When I queried `system.metrics` table, I found some negative values which hint to some potential internal overflows.

```
SELECT *
FROM system.metrics
FORMAT Vertical

...

Row 31:
───────
metric:      MemoryTrackingInBackgroundProcessingPool
value:       -580863171
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround merges, mutations and fetches). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 32:
───────
metric:      MemoryTrackingInBackgroundMoveProcessingPool
value:       0
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround moves). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 33:
───────
metric:      MemoryTrackingInBackgroundSchedulePool
value:       -4461308831
description: Total amount of memory (bytes) allocated in background schedule pool (that is dedicated for bookkeeping tasks of Replicated tables).

...

56 rows in set. Elapsed: 0.003 sec.
```

Server version: 20.8.2.3.
{
    return query_parameters;
}
void Context::setQueryParameter(const String & name, const String & value)
{
    if (!query_parameters.emplace(name, value).second)
        throw Exception("Duplicate name " + backQuote(name) + " of query parameter", ErrorCodes::BAD_ARGUMENTS);
}
#if USE_EMBEDDED_COMPILER
std::shared_ptr<CompiledExpressionCache> Context::getCompiledExpressionCache() const
{
    auto lock = getLock();
    return shared->compiled_expression_cache;
}
void Context::setCompiledExpressionCache(size_t cache_size)
{
    auto lock = getLock();
    if (shared->compiled_expression_cache)
        throw Exception("Compiled expressions cache has been already created.", ErrorCodes::LOGICAL_ERROR);
    shared->compiled_expression_cache = std::make_shared<CompiledExpressionCache>(cache_size);
}
void Context::dropCompiledExpressionCache() const
{
    auto lock = getLock();
    if (shared->compiled_expression_cache)
        shared->compiled_expression_cache->reset();
}
#endif
void Context::addXDBCBridgeCommand(std::unique_ptr<ShellCommand> cmd) const