mysql decimal nullable -> DB::Exception: Attempt to read after eof

[PHaroZ]

Hi,

Describe the bug or unexpected behaviour
When I try to INSERT SELECT from a remote mysql table it leads to DB::Exception: Attempt to read after eof when a source column is of type decimal(xx,yy) NULL and have null value.
This issue also occurs when I try to cast a column from a mysql decimal(xx,yy) NULL to a clickhouse Nullable(Decimal(xx,yy))

How to reproduce
CH version : 19.13.3.26 and 19.16.2.2 (official build)

First run the following mysql statements on a mysql server

create table chSource (dn decimal(10,2) null);
insert into chSource VALUES(42.1), (null);

Then in a clickhouse server run

SELECT CAST(dn AS Nullable(Decimal(10,2)))
FROM mysql('mysqlServer:3306','mysqlDatabase','chSource','user','password');

and you obtain

[2a12e65e4fac] 2019.11.08 13:12:23.326313 {c65e05cd-d0c9-4dcd-99b1-218180d10eaf} [ 44 ] <Error> executeQuery: Code: 32, e.displayText() = DB::Exception: Attempt to read after eof (version 19.13.3.26 (official build)) (from 127.0.0.1:36672) (in query: SELECT CAST(dn, 'Nullable(Decimal(10, 2))') FROM mysql('172.23.0.1:3306', 'test', 'chSource', 'root', 'root')), Stack trace:

0. /usr/bin/clickhouse-server(StackTrace::StackTrace()+0x30) [0x7f6b5f0]
1. /usr/bin/clickhouse-server(DB::Exception::Exception(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)+0x25) [0x3c46865]
2. /usr/bin/clickhouse-server(DB::throwReadAfterEOF()+0x55) [0x37b517d]
3. /usr/bin/clickhouse-server(void DB::readDecimalText<DB::Decimal<long> >(DB::ReadBuffer&, DB::Decimal<long>&, unsigned int, unsigned int&, bool)+0x4d7) [0x6cd5337]
4. /usr/bin/clickhouse-server(DB::DataTypeDecimal<DB::Decimal<long> >::readText(DB::Decimal<long>&, DB::ReadBuffer&, unsigned int, unsigned int, bool)+0x5a) [0x6cd56ea]
5. /usr/bin/clickhouse-server(void DB::ConvertThroughParsing<DB::DataTypeString, DB::DataTypeDecimal<DB::Decimal<long> >, DB::NameCast, (DB::ConvertFromStringExceptionMode)0, (DB::ConvertFromStringParsingMode)0>::execute<unsigned int>(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long, unsigned int)+0x22d) [0x400da8d]
6. /usr/bin/clickhouse-server(std::_Function_handler<void (DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long), DB::FunctionCast::createDecimalWrapper<DB::Decimal<long> >(std::shared_ptr<DB::IDataType const> const&, DB::DataTypeDecimal<DB::Decimal<long> > const*) const::{lambda(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long)#1}>::_M_invoke(std::_Any_data const&, DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long&&, std::_Any_data const&)+0x87f) [0x401007f]
7. /usr/bin/clickhouse-server(DB::FunctionCast::prepareRemoveNullable(std::shared_ptr<DB::IDataType const> const&, std::shared_ptr<DB::IDataType const> const&, bool) const::{lambda(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long)#1}::operator()(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long) const+0x3bc) [0x3ff0e6c]
8. /usr/bin/clickhouse-server(DB::PreparedFunctionCast::executeImpl(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long)+0xa3) [0x3ff0803]
9. /usr/bin/clickhouse-server(DB::PreparedFunctionImpl::execute(DB::Block&, std::vector<unsigned long, std::allocator<unsigned long> > const&, unsigned long, unsigned long, bool)+0x27c) [0x72a473c]
10. /usr/bin/clickhouse-server(DB::ExpressionAction::execute(DB::Block&, bool) const+0x281) [0x7488a11]
11. /usr/bin/clickhouse-server(DB::ExpressionActions::execute(DB::Block&, bool) const+0x45) [0x748a135]
12. /usr/bin/clickhouse-server(DB::ExpressionBlockInputStream::readImpl()+0x4b) [0x73276ab]
13. /usr/bin/clickhouse-server(DB::IBlockInputStream::read()+0x187) [0x6c160a7]
14. /usr/bin/clickhouse-server(DB::ExpressionBlockInputStream::readImpl()+0x2f) [0x732768f]
15. /usr/bin/clickhouse-server(DB::IBlockInputStream::read()+0x187) [0x6c160a7]
16. /usr/bin/clickhouse-server(DB::AsynchronousBlockInputStream::calculate()+0x5b) [0x6c0fadb]
17. /usr/bin/clickhouse-server() [0x6c0fea0]
18. /usr/bin/clickhouse-server(ThreadPoolImpl<ThreadFromGlobalPool>::worker(std::_List_iterator<ThreadFromGlobalPool>)+0x1a7) [0x3c785e7]
19. /usr/bin/clickhouse-server(ThreadFromGlobalPool::ThreadFromGlobalPool<ThreadPoolImpl<ThreadFromGlobalPool>::scheduleImpl<void>(std::function<void ()>, int, std::optional<unsigned long>)::{lambda()#3}>(ThreadPoolImpl<ThreadFromGlobalPool>::scheduleImpl<void>(std::function<void ()>, int, std::optional<unsigned long>)::{lambda()#3}&&)::{lambda()#1}::operator()() const+0x3e) [0x3c78bce]
20. /usr/bin/clickhouse-server(ThreadPoolImpl<std::thread>::worker(std::_List_iterator<std::thread>)+0x1a6) [0x3c760f6]
21. /usr/bin/clickhouse-server() [0xba3e1a0]
22. /lib/x86_64-linux-gnu/libpthread.so.0(+0x76db) [0x7f8e7dc5c6db]
23. /lib/x86_64-linux-gnu/libc.so.6(clone+0x3f) [0x7f8e7d3e388f]

Received exception from server (version 19.13.3):
Code: 32. DB::Exception: Received from localhost:9000. DB::Exception: Attempt to read after eof. 

Then same query with non-null value in he mysql source table return the expected result.

Nonetheless I would like to thank you for your job, CH rocks 👍

[Slach]

still reproduced on Clickhouse 19.17 and MySQL 5.1

[Slach]

temp workaround is using Nullable(Float64) or Nullable(Float32) is not good solution

[Slach]

@4ertus2 any news about this issue?

[PHaroZ]

@Slach The issue still exist with v20.3.7.46 (the latest current version)

[Slach]

@Enmk any news about this issue?

[keyboardblue]

Still reproduce on 20.5.3.27, any updates there?

[filimonov]

See #11512

[fktr]

Still reproduce on 20.6.3, any updates there?

[qoega]

You can check on build from master(for example via testing release) or wait 20.10 release.

[webparadoxer]

HttpCode:500 ; ;Code: 32, e.displayText() = DB::Exception: Attempt to read after eof: while executing 'FUNCTION CAST(_dummy_0 : 0, 'Nullable(Decimal(9, 2))' :: 1) -> CAST(_dummy_0, 'Nullable(Decimal(9, 2))') Nullable(Decimal(9, 2)) : 2' (version 20.12.4.5 (official build))

[filimonov]

So that didn't help #14535 ...
@zhang2014 are you interested in fixing that?

[zhang2014]

Minimal example : SELECT CAST(arrayJoin(['42.1', NULL]) AS Nullable(Decimal(10,2)));

I will try to fix it.

[leandrogutierrez148]

instead of use

SELECT ... CAST(expr as Nullable(Decimal64(2))), ... FROM ...

try

SELECT ... toDecimal64OrNull(expr, S), ... FROM ..