Panic when calling array_to_string on an empty array

[andrioni]

What version of Materialize are you using?

v0.22.1-dev (9611cc6)

How did you install Materialize?

Built from source

What was the issue?

Materialize panics when the following query is executed:

select array_to_string('{}'::int[], ' ');

This query was reduced from a query used by psql when running \d+ on a table.

Relevant log output

Full panic backtrace:


2022-03-07T12:31:10.305119Z ERROR panic: attempt to subtract with overflow
thread: coordinator
location: src/expr/src/scalar/func.rs:5129:18
version: 0.22.1-dev (9611cc69528eee6228fe17e931340b1bb91e5684)
backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.64/src/backtrace/libunwind.rs:93:5
      backtrace::backtrace::trace_unsynchronized
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.64/src/backtrace/mod.rs:66:5
      backtrace::backtrace::trace
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.64/src/backtrace/mod.rs:53:14
   1: backtrace::capture::Backtrace::create
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.64/src/capture.rs:176:9
      backtrace::capture::Backtrace::new
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.64/src/capture.rs:140:22
   2: materialized::handle_panic
             at src/materialized/src/bin/materialized/main.rs:937:21
   3: core::ops::function::Fn::call
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:70:5
   4: std::panicking::rust_panic_with_hook
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:610:17
   5: std::panicking::begin_panic_handler::{{closure}}
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:500:13
   6: std::sys_common::backtrace::__rust_end_short_backtrace
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/sys_common/backtrace.rs:139:18
   7: rust_begin_unwind
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
   8: core::panicking::panic_fmt
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
   9: core::panicking::panic
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:48:5
  10: mz_expr::scalar::func::array_to_string
             at src/expr/src/scalar/func.rs:5129:18
  11: mz_expr::scalar::func::VariadicFunc::eval
             at src/expr/src/scalar/func.rs:5876:17
  12: mz_expr::scalar::MirScalarExpr::eval
             at src/expr/src/scalar/mod.rs:1015:60
  13: mz_expr::scalar::MirScalarExpr::reduce::{{closure}}
             at src/expr/src/scalar/mod.rs:290:36
  14: mz_expr::scalar::MirScalarExpr::reduce::{{closure}}
             at src/expr/src/scalar/mod.rs:610:34
  15: mz_expr::scalar::MirScalarExprVisitor::visit_mut_pre_post::{{closure}}
             at src/expr/src/scalar/mod.rs:1205:13
  16: stacker::maybe_grow
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/stacker-0.1.14/src/lib.rs:55:9
      mz_ore::stack::maybe_grow
             at src/ore/src/stack.rs:100:5
      mz_expr::scalar::MirScalarExprVisitor::visit_mut_pre_post
             at src/expr/src/scalar/mod.rs:1196:9
  17: mz_expr::scalar::MirScalarExpr::visit_mut_pre_post
             at src/expr/src/scalar/mod.rs:170:9
  18: mz_expr::scalar::MirScalarExpr::reduce
             at src/expr/src/scalar/mod.rs:298:13
  19: mz_transform::reduction::FoldConstants::action
             at src/transform/src/reduction.rs:159:21
  20: <mz_transform::reduction::FoldConstants as mz_transform::Transform>::transform::{{closure}}
             at src/transform/src/reduction.rs:44:13
  21: mz_expr::relation::MirRelationExprVisitor::try_visit_mut_post::{{closure}}
             at src/expr/src/relation/mod.rs:1627:13
  22: mz_ore::stack::CheckedRecursion::checked_recur::{{closure}}
             at src/ore/src/stack.rs:191:33
  23: stacker::maybe_grow
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/stacker-0.1.14/src/lib.rs:55:9
      mz_ore::stack::maybe_grow
             at src/ore/src/stack.rs:100:5
      mz_ore::stack::CheckedRecursion::checked_recur
             at src/ore/src/stack.rs:191:19
      mz_expr::relation::MirRelationExprVisitor::try_visit_mut_post
             at src/expr/src/relation/mod.rs:1625:9
  24: mz_expr::relation::MirRelationExpr::try_visit_mut_post
             at src/expr/src/relation/mod.rs:1266:9
  25: <mz_transform::reduction::FoldConstants as mz_transform::Transform>::transform
             at src/transform/src/reduction.rs:40:9
  26: <mz_transform::FuseAndCollapse as mz_transform::Transform>::transform
             at src/transform/src/lib.rs:230:13
  27: <mz_transform::Fixpoint as mz_transform::Transform>::transform
             at src/transform/src/lib.rs:135:21
  28: mz_transform::Optimizer::transform
             at src/transform/src/lib.rs:392:13
  29: mz_transform::Optimizer::optimize
             at src/transform/src/lib.rs:377:9
  30: mz_coord::coord::Coordinator::sequence_peek::{{closure}}
             at src/coord/src/coord.rs:2937:22
  31: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  32: mz_coord::coord::Coordinator::sequence_plan::{{closure}}
             at src/coord/src/coord.rs:1664:63
  33: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  34: mz_coord::coord::Coordinator::message_statement_ready::{{closure}}
             at src/coord/src/coord.rs:898:62
  35: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  36: mz_coord::coord::Coordinator::serve::{{closure}}
             at src/coord/src/coord.rs:694:86
  37: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  38: tokio::park::thread::CachedParkThread::block_on::{{closure}}
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/park/thread.rs:263:54
  39: tokio::coop::with_budget::{{closure}}
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/coop.rs:102:9
  40: std::thread::local::LocalKey<T>::try_with
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:412:16
  41: std::thread::local::LocalKey<T>::with
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:388:9
  42: tokio::coop::with_budget
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/coop.rs:95:5
      tokio::coop::budget
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/coop.rs:72:5
      tokio::park::thread::CachedParkThread::block_on
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/park/thread.rs:263:31
  43: tokio::runtime::enter::Enter::block_on
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/runtime/enter.rs:151:13
  44: tokio::runtime::handle::Handle::block_on
             at /Users/alessandro/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.17.0/src/runtime/handle.rs:355:9
  45: mz_coord::coord::serve::{{closure}}::{{closure}}
             at src/coord/src/coord.rs:4531:17
  46: std::sys_common::backtrace::__rust_begin_short_backtrace
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/sys_common/backtrace.rs:123:18
  47: std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/mod.rs:477:17
  48: <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panic/unwind_safe.rs:271:9
  49: std::panicking::try::do_call
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:406:40
  50: <unknown>
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:441:2
  51: std::panicking::try
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:370:19
  52: std::panic::catch_unwind
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panic.rs:133:14
  53: std::thread::Builder::spawn_unchecked::{{closure}}
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/mod.rs:476:30
  54: core::ops::function::FnOnce::call_once{{vtable.shim}}
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5
  55: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/alloc/src/boxed.rs:1854:9
      <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/alloc/src/boxed.rs:1854:9
      std::sys::unix::thread::Thread::new::thread_start
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/sys/unix/thread.rs:108:17
  56: _pthread_jit_write_protect_np