func (this *builder) beginMutate(keyspace datastore.Keyspace, ksref *algebra.KeyspaceRef,
keys expression.Expression, indexes algebra.IndexRefs, limit expression.Expression, isDelete bool) error {
ksref.SetDefaultNamespace(this.namespace)
term := algebra.NewKeyspaceTerm(ksref.Namespace(), ksref.Keyspace(), nil, ksref.As(), keys, indexes)
this.children = make([]plan.Operator, 0, 8)
this.subChildren = make([]plan.Operator, 0, 8)
if this.where != nil {
limit = nil
}
scan, err := this.selectScan(keyspace, term, limit)
if err != nil {
return err
}
this.children = append(this.children, scan)
if this.coveringScan != nil {
coverer := expression.NewCoverer(this.coveringScan.Covers())
err = this.cover.MapExpressions(coverer)
if err != nil {
return err
}
if this.where != nil {
this.where, err = coverer.Map(this.where)
if err != nil {
return err
}
}
} else {
var fetch plan.Operator
if isDelete && this.where == nil && isKeyScan(scan) {
fetch = plan.NewDummyFetch(keyspace, term)
} else {
fetch = plan.NewFetch(keyspace, term)
}
this.subChildren = append(this.subChildren, fetch)
}
if this.where != nil {
this.subChildren = append(this.subChildren, plan.NewFilter(this.where))
}
return nil
}
func (this *builder) VisitSubselect(node *algebra.Subselect) (interface{}, error) {
prevCover := this.cover
prevCorrelated := this.correlated
defer func() {
this.cover = prevCover
this.correlated = prevCorrelated
}()
this.correlated = node.IsCorrelated()
if this.cover == nil {
this.cover = node
}
aggs, err := allAggregates(node, this.order)
if err != nil {
return nil, err
}
this.where = node.Where()
group := node.Group()
if group == nil && len(aggs) > 0 {
group = algebra.NewGroup(nil, nil, nil)
this.where = constrainAggregate(this.where, aggs)
}
this.children = make([]plan.Operator, 0, 16) // top-level children, executed sequentially
this.subChildren = make([]plan.Operator, 0, 16) // sub-children, executed across data-parallel streams
err = this.visitFrom(node, group)
if err != nil {
return nil, err
}
if this.coveringScan != nil {
coverer := expression.NewCoverer(this.coveringScan.Covers())
err = this.cover.MapExpressions(coverer)
if err != nil {
return nil, err
}
if this.where != nil {
this.where, err = coverer.Map(this.where)
if err != nil {
return nil, err
}
}
}
if node.Let() != nil {
this.subChildren = append(this.subChildren, plan.NewLet(node.Let()))
}
if node.Where() != nil {
this.subChildren = append(this.subChildren, plan.NewFilter(node.Where()))
}
if group != nil {
this.visitGroup(group, aggs)
}
projection := node.Projection()
this.subChildren = append(this.subChildren, plan.NewInitialProject(projection))
// Initial DISTINCT (parallel)
if projection.Distinct() || this.distinct {
this.subChildren = append(this.subChildren, plan.NewDistinct())
}
if !this.delayProjection {
// Perform the final projection if there is no subsequent ORDER BY
this.subChildren = append(this.subChildren, plan.NewFinalProject())
}
// Parallelize the subChildren
this.children = append(this.children, plan.NewParallel(plan.NewSequence(this.subChildren...), this.maxParallelism))
// Final DISTINCT (serial)
if projection.Distinct() || this.distinct {
this.children = append(this.children, plan.NewDistinct())
}
// Serialize the top-level children
return plan.NewSequence(this.children...), nil
}