unsupported aggregate function caused a "nil pointer dereference" panic

[XuHuaiyu]

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

./gentest.pl --dsn dbi:mysql:host=127.0.0.1:port=4000:user=root:database=test --grammar=conf/subquery_semijoin.yy --gendata --thread=1

SELECT DISTINCT BIT_OR( OUTR . `col_varchar_key` ) AS X FROM C AS OUTR WHERE ( OUTR . `col_int_key` , OUTR . `col_int_nokey` ) IN ( SELECT DISTINCT INNR . `col_int_nokey` AS X , INNR . `col_int_key` AS Y FROM CC AS INNR2 LEFT JOIN BB AS INNR ON ( INNR2 . `col_varchar_key` < INNR . `col_varchar_nokey` ) WHERE OUTR . `col_time_nokey` >= '2003-04-22' ORDER BY INNR . `col_int_nokey` ) AND OUTR . `col_varchar_nokey` IS NULL  ORDER BY OUTR . `col_varchar_nokey` , OUTR . `pk`;

aggissue.txt
2. What did you expect to see?

no error

3. What did you see instead?

runtime error: invalid memory address or nil pointer dereference, goroutine 30848 [running]:
github.com/pingcap/tidb/server.(*clientConn).Run.func1(0xc420b04b00)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/conn.go:389 +0xfd
panic(0x1c4fa20, 0x274d2f0)
	/Users/xuhuaiyu/.gvm/gos/go1.9/src/runtime/panic.go:491 +0x283
github.com/pingcap/tidb/plan.(*planBuilder).buildAggregation(0xc4211ac1e0, 0x2561980, 0xc420c46780, 0xc421646290, 0x1, 0x1, 0x0, 0x0, 0x0, 0xc420cbae01, ...)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/plan/logical_plan_builder.go:100 +0x837
github.com/pingcap/tidb/plan.(*planBuilder).buildSelect(0xc4211ac1e0, 0xc4211ac140, 0x0, 0x0)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/plan/logical_plan_builder.go:1503 +0x992
github.com/pingcap/tidb/plan.(*planBuilder).build(0xc4211ac1e0, 0x253d900, 0xc4211ac140, 0x0, 0xc420c46660)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/plan/planbuilder.go:189 +0x55b
github.com/pingcap/tidb/plan.Optimize(0x254b7a0, 0xc4213b7a70, 0x253d900, 0xc4211ac140, 0x25497c0, 0xc4211e3950, 0x27be900, 0x0, 0x0, 0xc4205b3870)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/plan/optimizer.go:66 +0x12c
github.com/pingcap/tidb/executor.(*Compiler).Compile(0xc4205b3aa0, 0x2b571c8, 0xc420cbadc0, 0x2541740, 0xc4211ac140, 0x0, 0x0, 0x0)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/executor/compiler.go:44 +0x1eb
github.com/pingcap/tidb.(*session).Execute(0xc4213b7a70, 0x2b57208, 0xc420c46120, 0xc4201505a1, 0x1d9, 0x0, 0x0, 0x0, 0x0, 0x0)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/session.go:761 +0xb8c
github.com/pingcap/tidb/server.(*TiDBContext).Execute(0xc421057650, 0x2b57208, 0xc420c46120, 0xc4201505a1, 0x1d9, 0xc4205b3c60, 0x1029ee9, 0xc4209b07b0, 0xc4205b3c80, 0x20)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/driver_tidb.go:196 +0x7c
github.com/pingcap/tidb/server.(*clientConn).handleQuery(0xc420b04b00, 0x2b57208, 0xc420c46120, 0xc4201505a1, 0x1d9, 0x0, 0x0)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/conn.go:741 +0x8d
github.com/pingcap/tidb/server.(*clientConn).dispatch(0xc420b04b00, 0xc4201505a1, 0x1da, 0x1da, 0x0, 0x0)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/conn.go:530 +0x511
github.com/pingcap/tidb/server.(*clientConn).Run(0xc420b04b00)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/conn.go:412 +0x18a
github.com/pingcap/tidb/server.(*Server).onConn(0xc4203fce40, 0x2547620, 0xc4202dbb60)
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/server.go:315 +0x144
created by github.com/pingcap/tidb/server.(*Server).Run
	/Users/xuhuaiyu/Development/GOPATH/src/github.com/pingcap/tidb/server/server.go:261 +0x496

4. What version of TiDB are you using (tidb-server -V)?

648e51d19e51120e9158f6333c060f17260b7ea6

[zz-jason]

in expression/aggregation/aggregation.go:

 82 // NewAggFunction creates a new Aggregation.
 83 func NewAggFunction(funcType string, funcArgs []expression.Expression, distinct bool) Aggregation {
 84     switch tp := strings.ToLower(funcType); tp {
 85     case ast.AggFuncSum:
 86         return &sumFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
 87     case ast.AggFuncCount:
 88         return &countFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
 89     case ast.AggFuncAvg:
 90         return &avgFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
 91     case ast.AggFuncGroupConcat:
 92         return &concatFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
 93     case ast.AggFuncMax:
 94         return &maxMinFunction{aggFunction: newAggFunc(tp, funcArgs, distinct), isMax: true}
 95     case ast.AggFuncMin:
 96         return &maxMinFunction{aggFunction: newAggFunc(tp, funcArgs, distinct), isMax: false}
 97     case ast.AggFuncFirstRow:
 98         return &firstRowFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
 99     case ast.AggFuncBitXor:
100         return &bitXorFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
101     case ast.AggFuncBitAnd:
102         return &bitAndFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
103     }
104     return nil
105 }

BIT_OR is not supported yet, so we got a nil pointer after NewAggFunction and paniced during the following procession.

[zz-jason]

#5145 should fix this.

By the way, we should throw an error in NewAggFunction or just panic here in case there is an unsupported aggregation function.

[zz-jason]

1. bit_xor is supported now.
2. we will not panic when a aggregation function is not supported now.