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filesort.cc
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/*
Copyright (c) 2000, 2021, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is also distributed with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have included with MySQL.
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, version 2.0, 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 St, Fifth Floor, Boston, MA 02110-1301 USA */
/**
@file sql/filesort.cc
Standard external sort. We read rows into a buffer until there's no more room.
At that point, we use it (using the sorting algorithms from STL), and write it
to disk (thus the name “filesort”). When there are no more rows, we merge
chunks recursively, seven and seven (although we can go all the way up to 15
in the final pass if it helps us do one pass less).
If all the rows fit in a single chunk, the data never hits disk, but remains
in RAM.
*/
#include "sql/filesort.h"
#include <limits.h>
#include <math.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <atomic>
#include <memory>
#include <new>
#include <optional>
#include <vector>
#include "add_with_saturate.h"
#include "decimal.h"
#include "field_types.h" // enum_field_types
#include "m_ctype.h"
#include "map_helpers.h"
#include "my_basename.h"
#include "my_bitmap.h"
#include "my_byteorder.h"
#include "my_compiler.h"
#include "my_config.h"
#include "my_dbug.h"
#include "my_inttypes.h"
#include "my_loglevel.h"
#include "my_sys.h"
#include "mysql/components/services/log_builtins.h"
#include "mysql/components/services/log_shared.h"
#include "mysql/psi/mysql_file.h"
#include "mysql/service_mysql_alloc.h"
#include "mysql/udf_registration_types.h"
#include "mysql_com.h"
#include "mysqld_error.h"
#include "priority_queue.h"
#include "sql/auth/sql_security_ctx.h"
#include "sql/bounded_queue.h"
#include "sql/cmp_varlen_keys.h"
#include "sql/debug_sync.h"
#include "sql/derror.h"
#include "sql/error_handler.h"
#include "sql/field.h"
#include "sql/filesort_utils.h"
#include "sql/handler.h"
#include "sql/item.h"
#include "sql/item_subselect.h"
#include "sql/json_dom.h" // Json_wrapper
#include "sql/key_spec.h"
#include "sql/malloc_allocator.h"
#include "sql/merge_many_buff.h"
#include "sql/my_decimal.h"
#include "sql/mysqld.h" // mysql_tmpdir
#include "sql/opt_costmodel.h"
#include "sql/opt_trace.h"
#include "sql/opt_trace_context.h"
#include "sql/pfs_batch_mode.h"
#include "sql/psi_memory_key.h"
#include "sql/row_iterator.h"
#include "sql/sort_param.h"
#include "sql/sorting_iterator.h"
#include "sql/sql_array.h"
#include "sql/sql_base.h"
#include "sql/sql_bitmap.h"
#include "sql/sql_class.h"
#include "sql/sql_const.h"
#include "sql/sql_error.h"
#include "sql/sql_lex.h"
#include "sql/sql_optimizer.h" // JOIN
#include "sql/sql_sort.h"
#include "sql/system_variables.h"
#include "sql/table.h"
#include "sql/thr_malloc.h"
#include "sql/tztime.h"
#include "sql_string.h"
#include "template_utils.h"
using std::max;
using std::min;
namespace {
struct Mem_compare_queue_key {
Mem_compare_queue_key() : m_compare_length(0), m_param(nullptr) {}
Mem_compare_queue_key(const Mem_compare_queue_key &that) = default;
bool operator()(const uchar *s1, const uchar *s2) const {
if (m_param)
return cmp_varlen_keys(m_param->local_sortorder, m_param->use_hash, s1,
s2);
// memcmp(s1, s2, 0) is guaranteed to return zero.
return memcmp(s1, s2, m_compare_length) < 0;
}
size_t m_compare_length;
Sort_param *m_param;
};
} // namespace
/* functions defined in this file */
static ha_rows read_all_rows(
THD *thd, Sort_param *param, const Mem_root_array<TABLE *> &tables,
table_map tables_to_get_rowid_for, Filesort_info *fs_info,
IO_CACHE *chunk_file, IO_CACHE *tempfile,
Bounded_queue<uchar *, uchar *, Sort_param, Mem_compare_queue_key> *pq,
RowIterator *source_iterator, ha_rows *found_rows, size_t *longest_key,
size_t *longest_addon);
static int write_keys(Sort_param *param, Filesort_info *fs_info, uint count,
IO_CACHE *buffer_file, IO_CACHE *tempfile);
static int merge_index(THD *thd, Sort_param *param, Sort_buffer sort_buffer,
Merge_chunk_array chunk_array, IO_CACHE *tempfile,
IO_CACHE *outfile);
static bool save_index(Sort_param *param, uint count, Filesort_info *table_sort,
Sort_result *sort_result);
static bool check_if_pq_applicable(Opt_trace_context *trace, Sort_param *param,
Filesort_info *info, ha_rows records,
ulong memory_available);
void Sort_param::decide_addon_fields(Filesort *file_sort,
const Mem_root_array<TABLE *> &tables,
bool force_sort_positions) {
if (m_addon_fields_status != Addon_fields_status::unknown_status) {
// Already decided.
return;
}
DBUG_EXECUTE_IF("filesort_force_sort_row_ids", {
m_addon_fields_status = Addon_fields_status::keep_rowid;
return;
});
// Generally, prefer using addon fields (ie., sorting rows instead of just
// row IDs) if we can.
//
// NOTE: If the table is already in memory (e.g. the MEMORY engine; see the
// HA_FAST_KEY_READ flag), it would normally be beneficial to sort row IDs
// over rows to get smaller sort chunks. However, eliding the temporary table
// entirely is even better than using row IDs, and only possible if we sort
// rows. Furthermore, since we set up filesort at optimize time, we don't know
// yet whether the source table would _remain_ in memory, or could be spilled
// to disk using InnoDB. Thus, the only case that reasonably remains where
// we'd want to use row IDs without being forced would be on user (ie.,
// non-temporary) MEMORY tables, which doesn't seem reasonable to add
// complexity for.
for (TABLE *table : tables) {
if (table->pos_in_table_list &&
table->pos_in_table_list->is_fulltext_searched()) {
// See comment in SortWillBeOnRowId().
m_addon_fields_status = Addon_fields_status::fulltext_searched;
return;
}
}
if (force_sort_positions) {
m_addon_fields_status = Addon_fields_status::keep_rowid;
} else {
/*
Get the descriptors of all fields whose values are appended
to sorted fields and get its total length in m_addon_length.
*/
addon_fields = file_sort->get_addon_fields(
&m_addon_fields_status, &m_addon_length, &m_packable_length);
}
}
void Sort_param::clear_addon_fields() {
m_addon_fields_status = Addon_fields_status::unknown_status;
addon_fields = nullptr;
}
void Sort_param::init_for_filesort(Filesort *file_sort,
Bounds_checked_array<st_sort_field> sf_array,
uint sortlen,
const Mem_root_array<TABLE *> &tables,
ha_rows maxrows, bool remove_duplicates) {
m_fixed_sort_length = sortlen;
m_force_stable_sort = file_sort->m_force_stable_sort;
m_remove_duplicates = remove_duplicates;
sum_ref_length = 0;
for (TABLE *table : tables) {
if (table->is_nullable()) {
// TODO(sgunders): Allow variable-length ref, so that we don't
// have to store the row ID for NULL rows.
++sum_ref_length;
}
sum_ref_length += table->file->ref_length;
}
local_sortorder = sf_array;
decide_addon_fields(file_sort, tables, file_sort->m_force_sort_positions);
if (using_addon_fields()) {
fixed_res_length = m_addon_length;
} else {
fixed_res_length = sum_ref_length;
/*
The reference to the record is considered
as an additional sorted field
*/
AddWithSaturate(sum_ref_length, &m_fixed_sort_length);
}
m_num_varlen_keys = count_varlen_keys();
m_num_json_keys = count_json_keys();
if (using_varlen_keys()) {
AddWithSaturate(size_of_varlength_field, &m_fixed_sort_length);
}
/*
Add hash at the end of sort key to order cut values correctly.
Needed for GROUPing, rather than for ORDERing.
*/
if (using_json_keys()) {
use_hash = true;
AddWithSaturate(sizeof(ulonglong), &m_fixed_sort_length);
}
m_fixed_rec_length = AddWithSaturate(m_fixed_sort_length, m_addon_length);
max_rows = maxrows;
}
void Sort_param::try_to_pack_addons() {
if (!using_addon_fields() || // no addons, or
using_packed_addons()) // already packed
return;
// Heuristic: skip packing if potential savings are less than 10 bytes.
const uint sz = Addon_fields::size_of_length_field;
if (m_packable_length < (10 + sz)) {
m_addon_fields_status = Addon_fields_status::skip_heuristic;
return;
}
addon_fields->set_using_packed_addons(true);
m_using_packed_addons = true;
AddWithSaturate(sz, &m_addon_length);
AddWithSaturate(sz, &fixed_res_length);
AddWithSaturate(sz, &m_fixed_rec_length);
}
int Sort_param::count_json_keys() const {
int retval = 0;
for (const auto &sf : local_sortorder) {
if (sf.field_type == MYSQL_TYPE_JSON) {
++retval;
}
}
return retval;
}
size_t Sort_param::get_record_length(uchar *p) const {
uchar *start_of_payload = get_start_of_payload(p);
uint size_of_payload = using_packed_addons()
? Addon_fields::read_addon_length(start_of_payload)
: fixed_res_length;
uchar *end_of_payload = start_of_payload + size_of_payload;
return end_of_payload - p;
}
void Sort_param::get_rec_and_res_len(uchar *record_start, uint *recl,
uint *resl) {
if (!using_packed_addons() && !using_varlen_keys()) {
*recl = m_fixed_rec_length;
*resl = fixed_res_length;
return;
}
uchar *plen = get_start_of_payload(record_start);
if (using_packed_addons())
*resl = Addon_fields::read_addon_length(plen);
else
*resl = fixed_res_length;
assert(*resl <= fixed_res_length);
const uchar *record_end = plen + *resl;
*recl = static_cast<uint>(record_end - record_start);
}
static void trace_filesort_information(Opt_trace_context *trace,
const st_sort_field *sortorder,
uint s_length) {
if (!trace->is_started()) return;
Opt_trace_array trace_filesort(trace, "filesort_information");
for (; s_length--; sortorder++) {
Opt_trace_object oto(trace);
oto.add_alnum("direction", sortorder->reverse ? "desc" : "asc");
oto.add("expression", sortorder->item);
}
}
/**
Sort a table.
Creates a set of pointers that can be used to read the rows
in sorted order. This should be done with the functions
in records.cc.
The result set is stored in fs_info->io_cache or
fs_info->sorted_result, or left in the main filesort buffer.
@param thd Current thread
@param filesort How to sort the table
@param source_iterator Where to read the rows to be sorted from.
@param tables_to_get_rowid_for
Which tables we are responsible for getting row IDs
for. Tables in this set that are not also in
"tables" are ignored.
@param num_rows_estimate How many rows source_iterator is expected
to produce. Only used for whether we intend
to use the priority queue optimization or not;
if we estimate fewer rows than we can fit into
RAM, we never use the priority queue.
@param fs_info Owns the buffers for sort_result.
@param sort_result Where to store the sort result.
@param[out] found_rows Store the number of found rows here.
This is the number of found rows after
applying WHERE condition.
@note
If we sort by position (like if sort_positions is 1) filesort() will
call table->prepare_for_position().
@returns False if success, true if error
*/
bool filesort(THD *thd, Filesort *filesort, RowIterator *source_iterator,
table_map tables_to_get_rowid_for, ha_rows num_rows_estimate,
Filesort_info *fs_info, Sort_result *sort_result,
ha_rows *found_rows) {
int error;
ulong memory_available = thd->variables.sortbuff_size;
ha_rows num_rows_found = HA_POS_ERROR;
IO_CACHE tempfile; // Temporary file for storing intermediate results.
IO_CACHE chunk_file; // For saving Merge_chunk structs.
IO_CACHE *outfile; // Contains the final, sorted result.
Sort_param *param = &filesort->m_sort_param;
ha_rows max_rows = filesort->limit;
uint s_length = 0;
DBUG_TRACE;
#ifndef NDEBUG
// 'pushed_join' feature need to read the partial joined results directly
// from the NDB API. First storing it into a temporary table, means that
// any joined child results are effectively wasted, and we will have to
// re-read them as non-pushed later.
for (TABLE *table : filesort->tables) {
assert(!table->file->member_of_pushed_join());
}
#endif
if (!(s_length = filesort->sort_order_length()))
return true; /* purecov: inspected */
DEBUG_SYNC(thd, "filesort_start");
assert(sort_result->sorted_result == nullptr);
sort_result->sorted_result_in_fsbuf = false;
outfile = sort_result->io_cache;
my_b_clear(&tempfile);
my_b_clear(&chunk_file);
error = 1;
if (!param->using_addon_fields()) {
for (TABLE *table : filesort->tables) {
if (table->pos_in_table_list == nullptr ||
(tables_to_get_rowid_for & table->pos_in_table_list->map())) {
table->prepare_for_position();
}
}
}
// Make sure the source iterator is initialized before init_for_filesort(),
// since table->file (and in particular, ref_length) may not be initialized
// before that.
DBUG_EXECUTE_IF("bug14365043_1", DBUG_SET("+d,ha_rnd_init_fail"););
if (source_iterator->Init()) {
return HA_POS_ERROR;
}
/*
We need a nameless wrapper, since we may be inside the "steps" of
"join_execution".
*/
Opt_trace_context *const trace = &thd->opt_trace;
Opt_trace_object trace_wrapper(trace);
if (filesort->tables.size() == 1) {
trace_wrapper.add_alnum("sorting_table", filesort->tables[0]->alias);
}
trace_filesort_information(trace, filesort->sortorder, s_length);
param->init_for_filesort(filesort, make_array(filesort->sortorder, s_length),
sortlength(thd, filesort->sortorder, s_length),
filesort->tables, max_rows,
filesort->m_remove_duplicates);
fs_info->addon_fields = param->addon_fields;
thd->inc_status_sort_scan();
Bounded_queue<uchar *, uchar *, Sort_param, Mem_compare_queue_key> pq(
param->max_record_length(),
(Malloc_allocator<uchar *>(key_memory_Filesort_info_record_pointers)));
// We would have liked to do this ahead-of-time so that we can show it
// in EXPLAIN. However, we don't know the table->file->ref_length before
// sorting time, which makes it hard to make the decision if we're row IDs.
// (If we sort rows, we would know, but it's not much use knowing it
// ahead-of-time _sometimes_.)
//
// However, do note this cannot change the addon fields status,
// so that we at least know that when checking whether we can skip
// in-between temporary tables (StreamingIterator).
if (check_if_pq_applicable(trace, param, fs_info, num_rows_estimate,
memory_available)) {
DBUG_PRINT("info", ("filesort PQ is applicable"));
/*
For PQ queries (with limit) we know exactly how many pointers/records
we have in the buffer, so to simplify things, we initialize
all pointers here. (We cannot pack fields anyways, so there is no
point in doing incremental allocation).
*/
if (fs_info->preallocate_records(param->max_rows_per_buffer)) {
my_error(ER_OUT_OF_SORTMEMORY, ME_FATALERROR);
LogErr(ERROR_LEVEL, ER_SERVER_OUT_OF_SORTMEMORY);
goto err;
}
if (pq.init(param->max_rows, param, fs_info->get_sort_keys())) {
/*
If we fail to init pq, we have to give up:
out of memory means my_malloc() will call my_error().
*/
DBUG_PRINT("info", ("failed to allocate PQ"));
fs_info->free_sort_buffer();
assert(thd->is_error());
goto err;
}
filesort->using_pq = true;
param->using_pq = true;
param->m_addon_fields_status = Addon_fields_status::using_priority_queue;
} else {
DBUG_PRINT("info", ("filesort PQ is not applicable"));
filesort->using_pq = false;
param->using_pq = false;
/*
When sorting using priority queue, we cannot use packed addons.
Without PQ, we can try.
*/
param->try_to_pack_addons();
/*
NOTE: param->max_rows_per_buffer is merely informative (for optimizer
trace) in this case, not actually used.
*/
if (num_rows_estimate < MERGEBUFF2) num_rows_estimate = MERGEBUFF2;
ha_rows keys =
memory_available / (param->max_record_length() + sizeof(char *));
param->max_rows_per_buffer =
min(num_rows_estimate > 0 ? num_rows_estimate : 1, keys);
fs_info->set_max_size(memory_available, param->max_record_length());
}
size_t longest_key, longest_addons;
longest_addons = 0;
// New scope, because subquery execution must be traced within an array.
{
Opt_trace_array ota(trace, "filesort_execution");
num_rows_found = read_all_rows(
thd, param, filesort->tables, tables_to_get_rowid_for, fs_info,
&chunk_file, &tempfile, param->using_pq ? &pq : nullptr,
source_iterator, found_rows, &longest_key, &longest_addons);
if (num_rows_found == HA_POS_ERROR) goto err;
}
size_t num_chunks, num_initial_chunks;
if (my_b_inited(&chunk_file)) {
num_chunks =
static_cast<size_t>(my_b_tell(&chunk_file)) / sizeof(Merge_chunk);
} else {
num_chunks = 0;
}
num_initial_chunks = num_chunks;
if (num_chunks == 0) // The whole set is in memory
{
ha_rows rows_in_chunk =
param->using_pq ? pq.num_elements() : num_rows_found;
if (save_index(param, rows_in_chunk, fs_info, sort_result)) goto err;
} else {
// If deduplicating, we'll need to remember the previous key somehow.
if (filesort->m_remove_duplicates) {
param->m_last_key_seen =
static_cast<uchar *>(thd->mem_root->Alloc(longest_key));
}
// We will need an extra buffer in SortFileIndirectIterator
if (fs_info->addon_fields != nullptr &&
!(fs_info->addon_fields->allocate_addon_buf(longest_addons)))
goto err; /* purecov: inspected */
fs_info->read_chunk_descriptors(&chunk_file, num_chunks);
if (fs_info->merge_chunks.is_null()) goto err; /* purecov: inspected */
close_cached_file(&chunk_file);
/* Open cached file if it isn't open */
if (!my_b_inited(outfile) &&
open_cached_file(outfile, mysql_tmpdir, TEMP_PREFIX, READ_RECORD_BUFFER,
MYF(MY_WME)))
goto err;
if (reinit_io_cache(outfile, WRITE_CACHE, 0L, false, false)) goto err;
param->max_rows_per_buffer = static_cast<uint>(
fs_info->max_size_in_bytes() / param->max_record_length());
Bounds_checked_array<uchar> merge_buf = fs_info->get_contiguous_buffer();
if (merge_buf.array() == nullptr) {
my_error(ER_OUT_OF_SORTMEMORY, ME_FATALERROR);
LogErr(ERROR_LEVEL, ER_SERVER_OUT_OF_SORTMEMORY);
goto err;
}
if (merge_many_buff(thd, param, merge_buf, fs_info->merge_chunks,
&num_chunks, &tempfile))
goto err;
if (flush_io_cache(&tempfile) ||
reinit_io_cache(&tempfile, READ_CACHE, 0L, false, false))
goto err;
if (merge_index(
thd, param, merge_buf,
Merge_chunk_array(fs_info->merge_chunks.begin(), num_chunks),
&tempfile, outfile))
goto err;
sort_result->found_records = num_rows_found;
}
if (trace->is_started()) {
char buffer[100];
String sort_mode(buffer, sizeof(buffer), &my_charset_bin);
sort_mode.length(0);
sort_mode.append("<");
if (param->using_varlen_keys())
sort_mode.append("varlen_sort_key");
else
sort_mode.append("fixed_sort_key");
sort_mode.append(", ");
sort_mode.append(param->using_packed_addons()
? "packed_additional_fields"
: param->using_addon_fields() ? "additional_fields"
: "rowid");
sort_mode.append(">");
const char *algo_text[] = {"none", "std::sort", "std::stable_sort"};
Opt_trace_object filesort_summary(trace, "filesort_summary");
filesort_summary.add("memory_available", memory_available)
.add("key_size", param->max_compare_length())
.add("row_size", param->max_record_length())
.add("max_rows_per_buffer", param->max_rows_per_buffer)
.add("num_rows_estimate", num_rows_estimate)
.add("num_rows_found", num_rows_found)
.add("num_initial_chunks_spilled_to_disk", num_initial_chunks)
.add("peak_memory_used", fs_info->peak_memory_used())
.add_alnum("sort_algorithm", algo_text[param->m_sort_algorithm]);
if (!param->using_packed_addons())
filesort_summary.add_alnum(
"unpacked_addon_fields",
addon_fields_text(param->m_addon_fields_status));
filesort_summary.add_alnum("sort_mode", sort_mode.c_ptr());
}
if (num_rows_found > param->max_rows) {
// If read_all_rows() produced more results than the query LIMIT.
num_rows_found = param->max_rows;
}
error = 0;
err:
if (!filesort->keep_buffers) {
if (!sort_result->sorted_result_in_fsbuf) fs_info->free_sort_buffer();
my_free(fs_info->merge_chunks.array());
fs_info->merge_chunks = Merge_chunk_array(nullptr, 0);
}
close_cached_file(&tempfile);
close_cached_file(&chunk_file);
if (my_b_inited(outfile)) {
if (flush_io_cache(outfile)) error = 1;
{
my_off_t save_pos = outfile->pos_in_file;
/* For following reads */
if (reinit_io_cache(outfile, READ_CACHE, 0L, false, false)) error = 1;
outfile->end_of_file = save_pos;
}
}
if (error) {
assert(thd->is_error() || thd->killed);
} else
thd->inc_status_sort_rows(num_rows_found);
return error;
} /* filesort */
void filesort_free_buffers(TABLE *table, bool full) {
DBUG_TRACE;
table->unique_result.sorted_result.reset();
assert(!table->unique_result.sorted_result_in_fsbuf);
table->unique_result.sorted_result_in_fsbuf = false;
if (full) {
if (table->sorting_iterator != nullptr) {
table->sorting_iterator->CleanupAfterQuery();
table->sorting_iterator = nullptr; // The TABLE object can be reused.
}
if (table->duplicate_removal_iterator != nullptr) {
table->duplicate_removal_iterator->CleanupAfterQuery();
table->duplicate_removal_iterator =
nullptr; // The TABLE object can be reused.
}
}
}
Filesort::Filesort(THD *thd, Mem_root_array<TABLE *> tables_arg,
bool keep_buffers_arg, ORDER *order, ha_rows limit_arg,
bool force_stable_sort, bool remove_duplicates,
bool sort_positions, bool unwrap_rollup)
: m_thd(thd),
tables(std::move(tables_arg)),
keep_buffers(keep_buffers_arg),
limit(limit_arg),
sortorder(nullptr),
using_pq(false),
m_force_stable_sort(
force_stable_sort), // keep relative order of equiv. elts
m_remove_duplicates(remove_duplicates),
m_force_sort_positions(sort_positions),
m_sort_order_length(make_sortorder(order, unwrap_rollup)) {}
uint Filesort::make_sortorder(ORDER *order, bool unwrap_rollup) {
uint count;
st_sort_field *sort, *pos;
ORDER *ord;
DBUG_TRACE;
count = 0;
for (ord = order; ord; ord = ord->next) count++;
assert(count > 0);
const size_t sortorder_size = sizeof(*sortorder) * (count + 1);
if (sortorder == nullptr)
sortorder =
static_cast<st_sort_field *>((*THR_MALLOC)->Alloc(sortorder_size));
if (sortorder == nullptr) return 0; /* purecov: inspected */
memset(sortorder, 0, sortorder_size);
pos = sort = sortorder;
for (ord = order; ord; ord = ord->next, pos++) {
Item *const item = ord->item[0], *const real_item = item->real_item();
pos->item = real_item;
// If filesort runs before GROUP BY (potentially to sort rows
// in preparation for grouping), we cannot have any rollup NULLs
// (and they don't have any rollup state to query), so we need to
// remove the wrappers.
if (unwrap_rollup) {
pos->item = unwrap_rollup_group(pos->item);
}
pos->reverse = (ord->direction == ORDER_DESC);
}
return count;
}
void Filesort_info::read_chunk_descriptors(IO_CACHE *chunk_file, uint count) {
DBUG_TRACE;
// If we already have a chunk array, we're doing sort in a subquery.
if (!merge_chunks.is_null() && merge_chunks.size() < count) {
my_free(merge_chunks.array()); /* purecov: inspected */
merge_chunks = Merge_chunk_array(nullptr, 0); /* purecov: inspected */
}
void *rawmem = merge_chunks.array();
const size_t length = sizeof(Merge_chunk) * count;
if (nullptr == rawmem) {
rawmem = my_malloc(key_memory_Filesort_info_merge, length, MYF(MY_WME));
if (rawmem == nullptr) return; /* purecov: inspected */
}
if (reinit_io_cache(chunk_file, READ_CACHE, 0L, false, false) ||
my_b_read(chunk_file, static_cast<uchar *>(rawmem), length)) {
my_free(rawmem); /* purecov: inspected */
rawmem = nullptr; /* purecov: inspected */
count = 0; /* purecov: inspected */
}
merge_chunks = Merge_chunk_array(static_cast<Merge_chunk *>(rawmem), count);
}
#ifndef NDEBUG
/*
Print a text, SQL-like record representation into dbug trace.
Note: this function is a work in progress: at the moment
- column read bitmap is ignored (can print garbage for unused columns)
- there is no quoting
*/
static void dbug_print_record(TABLE *table, bool print_rowid) {
char buff[1024];
Field **pfield;
String tmp(buff, sizeof(buff), &my_charset_bin);
DBUG_LOCK_FILE;
fprintf(DBUG_FILE, "record (");
for (pfield = table->field; *pfield; pfield++)
fprintf(DBUG_FILE, "%s%s", (*pfield)->field_name, (pfield[1]) ? ", " : "");
fprintf(DBUG_FILE, ") = ");
fprintf(DBUG_FILE, "(");
for (pfield = table->field; *pfield; pfield++) {
Field *field = *pfield;
if (field->is_null()) {
if (fwrite("NULL", sizeof(char), 4, DBUG_FILE) != 4) {
goto unlock_file_and_quit;
}
}
if (field->type() == MYSQL_TYPE_BIT)
(void)field->val_int_as_str(&tmp, true);
else
field->val_str(&tmp);
if (fwrite(tmp.ptr(), sizeof(char), tmp.length(), DBUG_FILE) !=
tmp.length()) {
goto unlock_file_and_quit;
}
if (pfield[1]) {
if (fwrite(", ", sizeof(char), 2, DBUG_FILE) != 2) {
goto unlock_file_and_quit;
}
}
}
fprintf(DBUG_FILE, ")");
if (print_rowid) {
fprintf(DBUG_FILE, " rowid ");
for (uint i = 0; i < table->file->ref_length; i++) {
fprintf(DBUG_FILE, "%x", table->file->ref[i]);
}
}
fprintf(DBUG_FILE, "\n");
unlock_file_and_quit:
DBUG_UNLOCK_FILE;
}
#endif
/// Error handler for filesort.
class Filesort_error_handler : public Internal_error_handler {
THD *m_thd; ///< The THD in which filesort is executed.
bool m_seen_not_supported; ///< Has a not supported warning has been seen?
public:
/**
Create an error handler and push it onto the error handler
stack. The handler will be automatically popped from the error
handler stack when it is destroyed.
*/
Filesort_error_handler(THD *thd) : m_thd(thd), m_seen_not_supported(false) {
thd->push_internal_handler(this);
}
/**
Pop the error handler from the error handler stack, and destroy
it.
*/
~Filesort_error_handler() override { m_thd->pop_internal_handler(); }
/**
Handle a condition.
The handler will make sure that no more than a single
ER_NOT_SUPPORTED_YET warning will be seen by the higher
layers. This warning is generated by Json_wrapper::make_sort_key()
for every value that it doesn't know how to create a sort key
for. It is sufficient for the higher layers to report this warning
only once per sort.
*/
bool handle_condition(THD *, uint sql_errno, const char *,
Sql_condition::enum_severity_level *level,
const char *) override {
if (*level == Sql_condition::SL_WARNING &&
sql_errno == ER_NOT_SUPPORTED_YET) {
if (m_seen_not_supported) return true;
m_seen_not_supported = true;
}
return false;
}
};
static bool alloc_and_make_sortkey(Sort_param *param, Filesort_info *fs_info,
const Mem_root_array<TABLE *> &tables,
size_t *key_length, size_t *longest_addons) {
size_t min_bytes = 1;
for (;;) { // Termination condition within loop.
Bounds_checked_array<uchar> sort_key_buf =
fs_info->get_next_record_pointer(min_bytes);
if (sort_key_buf.array() == nullptr) return true;
const uint rec_sz =
param->make_sortkey(sort_key_buf, tables, longest_addons);
if (rec_sz > sort_key_buf.size()) {
// The record wouldn't fit. Try again, asking for a larger buffer.
min_bytes = sort_key_buf.size() + 1;
} else {
fs_info->commit_used_memory(rec_sz);
*key_length = rec_sz;
return false;
}
}
}
/**
Read all rows, and write them into a temporary file
(if we run out of space in the sort buffer).
All produced sequences are guaranteed to be non-empty.
@param thd Thread handle
@param param Sorting parameter
@param tables List of all tables being sorted.
@param tables_to_get_rowid_for
Which tables we are responsible for getting row IDs
for. Tables in this set that are not also in "tables"
are ignored.
@param fs_info Struct containing sort buffer etc.
@param chunk_file File to write Merge_chunks describing sorted segments
in tempfile.
@param tempfile File to write sorted sequences of sortkeys to.
@param pq If !NULL, use it for keeping top N elements
@param source_iterator Where to read the rows to be sorted from.
@param [out] found_rows The number of FOUND_ROWS().
For a query with LIMIT, this value will typically
be larger than the function return value.
@param [out] longest_key The largest single key found, in bytes.
@param [out] longest_addons
The longest addon field row (sum of all addon fields for any single
given row) found.
@note
Basic idea:
@verbatim
while (get_next_sortkey())
{
if (using priority queue)
push sort key into queue
else
{
try to put sort key into buffer;
if (no free space in sort buffer)
{
do {
allocate new, larger buffer;
retry putting sort key into buffer;
} until (record fits or no space for new buffer)
if (no space for new buffer)
{
sort record pointers (all buffers);
dump sorted sequence to 'tempfile';
dump Merge_chunk describing sequence location into 'chunk_file';
}
}
if (key was packed)
tell sort buffer the actual number of bytes used;
}
}
if (buffer has some elements && dumped at least once)
sort-dump-dump as above;
else
don't sort, leave sort buffer to be sorted by caller.
@endverbatim
@returns
Number of records written on success.
@returns
HA_POS_ERROR on error.
*/
static ha_rows read_all_rows(
THD *thd, Sort_param *param, const Mem_root_array<TABLE *> &tables,
table_map tables_to_get_rowid_for, Filesort_info *fs_info,
IO_CACHE *chunk_file, IO_CACHE *tempfile,
Bounded_queue<uchar *, uchar *, Sort_param, Mem_compare_queue_key> *pq,
RowIterator *source_iterator, ha_rows *found_rows, size_t *longest_key,
size_t *longest_addons) {
/*
Set up an error handler for filesort. It is automatically pushed
onto the internal error handler stack upon creation, and will be
popped off the stack automatically when the handler goes out of
scope.
*/
Filesort_error_handler error_handler(thd);
DBUG_TRACE;
int error = 0;
*found_rows = 0;
size_t longest_key_so_far = 0;
size_t longest_addon_so_far = 0;
// NOTE(sgunders): When we sort row IDs, our read sets are a bit larger
// than required by read_all_rows(); in particular, columns that we
// don't sort on will still be read. (In particular, this makes us read
// and allocate blobs, where present.) However, with sorting row IDs being
// a rather marginal case, it's not worth it for us to try to compute new
// read sets to have different ones in the first phase of such sorts.
//
// This isn't the only case of too large read sets. For a query such as
// SELECT a FROM t1 WHERE b ORDER BY c, all three fields a,b,c will be in
// the read set; in particular, find_order_in_list() will include any
// columns used in ORDER BY in the read sets, as part of resolving them.
// This is required for correct operation. However, anything that is part
// of the read set will by extension be included as addon fields,
// unless we sort row IDs for some reason -- even c, which is part of
// the key. To remedy this, one would probably need a system
// of pushing read sets through the iterator tree (except it should
// ideally be done before optimization, where we set them up), so that
// each iterator can use the right read set for its time.
DEBUG_SYNC(thd, "after_index_merge_phase1");
ha_rows num_total_records = 0, num_records_this_chunk = 0;
uint num_written_chunks = 0;
if (pq == nullptr) {
fs_info->reset();
fs_info->clear_peak_memory_used();
}
PFSBatchMode batch_mode(source_iterator);
for (;;) {
DBUG_EXECUTE_IF("bug19656296", DBUG_SET("+d,ha_rnd_next_deadlock"););
if ((error = source_iterator->Read())) {
break;
}
// Note where we are, for the case where we are not using addon fields.
if (!param->using_addon_fields()) {
for (TABLE *table : tables) {
if (!can_call_position(table)) {
continue;
}
if (table->pos_in_table_list == nullptr ||
(table->pos_in_table_list->map() & tables_to_get_rowid_for)) {
table->file->position(table->record[0]);
}
}