emqx/kuiper: xstream/operators/join_operator.go; 33 LoC

Found a possible issue in [emqx/kuiper](https://www.github.com/emqx/kuiper) at [xstream/operators/join_operator.go](https://github.com/emqx/kuiper/blob/91eacc9baea40bd1dedf0267c18ef39a3296c829/xstream/operators/join_operator.go#L220-L252)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> reference to left was used in a composite literal at line 230

[Click here to see the code in its original context.](https://github.com/emqx/kuiper/blob/91eacc9baea40bd1dedf0267c18ef39a3296c829/xstream/operators/join_operator.go#L220-L252)

Click here to show the 33 line(s) of Go which triggered the analyzer.

```go
for _, left := range *set {
merged := &xsql.JoinTuple{}
if join.JoinType == xsql.LEFT_JOIN || join.JoinType == xsql.FULL_JOIN || join.JoinType == xsql.CROSS_JOIN {
merged.AddTuples(left.Tuples)
}
innerAppend := false
for _, right := range rights {
if join.JoinType == xsql.CROSS_JOIN {
merged.AddTuple(right)
} else {
ve := &xsql.ValuerEval{Valuer: xsql.MultiValuer(&left, &right, fv)}
result := ve.Eval(join.Expr)
switch val := result.(type) {
case error:
return nil, val
case bool:
if val {
if join.JoinType == xsql.INNER_JOIN && !innerAppend {
merged.AddTuples(left.Tuples)
innerAppend = true
}
merged.AddTuple(right)
}
default:
return nil, fmt.Errorf("invalid join condition that returns non-bool value %[1]T(%[1]v)", val)
}
}
}

if len(merged.Tuples) > 0 {
newSets = append(newSets, *merged)
}
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 91eacc9baea40bd1dedf0267c18ef39a3296c829

Start with xstream/operators/join_operator.go at the referenced lines and inspect how left is passed into xsql.MultiValuer inside the range loop. Check the relevant Go range-variable pointer behavior and surrounding join tests, if available. Done means determining whether the analyzer finding is a real bug, mitigated, or desirable behavior and applying the corresponding reaction.

Written by the indexing model from the issue text.