Bug Report: planbuilder vtgate panic on DESC of hash vindex

[aquarapid]

Overview of the Issue

• Create sharded keyspace:
• Apply VSchema as per below
• Run DESC hash
• Observe vtgate connection dropping and panic in vtgate log
• vtgate continues serving

Reproduction Steps

Apply vSchema:

{
    "sharded": true,
    "vindexes": {
        "hash": {
            "type": "hash"
        }
    }
}

Sharded keyspace:

zone1-0000000200 sharded -80 primary 192.168.0.134:15200 192.168.0.134:17200 [] 2022-04-01T04:08:41Z
zone1-0000000201 sharded 80- primary 192.168.0.134:15201 192.168.0.134:17201 [] 2022-04-01T04:08:41Z
zone1-0000000300 sharded -80 replica 192.168.0.134:15300 192.168.0.134:17300 [] <null>
zone1-0000000301 sharded 80- replica 192.168.0.134:15301 192.168.0.134:17301 [] <null>

Observe issue:

mysql> desc hash;
ERROR 2013 (HY000): Lost connection to MySQL server during query

Panic from vtgate log:

E0331 21:09:56.522102  146947 server.go:322] mysql_server caught panic:
runtime error: invalid memory address or nil pointer dereference
runtime/panic.go:220 (0x44c795)
runtime/signal_unix.go:818 (0x44c765)
vitess.io/vitess/go/vt/vtgate/planbuilder/explain.go:59 (0xe61978)
vitess.io/vitess/go/vt/vtgate/planbuilder/explain.go:37 (0xe61792)
vitess.io/vitess/go/vt/vtgate/planbuilder/builder.go:213 (0xe5920b)
vitess.io/vitess/go/vt/vtgate/planbuilder/builder.go:84 (0xe57f97)
vitess.io/vitess/go/vt/vtgate/executor.go:1382 (0xec3ee5)
vitess.io/vitess/go/vt/vtgate/plan_execute.go:63 (0xec901d)
vitess.io/vitess/go/vt/vtgate/executor.go:362 (0xeb8209)
vitess.io/vitess/go/vt/vtgate/executor.go:177 (0xeb682e)
vitess.io/vitess/go/vt/vtgate/vtgate.go:383 (0xef097c)
vitess.io/vitess/go/vt/vtgate/plugin_mysql_server.go:224 (0xecb8ad)
vitess.io/vitess/go/mysql/conn.go:1291 (0xc60d55)
vitess.io/vitess/go/mysql/conn.go:1276 (0xc609dd)
vitess.io/vitess/go/mysql/conn.go:891 (0xc5d56e)
vitess.io/vitess/go/mysql/server.go:497 (0xc7cc71)
vitess.io/vitess/go/mysql/server.go:305 (0xc7b83e)
runtime/asm_amd64.s:1571 (0x469240)

Binary Version

14.0.0-SNAPSHOT (Git revision 2b7e2ef42e23fb9809d5032249e48a0cd4a75c7f branch 'main') built on Thu Mar 31 21:07:23 PDT 2022 by jacques@dhoomdeskw.localdomain using go1.18 linux/amd64

Operating System and Environment details

Fedora 35 on kernel 5.16.18-200.fc35.x86_64

Log Fragments

See above

[deepthi]

@vitessio/query-serving