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join.go
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join.go
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// Copyright 2016, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package planbuilder
import (
"github.com/youtube/vitess/go/vt/sqlparser"
"github.com/youtube/vitess/go/vt/vtgate/engine"
)
// join is used to build a Join primitive.
// It's used to buid a normal join or a left join
// operation.
type join struct {
// LeftOrder and RightOrder store the order
// of the left node and right node. The Order
// of this join will be the same as RightOrder.
// This information is used for traversal.
LeftOrder, RightOrder int
// Left and Right are the nodes for the join.
Left, Right builder
symtab *symtab
// Colsyms specifies the colsyms supplied by this
// join.
Colsyms []*colsym
ejoin *engine.Join
}
// newJoin makes a new joinBuilder using the two nodes. ajoin can be nil
// if the join is on a ',' operator.
func newJoin(lhs, rhs builder, ajoin *sqlparser.JoinTableExpr) (*join, error) {
// This function converts ON clauses to WHERE clauses. The WHERE clause
// scope can see all tables, whereas the ON clause can only see the
// participants of the JOIN. However, since the ON clause doesn't allow
// external references, and the FROM clause doesn't allow duplicates,
// it's safe to perform this conversion and still expect the same behavior.
err := lhs.Symtab().Merge(rhs.Symtab())
if err != nil {
return nil, err
}
rhs.SetSymtab(lhs.Symtab())
rhs.SetOrder(lhs.Order())
opcode := engine.NormalJoin
if ajoin != nil && ajoin.Join == sqlparser.LeftJoinStr {
opcode = engine.LeftJoin
}
jb := &join{
LeftOrder: lhs.Order(),
RightOrder: rhs.Order(),
Left: lhs,
Right: rhs,
symtab: lhs.Symtab(),
ejoin: &engine.Join{
Opcode: opcode,
Left: lhs.Primitive(),
Right: rhs.Primitive(),
Vars: make(map[string]int),
},
}
if ajoin == nil {
return jb, nil
}
if opcode == engine.LeftJoin {
err := pushFilter(ajoin.On, rhs, sqlparser.WhereStr)
if err != nil {
return nil, err
}
rhs.SetRHS()
return jb, nil
}
err = pushFilter(ajoin.On, jb, sqlparser.WhereStr)
if err != nil {
return nil, err
}
return jb, nil
}
// Symtab returns the associated symtab.
func (jb *join) Symtab() *symtab {
return jb.symtab
}
// SetSymtab sets the symtab for the current node and its
// non-subquery children.
func (jb *join) SetSymtab(symtab *symtab) {
jb.symtab = symtab
jb.Left.SetSymtab(symtab)
jb.Right.SetSymtab(symtab)
}
// Order returns the order of the node.
func (jb *join) Order() int {
return jb.RightOrder
}
// SetOrder sets the order for the unerlying routes.
func (jb *join) SetOrder(order int) {
jb.Left.SetOrder(order)
jb.LeftOrder = jb.Left.Order()
jb.Right.SetOrder(jb.LeftOrder)
jb.RightOrder = jb.Right.Order()
}
// Primitve returns the built primitive.
func (jb *join) Primitive() engine.Primitive {
return jb.ejoin
}
// Leftmost returns the leftmost route.
func (jb *join) Leftmost() *route {
return jb.Left.Leftmost()
}
// Join creates new joined node using the two plans.
func (jb *join) Join(rhs builder, ajoin *sqlparser.JoinTableExpr) (builder, error) {
return newJoin(jb, rhs, ajoin)
}
// SetRHS sets all underlying routes to RHS.
func (jb *join) SetRHS() {
jb.Left.SetRHS()
jb.Right.SetRHS()
}
// PushSelect pushes the select expression into the join and
// recursively down.
func (jb *join) PushSelect(expr *sqlparser.NonStarExpr, rb *route) (colsym *colsym, colnum int, err error) {
if rb.Order() <= jb.LeftOrder {
colsym, colnum, err = jb.Left.PushSelect(expr, rb)
if err != nil {
return nil, 0, err
}
jb.ejoin.Cols = append(jb.ejoin.Cols, -colnum-1)
} else {
colsym, colnum, err = jb.Right.PushSelect(expr, rb)
if err != nil {
return nil, 0, err
}
jb.ejoin.Cols = append(jb.ejoin.Cols, colnum+1)
}
jb.Colsyms = append(jb.Colsyms, colsym)
return colsym, len(jb.Colsyms) - 1, nil
}
// PushOrderByNull pushes misc constructs to the underlying routes.
func (jb *join) PushOrderByNull() {
jb.Left.PushOrderByNull()
jb.Right.PushOrderByNull()
}
// PushMisc pushes misc constructs to the underlying routes.
func (jb *join) PushMisc(sel *sqlparser.Select) {
jb.Left.PushMisc(sel)
jb.Right.PushMisc(sel)
}
// Wireup performs the wireup for join.
func (jb *join) Wireup(bldr builder, jt *jointab) error {
err := jb.Right.Wireup(bldr, jt)
if err != nil {
return err
}
return jb.Left.Wireup(bldr, jt)
}
// SupplyVar updates the join to make it supply the requested
// column as a join variable. If the column is not already in
// its list, it requests the LHS node to supply it using SupplyCol.
func (jb *join) SupplyVar(from, to int, col *sqlparser.ColName, varname string) {
if from > jb.LeftOrder {
jb.Right.SupplyVar(from, to, col, varname)
return
}
if to <= jb.LeftOrder {
jb.Left.SupplyVar(from, to, col, varname)
return
}
if _, ok := jb.ejoin.Vars[varname]; ok {
// Looks like somebody else already requested this.
return
}
switch meta := col.Metadata.(type) {
case *colsym:
for i, colsym := range jb.Colsyms {
if jb.ejoin.Cols[i] > 0 {
continue
}
if meta == colsym {
jb.ejoin.Vars[varname] = -jb.ejoin.Cols[i] - 1
return
}
}
panic("unexpected: column not found")
case *tabsym:
ref := newColref(col)
for i, colsym := range jb.Colsyms {
if jb.ejoin.Cols[i] > 0 {
continue
}
if colsym.Underlying == ref {
jb.ejoin.Vars[varname] = -jb.ejoin.Cols[i] - 1
return
}
}
jb.ejoin.Vars[varname] = jb.Left.SupplyCol(ref)
return
}
panic("unreachable")
}
// SupplyCol changes the join to supply the requested column
// name, and returns the result column number. If the column
// is already in the list, it's reused.
func (jb *join) SupplyCol(ref colref) int {
for i, colsym := range jb.Colsyms {
if colsym.Underlying == ref {
return i
}
}
routeNumber := ref.Route().Order()
if routeNumber <= jb.LeftOrder {
ret := jb.Left.SupplyCol(ref)
jb.ejoin.Cols = append(jb.ejoin.Cols, -ret-1)
} else {
ret := jb.Right.SupplyCol(ref)
jb.ejoin.Cols = append(jb.ejoin.Cols, ret+1)
}
jb.Colsyms = append(jb.Colsyms, &colsym{Underlying: ref})
return len(jb.ejoin.Cols) - 1
}