forked from vitessio/vitess
/
union.go
97 lines (91 loc) · 2.44 KB
/
union.go
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package planbuilder
import (
"errors"
"github.com/youtube/vitess/go/vt/sqlparser"
"github.com/youtube/vitess/go/vt/vtgate/engine"
"github.com/youtube/vitess/go/vt/vtgate/vindexes"
)
func buildUnionPlan(union *sqlparser.Union, vschema VSchema) (primitive engine.Primitive, err error) {
bindvars := sqlparser.GetBindvars(union)
bldr, err := processUnion(union, vschema, nil)
if err != nil {
return nil, err
}
jt := newJointab(bindvars)
err = bldr.Wireup(bldr, jt)
if err != nil {
return nil, err
}
return bldr.Primitive(), nil
}
func processUnion(union *sqlparser.Union, vschema VSchema, outer builder) (builder, error) {
lbldr, err := processPart(union.Left, vschema, outer)
if err != nil {
return nil, err
}
rbldr, err := processPart(union.Right, vschema, outer)
if err != nil {
return nil, err
}
bldr, err := unionRouteMerge(union, lbldr, rbldr, vschema)
if err != nil {
return nil, err
}
if outer != nil {
bldr.Symtab().Outer = outer.Symtab()
}
err = pushOrderBy(union.OrderBy, bldr)
if err != nil {
return nil, err
}
err = pushLimit(union.Limit, bldr)
if err != nil {
return nil, err
}
return bldr, nil
}
func processPart(part sqlparser.SelectStatement, vschema VSchema, outer builder) (builder, error) {
var err error
var bldr builder
switch part := part.(type) {
case *sqlparser.Union:
bldr, err = processUnion(part, vschema, outer)
case *sqlparser.Select:
bldr, err = processSelect(part, vschema, outer)
case *sqlparser.ParenSelect:
bldr, err = processPart(part.Select, vschema, outer)
default:
panic("unreachable")
}
if err != nil {
return nil, err
}
return bldr, nil
}
func unionRouteMerge(union *sqlparser.Union, left, right builder, vschema VSchema) (builder, error) {
lroute, ok := left.(*route)
if !ok {
return nil, errors.New("unsupported construct: SELECT of UNION is non-trivial")
}
rroute, ok := right.(*route)
if !ok {
return nil, errors.New("unsupported construct: SELECT of UNION is non-trivial")
}
if err := routesCanMerge(lroute, rroute); err != nil {
return nil, err
}
table := &vindexes.Table{
Keyspace: lroute.ERoute.Keyspace,
}
rtb := newRoute(
&sqlparser.Union{Type: union.Type, Left: union.Left, Right: union.Right, Lock: union.Lock},
lroute.ERoute,
table,
vschema,
&sqlparser.TableName{Name: sqlparser.NewTableIdent("")}, // Unions don't have an addressable table name.
sqlparser.NewTableIdent(""),
)
lroute.Redirect = rtb
rroute.Redirect = rtb
return rtb, nil
}