**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 :)

#include <IO/ConcatReadBuffer.h>
#include <IO/Operators.h>
#include <IO/ReadBufferFromMemory.h>
#include <IO/WriteBufferFromString.h>
#include <Interpreters/Aggregator.h>
#include <Interpreters/ExpressionAnalyzer.h>
#include <Interpreters/PartLog.h>
#include <Interpreters/TreeRewriter.h>
#include <Interpreters/inplaceBlockConversions.h>
#include <Interpreters/MergeTreeTransaction.h>
#include <Interpreters/Context.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Interpreters/TransactionLog.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Interpreters/convertFieldToType.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTNameTypePair.h>
#include <Parsers/ASTPartition.h>
#include <Parsers/ASTSetQuery.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Parsers/ExpressionListParsers.h>
#include <Parsers/parseQuery.h>
#include <Parsers/queryToString.h>
#include <Storages/AlterCommands.h>
#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
#include <Storages/MergeTree/MergeTreeDataPartCompact.h>
#include <Storages/MergeTree/MergeTreeDataPartInMemory.h>
#include <Storages/MergeTree/MergeTreeDataPartWide.h>
#include <Storages/MergeTree/DataPartStorageOnDisk.h>