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hnwyllmm
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Oct 22, 2024
### What problem were solved in this pull request?
**Problem:**
When I attempted to join multiple tables, `libsanitizer` detected a
memory leak. The error log is as follows:
```
==23682==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 768 byte(s) in 12 object(s) allocated from:
#0 0x75f738946a2a in operator new(unsigned long) /usr/src/debug/gcc/gcc/libsanitizer/asan/asan_new_delete.cpp:95
#1 0x56870207d56f in RowTuple::set_schema(Table const*, std::vector<FieldMeta, std::allocator<FieldMeta> > const*) /home/pepefloyd/git/miniob/src/observer/sql/expr/tuple.h:184
#2 0x56870208f737 in TableScanPhysicalOperator::open(Trx*) /home/pepefloyd/git/miniob/src/observer/sql/operator/table_scan_physical_operator.cpp:25
#3 0x568702081888 in NestedLoopJoinPhysicalOperator::right_next() /home/pepefloyd/git/miniob/src/observer/sql/operator/join_physical_operator.cpp:113
#4 0x568702083b42 in PredicatePhysicalOperator::next() /home/pepefloyd/git/miniob/src/observer/sql/operator/predicate_physical_operator.cpp:41
#5 0x56870206f411 in HashGroupByPhysicalOperator::open(Trx*) /home/pepefloyd/git/miniob/src/observer/sql/operator/hash_group_by_physical_operator.cpp:44
#6 0x568702085740 in ProjectPhysicalOperator::open(Trx*) /home/pepefloyd/git/miniob/src/observer/sql/operator/project_physical_operator.cpp:34
#7 0x568702038e2c in PlainCommunicator::write_result_internal(SessionEvent*, bool&) /home/pepefloyd/git/miniob/src/observer/net/plain_communicator.cpp:193
#8 0x56870203a7cc in PlainCommunicator::write_result(SessionEvent*, bool&) /home/pepefloyd/git/miniob/src/observer/net/plain_communicator.cpp:162
#9 0x568701ee5e4b in SqlTaskHandler::handle_event(Communicator*) /home/pepefloyd/git/miniob/src/observer/net/sql_task_handler.cpp:45
#10 0x56870202f0d7 in Worker::operator()() /home/pepefloyd/git/miniob/src/observer/net/one_thread_per_connection_thread_handler.cpp:96
#11 0x75f7384f78b3 in execute_native_thread_routine /usr/src/debug/gcc/gcc/libstdc++-v3/src/c++11/thread.cc:104
SUMMARY: AddressSanitizer: 768 byte(s) leaked in 12 allocation(s).
```
### What is changed and how it works?
To fix the memory leak, I identified that in the function
`Tuple::set_schema`:
```cpp
void set_schema(const Table *table, const std::vector<FieldMeta> *fields)
{
table_ = table;
// fix: During a join, the right table's open is called multiple times,
// which invokes set_schema repeatedly. This causes Tuple to store
// unnecessary fields and values, so it is necessary to clear the existing ones first.
this->speces_.clear();
this->speces_.reserve(fields->size());
for (const FieldMeta &field : *fields) {
speces_.push_back(new FieldExpr(table, &field));
}
}
```
The call to `this->speces_.clear()` does not destruct the existing
`FieldExpr*` objects. As a result, the memory was not released properly.
The fix I applied is to manually delete the `FieldExpr*` before clearing
the vector, as shown below:
```cpp
for (FieldExpr *spec : speces_) {
delete spec;
}
```
This ensures that memory allocated for `FieldExpr` is properly released,
thus fixing the memory leak.
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What problem were solved in this pull request?
Issue Number: close #xxx
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What is changed and how it works?
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