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mariadb/storage/innobase/row/row0vers.cc
Marko Mäkelä 4dcb1b575b MDEV-35049: Use CRC-32C and avoid allocating heap 
For the adaptive hash index, dtuple_fold() and rec_fold() were employing
a slow rolling hash algorithm, computing hash values ("fold") for one
field and one byte at a time, while depending on calls to
rec_get_offsets().

We already have optimized implementations of CRC-32C and have been
successfully using that function in some other InnoDB tables, but not
yet in the adaptive hash index.

Any linear function such as any CRC will fail the avalanche test that
any cryptographically secure hash function is expected to pass:
any single-bit change in the input key should affect on average half
the bits in the output.

But we always were happy with less than cryptographically secure:
in fact, ut_fold_ulint_pair() or ut_fold_binary() are just about as
linear as any CRC, using a combination of multiplication and addition,
partly carry-less. It is worth noting that exclusive-or corresponds to
carry-less subtraction or addition in a binary Galois field, or GF(2).

We only need some way of reducing key prefixes into hash values.
The CRC-32C should be better than a Rabin–Karp rolling hash algorithm.
Compared to the old hash algorithm, it has the drawback that there will
be only 32 bits of entropy before we choose the hash table cell by a
modulus operation. The size of each adaptive hash index array is
(innodb_buffer_pool_size / 512) / innodb_adaptive_hash_index_parts.
With the maximum number of partitions (512), we would not exceed 1<<32
elements per array until the buffer pool size exceeds 1<<50 bytes (1 PiB).
We would hit other limits before that: the virtual address space on many
contemporary 64-bit processor implementations is only 48 bits (256 TiB).
So, we can simply go for the SIMD accelerated CRC-32C.

rec_fold(): Take a combined parameter n_bytes_fields. Determine the
length of each field on the fly, and compute CRC-32C over a single
contiguous range of bytes, from the start of the record payload area
to the end of the last full or partial field. For secondary index records
in ROW_FORMAT=REDUNDANT, also the data area that is reserved for NULL
values (to facilitate in-place updates between NULL and NOT NULL values)
will be included in the count. Luckily, InnoDB always zero-initialized
such unused area; refer to data_write_sql_null() in
rec_convert_dtuple_to_rec_old(). For other than ROW_FORMAT=REDUNDANT,
no space is allocated for NULL values, and therefore the CRC-32C will
only cover the actual payload of the key prefix.

dtuple_fold(): For ROW_FORMAT=REDUNDANT, include the dummy NULL values
in the CRC-32C, so that the values will be comparable with rec_fold().

innodb_ahi-t: A unit test for rec_fold() and dtuple_fold().

btr_search_build_page_hash_index(), btr_search_drop_page_hash_index():
Use a fixed-size stack buffer for computing the fold values, to avoid
dynamic memory allocation.

btr_search_drop_page_hash_index(): Do not release part.latch if we
need to invoke multiple batches of rec_fold().

dtuple_t: Allocate fewer bits for the fields. The maximum number of
data fields is about 1023, so uint16_t will be fine for them. The
info_bits is stored in less than 1 byte.

ut_pair_min(), ut_pair_cmp(): Remove. We can actually combine and compare
int(n_fields << 16 | n_bytes).

PAGE_CUR_LE_OR_EXTENDS, PAGE_CUR_DBG: Remove. These were never defined,
because they would only work with latin1_swedish_ci if at all.

btr_cur_t::check_mismatch(): Replaces !btr_search_check_guess().

cmp_dtuple_rec_bytes(): Replaces cmp_dtuple_rec_with_match_bytes().
Determine the offsets of fields on the fly.

page_cur_try_search_shortcut_bytes(): This caller of
cmp_dtuple_rec_bytes() will not be invoked on the change buffer tree.

cmp_dtuple_rec_leaf(): Replaces cmp_dtuple_rec_with_match()
for comparing leaf-page records.

buf_block_t::ahi_left_bytes_fields: Consolidated Atomic_relaxed<uint32_t>
of curr_left_side << 31 | curr_n_bytes << 16 | curr_n_fields.
The other set of parameters (n_fields, n_bytes, left_side) was removed
as redundant.

btr_search_update_hash_node_on_insert(): Merged to
btr_search_update_hash_on_insert().

btr_search_build_page_hash_index(): Take combined left_bytes_fields
instead of n_fields, n_bytes, left_side.

btr_search_update_block_hash_info(), btr_search_update_hash_ref():
Merged to btr_search_info_update_hash().

btr_cur_t::n_bytes_fields: Replaces n_bytes << 16 | n_fields.

We also remove many redundant checks of btr_search.enabled.
If we are holding any btr_sea::partition::latch, then a nonnull pointer
in buf_block_t::index must imply that the adaptive hash index is enabled.

Reviewed by: Vladislav Lesin
2025-01-10 16:39:44 +02:00

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/*****************************************************************************
Copyright (c) 1997, 2017, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2017, 2022, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file row/row0vers.cc
Row versions
Created 2/6/1997 Heikki Tuuri
*******************************************************/
#include "row0vers.h"
#include "dict0dict.h"
#include "dict0boot.h"
#include "btr0btr.h"
#include "mach0data.h"
#include "trx0rseg.h"
#include "trx0trx.h"
#include "trx0roll.h"
#include "trx0undo.h"
#include "trx0purge.h"
#include "trx0rec.h"
#include "que0que.h"
#include "row0row.h"
#include "row0upd.h"
#include "rem0cmp.h"
#include "lock0lock.h"
#include "row0mysql.h"
/** Check whether all non-virtual index fields are equal.
@param[in] index the secondary index
@param[in] a first index entry to compare
@param[in] b second index entry to compare
@return whether all non-virtual fields are equal */
static
bool
row_vers_non_virtual_fields_equal(
const dict_index_t* index,
const dfield_t* a,
const dfield_t* b)
{
const dict_field_t* end = &index->fields[index->n_fields];
for (const dict_field_t* ifield = index->fields; ifield != end;
ifield++) {
if (!ifield->col->is_virtual()
&& cmp_dfield_dfield(a++, b++)) {
return false;
}
}
return true;
}
/** Determine if an active transaction has inserted or modified a secondary
index record.
@param[in,out] caller_trx trx of current thread
@param[in] clust_rec clustered index record
@param[in] clust_index clustered index
@param[in] rec secondary index record
@param[in] index secondary index
@param[in] offsets rec_get_offsets(rec, index)
@param[in,out] mtr mini-transaction
@return the active transaction; state must be rechecked after
acquiring trx->mutex, and trx->release_reference() must be invoked
@retval NULL if the record was committed */
UNIV_INLINE
trx_t*
row_vers_impl_x_locked_low(
trx_t* caller_trx,
const rec_t* clust_rec,
dict_index_t* clust_index,
const rec_t* rec,
dict_index_t* index,
const rec_offs* offsets,
mtr_t* mtr)
{
trx_id_t trx_id;
rec_t* prev_version = NULL;
rec_offs clust_offsets_[REC_OFFS_NORMAL_SIZE];
rec_offs* clust_offsets;
mem_heap_t* heap;
dtuple_t* ientry = NULL;
mem_heap_t* v_heap = NULL;
dtuple_t* cur_vrow = NULL;
rec_offs_init(clust_offsets_);
DBUG_ENTER("row_vers_impl_x_locked_low");
ut_ad(rec_offs_validate(rec, index, offsets));
ut_ad(mtr->memo_contains_page_flagged(clust_rec,
MTR_MEMO_PAGE_S_FIX
| MTR_MEMO_PAGE_X_FIX));
if (ulint trx_id_offset = clust_index->trx_id_offset) {
trx_id = mach_read_from_6(clust_rec + trx_id_offset);
if (trx_id == 0) {
/* The transaction history was already purged. */
DBUG_RETURN(0);
}
}
heap = mem_heap_create(1024);
clust_offsets = rec_get_offsets(clust_rec, clust_index, clust_offsets_,
clust_index->n_core_fields,
ULINT_UNDEFINED, &heap);
trx_id = row_get_rec_trx_id(clust_rec, clust_index, clust_offsets);
if (trx_id == 0) {
/* The transaction history was already purged. */
mem_heap_free(heap);
DBUG_RETURN(0);
}
ut_ad(!clust_index->table->is_temporary());
trx_t* trx;
if (trx_id == caller_trx->id) {
trx = caller_trx;
trx->reference();
} else {
trx = trx_sys.find(caller_trx, trx_id);
if (trx == 0) {
/* The transaction that modified or inserted
clust_rec is no longer active, or it is
corrupt: no implicit lock on rec */
lock_check_trx_id_sanity(trx_id, clust_rec,
clust_index, clust_offsets);
mem_heap_free(heap);
DBUG_RETURN(0);
}
}
const bool comp = index->table->not_redundant();
ut_ad(!!page_rec_is_comp(rec) == comp);
ut_ad(index->table == clust_index->table);
ut_ad(!comp == !page_rec_is_comp(clust_rec));
const ulint rec_del = rec_get_deleted_flag(rec, comp);
if (dict_index_has_virtual(index)) {
ulint est_size = DTUPLE_EST_ALLOC(index->n_fields);
/* Allocate the dtuple for virtual columns extracted from undo
log with its own heap, so to avoid it being freed as we
iterating in the version loop below. */
v_heap = mem_heap_create(est_size);
ientry = row_rec_to_index_entry(rec, index, offsets, v_heap);
}
/* We look up if some earlier version, which was modified by
the trx_id transaction, of the clustered index record would
require rec to be in a different state (delete marked or
unmarked, or have different field values, or not existing). If
there is such a version, then rec was modified by the trx_id
transaction, and it has an implicit x-lock on rec. Note that
if clust_rec itself would require rec to be in a different
state, then the trx_id transaction has not yet had time to
modify rec, and does not necessarily have an implicit x-lock
on rec. */
for (const rec_t* version = clust_rec;; version = prev_version) {
row_ext_t* ext;
dtuple_t* row;
dtuple_t* entry;
ulint vers_del;
trx_id_t prev_trx_id;
mem_heap_t* old_heap = heap;
dtuple_t* vrow = NULL;
/* We keep the semaphore in mtr on the clust_rec page, so
that no other transaction can update it and get an
implicit x-lock on rec until mtr_commit(mtr). */
heap = mem_heap_create(1024);
trx_undo_prev_version_build(
version, clust_index, clust_offsets,
heap, &prev_version, mtr, 0, NULL,
dict_index_has_virtual(index) ? &vrow : NULL);
ut_d(bool owns_trx_mutex = trx->mutex_is_owner());
ut_d(if (!owns_trx_mutex)
trx->mutex_lock();)
const bool committed = trx_state_eq(
trx, TRX_STATE_COMMITTED_IN_MEMORY);
ut_d(if (!owns_trx_mutex)
trx->mutex_unlock();)
/* The oldest visible clustered index version must not be
delete-marked, because we never start a transaction by
inserting a delete-marked record. */
ut_ad(committed || prev_version
|| !rec_get_deleted_flag(version, comp));
/* Free version and clust_offsets. */
mem_heap_free(old_heap);
if (committed) {
goto not_locked;
}
if (prev_version == NULL) {
/* We reached the oldest visible version without
finding an older version of clust_rec that would
match the secondary index record. If the secondary
index record is not delete marked, then clust_rec
is considered the correct match of the secondary
index record and hence holds the implicit lock. */
if (rec_del) {
/* The secondary index record is del marked.
So, the implicit lock holder of clust_rec
did not modify the secondary index record yet,
and is not holding an implicit lock on it.
This assumes that whenever a row is inserted
or updated, the leaf page record always is
created with a clear delete-mark flag.
(We never insert a delete-marked record.) */
not_locked:
trx->release_reference();
trx = 0;
}
break;
}
clust_offsets = rec_get_offsets(
prev_version, clust_index, clust_offsets_,
clust_index->n_core_fields,
ULINT_UNDEFINED, &heap);
vers_del = rec_get_deleted_flag(prev_version, comp);
prev_trx_id = row_get_rec_trx_id(prev_version, clust_index,
clust_offsets);
/* The stack of versions is locked by mtr. Thus, it
is safe to fetch the prefixes for externally stored
columns. */
row = row_build(ROW_COPY_POINTERS, clust_index, prev_version,
clust_offsets,
NULL, NULL, NULL, &ext, heap);
if (dict_index_has_virtual(index)) {
if (vrow) {
/* Keep the virtual row info for the next
version */
cur_vrow = dtuple_copy(vrow, v_heap);
dtuple_dup_v_fld(cur_vrow, v_heap);
}
if (!cur_vrow) {
/* Build index entry out of row */
entry = row_build_index_entry(row, ext, index,
heap);
/* entry could only be NULL (the
clustered index record could contain
BLOB pointers that are NULL) if we
were accessing a freshly inserted
record before it was fully inserted.
prev_version cannot possibly be such
an incomplete record, because its
transaction would have to be committed
in order for later versions of the
record to be able to exist. */
ut_ad(entry);
/* If the indexed virtual columns has changed,
there must be log record to generate vrow.
Otherwise, it is not changed, so no need
to compare */
if (!row_vers_non_virtual_fields_equal(
index,
ientry->fields, entry->fields)) {
if (rec_del != vers_del) {
break;
}
} else if (!rec_del) {
break;
}
goto result_check;
} else {
ut_ad(row->n_v_fields == cur_vrow->n_v_fields);
dtuple_copy_v_fields(row, cur_vrow);
}
}
entry = row_build_index_entry(row, ext, index, heap);
/* entry could only be NULL (the clustered index
record could contain BLOB pointers that are NULL) if
we were accessing a freshly inserted record before it
was fully inserted. prev_version cannot possibly be
such an incomplete record, because its transaction
would have to be committed in order for later versions
of the record to be able to exist. */
ut_ad(entry);
/* If we get here, we know that the trx_id transaction
modified prev_version. Let us check if prev_version
would require rec to be in a different state. */
/* The previous version of clust_rec must be
accessible, because clust_rec was not a fresh insert.
There is no guarantee that the transaction is still
active. */
/* We check if entry and rec are identified in the alphabetical
ordering */
if (0 == cmp_dtuple_rec(entry, rec, index, offsets)) {
/* The delete marks of rec and prev_version should be
equal for rec to be in the state required by
prev_version */
if (rec_del != vers_del) {
break;
}
/* It is possible that the row was updated so that the
secondary index record remained the same in
alphabetical ordering, but the field values changed
still. For example, 'abc' -> 'ABC'. Check also that. */
dtuple_set_types_binary(
entry, dtuple_get_n_fields(entry));
if (cmp_dtuple_rec(entry, rec, index, offsets)) {
break;
}
} else if (!rec_del) {
/* The delete mark should be set in rec for it to be
in the state required by prev_version */
break;
}
result_check:
if (trx->id != prev_trx_id) {
/* prev_version was the first version modified by
the trx_id transaction: no implicit x-lock */
goto not_locked;
}
}
if (trx) {
DBUG_PRINT("info", ("Implicit lock is held by trx:" TRX_ID_FMT,
trx_id));
}
if (v_heap != NULL) {
mem_heap_free(v_heap);
}
mem_heap_free(heap);
DBUG_RETURN(trx);
}
/** Determine if an active transaction has inserted or modified a secondary
index record.
@param[in,out] caller_trx trx of current thread
@param[in] rec secondary index record
@param[in] index secondary index
@param[in] offsets rec_get_offsets(rec, index)
@return the active transaction; state must be rechecked after
acquiring trx->mutex, and trx->release_reference() must be invoked
@retval NULL if the record was committed */
trx_t*
row_vers_impl_x_locked(
trx_t* caller_trx,
const rec_t* rec,
dict_index_t* index,
const rec_offs* offsets)
{
mtr_t mtr;
trx_t* trx;
const rec_t* clust_rec;
dict_index_t* clust_index;
/* The function must not be invoked under lock_sys latch to prevert
latching orded violation, i.e. page latch must be acquired before
lock_sys latch */
lock_sys.assert_unlocked();
/* The current function can be called from lock_rec_unlock_unmodified()
under lock_sys.wr_lock() */
mtr_start(&mtr);
/* Search for the clustered index record. The latch on the
page of clust_rec locks the top of the stack of versions. The
bottom of the version stack is not locked; oldest versions may
disappear by the fact that transactions may be committed and
collected by the purge. This is not a problem, because we are
only interested in active transactions. */
clust_rec = row_get_clust_rec(
BTR_SEARCH_LEAF, rec, index, &clust_index, &mtr);
if (!clust_rec) {
/* In a rare case it is possible that no clust rec is found
for a secondary index record: if in row0umod.cc
row_undo_mod_remove_clust_low() we have already removed the
clust rec, while purge is still cleaning and removing
secondary index records associated with earlier versions of
the clustered index record. In that case there cannot be
any implicit lock on the secondary index record, because
an active transaction which has modified the secondary index
record has also modified the clustered index record. And in
a rollback we always undo the modifications to secondary index
records before the clustered index record. */
trx = 0;
} else {
trx = row_vers_impl_x_locked_low(
caller_trx, clust_rec, clust_index, rec, index,
offsets, &mtr);
ut_ad(trx == 0 || trx->is_referenced());
}
mtr_commit(&mtr);
return(trx);
}
/** build virtual column value from current cluster index record data
@param[in,out] row the cluster index row in dtuple form
@param[in] clust_index clustered index
@param[in] index the secondary index
@param[in] heap heap used to build virtual dtuple. */
bool
row_vers_build_clust_v_col(
dtuple_t* row,
dict_index_t* clust_index,
dict_index_t* index,
mem_heap_t* heap)
{
THD* thd= current_thd;
TABLE* maria_table= 0;
ut_ad(dict_index_has_virtual(index));
ut_ad(index->table == clust_index->table);
DEBUG_SYNC(current_thd, "ib_clust_v_col_before_row_allocated");
ib_vcol_row vc(nullptr);
byte *record = vc.record(thd, index, &maria_table);
ut_ad(maria_table);
for (ulint i = 0; i < dict_index_get_n_fields(index); i++) {
const dict_col_t* c = dict_index_get_nth_col(index, i);
if (c->is_virtual()) {
const dict_v_col_t* col
= reinterpret_cast<const dict_v_col_t*>(c);
dfield_t *vfield = innobase_get_computed_value(
row, col, clust_index, &vc.heap,
heap, NULL, thd, maria_table, record, NULL,
NULL);
if (!vfield) {
innobase_report_computed_value_failed(row);
ut_ad(0);
return false;
}
}
}
return true;
}
/** Build latest virtual column data from undo log
@param[in] rec clustered index record
@param[in] clust_index clustered index
@param[in,out] clust_offsets offsets on the clustered index record
@param[in] index the secondary index
@param[in] trx_id transaction ID on the purging record,
or 0 if called outside purge
@param[in] roll_ptr the rollback pointer for the purging record
@param[in,out] v_heap heap used to build vrow
@param[out] v_row dtuple holding the virtual rows
@param[in,out] mtr mtr holding the latch on rec */
static
void
row_vers_build_cur_vrow_low(
const rec_t* rec,
dict_index_t* clust_index,
rec_offs* clust_offsets,
dict_index_t* index,
trx_id_t trx_id,
roll_ptr_t roll_ptr,
mem_heap_t* v_heap,
dtuple_t** vrow,
mtr_t* mtr)
{
const rec_t* version;
rec_t* prev_version;
mem_heap_t* heap = NULL;
const auto num_v = dict_table_get_n_v_cols(index->table);
const dfield_t* field;
ulint i;
bool all_filled = false;
*vrow = dtuple_create_with_vcol(v_heap, 0, num_v);
dtuple_init_v_fld(*vrow);
for (i = 0; i < num_v; i++) {
dfield_get_type(dtuple_get_nth_v_field(*vrow, i))->mtype
= DATA_MISSING;
}
ut_ad(mtr->memo_contains_page_flagged(rec,
MTR_MEMO_PAGE_S_FIX
| MTR_MEMO_PAGE_X_FIX));
version = rec;
/* If this is called by purge thread, set TRX_UNDO_PREV_IN_PURGE
bit to search the undo log until we hit the current undo log with
roll_ptr */
const ulint status = trx_id
? TRX_UNDO_PREV_IN_PURGE | TRX_UNDO_GET_OLD_V_VALUE
: TRX_UNDO_GET_OLD_V_VALUE;
while (!all_filled) {
mem_heap_t* heap2 = heap;
heap = mem_heap_create(1024);
roll_ptr_t cur_roll_ptr = row_get_rec_roll_ptr(
version, clust_index, clust_offsets);
trx_undo_prev_version_build(
version, clust_index, clust_offsets,
heap, &prev_version, mtr, status, nullptr, vrow);
if (heap2) {
mem_heap_free(heap2);
}
if (!prev_version) {
/* Versions end here */
break;
}
clust_offsets = rec_get_offsets(prev_version, clust_index,
NULL,
clust_index->n_core_fields,
ULINT_UNDEFINED, &heap);
ulint entry_len = dict_index_get_n_fields(index);
all_filled = true;
for (i = 0; i < entry_len; i++) {
const dict_col_t* col
= dict_index_get_nth_col(index, i);
if (!col->is_virtual()) {
continue;
}
const dict_v_col_t* v_col
= reinterpret_cast<const dict_v_col_t*>(col);
field = dtuple_get_nth_v_field(*vrow, v_col->v_pos);
if (dfield_get_type(field)->mtype == DATA_MISSING) {
all_filled = false;
break;
}
}
trx_id_t rec_trx_id = row_get_rec_trx_id(
prev_version, clust_index, clust_offsets);
if (rec_trx_id < trx_id || roll_ptr == cur_roll_ptr) {
break;
}
version = prev_version;
}
mem_heap_free(heap);
}
/** Build a dtuple contains virtual column data for current cluster index
@param[in] in_purge called by purge thread
@param[in] rec cluster index rec
@param[in] clust_index cluster index
@param[in] clust_offsets cluster rec offset
@param[in] index secondary index
@param[in] trx_id transaction ID on the purging record,
or 0 if called outside purge
@param[in] roll_ptr roll_ptr for the purge record
@param[in,out] heap heap memory
@param[in,out] v_heap heap memory to keep virtual column tuple
@param[in,out] mtr mini-transaction
@return dtuple contains virtual column data */
dtuple_t*
row_vers_build_cur_vrow(
const rec_t* rec,
dict_index_t* clust_index,
rec_offs** clust_offsets,
dict_index_t* index,
trx_id_t trx_id,
roll_ptr_t roll_ptr,
mem_heap_t* heap,
mem_heap_t* v_heap,
mtr_t* mtr)
{
dtuple_t* cur_vrow = NULL;
roll_ptr_t t_roll_ptr = row_get_rec_roll_ptr(
rec, clust_index, *clust_offsets);
/* if the row is newly inserted, then the virtual
columns need to be computed */
if (trx_undo_roll_ptr_is_insert(t_roll_ptr)) {
ut_ad(!rec_get_deleted_flag(rec, page_rec_is_comp(rec)));
/* This is a newly inserted record and cannot
be deleted, So the externally stored field
cannot be freed yet. */
dtuple_t* row = row_build(ROW_COPY_POINTERS, clust_index,
rec, *clust_offsets,
NULL, NULL, NULL, NULL, heap);
if (!row_vers_build_clust_v_col(row, clust_index, index,
heap)) {
return nullptr;
}
cur_vrow = dtuple_copy(row, v_heap);
dtuple_dup_v_fld(cur_vrow, v_heap);
} else {
/* Try to fetch virtual column data from undo log */
row_vers_build_cur_vrow_low(
rec, clust_index, *clust_offsets,
index, trx_id, roll_ptr, v_heap, &cur_vrow, mtr);
}
*clust_offsets = rec_get_offsets(rec, clust_index, NULL,
clust_index->n_core_fields,
ULINT_UNDEFINED, &heap);
return(cur_vrow);
}
/** Find out whether data tuple has missing data type
for indexed virtual column.
@param tuple data tuple
@param index virtual index
@return true if tuple has missing column type */
bool dtuple_vcol_data_missing(const dtuple_t &tuple,
const dict_index_t &index)
{
for (ulint i= 0; i < index.n_uniq; i++)
{
dict_col_t *col= index.fields[i].col;
if (!col->is_virtual())
continue;
dict_v_col_t *vcol= reinterpret_cast<dict_v_col_t*>(col);
for (ulint j= 0; j < index.table->n_v_cols; j++)
if (vcol == &index.table->v_cols[j] &&
tuple.v_fields[j].type.mtype == DATA_MISSING)
return true;
}
return false;
}
/*****************************************************************//**
Constructs the version of a clustered index record which a consistent
read should see. We assume that the trx id stored in rec is such that
the consistent read should not see rec in its present version.
@return error code
@retval DB_SUCCESS if a previous version was fetched
@retval DB_MISSING_HISTORY if the history is missing (a sign of corruption) */
dberr_t
row_vers_build_for_consistent_read(
/*===============================*/
const rec_t* rec, /*!< in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /*!< in: mtr holding the latch on rec */
dict_index_t* index, /*!< in: the clustered index */
rec_offs** offsets,/*!< in/out: offsets returned by
rec_get_offsets(rec, index) */
ReadView* view, /*!< in: the consistent read view */
mem_heap_t** offset_heap,/*!< in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/*!< in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
rec_t** old_vers,/*!< out, own: old version, or NULL
if the history is missing or the record
does not exist in the view, that is,
it was freshly inserted afterwards */
dtuple_t** vrow) /*!< out: virtual row */
{
const rec_t* version;
rec_t* prev_version;
trx_id_t trx_id;
mem_heap_t* heap = NULL;
byte* buf;
dberr_t err;
ut_ad(index->is_primary());
ut_ad(mtr->memo_contains_page_flagged(rec, MTR_MEMO_PAGE_X_FIX
| MTR_MEMO_PAGE_S_FIX));
ut_ad(rec_offs_validate(rec, index, *offsets));
trx_id = row_get_rec_trx_id(rec, index, *offsets);
ut_ad(!view->changes_visible(trx_id));
ut_ad(!vrow || !(*vrow));
version = rec;
for (;;) {
mem_heap_t* prev_heap = heap;
heap = mem_heap_create(1024);
if (vrow) {
*vrow = NULL;
}
/* If purge can't see the record then we can't rely on
the UNDO log record. */
err = trx_undo_prev_version_build(
version, index, *offsets, heap,
&prev_version, mtr, 0, NULL, vrow);
if (prev_heap != NULL) {
mem_heap_free(prev_heap);
}
if (prev_version == NULL) {
/* It was a freshly inserted version */
*old_vers = NULL;
ut_ad(!vrow || !(*vrow));
break;
}
*offsets = rec_get_offsets(
prev_version, index, *offsets,
index->n_core_fields, ULINT_UNDEFINED, offset_heap);
#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
ut_a(!rec_offs_any_null_extern(prev_version, *offsets));
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
trx_id = row_get_rec_trx_id(prev_version, index, *offsets);
if (view->changes_visible(trx_id)) {
/* The view already sees this version: we can copy
it to in_heap and return */
buf = static_cast<byte*>(
mem_heap_alloc(
in_heap, rec_offs_size(*offsets)));
*old_vers = rec_copy(buf, prev_version, *offsets);
rec_offs_make_valid(*old_vers, index, true, *offsets);
if (vrow && *vrow) {
*vrow = dtuple_copy(*vrow, in_heap);
dtuple_dup_v_fld(*vrow, in_heap);
}
break;
} else if (trx_id >= view->low_limit_id()
&& trx_id >= trx_sys.get_max_trx_id()) {
err = DB_CORRUPTION;
break;
}
version = prev_version;
}
mem_heap_free(heap);
return(err);
}
#if defined __aarch64__&&defined __GNUC__&&__GNUC__==4&&!defined __clang__
/* Avoid GCC 4.8.5 internal compiler error "could not split insn". */
# pragma GCC optimize ("O0")
#endif
/*****************************************************************//**
Constructs the last committed version of a clustered index record,
which should be seen by a semi-consistent read. */
void
row_vers_build_for_semi_consistent_read(
/*====================================*/
trx_t* caller_trx,/*!<in/out: trx of current thread */
const rec_t* rec, /*!< in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /*!< in: mtr holding the latch on rec */
dict_index_t* index, /*!< in: the clustered index */
rec_offs** offsets,/*!< in/out: offsets returned by
rec_get_offsets(rec, index) */
mem_heap_t** offset_heap,/*!< in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/*!< in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
const rec_t** old_vers,/*!< out: rec, old version, or NULL if the
record does not exist in the view, that is,
it was freshly inserted afterwards */
dtuple_t** vrow) /*!< out: virtual row, old version, or NULL
if it is not updated in the view */
{
const rec_t* version;
mem_heap_t* heap = NULL;
byte* buf;
trx_id_t rec_trx_id = 0;
ut_ad(index->is_primary());
ut_ad(mtr->memo_contains_page_flagged(rec, MTR_MEMO_PAGE_X_FIX
| MTR_MEMO_PAGE_S_FIX));
ut_ad(rec_offs_validate(rec, index, *offsets));
version = rec;
ut_ad(!vrow || !(*vrow));
for (;;) {
mem_heap_t* heap2;
rec_t* prev_version;
trx_id_t version_trx_id;
version_trx_id = row_get_rec_trx_id(version, index, *offsets);
if (rec == version) {
rec_trx_id = version_trx_id;
}
if (!trx_sys.is_registered(caller_trx, version_trx_id)) {
committed_version_trx:
/* We found a version that belongs to a
committed transaction: return it. */
#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
ut_a(!rec_offs_any_null_extern(version, *offsets));
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
if (rec == version) {
*old_vers = rec;
if (vrow) {
*vrow = NULL;
}
break;
}
/* We assume that a rolled-back transaction stays in
TRX_STATE_ACTIVE state until all the changes have been
rolled back and the transaction is removed from
the global list of transactions. */
if (rec_trx_id == version_trx_id) {
/* The transaction was committed while
we searched for earlier versions.
Return the current version as a
semi-consistent read. */
version = rec;
*offsets = rec_get_offsets(
version, index, *offsets,
index->n_core_fields, ULINT_UNDEFINED,
offset_heap);
}
buf = static_cast<byte*>(
mem_heap_alloc(
in_heap, rec_offs_size(*offsets)));
*old_vers = rec_copy(buf, version, *offsets);
rec_offs_make_valid(*old_vers, index, true, *offsets);
if (vrow && *vrow) {
*vrow = dtuple_copy(*vrow, in_heap);
dtuple_dup_v_fld(*vrow, in_heap);
}
break;
}
DEBUG_SYNC_C("after_row_vers_check_trx_active");
heap2 = heap;
heap = mem_heap_create(1024);
if (trx_undo_prev_version_build(version, index, *offsets, heap,
&prev_version, mtr, 0,
in_heap, vrow) != DB_SUCCESS) {
mem_heap_free(heap);
heap = heap2;
heap2 = NULL;
goto committed_version_trx;
}
if (heap2) {
mem_heap_free(heap2); /* free version */
}
if (prev_version == NULL) {
/* It was a freshly inserted version */
*old_vers = NULL;
ut_ad(!vrow || !(*vrow));
break;
}
version = prev_version;
*offsets = rec_get_offsets(version, index, *offsets,
index->n_core_fields,
ULINT_UNDEFINED, offset_heap);
#if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG
ut_a(!rec_offs_any_null_extern(version, *offsets));
#endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */
}/* for (;;) */
if (heap) {
mem_heap_free(heap);
}
}
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