attempt to subtract with overflow bug for WitnessGenerator

[berryjam]

Problem: When start the witness generator the first time,it will cause an overflow bug.Because the verified block is 0 and NUMBER_OF_STORED_ACCOUNT_TREE_CACHE is 300 while BlockNumber is unsigned type, block - NUMBER_OF_STORED_ACCOUNT_TREE_CACHE will get an negative num.The code is located on function store_account_tree_cache in file database.rs.

connection
            .chain()
            .block_schema()
            .remove_old_account_tree_cache(block - NUMBER_OF_STORED_ACCOUNT_TREE_CACHE)
            .await?;

CodeBase: branch: master commit: f958bd54000c5203ed54b55dee073d5b03f192be

Call Stack: thread 'prover_server_pool' panicked at 'attempt to subtract with overflow', core/lib/basic_types/src/lib.rs:27:1 stack backtrace: 0: rust_begin_unwind at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5 1: core::panicking::panic_fmt at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14 2: core::panicking::panic at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:48:5 3: <zksync_basic_types::BlockNumber as core::ops::arith::Sub>::sub at ./core/lib/basic_types/src/macros.rs:56:22 4: <zksync_witness_generator::database::Database as zksync_witness_generator::database_interface::DatabaseInterface>::store_account_tree_cache::{{closure}} at ./core/bin/zksync_witness_generator/src/database.rs:268:44 5: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19 6: <core::pin::Pin<P> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/future.rs:123:9 7: zksync_witness_generator::witness_generator::WitnessGenerator<DB>::load_account_tree::{{closure}} at ./core/bin/zksync_witness_generator/src/witness_generator.rs:162:22 8: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19 9: zksync_witness_generator::witness_generator::WitnessGenerator<DB>::prepare_witness_and_save_it::{{closure}} at ./core/bin/zksync_witness_generator/src/witness_generator.rs:217:86 10: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19 11: zksync_witness_generator::witness_generator::WitnessGenerator<DB>::maintain::{{closure}} at ./core/bin/zksync_witness_generator/src/witness_generator.rs:274:74 12: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19 13: zksync_witness_generator::witness_generator::WitnessGenerator<DB>::start::{{closure}}::{{closure}} at ./core/bin/zksync_witness_generator/src/witness_generator.rs:67:36 14: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19 15: tokio::park::thread::CachedParkThread::block_on::{{closure}} at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/park/thread.rs:263:54 16: tokio::coop::with_budget::{{closure}} at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/coop.rs:106:9 17: std::thread::local::LocalKey<T>::try_with at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:412:16 18: std::thread::local::LocalKey<T>::with at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:388:9 19: tokio::coop::with_budget at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/coop.rs:99:5 20: tokio::coop::budget at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/coop.rs:76:5 21: tokio::park::thread::CachedParkThread::block_on at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/park/thread.rs:263:31 22: tokio::runtime::enter::Enter::block_on at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/runtime/enter.rs:151:13 23: tokio::runtime::thread_pool::ThreadPool::block_on at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/runtime/thread_pool/mod.rs:77:9 24: tokio::runtime::Runtime::block_on at /Users/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/runtime/mod.rs:463:43 25: zksync_witness_generator::witness_generator::WitnessGenerator<DB>::start::{{closure}} at ./core/bin/zksync_witness_generator/src/witness_generator.rs:66:17 note: Some details are omitted, run with RUST_BACKTRACE=full for a verbose backtrace.

[berryjam]

It should check current block and NUMBER_OF_STORED_ACCOUNT_TREE_CACHE before remove old account tree cache.

[bxpana]

Let me see if I can find out more for you.

[berryjam]

Let me see if I can find out more for you.

Thanks and wait for your help.