as we may race with other
* threads that are trying to decrease the sizes concurrently.
*/
(void)__wt_atomic_add64(&cache->bytes_inmem, size);
(void)__wt_atomic_add64(&btree->bytes_inmem, size);
if (WT_PAGE_IS_INTERNAL(page)) {
(void)__wt_atomic_add64(&cache->bytes_internal, size);
(void)__wt_atomic_add64(&btree->bytes_internal, size);
}
(void)__wt_atomic_addsize(&page->memory_footprint, size);
if (page->modify != NULL) {
if (!WT_PAGE_IS_INTERNAL(page) && !btree->lsm_primary) {
(void)__wt_atomic_add64(&cache->bytes_updates, size);
(void)__wt_atomic_add64(&btree->bytes_updates, size);
(void)__wt_atomic_addsize(&page->modify->bytes_updates, size);
}
if (__wt_page_is_modified(page)) {
if (WT_PAGE_IS_INTERNAL(page)) {
(void)__wt_atomic_add64(&cache->bytes_dirty_intl, size);
(void)__wt_atomic_add64(&btree->bytes_dirty_intl, size);
} else if (!btree->lsm_primary) {
(void)__wt_atomic_add64(&cache->bytes_dirty_leaf, size);
(void)__wt_atomic_add64(&btree->bytes_dirty_leaf, size);
}
(void)__wt_atomic_addsize(&page->modify->bytes_dirty, size);
}
}
}
/*
* __wt_cache_decr_check_size --
* Decrement a size_t cache value and check for underflow.
*/
static inline void
__wt_cache_decr_check_size(WT_SESSION_IMPL *session, size_t *vp, size_t v, const char *fld)
{
if (v == 0 || __wt_atomic_subsize(vp, v) < WT_EXABYTE)
return;
/*
* It's a bug if this accounting underflowed but allow the application to proceed - the
* consequence is we use more cache than configured.
*/
*vp = 0;
__wt_errx(session, "%s went negative with decrement of %" WT_SIZET_FMT, fld, v);
#ifdef HAVE_DIAGNOSTIC
__wt_abort(session);
#endif
}
/*
* __wt_cache_decr_check_uint64 --
* Decrement a uint64_t cache value and check for underflow.
*/
static inline void
__wt_cache_decr_check_uint64(WT_SESSION_IMPL *session, uint64_t *vp, uint64_t v, const char *fld)
{
uint64_t orig = *vp;
if (v == 0 || __wt_atomic_sub64(vp, v) < WT_EXABYTE)
return;
/*
* It's a bug if this accounting underflowed but allow the application to proceed - the
* consequence is we use more cache than configured.
*/
*vp = 0;
__wt_errx(
session, "%s was %" PRIu64 ", went negative with decrement of %" PRIu64, fld, orig, v);
#ifdef HAVE_DIAGNOSTIC
__wt_abort(session);
#endif
}
/*
* __wt_cache_page_byte_dirty_decr --
* Decrement the page's dirty byte count, guarding from underflow.
*/
static inline void
__wt_cache_page_byte_dirty_decr(WT_SESSION_IMPL *session, WT_PAGE *page, size_t size)
{
WT_BTREE *btree;
WT_CACHE *cache;
size_t decr, orig;
int i;
btree = S2BT(session);
cache = S2C(session)->cache;
decr = 0; /* [-Wconditional-uninitialized] */
/*
* We don't have exclusive access and there are ways of decrementing the
* page's dirty byte count by a too-large value. For example:
* T1: __wt_cache_page_inmem_incr(page, size)
* page is clean, don't increment dirty byte count
* T2: mark page dirty
* T1: __wt_cache_page_inmem_decr(page, size)
* page is dirty, decrement dirty byte count
* and, of course, the reverse where the page is dirty at the increment
* and clean at the decrement.
*
* The page's dirty-byte value always reflects bytes represented in the
* cache's dirty-byte count, decrement the page/cache as much as we can
* without underflow. If we can't decrement the dirty byte counts after
* few tries, give up: the cache's value will be wrong, but consistent,
* and we'll fix it the next time this page is marked clean, or evicted.
*
* Always decrease the size in sequence of page, btree, and cache as we may race with other
* threads that are trying to increase the sizes concurrently.
*/
for (i = 0; i < 5; ++i) {
/*
* Take care to read the dirty-byte count only once in case we're racing with updates.
*/
WT_ORDERED_READ(orig, page->modify->bytes_dirty);
decr = WT_MIN(size, orig);
if (__wt_atomic_cassize(&page->modify->bytes_dirty, orig, orig - decr))
break;
}
if (i == 5)
return;
if (WT_PAGE_IS_INTERNAL(page)) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_dirty_intl, decr, "WT_BTREE.bytes_dirty_intl");
__wt_cache_decr_check_uint64(
session, &cache->bytes_dirty_intl, decr, "WT_CACHE.bytes_dirty_intl");
} else if (!btree->lsm_primary) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_dirty_leaf, decr, "WT_BTREE.bytes_dirty_leaf");
__wt_cache_decr_check_uint64(
session, &cache->bytes_dirty_leaf, decr, "WT_CACHE.bytes_dirty_leaf");
}
}
/*
* __wt_cache_page_byte_updates_decr --
* Decrement the page's update byte count, guarding from underflow.
*/
static inline void
__wt_cache_page_byte_updates_decr(WT_SESSION_IMPL *session, WT_PAGE *page, size_t size)
{
WT_BTREE *btree;
WT_CACHE *cache;
size_t decr, orig;
int i;
btree = S2BT(session);
cache = S2C(session)->cache;
decr = 0; /* [-Wconditional-uninitialized] */
WT_ASSERT(session, !WT_PAGE_IS_INTERNAL(page) && !btree->lsm_primary && page->modify != NULL);
/* See above for why this can race. */
for (i = 0; i < 5; ++i) {
WT_ORDERED_READ(orig, page->modify->bytes_updates);
decr = WT_MIN(size, orig);
if (__wt_atomic_cassize(&page->modify->bytes_updates, orig, orig - decr))
break;
}
if (i == 5)
return;
__wt_cache_decr_check_uint64(session, &btree->bytes_updates, decr, "WT_BTREE.bytes_updates");
__wt_cache_decr_check_uint64(session, &cache->bytes_updates, decr, "WT_CACHE.bytes_updates");
}
/*
* __wt_cache_page_inmem_decr --
* Decrement a page's memory footprint in the cache.
*/
static inline void
__wt_cache_page_inmem_decr(WT_SESSION_IMPL *session, WT_PAGE *page, size_t size)
{
WT_BTREE *btree;
WT_CACHE *cache;
btree = S2BT(session);
cache = S2C(session)->cache;
WT_ASSERT(session, size < WT_EXABYTE);
/*
* Always decrease the size in sequence of page, btree, and cache as we may race with other
* threads that are trying to increase the sizes concurrently.
*/
__wt_cache_decr_check_size(session, &page->memory_footprint, size, "WT_PAGE.memory_footprint");
__wt_cache_decr_check_uint64(session, &btree->bytes_inmem, size, "WT_BTREE.bytes_inmem");
__wt_cache_decr_check_uint64(session, &cache->bytes_inmem, size, "WT_CACHE.bytes_inmem");
if (page->modify != NULL && !WT_PAGE_IS_INTERNAL(page) && !btree->lsm_primary)
__wt_cache_page_byte_updates_decr(session, page, size);
if (__wt_page_is_modified(page))
__wt_cache_page_byte_dirty_decr(session, page, size);
/* Track internal size in cache. */
if (WT_PAGE_IS_INTERNAL(page)) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_internal, size, "WT_BTREE.bytes_internal");
__wt_cache_decr_check_uint64(
session, &cache->bytes_internal, size, "WT_CACHE.bytes_internal");
}
}
/*
* __wt_cache_dirty_incr --
* Page switch from clean to dirty: increment the cache dirty page/byte counts.
*/
static inline void
__wt_cache_dirty_incr(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_BTREE *btree;
WT_CACHE *cache;
size_t size;
btree = S2BT(session);
cache = S2C(session)->cache;
/*
* Always increase the size in sequence of cache, btree, and page as we may race with other
* threads that are trying to decrease the sizes concurrently.
*
* Take care to read the memory_footprint once in case we are racing with updates.
*/
size = page->memory_footprint;
if (WT_PAGE_IS_INTERNAL(page)) {
(void)__wt_atomic_add64(&cache->pages_dirty_intl, 1);
(void)__wt_atomic_add64(&cache->bytes_dirty_intl, size);
(void)__wt_atomic_add64(&btree->bytes_dirty_intl, size);
} else {
if (!btree->lsm_primary) {
(void)__wt_atomic_add64(&cache->bytes_dirty_leaf, size);
(void)__wt_atomic_add64(&btree->bytes_dirty_leaf, size);
}
(void)__wt_atomic_add64(&cache->pages_dirty_leaf, 1);
}
(void)__wt_atomic_add64(&cache->bytes_dirty_total, size);
(void)__wt_atomic_add64(&btree->bytes_dirty_total, size);
(void)__wt_atomic_addsize(&page->modify->bytes_dirty, size);
}
/*
* __wt_cache_dirty_decr --
* Page switch from dirty to clean: decrement the cache dirty page/byte counts.
*/
static inline void
__wt_cache_dirty_decr(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_CACHE *cache;
WT_PAGE_MODIFY *modify;
cache = S2C(session)->cache;
if (WT_PAGE_IS_INTERNAL(page))
__wt_cache_decr_check_uint64(
session, &cache->pages_dirty_intl, 1, "dirty internal page count");
else
__wt_cache_decr_check_uint64(session, &cache->pages_dirty_leaf, 1, "dirty leaf page count");
modify = page->modify;
if (modify != NULL && modify->bytes_dirty != 0)
__wt_cache_page_byte_dirty_decr(session, page, modify->bytes_dirty);
}
/*
* __wt_cache_page_image_decr --
* Decrement a page image's size to the cache.
*/
static inline void
__wt_cache_page_image_decr(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_CACHE *cache;
cache = S2C(session)->cache;
if (WT_PAGE_IS_INTERNAL(page))
__wt_cache_decr_check_uint64(
session, &cache->bytes_image_intl, page->dsk->mem_size, "WT_CACHE.bytes_image");
else
__wt_cache_decr_check_uint64(
session, &cache->bytes_image_leaf, page->dsk->mem_size, "WT_CACHE.bytes_image");
}
/*
* __wt_cache_page_image_incr --
* Increment a page image's size to the cache.
*/
static inline void
__wt_cache_page_image_incr(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_CACHE *cache;
cache = S2C(session)->cache;
if (WT_PAGE_IS_INTERNAL(page))
(void)__wt_atomic_add64(&cache->bytes_image_intl, page->dsk->mem_size);
else
(void)__wt_atomic_add64(&cache->bytes_image_leaf, page->dsk->mem_size);
}
/*
* __wt_cache_page_evict --
* Evict pages from the cache.
*/
static inline void
__wt_cache_page_evict(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_BTREE *btree;
WT_CACHE *cache;
WT_PAGE_MODIFY *modify;
btree = S2BT(session);
cache = S2C(session)->cache;
modify = page->modify;
/* Update the bytes in-memory to reflect the eviction. */
__wt_cache_decr_check_uint64(
session, &btree->bytes_inmem, page->memory_footprint, "WT_BTREE.bytes_inmem");
__wt_cache_decr_check_uint64(
session, &cache->bytes_inmem, page->memory_footprint, "WT_CACHE.bytes_inmem");
/* Update the bytes_internal value to reflect the eviction */
if (WT_PAGE_IS_INTERNAL(page)) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_internal, page->memory_footprint, "WT_BTREE.bytes_internal");
__wt_cache_decr_check_uint64(
session, &cache->bytes_internal, page->memory_footprint, "WT_CACHE.bytes_internal");
}
/* Update the cache's dirty-byte count. */
if (modify != NULL && modify->bytes_dirty != 0) {
if (WT_PAGE_IS_INTERNAL(page)) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_dirty_intl, modify->bytes_dirty, "WT_BTREE.bytes_dirty_intl");
__wt_cache_decr_check_uint64(
session, &cache->bytes_dirty_intl, modify->bytes_dirty, "WT_CACHE.bytes_dirty_intl");
} else if (!btree->lsm_primary) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_dirty_leaf, modify->bytes_dirty, "WT_BTREE.bytes_dirty_leaf");
__wt_cache_decr_check_uint64(
session, &cache->bytes_dirty_leaf, modify->bytes_dirty, "WT_CACHE.bytes_dirty_leaf");
}
}
/* Update the cache's updates-byte count. */
if (modify != NULL) {
__wt_cache_decr_check_uint64(
session, &btree->bytes_updates, modify->bytes_updates, "WT_BTREE.bytes_updates");
__wt_cache_decr_check_uint64(
session, &cache->bytes_updates, modify->bytes_updates, "WT_CACHE.bytes_updates");
}
/* Update bytes and pages evicted. */
(void)__wt_atomic_add64(&cache->bytes_evict, page->memory_footprint);
(void)__wt_atomic_addv64(&cache->pages_evicted, 1);
/*
* Track if eviction makes progress. This is used in various places to determine whether
* eviction is stuck.
*/
if (!F_ISSET_ATOMIC_16(page, WT_PAGE_EVICT_NO_PROGRESS))
(void)__wt_atomic_addv64(&cache->eviction_progress, 1);
}
/*
* __wt_update_list_memsize --
* The size in memory of a list of updates.
*/
static inline size_t
__wt_update_list_memsize(WT_UPDATE *upd)
{
size_t upd_size;
for (upd_size = 0; upd != NULL; upd = upd->next)
upd_size += WT_UPDATE_MEMSIZE(upd);
return (upd_size);
}
/*
* __wt_page_modify_init --
* A page is about to be modified, allocate the modification structure.
*/
static inline int
__wt_page_modify_init(WT_SESSION_IMPL *session, WT_PAGE *page)
{
return (page->modify == NULL ? __wt_page_modify_alloc(session, page) : 0);
}
/*
* __wt_page_only_modify_set --
* Mark the page (but only the page) dirty.
*/
static inline void
__wt_page_only_modify_set(WT_SESSION_IMPL *session, WT_PAGE *page)
{
uint64_t last_running;
WT_ASSERT(session, !F_ISSET(session->dhandle, WT_DHANDLE_DEAD));
last_running = 0;
if (page->modify->page_state == WT_PAGE_CLEAN)
last_running = S2C(session)->txn_global.last_running;
/*
* We depend on the atomic operation being a write barrier, that is, a barrier to ensure all
* changes to the page are flushed before updating the page state and/or marking the tree dirty,
* otherwise checkpoints and/or page reconciliation might be looking at a clean page/tree.
*
* Every time the page transitions from clean to dirty, update the cache and transactional
* information.
*
* The page state can only ever be incremented above dirty by the number of concurrently running
* threads, so the counter will never approach the point where it would wrap.
*/
if (page->modify->page_state < WT_PAGE_DIRTY &&
__wt_atomic_add32(&page->modify->page_state, 1) == WT_PAGE_DIRTY_FIRST) {
__wt_cache_dirty_incr(session, page);
/*
* In the event we dirty a page which is flagged for eviction soon, we update its read
* generation to avoid evicting a dirty page prematurely.
*/
if (page->read_gen == WT_READGEN_WONT_NEED)
__wt_cache_read_gen_new(session, page);
/*
* We won the race to dirty the page, but another thread could have committed in the
* meantime, and the last_running field been updated past it. That is all very unlikely, but
* not impossible, so we take care to read the global state before the atomic increment.
*
* If the page was dirty on entry, then last_running == 0. The page could have become clean
* since then, if reconciliation completed. In that case, we leave the previous value for
* first_dirty_txn rather than potentially racing to update it, at worst, we'll
* unnecessarily write a page in a checkpoint.
*/
if (last_running != 0)
page->modify->first_dirty_txn = last_running;
}
/* Check if this is the largest transaction ID to update the page. */
if (WT_TXNID_LT(page->modify->update_txn, session->txn->id))
page->modify->update_txn = session->txn->id;
}
/*
* __wt_tree_modify_set --
* Mark the tree dirty.
*/
static inline void
__wt_tree_modify_set(WT_SESSION_IMPL *session)
{
/*
* Test before setting the dirty flag, it's a hot cache line.
*
* The tree's modified flag is cleared by the checkpoint thread: set it and insert a barrier
* before dirtying the page. (I don't think it's a problem if the tree is marked dirty with all
* the pages clean, it might result in an extra checkpoint that doesn't do any work but it
* shouldn't cause problems; regardless, let's play it safe.)
*/
if (!S2BT(session)->modified) {
/* Assert we never dirty a checkpoint handle. */
WT_ASSERT(session, !WT_READING_CHECKPOINT(session));
S2BT(session)->modified = true;
WT_FULL_BARRIER();
}
/*
* The btree may already be marked dirty while the connection is still clean; mark the
* connection dirty outside the test of the btree state.
*/
if (!S2C(session)->modified)
S2C(session)->modified = true;
}
/*
* __wt_page_modify_clear --
* Clean a modified page.
*/
static inline void
__wt_page_modify_clear(WT_SESSION_IMPL *session, WT_PAGE *page)
{
/*
* The page must be held exclusive when this call is made, this call can only be used when the
* page is owned by a single thread.
*
* Allow the call to be made on clean pages.
*/
if (__wt_page_is_modified(page)) {
/*
* The only part where ordering matters is during reconciliation where updates on other
* threads are performing writes to the page state that need to be visible to the
* reconciliation thread.
*
* Since clearing of the page state is not going to be happening during reconciliation on a
* separate thread, there's no write barrier needed here.
*/
page->modify->page_state = WT_PAGE_CLEAN;
__wt_cache_dirty_decr(session, page);
}
}
/*
* __wt_page_modify_set --
* Mark the page and tree dirty.
*/
static inline void
__wt_page_modify_set(WT_SESSION_IMPL *session, WT_PAGE *page)
{
/*
* Prepared records in the datastore require page updates, even for read-only handles, don't
* mark the tree or page dirty.
*/
if (F_ISSET(S2BT(session), WT_BTREE_READONLY))
return;
/*
* Mark the tree dirty (even if the page is already marked dirty), newly created pages to
* support "empty" files are dirty, but the file isn't marked dirty until there's a real change
* needing to be written.
*/
__wt_tree_modify_set(session);
__wt_page_only_modify_set(session, page);
}
/*
* __wt_page_parent_modify_set --
* Mark the parent page, and optionally the tree, dirty.
*/
static inline int
__wt_page_parent_modify_set(WT_SESSION_IMPL *session, WT_REF *ref, bool page_only)
{
WT_PAGE *parent;
/*
* This function exists as a place to stash this comment. There are a few places where we need
* to dirty a page's parent. The trick is the page's parent might split at any point, and the
* page parent might be the wrong parent at any particular time. We ignore this and dirty
* whatever page the page's reference structure points to. This is safe because if we're
* pointing to the wrong parent, that parent must have split, deepening the tree, which implies
* marking the original parent and all of the newly-created children as dirty. In other words,
* if we have the wrong parent page, everything was marked dirty already.
*/
parent = ref->home;
WT_RET(__wt_page_modify_init(session, parent));
if (page_only)
__wt_page_only_modify_set(session, parent);
else
__wt_page_modify_set(session, parent);
return (0);
}
/*
* __wt_off_page --
* Return if a pointer references off-page data.
*/
static inline bool
__wt_off_page(WT_PAGE *page, const void *p)
{
/*
* There may be no underlying page, in which case the reference is off-page by definition.
*/
return (page->dsk == NULL || p < (void *)page->dsk ||
p >= (void *)((uint8_t *)page->dsk + page->dsk->mem_size));
}
/*
* __wt_ref_key --
* Return a reference to a row-store internal page key as cheaply as possible.
*/
static inline void
__wt_ref_key(WT_PAGE *page, WT_REF *ref, void *keyp, size_t *sizep)
{
uintptr_t v;
/*
* An internal page key is in one of two places: if we instantiated the
* key (for example, when reading the page), WT_REF.ref_ikey references
* a WT_IKEY structure, otherwise WT_REF.ref_ikey references an on-page
* key offset/length pair.
*
* Now the magic: allocated memory must be aligned to store any standard
* type, and we expect some standard type to require at least quad-byte
* alignment, so allocated memory should have some clear low-order bits.
* On-page objects consist of an offset/length pair: the maximum page
* size currently fits into 29 bits, so we use the low-order bits of the
* pointer to mark the other bits of the pointer as encoding the key's
* location and length. This breaks if allocated memory isn't aligned,
* of course.
*
* In this specific case, we use bit 0x01 to mark an on-page key, else
* it's a WT_IKEY reference. The bit pattern for internal row-store
* on-page keys is:
* 32 bits key length
* 31 bits page offset of the key's bytes,
* 1 bits flags
*/
#define WT_IK_FLAG 0x01
#define WT_IK_ENCODE_KEY_LEN(v) ((uintptr_t)(v) << 32)
#define WT_IK_DECODE_KEY_LEN(v) ((v) >> 32)
#define WT_IK_ENCODE_KEY_OFFSET(v) ((uintptr_t)(v) << 1)
#define WT_IK_DECODE_KEY_OFFSET(v) (((v)&0xFFFFFFFF) >> 1)
v = (uintptr_t)ref->ref_ikey;
if (v & WT_IK_FLAG) {
*(void **)keyp = WT_PAGE_REF_OFFSET(page, WT_IK_DECODE_KEY_OFFSET(v));
*sizep = WT_IK_DECODE_KEY_LEN(v);
} else {
*(void **)keyp = WT_IKEY_DATA(ref->ref_ikey);
*sizep = ((WT_IKEY *)ref->ref_ikey)->size;
}
}
/*
* __wt_ref_key_onpage_set --
* Set a WT_REF to reference an on-page key.
*/
static inline void
__wt_ref_key_onpage_set(WT_PAGE *page, WT_REF *ref, WT_CELL_UNPACK_ADDR *unpack)
{
uintptr_t v;
/*
* See the comment in __wt_ref_key for an explanation of the magic.
*/
v = WT_IK_ENCODE_KEY_LEN(unpack->size) |
WT_IK_ENCODE_KEY_OFFSET(WT_PAGE_DISK_OFFSET(page, unpack->data)) | WT_IK_FLAG;
ref->ref_ikey = (void *)v;
}
/*
* __wt_ref_key_instantiated --
* Return if a WT_REF key is instantiated.
*/
static inline WT_IKEY *
__wt_ref_key_instantiated(WT_REF *ref)
{
uintptr_t v;
/*
* See the comment in __wt_ref_key for an explanation of the magic.
*/
v = (uintptr_t)ref->ref_ikey;
return (v & WT_IK_FLAG ? NULL : (WT_IKEY *)ref->ref_ikey);
}
/*
* __wt_ref_key_clear --
* Clear a WT_REF key.
*/
static inline void
__wt_ref_key_clear(WT_REF *ref)
{
/*
* The key union has 2 8B fields; this is equivalent to:
*
* ref->ref_recno = WT_RECNO_OOB;
* ref->ref_ikey = NULL;
*/
ref->ref_recno = 0;
}
/*
* __wt_row_leaf_key_info --
* Return a row-store leaf page key referenced by a WT_ROW if it can be had without unpacking a
* cell, and information about the cell, if the key isn't cheaply available.
*/
static inline void
__wt_row_leaf_key_info(WT_PAGE *page, void *copy, WT_IKEY **ikeyp, WT_CELL **cellp, void *datap,
size_t *sizep, uint8_t *prefixp)
{
WT_IKEY *ikey;
uintptr_t v;
v = (uintptr_t)copy;
/*
* A row-store leaf page key is in one of two places: if instantiated, the WT_ROW pointer
* references a WT_IKEY structure, otherwise, it references an on-page item. Further, on-page
* items are in one of two states: if the key is a simple key (not an overflow key, which is
* likely), the key's offset, size and prefix is encoded in the 8B of pointer. Otherwise, the
* offset is to the key's on-page cell.
*
* This function returns information from a set of things about the key (WT_IKEY reference, cell
* reference and/or key/length/prefix triplet). Our callers know the order we resolve items and
* what information will be returned. Specifically, the caller gets a key (in the form of a
* pointer to the bytes, a length and a prefix length in all cases where we can get it without
* unpacking a cell), plus an optional WT_IKEY reference, and in all cases, a pointer to the
* on-page cell. Our caller's test is generally if there is a returned key or not, falling back
* to the returned cell.
*
* Now the magic: allocated memory must be aligned to store any standard type and we expect some
* standard type to require at least quad-byte alignment, so allocated memory should have two
* clear low-order bits. On-page objects consist of an offset/length pair and a prefix in the
* case of a key: the maximum page size is 29 bits (512MB), the remaining bits hold the key or
* value location and bytes. This breaks if allocated memory isn't aligned, of course.
*
* In this specific case, we use bit 0x01 to mark an on-page cell, bit 0x02 to mark an on-page
* key, 0x03 to mark an on-page key/value pair, otherwise it's a WT_IKEY reference. The bit
* pattern for on-page cells is:
*
* 29 bits offset of the key's cell (512MB)
* 2 bits 0x01 flag
*
* The on-page cell is our fallback: if a key or value won't fit into our encoding (unlikely,
* but possible), we fall back to using a cell reference, which obviously has enough room for
* all possible values.
*
* The next encoding is for on-page keys:
*
* 19 bits key's length (512KB)
* 6 bits offset of the key's bytes from the key's cell (32B)
* 8 bits key's prefix length (256B, the maximum possible value)
* 29 bits offset of the key's cell (512MB)
* 2 bits 0x02 flag
*
* But, while that allows us to skip decoding simple key cells, we also want to skip decoding
* value cells in the case where the value cell is also simple/short. We use bit 0x03 to mark
* an encoded on-page key and value pair. The encoding for on-page key/value pairs is:
*
* 13 bits value's length (8KB)
* 6 bits offset of the value's bytes from the end of the key's cell (32B)
* 12 bits key's length (4KB)
* 6 bits offset of the key's bytes from the key's cell (32B)
* 8 bits key's prefix length (256B, the maximum possible value)
* 17 bits offset of the key's cell (128KB)
* 2 bits 0x03 flag
*
* A reason for the complexity here is we need to be able to find the key and value cells from
* the encoded form: for that reason we store an offset to the key cell plus a second offset to
* the start of the key's bytes. Finding the value cell is reasonably straight-forward, we use
* the location of the key to find the cell immediately following the key.
*
* A simple extension of this encoding would be to encode zero-length values similarly to how we
* encode short values. However, zero-length values are noted by adjacent key cells on the page,
* and we detect that without decoding the second cell by checking the cell's type byte. Tests
* indicate it's slightly slower to encode missing value cells than to check the cell type, so
* we don't bother with the encoding.
*
* Generally, the bitfields are expected to be larger than the stored items (4/8KB keys/values,
* 128KB pages), but the underlying limits are larger and we can see items we cannot encode in
* this way. For example, if an application creates pages larger than 128KB, encoded key/value
* offsets after the maximum offset (the offsets of cells at the end of the page), couldn't be
* encoded. If that's not working, these bit patterns can be changed as they are in-memory only
* (we could even tune for specific workloads in specific trees).
*/
#define WT_KEY_FLAG_BITS 0x03
#define WT_CELL_FLAG 0x01
/* key cell offset field size can hold maximum value, WT_CELL_MAX_KEY_CELL_OFFSET not needed. */
#define WT_CELL_ENCODE_OFFSET(v) ((uintptr_t)(v) << 2)
#define WT_CELL_DECODE_OFFSET(v) ((v) >> 2)
#define WT_K_FLAG 0x02
#define WT_K_MAX_KEY_LEN (0x80000 - 1)
#define WT_K_DECODE_KEY_LEN(v) (((v)&0xffffe00000000000) >> 45)
#define WT_K_ENCODE_KEY_LEN(v) ((uintptr_t)(v) << 45)
#define WT_K_MAX_KEY_OFFSET (0x40 - 1)
#define WT_K_DECODE_KEY_OFFSET(v) (((v)&0x001f8000000000) >> 39)
#define WT_K_ENCODE_KEY_OFFSET(v) ((uintptr_t)(v) << 39)
/* Key prefix field size can hold maximum value, WT_K_MAX_KEY_PREFIX not needed. */
#define WT_K_DECODE_KEY_PREFIX(v) (((v)&0x00007f80000000) >> 31)
#define WT_K_ENCODE_KEY_PREFIX(v) ((uintptr_t)(v) << 31)
/* Key cell offset field size can hold maximum value, WT_K_MAX_KEY_CELL_OFFSET not needed. */
#define WT_K_DECODE_KEY_CELL_OFFSET(v) (((v)&0x0000007ffffffc) >> 2)
#define WT_K_ENCODE_KEY_CELL_OFFSET(v) ((uintptr_t)(v) << 2)
#define WT_KV_FLAG 0x03
#define WT_KV_MAX_VALUE_LEN (0x2000 - 1)
#define WT_KV_DECODE_VALUE_LEN(v) (((v)&0xfff8000000000000) >> 51)
#define WT_KV_ENCODE_VALUE_LEN(v) ((uintptr_t)(v) << 51)
#define WT_KV_MAX_VALUE_OFFSET (0x40 - 1)
#define WT_KV_DECODE_VALUE_OFFSET(v) (((v)&0x07e00000000000) >> 45)
#define WT_KV_ENCODE_VALUE_OFFSET(v) ((uintptr_t)(v) << 45)
#define WT_KV_MAX_KEY_LEN (0x1000 - 1)
#define WT_KV_DECODE_KEY_LEN(v) (((v)&0x001ffe00000000) >> 33)
#define WT_KV_ENCODE_KEY_LEN(v) ((uintptr_t)(v) << 33)
/* Key offset encoding is the same for key and key/value forms, WT_KV_MAX_KEY_OFFSET not needed. */
#define WT_KV_DECODE_KEY_OFFSET(v) (((v)&0x000001f8000000) >> 27)
#define WT_KV_ENCODE_KEY_OFFSET(v) ((uintptr_t)(v) << 27)
/* Key prefix encoding is the same for key and key/value forms, WT_KV_MAX_KEY_PREFIX not needed. */
#define WT_KV_DECODE_KEY_PREFIX(v) (((v)&0x00000007f80000) >> 19)
#define WT_KV_ENCODE_KEY_PREFIX(v) ((uintptr_t)(v) << 19)
#define WT_KV_MAX_KEY_CELL_OFFSET (0x20000 - 1)
#define WT_KV_DECODE_KEY_CELL_OFFSET(v) (((v)&0x0000000007fffc) >> 2)
#define WT_KV_ENCODE_KEY_CELL_OFFSET(v) ((uintptr_t)(v) << 2)
switch (v & WT_KEY_FLAG_BITS) {
case WT_CELL_FLAG: /* On-page cell. */
if (ikeyp != NULL)
*ikeyp = NULL;
if (cellp != NULL)
*cellp = (WT_CELL *)WT_PAGE_REF_OFFSET(page, WT_CELL_DECODE_OFFSET(v));
if (datap != NULL) {
*(void **)datap = NULL;
*sizep = 0;
*prefixp = 0;
}
break;
case WT_K_FLAG: /* Encoded key. */
if (ikeyp != NULL)
*ikeyp = NULL;
if (cellp != NULL)
*cellp = (WT_CELL *)WT_PAGE_REF_OFFSET(page, WT_K_DECODE_KEY_CELL_OFFSET(v));
if (datap != NULL) {
*(void **)datap =
WT_PAGE_REF_OFFSET(page, WT_K_DECODE_KEY_CELL_OFFSET(v) + WT_K_DECODE_KEY_OFFSET(v));
*sizep = WT_K_DECODE_KEY_LEN(v);
*prefixp = (uint8_t)WT_K_DECODE_KEY_PREFIX(v);
}
break;
case WT_KV_FLAG: /* Encoded key/value pair. */
if (ikeyp != NULL)
*ikeyp = NULL;
if (cellp != NULL)
*cellp = (WT_CELL *)WT_PAGE_REF_OFFSET(page, WT_KV_DECODE_KEY_CELL_OFFSET(v));
if (datap != NULL) {
*(void **)datap = WT_PAGE_REF_OFFSET(
page, WT_KV_DECODE_KEY_CELL_OFFSET(v) + WT_KV_DECODE_KEY_OFFSET(v));
*sizep = WT_KV_DECODE_KEY_LEN(v);
*prefixp = (uint8_t)WT_KV_DECODE_KEY_PREFIX(v);
}
break;
default: /* Instantiated key. */
ikey = (WT_IKEY *)copy;
if (ikeyp != NULL)
*ikeyp = ikey;
if (cellp != NULL)
*cellp = ikey->cell_offset == 0 ?
NULL :
(WT_CELL *)WT_PAGE_REF_OFFSET(page, ikey->cell_offset);
if (datap != NULL) {
*(void **)datap = WT_IKEY_DATA(ikey);
*sizep = ikey->size;
*prefixp = 0;
}
break;
}
}
/*
* __wt_row_leaf_key_set --
* Set a WT_ROW to reference an on-page row-store leaf key.
*/
static inline void
__wt_row_leaf_key_set(WT_PAGE *page, WT_ROW *rip, WT_CELL_UNPACK_KV *unpack)
{
uintptr_t key_offset, v;
/*
* See the comment in __wt_row_leaf_key_info for an explanation of the magic.
*
* Not checking the prefix and cell offset sizes, the fields hold any legitimate value.
*/
key_offset = (uintptr_t)WT_PTRDIFF(unpack->data, unpack->cell);
if (unpack->type != WT_CELL_KEY || key_offset > WT_K_MAX_KEY_OFFSET ||
unpack->size > WT_K_MAX_KEY_LEN)
v = WT_CELL_ENCODE_OFFSET(WT_PAGE_DISK_OFFSET(page, unpack->cell)) | WT_CELL_FLAG;
else
v = WT_K_ENCODE_KEY_CELL_OFFSET(WT_PAGE_DISK_OFFSET(page, unpack->cell)) |
WT_K_ENCODE_KEY_PREFIX(unpack->prefix) | WT_K_ENCODE_KEY_OFFSET(key_offset) |
WT_K_ENCODE_KEY_LEN(unpack->size) | WT_K_FLAG;
WT_ROW_KEY_SET(rip, v);
}
/*
* __wt_row_leaf_value_set --
* Set a WT_ROW to reference an on-page row-store leaf key and value pair, if possible.
*/
static inline void
__wt_row_leaf_value_set(WT_ROW *rip, WT_CELL_UNPACK_KV *unpack)
{
uintptr_t value_offset, value_size, v;
/* The row-store key can change underfoot; explicitly take a copy. */
v = (uintptr_t)WT_ROW_KEY_COPY(rip);
/*
* See the comment in __wt_row_leaf_key_info for an explanation of the magic.
*
* Only encoded keys can be upgraded to encoded key/value pairs.
*/
if ((v & WT_KEY_FLAG_BITS) != WT_K_FLAG)
return;
if (WT_K_DECODE_KEY_CELL_OFFSET(v) > WT_KV_MAX_KEY_CELL_OFFSET) /* Key cell offset */
return;
/*
* Not checking the prefix size, the field sizes are the same in both encodings.
*
* Not checking the key offset, the field sizes are the same in both encodings.
*/
if (WT_K_DECODE_KEY_LEN(v) > WT_KV_MAX_KEY_LEN) /* Key len */
return;
value_offset = (uintptr_t)WT_PTRDIFF(unpack->data, unpack->cell);
if (value_offset > WT_KV_MAX_VALUE_OFFSET) /* Value offset */
return;
value_size = unpack->size;
if (value_size > WT_KV_MAX_VALUE_LEN) /* Value length */
return;
v = WT_KV_ENCODE_KEY_CELL_OFFSET(WT_K_DECODE_KEY_CELL_OFFSET(v)) |
WT_KV_ENCODE_KEY_PREFIX(WT_K_DECODE_KEY_PREFIX(v)) |
WT_KV_ENCODE_KEY_OFFSET(WT_K_DECODE_KEY_OFFSET(v)) |
WT_KV_ENCODE_KEY_LEN(WT_K_DECODE_KEY_LEN(v)) | WT_KV_ENCODE_VALUE_OFFSET(value_offset) |
WT_KV_ENCODE_VALUE_LEN(value_size) | WT_KV_FLAG;
WT_ROW_KEY_SET(rip, v);
}
/*
* __wt_row_leaf_key_free --
* Discard any memory allocated for an instantiated key.
*/
static inline void
__wt_row_leaf_key_free(WT_SESSION_IMPL *session, WT_PAGE *page, WT_ROW *rip)
{
WT_IKEY *ikey;
void *copy;
/* The row-store key can change underfoot; explicitly take a copy. */
copy = WT_ROW_KEY_COPY(rip);
/*
* If the key was a WT_IKEY allocation (that is, if it points somewhere other than the original
* page), free the memory.
*/
__wt_row_leaf_key_info(page, copy, &ikey, NULL, NULL, NULL, NULL);
__wt_free(session, ikey);
}
/*
* __wt_row_leaf_key --
* Set a buffer to reference a row-store leaf page key as cheaply as possible.
*/
static inline int
__wt_row_leaf_key(
WT_SESSION_IMPL *session, WT_PAGE *page, WT_ROW *rip, WT_ITEM *key, bool instantiate)
{
WT_CELL *cell;
size_t group_size, key_size;
uint32_t slot;
uint8_t group_prefix, key_prefix;
void *copy;
const void *group_key, *key_data;
/*
* A front-end for __wt_row_leaf_key_work, here to inline fast paths.
*
* The row-store key can change underfoot; explicitly take a copy.
*/
copy = WT_ROW_KEY_COPY(rip);
/*
* Handle keys taken directly from the disk image (which should be a common case), instantiated
* keys (rare initially, but possibly more common as leaf page search instantiates keys), and
* keys built using the most-used page key prefix.
*
* The most-used page key prefix: the longest group of compressed key prefixes on the page that
* can be built from a single, fully instantiated key on the page, was tracked when the page was
* read. Build keys in that group by appending the key's bytes to the root key from which it was
* compressed.
*/
__wt_row_leaf_key_info(page, copy, NULL, &cell, &key_data, &key_size, &key_prefix);
if (key_data != NULL && key_prefix == 0) {
key->data = key_data;
key->size = key_size;
return (0);
}
slot = WT_ROW_SLOT(page, rip);
if (key_data != NULL && slot > page->prefix_start && slot <= page->prefix_stop) {
/* The row-store key can change underfoot; explicitly take a copy. */
copy = WT_ROW_KEY_COPY(&page->pg_row[page->prefix_start]);
__wt_row_leaf_key_info(page, copy, NULL, NULL, &group_key, &group_size, &group_prefix);
if (group_key != NULL) {
WT_RET(__wt_buf_init(session, key, key_prefix + key_size));
memcpy(key->mem, group_key, key_prefix);
memcpy((uint8_t *)key->mem + key_prefix, key_data, key_size);
key->size = key_prefix + key_size;
return (0);
}
}
/*
* The alternative is an on-page cell with some kind of compressed or overflow key that's never
* been instantiated. Call the underlying worker function to figure it out.
*/
return (__wt_row_leaf_key_work(session, page, rip, key, instantiate));
}
/*
* __wt_row_leaf_key_instantiate --
* Instantiate the keys on a leaf page as needed.
*/
static inline int
__wt_row_leaf_key_instantiate(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_CELL *cell;
WT_DECL_ITEM(key);
WT_DECL_RET;
WT_ROW *rip;
size_t key_size;
uint32_t i, slot;
uint8_t key_prefix;
u_int skip;
void *copy;
const void *key_data;
/*
* Cursor previous traversals will be too slow in the case of a set of prefix-compressed keys
* requiring long roll-forward processing. In the worst case, each key would require processing
* every key appearing before it on the page as we walk backwards through the page. If we're
* doing a cursor previous call, and this page has never been checked for excessively long
* stretches of prefix-compressed keys, do it now.
*/
if (F_ISSET_ATOMIC_16(page, WT_PAGE_BUILD_KEYS))
return (0);
F_SET_ATOMIC_16(page, WT_PAGE_BUILD_KEYS);
/* Walk the keys, making sure there's something easy to work with periodically. */
skip = 0;
WT_ROW_FOREACH (page, rip, i) {
/*
* Get the key's information. The row-store key can change underfoot; explicitly take a
* copy.
*/
copy = WT_ROW_KEY_COPY(rip);
__wt_row_leaf_key_info(page, copy, NULL, &cell, &key_data, &key_size, &key_prefix);
/*
* If the key isn't prefix compressed, or is a prefix-compressed key we can derive from the
* group record, we're done.
*/
slot = WT_ROW_SLOT(page, rip);
if (key_data != NULL &&
(key_prefix == 0 || (slot > page->prefix_start && slot <= page->prefix_stop))) {
skip = 0;
continue;
}
/*
* Skip overflow keys: we'll instantiate them on demand and they don't require any special
* processing (but they don't help with long strings of prefix compressed keys, either, so
* we'll likely want to instantiate the first key we find after a long stretch of overflow
* keys). More importantly, we don't want to instantiate them for a cursor traversal, we
* only want to instantiate them for a tree search, as that's likely to happen repeatedly.
*/
if (__wt_cell_type(cell) == WT_CELL_KEY_OVFL) {
++skip;
continue;
}
/*
* If we skip 10 keys, instantiate one, limiting how far we're forced to roll backward. (The
* value 10 was chosen for no particular reason.) There are still cases where we might not
* need to instantiate this key (for example, a key too large to be encoded, but still
* on-page and not prefix-compressed). Let the underlying worker function figure that out,
* we should have found the vast majority of cases by now.
*/
if (++skip >= 10) {
if (key == NULL)
WT_ERR(__wt_scr_alloc(session, 0, &key));
WT_ERR(__wt_row_leaf_key(session, page, rip, key, true));
skip = 0;
}
}
err:
__wt_scr_free(session, &key);
return (ret);
}
/*
* __wt_row_leaf_value_is_encoded --
* Return if the value for a row-store leaf page is an encoded key/value pair.
*/
static inline bool
__wt_row_leaf_value_is_encoded(WT_ROW *rip)
{
uintptr_t v;
/* The row-store key can change underfoot; explicitly take a copy. */
v = (uintptr_t)WT_ROW_KEY_COPY(rip);
/*
* See the comment in __wt_row_leaf_key_info for an explanation of the magic.
*/
return ((v & WT_KEY_FLAG_BITS) == WT_KV_FLAG);
}
/*
* __wt_row_leaf_value --
* Return the value for a row-store leaf page encoded key/value pair.
*/
static inline bool
__wt_row_leaf_value(WT_PAGE *page, WT_ROW *rip, WT_ITEM *value)
{
uintptr_t v;
/* The row-store key can change underfoot; explicitly take a copy. */
v = (uintptr_t)WT_ROW_KEY_COPY(rip);
if ((v & WT_KEY_FLAG_BITS) == WT_KV_FLAG) {
/*
* See the comment in __wt_row_leaf_key_info for an explanation of the magic.
*
* Normally a value is represented by the value's cell in the disk image (or an update), but
* there is a fast path for returning a simple value, where it's worth the additional effort
* of encoding the value in the per-row reference and retrieving it. This function does that
* work, while most value retrieval goes through the "return the unpacked cell" version.
*
* The value's data is the page offset of the key's cell, plus the key's offset, plus the
* key's size, plus the value's offset: in other words, we know where the key's cell starts,
* the key's data ends the key's cell, and the value cell immediately follows, Skip past the
* key cell to the value cell, then skip to the start of the value's data.
*/
value->data = (uint8_t *)WT_PAGE_REF_OFFSET(page, WT_KV_DECODE_KEY_CELL_OFFSET(v)) +
WT_KV_DECODE_KEY_OFFSET(v) + WT_KV_DECODE_KEY_LEN(v) + WT_KV_DECODE_VALUE_OFFSET(v);
value->size = WT_KV_DECODE_VALUE_LEN(v);
return (true);
}
return (false);
}
/*
* __wt_row_leaf_value_cell --
* Return the unpacked value for a row-store leaf page key.
*/
static inline void
__wt_row_leaf_value_cell(
WT_SESSION_IMPL *session, WT_PAGE *page, WT_ROW *rip, WT_CELL_UNPACK_KV *vpack)
{
WT_CELL *kcell, *vcell;
WT_CELL_UNPACK_KV unpack;
WT_IKEY *ikey;
uintptr_t v;
/* The row-store key can change underfoot; explicitly take a copy. */
v = (uintptr_t)WT_ROW_KEY_COPY(rip);
kcell = vcell = NULL;
switch (v & WT_KEY_FLAG_BITS) {
case WT_CELL_FLAG:
/* We have a direct reference the key's cell, step past it to the value's cell. */
kcell = (WT_CELL *)WT_PAGE_REF_OFFSET(page, WT_CELL_DECODE_OFFSET(v));
break;
case WT_K_FLAG:
/* We have an encoded on-page key, the value's cell follows the key's data. */
vcell = (WT_CELL *)((uint8_t *)WT_PAGE_REF_OFFSET(page, WT_K_DECODE_KEY_CELL_OFFSET(v)) +
WT_K_DECODE_KEY_OFFSET(v) + WT_K_DECODE_KEY_LEN(v));
break;
case WT_KV_FLAG:
/* We have an encoded on-page key/value pair, the value's cell follows the key's data. */
vcell = (WT_CELL *)((uint8_t *)WT_PAGE_REF_OFFSET(page, WT_KV_DECODE_KEY_CELL_OFFSET(v)) +
WT_KV_DECODE_KEY_OFFSET(v) + WT_KV_DECODE_KEY_LEN(v));
break;
default:
/* We have an instantiated key, the key cell's offset is included in the structure. */
ikey = (WT_IKEY *)v;
kcell =
ikey->cell_offset == 0 ? NULL : (WT_CELL *)WT_PAGE_REF_OFFSET(page, ikey->cell_offset);
break;
}
/* If we only have the key cell, unpack it and skip past it to the value cell. */
if (vcell == NULL) {
__wt_cell_unpack_kv(session, page->dsk, kcell, &unpack);
vcell = (WT_CELL *)((uint8_t *)unpack.cell + __wt_cell_total_len(&unpack));
}
__wt_cell_unpack_kv(session, page->dsk, __wt_cell_leaf_value_parse(page, vcell), vpack);
}
/*
* __wt_ref_addr_copy --
* Return a copy of the WT_REF address information.
*/
static inline bool
__wt_ref_addr_copy(WT_SESSION_IMPL *session, WT_REF *ref, WT_ADDR_COPY *copy)
{
WT_ADDR *addr;
WT_CELL_UNPACK_ADDR *unpack, _unpack;
WT_PAGE *page;
unpack = &_unpack;
page = ref->home;
/*
* To look at an on-page cell, we need to look at the parent page's disk image, and that can be
* dangerous. The problem is if the parent page splits, deepening the tree. As part of that
* process, the WT_REF WT_ADDRs pointing into the parent's disk image are copied into off-page
* WT_ADDRs and swapped into place. The content of the two WT_ADDRs are identical, and we don't
* care which version we get as long as we don't mix-and-match the two.
*/
WT_ORDERED_READ(addr, (WT_ADDR *)ref->addr);
/* If NULL, there is no information. */
if (addr == NULL)
return (false);
/* If off-page, the pointer references a WT_ADDR structure. */
if (__wt_off_page(page, addr)) {
WT_TIME_AGGREGATE_COPY(©->ta, &addr->ta);
copy->type = addr->type;
memcpy(copy->addr, addr->addr, copy->size = addr->size);
return (true);
}
/* If on-page, the pointer references a cell. */
__wt_cell_unpack_addr(session, page->dsk, (WT_CELL *)addr, unpack);
WT_TIME_AGGREGATE_COPY(©->ta, &unpack->ta);
copy->type = 0; /* Avoid static analyzer uninitialized value complaints. */
switch (unpack->raw) {
case WT_CELL_ADDR_INT:
copy->type = WT_ADDR_INT;
break;
case WT_CELL_ADDR_LEAF:
copy->type = WT_ADDR_LEAF;
break;
case WT_CELL_ADDR_LEAF_NO:
copy->type = WT_ADDR_LEAF_NO;
break;
}
memcpy(copy->addr, unpack->data, copy->size = (uint8_t)unpack->size);
return (true);
}
/*
* __wt_ref_block_free --
* Free the on-disk block for a reference and clear the address.
*/
static inline int
__wt_ref_block_free(WT_SESSION_IMPL *session, WT_REF *ref)
{
WT_ADDR_COPY addr;
if (!__wt_ref_addr_copy(session, ref, &addr))
return (0);
WT_RET(__wt_btree_block_free(session, addr.addr, addr.size));
/* Clear the address (so we don't free it twice). */
__wt_ref_addr_free(session, ref);
return (0);
}
/*
* __wt_page_del_active --
* Return if a truncate operation is active.
*/
static inline bool
__wt_page_del_active(WT_SESSION_IMPL *session, WT_REF *ref, bool visible_all)
{
WT_PAGE_DELETED *page_del;
uint8_t prepare_state;
WT_ASSERT(session, ref->state == WT_REF_LOCKED);
if ((page_del = ref->ft_info.del) == NULL)
return (false);
if (page_del->txnid == WT_TXN_ABORTED)
return (false);
/*
* If we are reading from a checkpoint, visible_all checks don't work (they check the current
* state of the world and not the checkpoint) so operate under the assumption that if the
* truncate operation appears in the checkpoint, it must have been visible to somebody, and
* because the checkpoint is immutable, that won't ever change.
*/
if (WT_READING_CHECKPOINT(session) && visible_all)
return (true);
WT_ORDERED_READ(prepare_state, page_del->prepare_state);
if (prepare_state == WT_PREPARE_INPROGRESS || prepare_state == WT_PREPARE_LOCKED)
return (true);
return (visible_all ? !__wt_txn_visible_all(session, page_del->txnid, page_del->timestamp) :
!__wt_txn_visible(session, page_del->txnid, page_del->timestamp));
}
/*
* __wt_btree_syncing_by_other_session --
* Returns true if the session's current btree is being synced by another thread.
*/
static inline bool
__wt_btree_syncing_by_other_session(WT_SESSION_IMPL *session)
{
WT_BTREE *btree;
btree = S2BT(session);
return (WT_BTREE_SYNCING(btree) && !WT_SESSION_BTREE_SYNC(session));
}
/*
* __wt_leaf_page_can_split --
* Check whether a page can be split in memory.
*/
static inline bool
__wt_leaf_page_can_split(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_BTREE *btree;
WT_INSERT *ins;
WT_INSERT_HEAD *ins_head;
size_t size;
int count;
btree = S2BT(session);
/*
* Checkpoints can't do in-memory splits in the tree they are walking: that can lead to
* corruption when the parent internal page is updated.
*/
if (WT_SESSION_BTREE_SYNC(session))
return (false);
/*
* Only split a page once, otherwise workloads that update in the middle of the page could
* continually split without benefit.
*/
if (F_ISSET_ATOMIC_16(page, WT_PAGE_SPLIT_INSERT))
return (false);
/*
* Check for pages with append-only workloads. A common application pattern is to have multiple
* threads frantically appending to the tree. We want to reconcile and evict this page, but we'd
* like to do it without making the appending threads wait. See if it's worth doing a split to
* let the threads continue before doing eviction.
*
* Ignore anything other than large, dirty leaf pages. We depend on the page being dirty for
* correctness (the page must be reconciled again before being evicted after the split,
* information from a previous reconciliation will be wrong, so we can't evict immediately).
*/
if (page->memory_footprint < btree->splitmempage)
return (false);
if (WT_PAGE_IS_INTERNAL(page))
return (false);
if (!__wt_page_is_modified(page))
return (false);
/*
* There is no point doing an in-memory split unless there is a lot of data in the last skiplist
* on the page. Split if there are enough items and the skiplist does not fit within a single
* disk page.
*/
ins_head = page->type == WT_PAGE_ROW_LEAF ?
(page->entries == 0 ? WT_ROW_INSERT_SMALLEST(page) :
WT_ROW_INSERT_SLOT(page, page->entries - 1)) :
WT_COL_APPEND(page);
if (ins_head == NULL)
return (false);
/*
* In the extreme case, where the page is much larger than the maximum size, split as soon as there
* are 5 items on the page.
*/
#define WT_MAX_SPLIT_COUNT 5
if (page->memory_footprint > (size_t)btree->maxleafpage * 2) {
for (count = 0, ins = ins_head->head[0]; ins != NULL; ins = ins->next[0]) {
if (++count < WT_MAX_SPLIT_COUNT)
continue;
WT_STAT_CONN_DATA_INCR(session, cache_inmem_splittable);
return (true);
}
return (false);
}
/*
* Rather than scanning the whole list, walk a higher level, which gives a sample of the items -- at
* level 0 we have all the items, at level 1 we have 1/4 and at level 2 we have 1/16th. If we see
* more than 30 items and more data than would fit in a disk page, split.
*/
#define WT_MIN_SPLIT_DEPTH 2
#define WT_MIN_SPLIT_COUNT 30
#define WT_MIN_SPLIT_MULTIPLIER 16 /* At level 2, we see 1/16th entries */
for (count = 0, size = 0, ins = ins_head->head[WT_MIN_SPLIT_DEPTH]; ins != NULL;
ins = ins->next[WT_MIN_SPLIT_DEPTH]) {
count += WT_MIN_SPLIT_MULTIPLIER;
size += WT_MIN_SPLIT_MULTIPLIER * (WT_INSERT_KEY_SIZE(ins) + WT_UPDATE_MEMSIZE(ins->upd));
if (count > WT_MIN_SPLIT_COUNT && size > (size_t)btree->maxleafpage) {
WT_STAT_CONN_DATA_INCR(session, cache_inmem_splittable);
return (true);
}
}
return (false);
}
/*
* __wt_page_evict_retry --
* Avoid busy-spinning attempting to evict the same page all the time.
*/
static inline bool
__wt_page_evict_retry(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_PAGE_MODIFY *mod;
WT_TXN_GLOBAL *txn_global;
wt_timestamp_t pinned_ts;
txn_global = &S2C(session)->txn_global;
/*
* If the page hasn't been through one round of update/restore, give it a try.
*/
if ((mod = page->modify) == NULL || !FLD_ISSET(mod->restore_state, WT_PAGE_RS_RESTORED))
return (true);
/*
* Retry if a reasonable amount of eviction time has passed, the choice of 5 eviction passes as
* a reasonable amount of time is currently pretty arbitrary.
*/
if (__wt_cache_aggressive(session) ||
mod->last_evict_pass_gen + 5 < S2C(session)->cache->evict_pass_gen)
return (true);
/* Retry if the global transaction state has moved forward. */
if (txn_global->current == txn_global->oldest_id ||
mod->last_eviction_id != __wt_txn_oldest_id(session))
return (true);
/*
* It is possible that we have not started using the timestamps just yet. So, check for the last
* time we evicted only if there is a timestamp set.
*/
if (mod->last_eviction_timestamp != WT_TS_NONE) {
__wt_txn_pinned_timestamp(session, &pinned_ts);
if (pinned_ts > mod->last_eviction_timestamp)
return (true);
}
return (false);
}
/*
* __wt_page_can_evict --
* Check whether a page can be evicted.
*/
static inline bool
__wt_page_can_evict(WT_SESSION_IMPL *session, WT_REF *ref, bool *inmem_splitp)
{
WT_PAGE *page;
WT_PAGE_MODIFY *mod;
bool modified;
if (inmem_splitp != NULL)
*inmem_splitp = false;
page = ref->page;
mod = page->modify;
/* Never modified pages can always be evicted. */
if (mod == NULL)
return (true);
/*
* If a fast-truncate page is subsequently instantiated, it can become an eviction candidate. If
* the fast-truncate itself has not resolved when the page is instantiated, a list of updates is
* created, which will be discarded as part of transaction resolution. Don't attempt to evict a
* fast-truncate page until any update list has been removed.
*/
if (ref->ft_info.update != NULL)
return (false);
/*
* We can't split or evict multiblock row-store pages where the parent's key for the page is an
* overflow item, because the split into the parent frees the backing blocks for no-longer-used
* overflow keys, which will corrupt the checkpoint's block management. (This is only for
* historical tables, reconciliation no longer writes overflow cookies on internal pages, no
* matter the size of the key.)
*/
if (__wt_btree_syncing_by_other_session(session) &&
F_ISSET_ATOMIC_16(ref->home, WT_PAGE_INTL_OVERFLOW_KEYS))
return (false);
/*
* Check for in-memory splits before other eviction tests. If the page should split in-memory,
* return success immediately and skip more detailed eviction tests. We don't need further tests
* since the page won't be written or discarded from the cache.
*/
if (__wt_leaf_page_can_split(session, page)) {
if (inmem_splitp != NULL)
*inmem_splitp = true;
return (true);
}
modified = __wt_page_is_modified(page);
/*
* If the file is being checkpointed, other threads can't evict dirty pages: if a page is
* written and the previous version freed, that previous version might be referenced by an
* internal page already written in the checkpoint, leaving the checkpoint inconsistent.
*/
if (modified && __wt_btree_syncing_by_other_session(session)) {
WT_STAT_CONN_DATA_INCR(session, cache_eviction_checkpoint);
return (false);
}
/*
* Check we are not evicting an accessible internal page with an active split generation.
*
* If a split created new internal pages, those newly created internal pages cannot be evicted
* until all threads are known to have exited the original parent page's index, because evicting
* an internal page discards its WT_REF array, and a thread traversing the original parent page
* index might see a freed WT_REF.
*
* One special case where we know this is safe is if the handle is dead or locked exclusively,
* that is, no readers can be looking at an old index.
*/
if (F_ISSET(ref, WT_REF_FLAG_INTERNAL) &&
!F_ISSET(session->dhandle, WT_DHANDLE_DEAD | WT_DHANDLE_EXCLUSIVE) &&
__wt_gen_active(session, WT_GEN_SPLIT, page->pg_intl_split_gen))
return (false);
/* If the metadata page is clean but has modifications that appear too new to evict, skip it. */
if (WT_IS_METADATA(S2BT(session)->dhandle) && !modified &&
!__wt_txn_visible_all(session, mod->rec_max_txn, mod->rec_max_timestamp))
return (false);
return (true);
}
/*
* __wt_page_release --
* Release a reference to a page.
*/
static inline int
__wt_page_release(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t flags)
{
WT_BTREE *btree;
WT_DECL_RET;
WT_PAGE *page;
bool inmem_split;
btree = S2BT(session);
/*
* Discard our hazard pointer. Ignore pages we don't have and the root page, which sticks in
* memory, regardless.
*/
if (ref == NULL || ref->page == NULL || __wt_ref_is_root(ref))
return (0);
/*
* If hazard pointers aren't necessary for this file, we can't be evicting, we're done.
*/
if (F_ISSET(btree, WT_BTREE_IN_MEMORY))
return (0);
/*
* If the session is configured with the release_evict_pages debug option, we will attempt to
* evict the pages when they are no longer needed.
*/
if (F_ISSET(session, WT_SESSION_DEBUG_RELEASE_EVICT)) {
WT_TRET_BUSY_OK(__wt_page_release_evict(session, ref, flags));
return (0);
}
/*
* Attempt to evict pages with the special "oldest" read generation. This is set for pages that
* grow larger than the configured memory_page_max setting, when we see many deleted items, and
* when we are attempting to scan without trashing the cache.
*
* Checkpoint should not queue pages for urgent eviction if they require dirty eviction: there
* is a special exemption that allows checkpoint to evict dirty pages in a tree that is being
* checkpointed, and no other thread can help with that. Checkpoints don't rely on this code for
* dirty eviction: that is handled explicitly in __wt_sync_file.
*
* If the operation has disabled eviction or splitting, or the session is preventing from
* reconciling, then just queue the page for urgent eviction. Otherwise, attempt to release and
* evict it.
*/
page = ref->page;
if (WT_READGEN_EVICT_SOON(page->read_gen) && btree->evict_disabled == 0 &&
__wt_page_can_evict(session, ref, &inmem_split) &&
(!WT_SESSION_IS_CHECKPOINT(session) || __wt_page_evict_clean(page))) {
if (LF_ISSET(WT_READ_NO_EVICT) ||
(inmem_split ? LF_ISSET(WT_READ_NO_SPLIT) : F_ISSET(session, WT_SESSION_NO_RECONCILE)))
WT_IGNORE_RET_BOOL(__wt_page_evict_urgent(session, ref));
else {
WT_RET_BUSY_OK(__wt_page_release_evict(session, ref, flags));
return (0);
}
}
return (__wt_hazard_clear(session, ref));
}
/*
* __wt_skip_choose_depth --
* Randomly choose a depth for a skiplist insert.
*/
static inline u_int
__wt_skip_choose_depth(WT_SESSION_IMPL *session)
{
u_int d;
for (d = 1; d < WT_SKIP_MAXDEPTH && __wt_random(&session->rnd) < WT_SKIP_PROBABILITY; d++)
;
return (d);
}
/*
* __wt_btree_lsm_over_size --
* Return if the size of an in-memory tree with a single leaf page is over a specified maximum.
* If called on anything other than a simple tree with a single leaf page, returns true so our
* LSM caller will switch to a new tree.
*/
static inline bool
__wt_btree_lsm_over_size(WT_SESSION_IMPL *session, uint64_t maxsize)
{
WT_BTREE *btree;
WT_PAGE *child, *root;
WT_PAGE_INDEX *pindex;
WT_REF *first;
btree = S2BT(session);
root = btree->root.page;
/* Check for a non-existent tree. */
if (root == NULL)
return (false);
/* A tree that can be evicted always requires a switch. */
if (btree->evict_disabled == 0)
return (true);
/* Check for a tree with a single leaf page. */
WT_INTL_INDEX_GET(session, root, pindex);
if (pindex->entries != 1) /* > 1 child page, switch */
return (true);
first = pindex->index[0];
if (first->state != WT_REF_MEM) /* no child page, ignore */
return (false);
/*
* We're reaching down into the page without a hazard pointer, but that's OK because we know
* that no-eviction is set and so the page cannot disappear.
*/
child = first->page;
if (child->type != WT_PAGE_ROW_LEAF) /* not a single leaf page */
return (true);
return (child->memory_footprint > maxsize);
}
/*
* __wt_split_descent_race --
* Return if we raced with an internal page split when descending the tree.
*/
static inline bool
__wt_split_descent_race(WT_SESSION_IMPL *session, WT_REF *ref, WT_PAGE_INDEX *saved_pindex)
{
WT_PAGE_INDEX *pindex;
/* No test when starting the descent (there's no home to check). */
if (__wt_ref_is_root(ref))
return (false);
/*
* A place to hang this comment...
*
* There's a page-split race when we walk the tree: if we're splitting
* an internal page into its parent, we update the parent's page index
* before updating the split page's page index, and it's not an atomic
* update. A thread can read the parent page's original page index and
* then read the split page's replacement index.
*
* For example, imagine a search descending the tree.
*
* Because internal page splits work by truncating the original page to
* the initial part of the original page, the result of this race is we
* will have a search key that points past the end of the current page.
* This is only an issue when we search past the end of the page, if we
* find a WT_REF in the page with the namespace we're searching for, we
* don't care if the WT_REF moved or not while we were searching, we
* have the correct page.
*
* For example, imagine an internal page with 3 child pages, with the
* namespaces a-f, g-h and i-j; the first child page splits. The parent
* starts out with the following page-index:
*
* | ... | a | g | i | ... |
*
* which changes to this:
*
* | ... | a | c | e | g | i | ... |
*
* The child starts out with the following page-index:
*
* | a | b | c | d | e | f |
*
* which changes to this:
*
* | a | b |
*
* The thread searches the original parent page index for the key "cat",
* it couples to the "a" child page; if it uses the replacement child
* page index, it will search past the end of the page and couple to the
* "b" page, which is wrong.
*
* To detect the problem, we remember the parent page's page index used
* to descend the tree. Whenever we search past the end of a page, we
* check to see if the parent's page index has changed since our use of
* it during descent. As the problem only appears if we read the split
* page's replacement index, the parent page's index must already have
* changed, ensuring we detect the problem.
*
* It's possible for the opposite race to happen (a thread could read
* the parent page's replacement page index and then read the split
* page's original index). This isn't a problem because internal splits
* work by truncating the split page, so the split page search is for
* content the split page retains after the split, and we ignore this
* race.
*
* This code is a general purpose check for a descent race and we call
* it in other cases, for example, a cursor traversing backwards through
* the tree.
*
* Presumably we acquired a page index on the child page before calling
* this code, don't re-order that acquisition with this check.
*/
WT_BARRIER();
WT_INTL_INDEX_GET(session, ref->home, pindex);
return (pindex != saved_pindex);
}
/*
* __wt_page_swap_func --
* Swap one page's hazard pointer for another one when hazard pointer coupling up/down the tree.
*/
static inline int
__wt_page_swap_func(WT_SESSION_IMPL *session, WT_REF *held, WT_REF *want, uint32_t flags
#ifdef HAVE_DIAGNOSTIC
,
const char *func, int line
#endif
)
{
WT_DECL_RET;
bool acquired;
/*
* This function is here to simplify the error handling during hazard pointer coupling so we
* never leave a hazard pointer dangling. The assumption is we're holding a hazard pointer on
* "held", and want to acquire a hazard pointer on "want", releasing the hazard pointer on
* "held" when we're done.
*
* When walking the tree, we sometimes swap to the same page. Fast-path that to avoid thinking
* about error handling.
*/
if (held == want)
return (0);
/* Get the wanted page. */
ret = __wt_page_in_func(session, want, flags
#ifdef HAVE_DIAGNOSTIC
,
func, line
#endif
);
/*
* Expected failures: page not found or restart. Our callers list the errors they're expecting
* to handle.
*/
if (LF_ISSET(WT_READ_NOTFOUND_OK) && ret == WT_NOTFOUND)
return (WT_NOTFOUND);
if (LF_ISSET(WT_READ_RESTART_OK) && ret == WT_RESTART)
return (WT_RESTART);
/* Discard the original held page on either success or error. */
acquired = ret == 0;
WT_TRET(__wt_page_release(session, held, flags));
/* Fast-path expected success. */
if (ret == 0)
return (0);
/*
* If there was an error at any point that our caller isn't prepared to handle, discard any page
* we acquired.
*/
if (acquired)
WT_TRET(__wt_page_release(session, want, flags));
/*
* If we're returning an error, don't let it be one our caller expects to handle as returned by
* page-in: the expectation includes the held page not having been released, and that's not the
* case.
*/
if (LF_ISSET(WT_READ_NOTFOUND_OK) && ret == WT_NOTFOUND)
WT_RET_MSG(session, EINVAL, "page-release WT_NOTFOUND error mapped to EINVAL");
if (LF_ISSET(WT_READ_RESTART_OK) && ret == WT_RESTART)
WT_RET_MSG(session, EINVAL, "page-release WT_RESTART error mapped to EINVAL");
return (ret);
}
/*
* __wt_btcur_skip_page --
* Return if the cursor is pointing to a page with deleted records and can be skipped for cursor
* traversal.
*/
static inline int
__wt_btcur_skip_page(
WT_SESSION_IMPL *session, WT_REF *ref, void *context, bool visible_all, bool *skipp)
{
WT_ADDR_COPY addr;
uint8_t previous_state;
WT_UNUSED(context);
WT_UNUSED(visible_all);
*skipp = false; /* Default to reading */
/* Don't skip pages in FLCS trees; deleted records need to read back as 0. */
if (S2BT(session)->type == BTREE_COL_FIX)
return (0);
/*
* Determine if all records on the page have been deleted and all the tombstones are visible to
* our transaction. If so, we can avoid reading the records on the page and move to the next
* page. We base this decision on the aggregate stop point added to the page during the last
* reconciliation. We can skip this test if the page has been modified since it was reconciled.
* We also skip this test on an internal page, as we rely on reconciliation to mark the internal
* page dirty. There could be a period of time when the internal page is marked clean but the
* leaf page is dirty and has newer data than let on by the internal page's aggregated
* information.
*
* We are making these decisions while holding a lock for the page as checkpoint or eviction can
* make changes to the data structures (i.e., aggregate timestamps) we are reading. It is okay
* if the page is not in memory, or gets evicted before we lock it. In such a case, we can forgo
* checking if the page has been modified. So, only do a page modified check if the page was in
* memory before locking.
*/
if (F_ISSET(ref, WT_REF_FLAG_INTERNAL))
return (0);
WT_REF_LOCK(session, ref, &previous_state);
if ((previous_state == WT_REF_DISK || previous_state == WT_REF_DELETED ||
(previous_state == WT_REF_MEM && !__wt_page_is_modified(ref->page))) &&
__wt_ref_addr_copy(session, ref, &addr) && addr.ta.newest_stop_txn != WT_TXN_MAX &&
addr.ta.newest_stop_ts != WT_TS_MAX &&
__wt_txn_visible(session, addr.ta.newest_stop_txn, addr.ta.newest_stop_ts))
*skipp = true;
WT_REF_UNLOCK(ref, previous_state);
return (0);
}
|