**Describe the bug**

Since we upgraded to 20.10.3.30, one of our clickhouse cluster takes much more time to start. (Up to 50 minutes, and before it took ~3 minutes)
The log file is filled with
>  <Debug> DiskLocal: Reserving 1.00 MiB on disk `default`, having unreserved 16.90 TiB

Additionally, the memory consumption increases, linearly, a lot (up to arround 230 G for us) and then drop back to normal values once clickhouse finished starting up. During that loading phase, a single CPU core is used at 100%.
If that memory is not available for the machine, clickhouse gets OOMed by the kernel.


**How to reproduce**
* Issue appeared after we upgraded to ClickHouse server version 20.10.3.30

* How could I find wich of our tables may be responsible for that ?


**Expected behavior**
A fast startup :)

const ASTPtr & partition_ast,
    const StorageMetadataPtr & metadata_snapshot,
    const String & with_name,
    ContextPtr local_context,
    TableLockHolder &)
{
    return freezePartitionsByMatcher(getPartitionMatcher(partition_ast, local_context), metadata_snapshot, with_name, local_context);
}
PartitionCommandsResultInfo MergeTreeData::freezeAll(
    const String & with_name,
    const StorageMetadataPtr & metadata_snapshot,
    ContextPtr local_context,
    TableLockHolder &)
{
    return freezePartitionsByMatcher([] (const String &) { return true; }, metadata_snapshot, with_name, local_context);
}
PartitionCommandsResultInfo MergeTreeData::freezePartitionsByMatcher(