error log: Failed to execute query: select $$

[evenyag]

What type of bug is this?

Other

What subsystems are affected?

Standalone mode, Frontend

What happened?

The server will print an error log while using MySQL client to connect to it.

What operating system did you use?

macOS

Relevant log output and stack trace

Failed to execute query: select $$ trace_id=7112803851606036243 err.msg=0: Table operation error, at src/frontend/src/instance.rs:424:14
1: Failed to plan statement, at /src/operator/src/statement.rs:200:14
2: Cannot plan SQL: SELECT $$, at src/query/src/planner.rs:79:60
3: SchemaError(FieldNotFound { field: Column { relation: None, name: "$$" }, valid_fields: [] }) err.code=PlanQuery

How can we reproduce the bug?

1. starts the server
2. execute mysql -h 127.0.0.1 -P 4002

[waynexia]

Can't reproduce it with the latest commit

2023-09-28T07:04:50.165559Z  INFO frontend::server: Starting GRPC_SERVER at 127.0.0.1:4001
2023-09-28T07:04:50.165639Z  INFO servers::grpc: gRPC server is bound to 127.0.0.1:4001
2023-09-28T07:04:50.171849Z  INFO frontend::server: Starting POSTGRES_SERVER at 127.0.0.1:4003
2023-09-28T07:04:50.171946Z  INFO servers::server: Postgres server started at 127.0.0.1:4003
2023-09-28T07:04:50.171990Z  INFO frontend::server: Starting HTTP_SERVER at 127.0.0.1:4000
2023-09-28T07:04:50.263047Z  INFO servers::http: HTTP server is bound to 127.0.0.1:4000
2023-09-28T07:04:50.263106Z  INFO frontend::server: Starting MYSQL_SERVER at 127.0.0.1:4002
2023-09-28T07:04:50.263145Z  INFO servers::server: MySQL server started at 127.0.0.1:4002
2023-09-28T07:04:50.263190Z  INFO frontend::server: Starting OPENTSDB_SERVER at 127.0.0.1:4242
2023-09-28T07:04:50.263218Z  INFO servers::server: OpenTSDB server started at 127.0.0.1:4242
2023-09-28T07:05:19.592541Z  INFO servers::mysql::server: MySQL connection coming from: 127.0.0.1:47966
2023-09-28T07:05:19.594468Z  INFO common_telemetry: initializing bucket with node_id: 0

What's your mysql version? Mine is mysql from 11.1.2-MariaDB, client 15.2 for Linux (x86_64) using readline 5.1

[evenyag]

Reproduce with commit 201acd

greptimedb
branch: develop
commit: 201acd152db2a961d804b367e23d2224b4397de8
dirty: false
version: 0.4.0-nightly

mysql client version

$ mysql --version
mysql  Ver 8.1.0 for macos12.6 on arm64 (Homebrew)

[MichaelScofield]

We could simply add a regex rule in federated.rs for this select $$ pattern.

[tisonkun]

I met this issue also and here is a patch #2896. However, I notice that our regex group solution is a bit brittle since it match exactly specially with spaces. But since it's mainly to workaround MySQL tools, this may be OK.