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operator.go
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operator.go
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/*
Copyright 2021 The Vitess Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package abstract
import (
vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
"vitess.io/vitess/go/vt/sqlparser"
"vitess.io/vitess/go/vt/vterrors"
"vitess.io/vitess/go/vt/vtgate/semantics"
)
type (
// Operator forms the tree of operators, representing the declarative query provided.
// An operator can be:
// * Derived - which represents an expression that generates a table.
// * QueryGraph - which represents a group of tables and predicates that can be evaluated in any order
// while still preserving the results
// * LeftJoin - A left join. These can't be evaluated in any order, so we keep them separate
// * Join - A join represents inner join.
// * SubQuery - Represents a query that encapsulates one or more sub-queries (SubQueryInner).
// * Vindex - Represents a query that selects from vindex tables.
// * Concatenate - Represents concatenation of the outputs of all the input sources
Operator interface {
// TableID returns a TableSet of the tables contained within
TableID() semantics.TableSet
// PushPredicate pushes a predicate to the closest possible operator
PushPredicate(expr sqlparser.Expr, semTable *semantics.SemTable) error
// UnsolvedPredicates returns any predicates that have dependencies on the given Operator and
// on the outside of it (a parent Select expression, any other table not used by Operator, etc).
UnsolvedPredicates(semTable *semantics.SemTable) []sqlparser.Expr
// CheckValid checks if we have a valid operator tree, and returns an error if something is wrong
CheckValid() error
// Compact will optimise the operator tree into a smaller but equivalent version
Compact(semTable *semantics.SemTable) (Operator, error)
}
)
func getOperatorFromTableExpr(tableExpr sqlparser.TableExpr, semTable *semantics.SemTable) (Operator, error) {
switch tableExpr := tableExpr.(type) {
case *sqlparser.AliasedTableExpr:
switch tbl := tableExpr.Expr.(type) {
case sqlparser.TableName:
tableID := semTable.TableSetFor(tableExpr)
tableInfo, err := semTable.TableInfoFor(tableID)
if err != nil {
return nil, err
}
if vt, isVindex := tableInfo.(*semantics.VindexTable); isVindex {
return &Vindex{Table: VindexTable{
TableID: tableID,
Alias: tableExpr,
Table: tbl,
VTable: vt.Table.GetVindexTable(),
}, Vindex: vt.Vindex}, nil
}
qg := newQueryGraph()
isInfSchema := tableInfo.IsInfSchema()
qt := &QueryTable{Alias: tableExpr, Table: tbl, TableID: tableID, IsInfSchema: isInfSchema}
qg.Tables = append(qg.Tables, qt)
return qg, nil
case *sqlparser.DerivedTable:
inner, err := CreateOperatorFromAST(tbl.Select, semTable)
if err != nil {
return nil, err
}
return &Derived{Alias: tableExpr.As.String(), Inner: inner, Sel: tbl.Select}, nil
default:
return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "unable to use: %T", tbl)
}
case *sqlparser.JoinTableExpr:
switch tableExpr.Join {
case sqlparser.NormalJoinType:
lhs, err := getOperatorFromTableExpr(tableExpr.LeftExpr, semTable)
if err != nil {
return nil, err
}
rhs, err := getOperatorFromTableExpr(tableExpr.RightExpr, semTable)
if err != nil {
return nil, err
}
op := createJoin(lhs, rhs)
if tableExpr.Condition.On != nil {
err = op.PushPredicate(sqlparser.RemoveKeyspaceFromColName(tableExpr.Condition.On), semTable)
if err != nil {
return nil, err
}
}
return op, nil
case sqlparser.LeftJoinType, sqlparser.RightJoinType:
lhs, err := getOperatorFromTableExpr(tableExpr.LeftExpr, semTable)
if err != nil {
return nil, err
}
rhs, err := getOperatorFromTableExpr(tableExpr.RightExpr, semTable)
if err != nil {
return nil, err
}
if tableExpr.Join == sqlparser.RightJoinType {
lhs, rhs = rhs, lhs
}
return &Join{LHS: lhs, RHS: rhs, LeftJoin: true, Predicate: sqlparser.RemoveKeyspaceFromColName(tableExpr.Condition.On)}, nil
case sqlparser.StraightJoinType:
return nil, semantics.Gen4NotSupportedF(tableExpr.Join.ToString())
default:
return nil, vterrors.Errorf(vtrpcpb.Code_UNIMPLEMENTED, "unsupported: %s", tableExpr.Join.ToString())
}
case *sqlparser.ParenTableExpr:
return crossJoin(tableExpr.Exprs, semTable)
default:
return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "unable to use: %T table type", tableExpr)
}
}
func crossJoin(exprs sqlparser.TableExprs, semTable *semantics.SemTable) (Operator, error) {
var output Operator
for _, tableExpr := range exprs {
op, err := getOperatorFromTableExpr(tableExpr, semTable)
if err != nil {
return nil, err
}
if output == nil {
output = op
} else {
output = createJoin(output, op)
}
}
return output, nil
}
func getSelect(s sqlparser.SelectStatement) *sqlparser.Select {
switch s := s.(type) {
case *sqlparser.Select:
return s
default:
return nil
}
}
// CreateOperatorFromAST creates an operator tree that represents the input SELECT or UNION query
func CreateOperatorFromAST(selStmt sqlparser.SelectStatement, semTable *semantics.SemTable) (op Operator, err error) {
switch node := selStmt.(type) {
case *sqlparser.Select:
op, err = createOperatorFromSelect(node, semTable)
case *sqlparser.Union:
op, err = createOperatorFromUnion(node, semTable)
default:
return nil, vterrors.Errorf(vtrpcpb.Code_UNIMPLEMENTED, "%T: operator not yet supported", selStmt)
}
if err != nil {
return nil, err
}
return op.Compact(semTable)
}
func createOperatorFromUnion(node *sqlparser.Union, semTable *semantics.SemTable) (Operator, error) {
opLHS, err := CreateOperatorFromAST(node.Left, semTable)
if err != nil {
return nil, err
}
_, isRHSUnion := node.Right.(*sqlparser.Union)
if isRHSUnion {
return nil, vterrors.Errorf(vtrpcpb.Code_UNIMPLEMENTED, "nesting of unions at the right-hand side is not yet supported")
}
opRHS, err := CreateOperatorFromAST(node.Right, semTable)
if err != nil {
return nil, err
}
return &Concatenate{
Distinct: node.Distinct,
SelectStmts: []*sqlparser.Select{getSelect(node.Left), getSelect(node.Right)},
Sources: []Operator{opLHS, opRHS},
OrderBy: node.OrderBy,
Limit: node.Limit,
}, nil
}
// createOperatorFromSelect creates an operator tree that represents the input SELECT query
func createOperatorFromSelect(sel *sqlparser.Select, semTable *semantics.SemTable) (Operator, error) {
var resultantOp *SubQuery
if len(semTable.SubqueryMap[sel]) > 0 {
resultantOp = &SubQuery{}
for _, sq := range semTable.SubqueryMap[sel] {
subquerySelectStatement, isSel := sq.SubQuery.Select.(*sqlparser.Select)
if !isSel {
return nil, semantics.Gen4NotSupportedF("UNION in subquery")
}
opInner, err := createOperatorFromSelect(subquerySelectStatement, semTable)
if err != nil {
return nil, err
}
resultantOp.Inner = append(resultantOp.Inner, &SubQueryInner{
SelectStatement: subquerySelectStatement,
Inner: opInner,
Type: sq.OpCode,
ArgName: sq.ArgName,
HasValues: sq.HasValues,
ExprsNeedReplace: sq.ExprsNeedReplace,
ReplaceBy: sq.ReplaceBy,
})
}
}
op, err := crossJoin(sel.From, semTable)
if err != nil {
return nil, err
}
if sel.Where != nil {
exprs := sqlparser.SplitAndExpression(nil, sel.Where.Expr)
for _, expr := range exprs {
err := op.PushPredicate(sqlparser.RemoveKeyspaceFromColName(expr), semTable)
if err != nil {
return nil, err
}
addColumnEquality(semTable, expr)
}
}
if resultantOp == nil {
return op, nil
}
resultantOp.Outer = op
return resultantOp, nil
}
func addColumnEquality(semTable *semantics.SemTable, expr sqlparser.Expr) {
switch expr := expr.(type) {
case *sqlparser.ComparisonExpr:
if expr.Operator != sqlparser.EqualOp {
return
}
if left, isCol := expr.Left.(*sqlparser.ColName); isCol {
semTable.AddColumnEquality(left, expr.Right)
}
if right, isCol := expr.Right.(*sqlparser.ColName); isCol {
semTable.AddColumnEquality(right, expr.Left)
}
}
}
func createJoin(LHS, RHS Operator) Operator {
lqg, lok := LHS.(*QueryGraph)
rqg, rok := RHS.(*QueryGraph)
if lok && rok {
op := &QueryGraph{
Tables: append(lqg.Tables, rqg.Tables...),
innerJoins: append(lqg.innerJoins, rqg.innerJoins...),
NoDeps: sqlparser.AndExpressions(lqg.NoDeps, rqg.NoDeps),
}
return op
}
return &Join{LHS: LHS, RHS: RHS}
}