// NewTagValuesIterator returns a new instance of TagValuesIterator.
func NewTagValuesIterator(sh *Shard, opt influxql.IteratorOptions) (influxql.Iterator, error) {
if opt.Condition == nil {
return nil, errors.New("a condition is required")
}
mms, ok, err := sh.index.measurementsByExpr(opt.Condition)
if err != nil {
return nil, err
} else if !ok {
mms = sh.index.Measurements()
sort.Sort(mms)
}
filterExpr := influxql.CloneExpr(opt.Condition)
filterExpr = influxql.RewriteExpr(filterExpr, func(e influxql.Expr) influxql.Expr {
switch e := e.(type) {
case *influxql.BinaryExpr:
switch e.Op {
case influxql.EQ, influxql.NEQ, influxql.EQREGEX, influxql.NEQREGEX:
tag, ok := e.LHS.(*influxql.VarRef)
if !ok || tag.Val == "name" || strings.HasPrefix(tag.Val, "_") {
return nil
}
}
}
return e
})
var series []*Series
keys := newStringSet()
for _, mm := range mms {
ss, ok, err := mm.tagKeysByExpr(opt.Condition)
if err != nil {
return nil, err
} else if !ok {
keys.add(mm.TagKeys()...)
} else {
keys = keys.union(ss)
}
ids, err := mm.seriesIDsAllOrByExpr(filterExpr)
if err != nil {
return nil, err
}
for _, id := range ids {
series = append(series, mm.SeriesByID(id))
}
}
return &tagValuesIterator{
series: series,
keys: keys.list(),
fields: opt.Aux,
}, nil
}
// Ensure an Expr can be rewritten handling nils.
func TestRewriteExpr(t *testing.T) {
expr := MustParseExpr(`(time > 1 AND time < 10) OR foo = 2`)
// Remove all time expressions.
act := influxql.RewriteExpr(expr, func(e influxql.Expr) influxql.Expr {
switch e := e.(type) {
case *influxql.BinaryExpr:
if lhs, ok := e.LHS.(*influxql.VarRef); ok && lhs.Val == "time" {
return nil
}
}
return e
})
// Verify that everything is flipped.
if act := act.String(); act != `foo = 2` {
t.Fatalf("unexpected result: %s", act)
}
}