/*
* __las_page_instantiate --
* Instantiate lookaside update records in a recently read page.
*/
static int
__las_page_instantiate(WT_SESSION_IMPL *session,
WT_REF *ref, uint32_t read_id, const uint8_t *addr, size_t addr_size)
{
WT_CURSOR *cursor;
WT_CURSOR_BTREE cbt;
WT_DECL_ITEM(current_key);
WT_DECL_ITEM(las_addr);
WT_DECL_ITEM(las_key);
WT_DECL_ITEM(las_value);
WT_DECL_RET;
WT_PAGE *page;
WT_UPDATE *first_upd, *last_upd, *upd;
size_t incr, total_incr;
uint64_t current_recno, las_counter, las_txnid, recno, upd_txnid;
uint32_t las_id, upd_size, session_flags;
int exact;
const uint8_t *p;
cursor = NULL;
page = ref->page;
first_upd = last_upd = upd = NULL;
total_incr = 0;
current_recno = recno = WT_RECNO_OOB;
session_flags = 0; /* [-Werror=maybe-uninitialized] */
__wt_btcur_init(session, &cbt);
__wt_btcur_open(&cbt);
WT_ERR(__wt_scr_alloc(session, 0, ¤t_key));
WT_ERR(__wt_scr_alloc(session, 0, &las_addr));
WT_ERR(__wt_scr_alloc(session, 0, &las_key));
WT_ERR(__wt_scr_alloc(session, 0, &las_value));
/* Open a lookaside table cursor. */
WT_ERR(__wt_las_cursor(session, &cursor, &session_flags));
/*
* The lookaside records are in key and update order, that is, there
* will be a set of in-order updates for a key, then another set of
* in-order updates for a subsequent key. We process all of the updates
* for a key and then insert those updates into the page, then all the
* updates for the next key, and so on.
*
* Search for the block's unique prefix, stepping through any matching
* records.
*/
las_addr->data = addr;
las_addr->size = addr_size;
las_key->size = 0;
cursor->set_key(
cursor, read_id, las_addr, (uint64_t)0, (uint32_t)0, las_key);
if ((ret = cursor->search_near(cursor, &exact)) == 0 && exact < 0)
ret = cursor->next(cursor);
for (; ret == 0; ret = cursor->next(cursor)) {
WT_ERR(cursor->get_key(cursor,
&las_id, las_addr, &las_counter, &las_txnid, las_key));
/*
* Confirm the search using the unique prefix; if not a match,
* we're done searching for records for this page.
*/
if (las_id != read_id ||
las_addr->size != addr_size ||
memcmp(las_addr->data, addr, addr_size) != 0)
break;
/*
* If the on-page value has become globally visible, this record
* is no longer needed.
*/
if (__wt_txn_visible_all(session, las_txnid))
continue;
/* Allocate the WT_UPDATE structure. */
WT_ERR(cursor->get_value(
cursor, &upd_txnid, &upd_size, las_value));
WT_ERR(__wt_update_alloc(session,
(upd_size == WT_UPDATE_DELETED_VALUE) ? NULL : las_value,
&upd, &incr));
total_incr += incr;
upd->txnid = upd_txnid;
switch (page->type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
p = las_key->data;
WT_ERR(__wt_vunpack_uint(&p, 0, &recno));
if (current_recno == recno)
break;
WT_ASSERT(session, current_recno < recno);
if (first_upd != NULL) {
WT_ERR(__col_instantiate(session,
current_recno, ref, &cbt, first_upd));
first_upd = NULL;
}
current_recno = recno;
break;
case WT_PAGE_ROW_LEAF:
if (current_key->size == las_key->size &&
memcmp(current_key->data,
las_key->data, las_key->size) == 0)
break;
if (first_upd != NULL) {
WT_ERR(__row_instantiate(session,
current_key, ref, &cbt, first_upd));
first_upd = NULL;
}
WT_ERR(__wt_buf_set(session,
current_key, las_key->data, las_key->size));
break;
WT_ILLEGAL_VALUE_ERR(session);
}
/* Append the latest update to the list. */
if (first_upd == NULL)
first_upd = last_upd = upd;
else {
last_upd->next = upd;
last_upd = upd;
}
upd = NULL;
}
WT_ERR_NOTFOUND_OK(ret);
/* Insert the last set of updates, if any. */
if (first_upd != NULL)
switch (page->type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
WT_ERR(__col_instantiate(session,
current_recno, ref, &cbt, first_upd));
first_upd = NULL;
break;
case WT_PAGE_ROW_LEAF:
WT_ERR(__row_instantiate(session,
current_key, ref, &cbt, first_upd));
first_upd = NULL;
break;
WT_ILLEGAL_VALUE_ERR(session);
}
/* Discard the cursor. */
WT_ERR(__wt_las_cursor_close(session, &cursor, session_flags));
if (total_incr != 0) {
__wt_cache_page_inmem_incr(session, page, total_incr);
/*
* We've modified/dirtied the page, but that's not necessary and
* if we keep the page clean, it's easier to evict. We leave the
* lookaside table updates in place, so if we evict this page
* without dirtying it, any future instantiation of it will find
* the records it needs. If the page is dirtied before eviction,
* then we'll write any needed lookaside table records for the
* new location of the page.
*/
__wt_page_modify_clear(session, page);
}
err: WT_TRET(__wt_las_cursor_close(session, &cursor, session_flags));
WT_TRET(__wt_btcur_close(&cbt, 1));
/*
* On error, upd points to a single unlinked WT_UPDATE structure,
* first_upd points to a list.
*/
if (upd != NULL)
__wt_free(session, upd);
if (first_upd != NULL)
__wt_free_update_list(session, first_upd);
__wt_scr_free(session, ¤t_key);
__wt_scr_free(session, &las_addr);
__wt_scr_free(session, &las_key);
__wt_scr_free(session, &las_value);
return (ret);
}
/*
* __wt_las_sweep --
* Sweep the lookaside table.
*/
int
__wt_las_sweep(WT_SESSION_IMPL *session)
{
WT_CONNECTION_IMPL *conn;
WT_CURSOR *cursor;
WT_DECL_ITEM(las_addr);
WT_DECL_ITEM(las_key);
WT_DECL_RET;
WT_ITEM *key;
uint64_t cnt, las_counter, las_txnid;
uint32_t las_id, session_flags;
int notused;
conn = S2C(session);
cursor = NULL;
key = &conn->las_sweep_key;
session_flags = 0; /* [-Werror=maybe-uninitialized] */
WT_ERR(__wt_scr_alloc(session, 0, &las_addr));
WT_ERR(__wt_scr_alloc(session, 0, &las_key));
WT_ERR(__wt_las_cursor(session, &cursor, &session_flags));
/*
* If we're not starting a new sweep, position the cursor using the key
* from the last call (we don't care if we're before or after the key,
* just roughly in the same spot is fine).
*/
if (conn->las_sweep_call != 0 && key->data != NULL) {
__wt_cursor_set_raw_key(cursor, key);
if ((ret = cursor->search_near(cursor, ¬used)) != 0)
goto srch_notfound;
}
/*
* The sweep server wakes up every 10 seconds (by default), it's a slow
* moving thread. Try to review the entire lookaside table once every 5
* minutes, or every 30 calls.
*
* The reason is because the lookaside table exists because we're seeing
* cache/eviction pressure (it allows us to trade performance and disk
* space for cache space), and it's likely lookaside blocks are being
* evicted, and reading them back in doesn't help things. A trickier,
* but possibly better, alternative might be to review all lookaside
* blocks in the cache in order to get rid of them, and slowly review
* lookaside blocks that have already been evicted.
*
* We can't know for sure how many records are in the lookaside table,
* the cursor insert and remove statistics aren't updated atomically.
* Start with reviewing 100 rows, and if it takes more than the target
* number of calls to finish, increase the number of rows checked on
* each call; if it takes less than the target calls to finish, then
* decrease the number of rows reviewed on each call (but never less
* than 100).
*/
#define WT_SWEEP_LOOKASIDE_MIN_CNT 100
#define WT_SWEEP_LOOKASIDE_PASS_TARGET 30
++conn->las_sweep_call;
if ((cnt = conn->las_sweep_cnt) < WT_SWEEP_LOOKASIDE_MIN_CNT)
cnt = conn->las_sweep_cnt = WT_SWEEP_LOOKASIDE_MIN_CNT;
/* Walk the file. */
for (; cnt > 0 && (ret = cursor->next(cursor)) == 0; --cnt) {
/*
* If the loop terminates after completing a work unit, we will
* continue the table sweep next time. Get a local copy of the
* sweep key, we're going to reset the cursor; do so before
* calling cursor.remove, cursor.remove can discard our hazard
* pointer and the page could be evicted from underneath us.
*/
if (cnt == 1) {
WT_ERR(__wt_cursor_get_raw_key(cursor, key));
if (!WT_DATA_IN_ITEM(key))
WT_ERR(__wt_buf_set(
session, key, key->data, key->size));
}
WT_ERR(cursor->get_key(cursor,
&las_id, las_addr, &las_counter, &las_txnid, las_key));
/*
* If the on-page record transaction ID associated with the
* record is globally visible, the record can be discarded.
*
* Cursor opened overwrite=true: won't return WT_NOTFOUND should
* another thread remove the record before we do, and the cursor
* remains positioned in that case.
*/
if (__wt_txn_visible_all(session, las_txnid))
WT_ERR(cursor->remove(cursor));
}
/*
* When reaching the lookaside table end or the target number of calls,
* adjust the row count. Decrease/increase the row count depending on
* if the number of calls is less/more than the target.
*/
if (ret == WT_NOTFOUND ||
conn->las_sweep_call > WT_SWEEP_LOOKASIDE_PASS_TARGET) {
if (conn->las_sweep_call < WT_SWEEP_LOOKASIDE_PASS_TARGET &&
conn->las_sweep_cnt > WT_SWEEP_LOOKASIDE_MIN_CNT)
conn->las_sweep_cnt -= WT_SWEEP_LOOKASIDE_MIN_CNT;
if (conn->las_sweep_call > WT_SWEEP_LOOKASIDE_PASS_TARGET)
conn->las_sweep_cnt += WT_SWEEP_LOOKASIDE_MIN_CNT;
}
srch_notfound:
if (ret == WT_NOTFOUND)
conn->las_sweep_call = 0;
WT_ERR_NOTFOUND_OK(ret);
if (0) {
err: __wt_buf_free(session, key);
}
WT_TRET(__wt_las_cursor_close(session, &cursor, session_flags));
__wt_scr_free(session, &las_addr);
__wt_scr_free(session, &las_key);
return (ret);
}
/*
* __wt_las_sweep --
* Sweep the lookaside table.
*/
int
__wt_las_sweep(WT_SESSION_IMPL *session)
{
WT_CONNECTION_IMPL *conn;
WT_CURSOR *cursor;
WT_DECL_ITEM(las_addr);
WT_DECL_ITEM(las_key);
WT_DECL_RET;
WT_ITEM *key;
uint64_t cnt, las_counter, las_txnid;
int64_t remove_cnt;
uint32_t las_id, session_flags;
int notused;
conn = S2C(session);
cursor = NULL;
key = &conn->las_sweep_key;
remove_cnt = 0;
session_flags = 0; /* [-Werror=maybe-uninitialized] */
WT_ERR(__wt_scr_alloc(session, 0, &las_addr));
WT_ERR(__wt_scr_alloc(session, 0, &las_key));
WT_ERR(__wt_las_cursor(session, &cursor, &session_flags));
/*
* If we're not starting a new sweep, position the cursor using the key
* from the last call (we don't care if we're before or after the key,
* just roughly in the same spot is fine).
*/
if (key->size != 0) {
__wt_cursor_set_raw_key(cursor, key);
ret = cursor->search_near(cursor, ¬used);
/*
* Don't search for the same key twice; if we don't set a new
* key below, it's because we've reached the end of the table
* and we want the next pass to start at the beginning of the
* table. Searching for the same key could leave us stuck at
* the end of the table, repeatedly checking the same rows.
*/
key->size = 0;
if (ret != 0)
goto srch_notfound;
}
/*
* The sweep server wakes up every 10 seconds (by default), it's a slow
* moving thread. Try to review the entire lookaside table once every 5
* minutes, or every 30 calls.
*
* The reason is because the lookaside table exists because we're seeing
* cache/eviction pressure (it allows us to trade performance and disk
* space for cache space), and it's likely lookaside blocks are being
* evicted, and reading them back in doesn't help things. A trickier,
* but possibly better, alternative might be to review all lookaside
* blocks in the cache in order to get rid of them, and slowly review
* lookaside blocks that have already been evicted.
*/
cnt = (uint64_t)WT_MAX(100, conn->las_record_cnt / 30);
/* Discard pages we read as soon as we're done with them. */
F_SET(session, WT_SESSION_NO_CACHE);
/* Walk the file. */
for (; cnt > 0 && (ret = cursor->next(cursor)) == 0; --cnt) {
/*
* If the loop terminates after completing a work unit, we will
* continue the table sweep next time. Get a local copy of the
* sweep key, we're going to reset the cursor; do so before
* calling cursor.remove, cursor.remove can discard our hazard
* pointer and the page could be evicted from underneath us.
*/
if (cnt == 1) {
WT_ERR(__wt_cursor_get_raw_key(cursor, key));
if (!WT_DATA_IN_ITEM(key))
WT_ERR(__wt_buf_set(
session, key, key->data, key->size));
}
WT_ERR(cursor->get_key(cursor,
&las_id, las_addr, &las_counter, &las_txnid, las_key));
/*
* If the on-page record transaction ID associated with the
* record is globally visible, the record can be discarded.
*
* Cursor opened overwrite=true: won't return WT_NOTFOUND should
* another thread remove the record before we do, and the cursor
* remains positioned in that case.
*/
if (__wt_txn_visible_all(session, las_txnid)) {
WT_ERR(cursor->remove(cursor));
++remove_cnt;
}
}
srch_notfound:
WT_ERR_NOTFOUND_OK(ret);
if (0) {
err: __wt_buf_free(session, key);
}
WT_TRET(__wt_las_cursor_close(session, &cursor, session_flags));
/*
* If there were races to remove records, we can over-count. All
* arithmetic is signed, so underflow isn't fatal, but check anyway so
* we don't skew low over time.
*/
if (remove_cnt > S2C(session)->las_record_cnt)
S2C(session)->las_record_cnt = 0;
else if (remove_cnt > 0)
(void)__wt_atomic_subi64(&conn->las_record_cnt, remove_cnt);
F_CLR(session, WT_SESSION_NO_CACHE);
__wt_scr_free(session, &las_addr);
__wt_scr_free(session, &las_key);
return (ret);
}
/*
* __txn_rollback_to_stable_lookaside_fixup --
* Remove any updates that need to be rolled back from the lookaside file.
*/
static int
__txn_rollback_to_stable_lookaside_fixup(WT_SESSION_IMPL *session)
{
WT_CONNECTION_IMPL *conn;
WT_CURSOR *cursor;
WT_DECL_RET;
WT_DECL_TIMESTAMP(rollback_timestamp)
WT_ITEM las_addr, las_key, las_timestamp;
WT_TXN_GLOBAL *txn_global;
uint64_t las_counter, las_txnid, remove_cnt;
uint32_t las_id, session_flags;
conn = S2C(session);
cursor = NULL;
remove_cnt = 0;
session_flags = 0; /* [-Werror=maybe-uninitialized] */
WT_CLEAR(las_timestamp);
/*
* Copy the stable timestamp, otherwise we'd need to lock it each time
* it's accessed. Even though the stable timestamp isn't supposed to be
* updated while rolling back, accessing it without a lock would
* violate protocol.
*/
txn_global = &S2C(session)->txn_global;
__wt_readlock(session, &txn_global->rwlock);
__wt_timestamp_set(&rollback_timestamp, &txn_global->stable_timestamp);
__wt_readunlock(session, &txn_global->rwlock);
__wt_las_cursor(session, &cursor, &session_flags);
/* Discard pages we read as soon as we're done with them. */
F_SET(session, WT_SESSION_NO_CACHE);
/* Walk the file. */
for (; (ret = cursor->next(cursor)) == 0; ) {
WT_ERR(cursor->get_key(cursor, &las_id, &las_addr, &las_counter,
&las_txnid, &las_timestamp, &las_key));
/* Check the file ID so we can skip durable tables */
if (__bit_test(conn->stable_rollback_bitstring, las_id))
continue;
/*
* Entries with no timestamp will have a timestamp of zero,
* which will fail the following check and cause them to never
* be removed.
*/
if (__wt_timestamp_cmp(
&rollback_timestamp, las_timestamp.data) < 0) {
WT_ERR(cursor->remove(cursor));
++remove_cnt;
}
}
WT_ERR_NOTFOUND_OK(ret);
err: WT_TRET(__wt_las_cursor_close(session, &cursor, session_flags));
/*
* If there were races to remove records, we can over-count. Underflow
* isn't fatal, but check anyway so we don't skew low over time.
*/
if (remove_cnt > conn->las_record_cnt)
conn->las_record_cnt = 0;
else if (remove_cnt > 0)
(void)__wt_atomic_sub64(&conn->las_record_cnt, remove_cnt);
F_CLR(session, WT_SESSION_NO_CACHE);
return (ret);
}
