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Copy pathob_limit_op.cpp
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530 lines (505 loc) · 20.3 KB
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/*
* Copyright (c) 2025 OceanBase.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define USING_LOG_PREFIX SQL_ENG
#include "ob_limit_op.h"
#include "sql/engine/basic/ob_material_op.h"
#include "sql/engine/sort/ob_sort_op.h"
namespace oceanbase
{
using namespace common;
namespace sql
{
ObLimitSpec::ObLimitSpec(ObIAllocator &alloc, const ObPhyOperatorType type)
: ObOpSpec(alloc, type),
limit_expr_(NULL),
offset_expr_(NULL),
percent_expr_(NULL),
calc_found_rows_(false),
is_top_limit_(false),
is_fetch_with_ties_(false),
sort_columns_(alloc)
{
}
OB_SERIALIZE_MEMBER((ObLimitSpec, ObOpSpec),
limit_expr_,
offset_expr_,
percent_expr_,
calc_found_rows_,
is_top_limit_,
is_fetch_with_ties_,
sort_columns_);
ObLimitOp::ObLimitOp(ObExecContext &exec_ctx, const ObOpSpec &spec, ObOpInput *input)
: ObOperator(exec_ctx, spec, input),
limit_(-1),
offset_(0),
input_cnt_(0),
output_cnt_(0),
total_cnt_(0),
is_percent_first_(false),
pre_sort_columns_(exec_ctx.get_allocator())
{
}
int ObLimitOp::inner_open()
{
int ret = OB_SUCCESS;
bool is_null_value = false;
if (OB_ISNULL(child_)) {
ret = OB_ERR_UNEXPECTED;
LOG_WARN("limit operator has no child", K(ret));
} else if (OB_FAIL(get_int_val(MY_SPEC.limit_expr_, eval_ctx_, limit_, is_null_value))) {
LOG_WARN("get limit values failed", K(ret));
} else if (!is_null_value && OB_FAIL(get_int_val(MY_SPEC.offset_expr_, eval_ctx_,
offset_, is_null_value))) {
LOG_WARN("get offset values failed", K(ret));
} else if (is_null_value) {
offset_ = 0;
limit_ = 0;
} else {
is_percent_first_ = NULL != MY_SPEC.percent_expr_;
// If limit is less than 0, offset_ has no meaning either, so we check them together here
//offset 2 rows fetch next -3 rows only --> is meaningless
offset_ = offset_ < 0 ? 0 : offset_;
if (MY_SPEC.limit_expr_ != NULL) {//Cannot be uniformly set to 0, because it needs to support the scenario with only offset}
limit_ = limit_ < 0 ? 0 : limit_;
}
pre_sort_columns_.reuse_ = true;
}
return ret;
}
int ObLimitOp::inner_rescan()
{
input_cnt_ = 0;
output_cnt_ = 0;
return ObOperator::inner_rescan();
}
int ObLimitOp::get_int_val(ObExpr *expr, ObEvalCtx &eval_ctx, int64_t &val, bool &is_null_value)
{
int ret = OB_SUCCESS;
if (NULL != expr) {
OB_ASSERT(ob_is_int_tc(expr->datum_meta_.type_));
ObDatum *datum = NULL;
if (OB_FAIL(expr->eval(eval_ctx, datum))) {
LOG_WARN("expr evaluate failed", K(ret), K(expr));
} else if (datum->null_) {
is_null_value = true;
val = 0;
} else {
val = *datum->int_;
}
}
return ret;
}
int ObLimitOp::get_double_val(ObExpr *expr, ObEvalCtx &eval_ctx, double &val)
{
int ret = OB_SUCCESS;
if (NULL != expr) {
OB_ASSERT(ob_is_double_tc(expr->datum_meta_.type_));
ObDatum *datum = NULL;
if (OB_FAIL(expr->eval(eval_ctx, datum))) {
LOG_WARN("expr evaluate failed", K(ret), K(expr));
} else if (datum->null_) {
val = 0.0;
} else {
val = *datum->double_;
}
}
return ret;
}
// copy from ObLimit::inner_get_next_row
int ObLimitOp::inner_get_next_row()
{
int ret = OB_SUCCESS;
clear_evaluated_flag();
LOG_DEBUG("limitop get_next_row start", K(limit_), K(offset_));
while (OB_SUCC(ret) && input_cnt_ < offset_) {
if (OB_FAIL(child_->get_next_row())) {
if (OB_ITER_END != ret) {
LOG_WARN("child_op failed to get next row", K(input_cnt_), K(offset_), K(ret));
}
} else if (is_percent_first_ && OB_FAIL(convert_limit_percent())) {
LOG_WARN("failed to convert limit percent", K(ret));
} else {
++input_cnt_;
}
} // end while
/*Due to the support of the fetch feature in oracle 12c, the execution flow below is relatively complex, here is a simple explanation:
* 1.is_percent_first_: indicates whether the fetch specifies the percentage of rows to be taken, for example: select * from t1 fetch next 50 percent rows only;
* takes out 50% of the total number of rows, at this time, is_percent_first_ needs to indicate whether the percentage is used, and our lower-level block operators (sort, hash group by, etc.)
* are set at get_next_row, so the corresponding limit quantity needs to be set for the first time, and after setting, is_percent_first_ needs to be reset to false;
* 2.is_fetch_with_ties_: indicates that when the required limit quantity is obtained, it is necessary to continue probing whether there are cases where the values of the order by sort columns are equal,
* for example, table t1 has 3 rows of data c1 c2 c3
* 1 2 3
* 1 2 4
* 2 2 3
* at this time, if sorted by column c1 of table t1, and only one column is output, but with ties is specified (sql: select * from t1 order by c1 fetch next 1 rows with ties);
* then each row taken from the child op needs to be saved at the same time, and the last row of data obtained needs to be saved, after obtaining the specified quantity,
* continue to probe the rows of the child op according to the saved last row of data, until the values of the order by sort columns are not equal or all rows of the child op are taken.
* For example, in the above example, after obtaining the row: 1 2 3, it will continue to probe the row: 1 2 4, find that the value of the sort column c1 is equal, will continue to probe and take the row: 2 2 3,
* at this point, the value of the sort column c1 is not equal, the entire get_next_row ends.
*
*/
int64_t left_count = 0;
if (OB_SUCC(ret)) {
if (is_percent_first_ || output_cnt_ < limit_ || limit_ < 0) {
if (OB_FAIL(child_->get_next_row())) {
if (OB_ITER_END != ret) {
LOG_WARN("child_op failed to get next row",
K(ret), K_(limit), K_(offset), K_(input_cnt), K_(output_cnt));
}
} else if (is_percent_first_ && OB_FAIL(convert_limit_percent())) {
LOG_WARN("failed to convert limit percent", K(ret));
} else if (limit_ == 0) {
ret = OB_ITER_END;
} else {
++output_cnt_;
LOG_DEBUG("output row", "row", ROWEXPR2STR(eval_ctx_, MY_SPEC.output_));
// If need to support fetch with ties feature, need to copy the last row taken out by limit for subsequent use
if (MY_SPEC.is_fetch_with_ties_ && output_cnt_ == limit_ &&
OB_FAIL(pre_sort_columns_.save_store_row(MY_SPEC.sort_columns_, eval_ctx_))) {
LOG_WARN("failed to deep copy limit last rows", K(ret));
}
}
// Explanation needs to continue judging if input rows can be output as equal values according to order by items
} else if (limit_ > 0 && MY_SPEC.is_fetch_with_ties_) {
bool is_equal = false;
if (OB_FAIL(child_->get_next_row())) {
if (OB_ITER_END != ret) {
LOG_WARN("child_op failed to get next row",
K(ret), K_(limit), K_(offset), K_(input_cnt), K_(output_cnt));
}
} else if (OB_FAIL(is_row_order_by_item_value_equal(is_equal))) {
LOG_WARN("failed to is row order by item value equal", K(ret));
} else if (is_equal) {
++output_cnt_;
} else {
// Overflow rows with equal order by sorting have already been found
ret = OB_ITER_END;
}
} else {
// Result count already satisfied
ret = OB_ITER_END;
if (MY_SPEC.calc_found_rows_) {
while (OB_SUCC(child_->get_next_row())) {
++left_count;
}
if (OB_ITER_END != ret) {
LOG_WARN("fail to get next row from child", K(ret));
}
}
}
}
if (OB_ITER_END == ret) {
if (MY_SPEC.is_top_limit_) {
total_cnt_ = left_count + output_cnt_ + input_cnt_;
ObPhysicalPlanCtx *plan_ctx = NULL;
if (OB_ISNULL(plan_ctx = ctx_.get_physical_plan_ctx())) {
ret = OB_ERR_NULL_VALUE;
LOG_WARN("get physical plan context failed");
} else {
NG_TRACE_EXT(found_rows,
OB_ID(total_count), total_cnt_, OB_ID(input_count), input_cnt_);
plan_ctx->set_found_rows(total_cnt_);
}
}
}
return ret;
}
// Batch version of ObLimitOp::inner_get_next_row
int ObLimitOp::inner_get_next_batch(const int64_t max_row_cnt)
{
int ret = OB_SUCCESS;
int64_t batch_cnt = min(max_row_cnt, MY_SPEC.max_batch_size_);
LOG_DEBUG("limitop get_next_batch start", K(limit_), K(offset_), K(batch_cnt),
K(is_percent_first_), K(output_cnt_), K(MY_SPEC.calc_found_rows_));
const ObBatchRows *child_brs = nullptr;
clear_evaluated_flag();
while (OB_SUCC(ret) && input_cnt_ < offset_) {
// Note: batch_cnt is NEVER bigger than offset
if (input_cnt_ + batch_cnt > offset_) {
batch_cnt = offset_ - input_cnt_;
}
if (OB_FAIL(child_->get_next_batch(batch_cnt, child_brs))) {
LOG_WARN("child_op failed to get next row", K(input_cnt_), K(offset_), K(ret));
} else if (is_percent_first_ && OB_FAIL(convert_limit_percent())) {
LOG_WARN("failed to convert limit percent", K(ret));
} else {
input_cnt_ += (child_brs->size_ - child_brs->skip_->accumulate_bit_cnt(child_brs->size_));
}
if (child_brs->end_) {
brs_.end_ = true;
break;
}
} // end while
LOG_DEBUG("limitop get_next_batch", K(brs_), K(input_cnt_), K(batch_cnt), K(output_cnt_));
auto skip_fetch_rows = false;
if (input_cnt_ > offset_ && output_cnt_ == 0) {
// offset error handling: child operator return more rows than expected
// mark offset rows as skipped and continue limit logic
brs_.copy(child_brs);
input_cnt_ -= (brs_.size_ - brs_.skip_->accumulate_bit_cnt(brs_.size_));
for (auto i = 0; i < child_brs->size_; i++) {
if (brs_.skip_->at(i)) {
continue;
} else {
++input_cnt_;
if (input_cnt_ <= offset_) {
brs_.skip_->set(i);
} else {
break;
}
}
}
// stop getting rows from child and setting brs_ when skip_fetch_rows is true
skip_fetch_rows = true;
}
// now the limit part
int64_t left_count = 0;
batch_cnt = min(max_row_cnt, MY_SPEC.max_batch_size_);
if (OB_UNLIKELY(brs_.end_) && !skip_fetch_rows) {
brs_.size_ = 0;
LOG_DEBUG("Offset num is bigger than child output num, return empty rows",
K(offset_), K(input_cnt_), K(child_brs->size_),
K(child_brs->end_));
} else if (OB_SUCC(ret)) {
if (is_percent_first_ || output_cnt_ < limit_ || limit_ < 0) {
// adjust iterating count for last batch
if (output_cnt_ + batch_cnt > limit_ && limit_ >= 0) {
batch_cnt = limit_ - output_cnt_;
}
if (is_percent_first_) {
// Fetch one row for percent first fetch, make sure %output_cnt_ never exceed %limit_
// in this round.
batch_cnt = 1;
}
if (!skip_fetch_rows && OB_FAIL(child_->get_next_batch(batch_cnt, child_brs))) {
LOG_WARN("child_op failed to get next row", K(ret), K(limit_), K(batch_cnt));
} else if (is_percent_first_ && OB_FAIL(convert_limit_percent())) {
LOG_WARN("failed to convert limit percent", K(ret));
} else if (limit_ == 0) {
brs_.size_ = 0;
brs_.end_ = true;
} else {
if (!skip_fetch_rows) {
// skip copy brs_ from child as it is already copied in offset error
// handing branch
brs_.copy(child_brs);
}
output_cnt_ += (brs_.size_ - brs_.skip_->accumulate_bit_cnt(brs_.size_));
if (output_cnt_ == limit_) {
// Don't mark brs_.end_, end iterating in next round
if (MY_SPEC.is_fetch_with_ties_) {
ObEvalCtx::BatchInfoScopeGuard batch_info_guard(eval_ctx_);
batch_info_guard.set_batch_size(brs_.size_);
batch_info_guard.set_batch_idx(find_last_available_row_cnt(*(brs_.skip_), brs_.size_));
if (OB_FAIL(pre_sort_columns_.save_store_row(MY_SPEC.sort_columns_, eval_ctx_))) {
LOG_WARN("failed to deep copy limit last rows", K(ret));
}
}
} else if (OB_UNLIKELY(
limit_ != -1 /*limit=-1 means no limit in oracle mode*/ &&
output_cnt_ > limit_)) {
// Notice: here is the error hanlding branch
// Child branch should NOT return rows more than batch_cnt.
// If it return more row, something out of expect take place.
// In order to keep limit logic NOT broken, update the batch size
// within limit operator to get correct result.
LOG_TRACE("child operator return more rows than expected",
K(output_cnt_), K(limit_), K(brs_), K(batch_cnt),
K(child_->get_spec().get_type()));
// recaculate output_cnt_ and update output brs_.size_
output_cnt_ -= (brs_.size_ - brs_.skip_->accumulate_bit_cnt(brs_.size_));
for (auto i = 0; i < child_brs->size_; i++) {
if (brs_.skip_->at(i)) {
continue;
} else {
++output_cnt_;
if (output_cnt_ >= limit_) {
brs_.size_ = i + 1;
break;
}
}
}
}
}
skip_fetch_rows = false;
} else if (limit_ > 0 && output_cnt_ >= limit_ &&
MY_SPEC.is_fetch_with_ties_) {
// keep fetching until a different value is found
batch_cnt = min(max_row_cnt, MY_SPEC.max_batch_size_);
bool keep_iterating = false;
uint32_t matched_row_count = 0;
if (OB_FAIL(child_->get_next_batch(batch_cnt, child_brs))) {
LOG_WARN("child_op failed to get next row",
K(ret), K(limit_), K(batch_cnt), K(child_brs->size_));
} else if (OB_FAIL(compare_value_in_batch(keep_iterating, *(child_brs->skip_),
child_brs->size_, matched_row_count))) {
LOG_WARN("failed to is row order by item value equal", K(ret));
}
brs_.copy(child_brs);
if (!keep_iterating) {
brs_.end_ = true;
brs_.size_ = matched_row_count;
}
output_cnt_ += brs_.size_;
} else {
brs_.end_ = true;
if (MY_SPEC.calc_found_rows_) {
batch_cnt = min(max_row_cnt, MY_SPEC.max_batch_size_);
while (OB_SUCC(child_->get_next_batch(batch_cnt, child_brs))) {
left_count += (child_brs->size_ -
child_brs->skip_->accumulate_bit_cnt(child_brs->size_));
if (child_brs->end_) {
break;
}
}
if (OB_SUCCESS != ret) {
LOG_WARN("fail to get next row from child", K(ret));
}
}
}
}
if (brs_.end_) {
if (MY_SPEC.is_top_limit_) {
total_cnt_ = left_count + output_cnt_ + input_cnt_;
ObPhysicalPlanCtx *plan_ctx = NULL;
if (OB_ISNULL(plan_ctx = ctx_.get_physical_plan_ctx())) {
ret = OB_ERR_NULL_VALUE;
LOG_WARN("get physical plan context failed");
} else {
NG_TRACE_EXT(found_rows,
OB_ID(total_count), total_cnt_, OB_ID(input_count), input_cnt_);
plan_ctx->set_found_rows(total_cnt_);
}
}
}
LOG_DEBUG("limitop get_next_batch finished", K(batch_cnt), K(output_cnt_),
K(brs_), K(limit_), K(input_cnt_));
return ret;
}
int ObLimitOp::is_row_order_by_item_value_equal(bool &is_equal)
{
int ret = OB_SUCCESS;
int cmp_ret = 0;
if (MY_SPEC.sort_columns_.empty()) {
// %sort_columns_ is empty if order by const value, set is_equal to true directly.
// pre_sort_columns_.store_row_ is NULL here.
is_equal = true;
} else {
is_equal = true;
CK(NULL != pre_sort_columns_.store_row_
&& pre_sort_columns_.store_row_->cnt_ == MY_SPEC.sort_columns_.count());
for (int64_t i = 0; OB_SUCC(ret) && is_equal && i < MY_SPEC.sort_columns_.count(); ++i) {
const ObExpr *expr = MY_SPEC.sort_columns_.at(i);
ObDatum *datum = NULL;
if (OB_FAIL(expr->eval(eval_ctx_, datum))) {
LOG_WARN("expression evaluate failed", K(ret));
} else if (OB_FAIL(expr->basic_funcs_->null_first_cmp_(
pre_sort_columns_.store_row_->cells()[i], *datum, cmp_ret))) {
LOG_WARN("compare failed", K(ret));
} else {
is_equal = 0 == cmp_ret;
}
}
}
return ret;
}
// batch version for is_row_order_by_item_value_equal
int ObLimitOp::compare_value_in_batch(bool &keep_iterating,
const ObBitVector &skip,
const int64_t batch_size,
uint32_t &row_count_matched)
{
int ret = OB_SUCCESS;
keep_iterating = true;
if (MY_SPEC.sort_columns_.empty()) {
// %sort_columns_ is empty if order by const value, set is_equal to true directly.
// pre_sort_columns_.store_row_ is NULL here.
} else {
CK(NULL != pre_sort_columns_.store_row_
&& pre_sort_columns_.store_row_->cnt_ == MY_SPEC.sort_columns_.count());
const int64_t size = MY_SPEC.sort_columns_.count();
ObSEArray<ObDatumVector, 16> datum_vectors;
for (int64_t i = 0; OB_SUCC(ret) && i < MY_SPEC.sort_columns_.count(); ++i) {
ObExpr *expr = MY_SPEC.sort_columns_.at(i);
if (OB_FAIL(expr->eval_batch(eval_ctx_, skip, batch_size))) {
LOG_WARN("expression evaluate failed", K(ret));
} else {
datum_vectors.push_back(expr->locate_expr_datumvector(eval_ctx_));
}
}
for (uint32_t row_idx = 0; OB_SUCC(ret) && keep_iterating && row_idx < batch_size; row_idx++) {
if (skip.at(row_idx)) {
continue;
}
for (int64_t col_idx = 0; OB_SUCC(ret) && keep_iterating && col_idx < datum_vectors.count();
++col_idx) {
ObExpr *expr = MY_SPEC.sort_columns_.at(col_idx);
int cmp_ret = 0;
if (OB_FAIL(expr->basic_funcs_->null_first_cmp_(
pre_sort_columns_.store_row_->cells()[col_idx],
*(datum_vectors[col_idx].at(row_idx)), cmp_ret))) {
LOG_WARN("compare failed", K(ret));
} else {
keep_iterating = (0 == cmp_ret);
}
}
if (keep_iterating) {
row_count_matched++;
}
}
}
return ret;
}
// For percent, need to convert to corresponding limit count based on total number of rows here
int ObLimitOp::convert_limit_percent()
{
int ret = OB_SUCCESS;
double percent = 0.0;
if (OB_FAIL(get_double_val(MY_SPEC.percent_expr_, eval_ctx_, percent))) {
LOG_WARN("failed to get double value", K(ret));
} else if (percent > 0) {
int64_t tot_count = 0;
if (OB_UNLIKELY(limit_ != -1) || OB_ISNULL(child_) ||
OB_UNLIKELY(child_->get_spec().get_type() != PHY_MATERIAL &&
child_->get_spec().get_type() != PHY_SORT)) {
ret = OB_ERR_UNEXPECTED;
LOG_WARN("get unexpected error", K(ret), K(limit_), K(child_));
} else if (child_->get_spec().get_type() == PHY_MATERIAL &&
OB_FAIL(static_cast<ObMaterialOp *>(child_)->get_material_row_count(tot_count))) {
LOG_WARN("failed to get op row count", K(ret));
} else if (child_->get_spec().get_type() == PHY_SORT &&
FALSE_IT(tot_count = static_cast<ObSortOp *>(child_)->get_sort_row_count())) {
LOG_WARN("failed to get op row count", K(ret));
} else if (OB_UNLIKELY(tot_count < 0)) {
ret = OB_ERR_UNEXPECTED;
LOG_WARN("get invalid child op row count", K(tot_count), K(ret));
} else if (percent < 100) {
// Compatible with oracle, round up
int64_t percent_int64 = static_cast<int64_t>(percent);
int64_t offset = (tot_count * percent / 100 - tot_count * percent_int64 / 100) > 0 ? 1 : 0;
limit_ = tot_count * percent_int64 / 100 + offset;
is_percent_first_ = false;
} else {
limit_ = tot_count;
is_percent_first_ = false;
}
} else {
limit_ = 0;
}
return ret;
}
} // end namespace sql
} // end namespace oceanbase