Detect scans from regional tables that can be satisfied in the local region.

expr.go

func (s *ScanPrivate) IsLocalOnly(md *opt.Metadata, evalCtx *eval.Context) bool {
	tab := md.Table(s.Table)
	tabMeta := md.TableMeta(s.Table)
	index := tabMeta.Table.Index(s.Index)
	homeRegion, hasHomeRegion := tab.HomeRegion()

	prefixSorter, ok := tabMeta.IndexPartitionLocality(index.Ordinal(), index, evalCtx)
	localRegion, hasLocalRegion := evalCtx.GetLocalRegion()

	if s.LocalityOptimized {
		return true
	} else if tab.IsGlobalTable() {
		return true
	} else if !ok && !hasHomeRegion {
		// Not regional by row or regional by table.
		return false
	} else if hasHomeRegion {
		if !hasLocalRegion || homeRegion != localRegion {
			return false
		}
		return true
	} else if !hasLocalRegion || s.Constraint == nil {
		return false
	} else if s.Constraint.HasRemoteSpans(prefixSorter) {
		return false
	}
	return true
}