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delete.go
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delete.go
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/*
Copyright 2022 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 operators
import (
"fmt"
"vitess.io/vitess/go/vt/sqlparser"
"vitess.io/vitess/go/vt/vterrors"
"vitess.io/vitess/go/vt/vtgate/engine"
"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
"vitess.io/vitess/go/vt/vtgate/semantics"
"vitess.io/vitess/go/vt/vtgate/vindexes"
)
type Delete struct {
Target TargetTable
OwnedVindexQuery *sqlparser.Select
Ignore bool
Source Operator
noColumns
noPredicates
}
type TargetTable struct {
ID semantics.TableSet
VTable *vindexes.Table
Name sqlparser.TableName
}
// Introduces implements the PhysicalOperator interface
func (d *Delete) introducesTableID() semantics.TableSet {
return d.Target.ID
}
// Clone implements the Operator interface
func (d *Delete) Clone(inputs []Operator) Operator {
newD := *d
newD.SetInputs(inputs)
return &newD
}
func (d *Delete) Inputs() []Operator {
return []Operator{d.Source}
}
func (d *Delete) SetInputs(inputs []Operator) {
if len(inputs) != 1 {
panic(vterrors.VT13001("unexpected number of inputs for Delete operator"))
}
d.Source = inputs[0]
}
func (d *Delete) TablesUsed() []string {
return SingleQualifiedIdentifier(d.Target.VTable.Keyspace, d.Target.VTable.Name)
}
func (d *Delete) GetOrdering(*plancontext.PlanningContext) []OrderBy {
return nil
}
func (d *Delete) ShortDescription() string {
return fmt.Sprintf("%s.%s", d.Target.VTable.Keyspace.Name, d.Target.VTable.Name.String())
}
func createOperatorFromDelete(ctx *plancontext.PlanningContext, deleteStmt *sqlparser.Delete) (op Operator) {
childFks := ctx.SemTable.GetChildForeignKeysForTable(deleteStmt.Targets[0])
// We check if delete with input plan is required. DML with input planning is generally
// slower, because it does a selection and then creates a delete statement wherein we have to
// list all the primary key values.
if deleteWithInputPlanningRequired(childFks, deleteStmt) {
return deleteWithInputPlanningForFk(ctx, deleteStmt)
}
delClone := sqlparser.CloneRefOfDelete(deleteStmt)
delOp := createDeleteOperator(ctx, deleteStmt)
op = delOp
if deleteStmt.Comments != nil {
op = &LockAndComment{
Source: op,
Comments: deleteStmt.Comments,
}
}
// If there are no foreign key constraints, then we don't need to do anything special.
if len(childFks) == 0 {
return op
}
return createFkCascadeOpForDelete(ctx, op, delClone, childFks, delOp.Target.VTable)
}
func deleteWithInputPlanningRequired(childFks []vindexes.ChildFKInfo, deleteStmt *sqlparser.Delete) bool {
// If there are no foreign keys, we don't need to use delete with input.
if len(childFks) == 0 {
return false
}
// Limit requires delete with input.
if deleteStmt.Limit != nil {
return true
}
// If there are no limit clauses, and it is not a multi-delete, we don't need delete with input.
// TODO: In the future, we can check if the tables involved in the multi-table delete are related by foreign keys or not.
// If they aren't then we don't need the multi-table delete. But this check isn't so straight-forward. We need to check if the two
// tables are connected in the undirected graph built from the tables related by foreign keys.
return !deleteStmt.IsSingleAliasExpr()
}
func deleteWithInputPlanningForFk(ctx *plancontext.PlanningContext, del *sqlparser.Delete) Operator {
delClone := ctx.SemTable.Clone(del).(*sqlparser.Delete)
del.Limit = nil
del.OrderBy = nil
selectStmt := &sqlparser.Select{
From: delClone.TableExprs,
Where: delClone.Where,
OrderBy: delClone.OrderBy,
Limit: delClone.Limit,
Lock: sqlparser.ForUpdateLock,
}
ts := ctx.SemTable.Targets[del.Targets[0].Name]
ti, err := ctx.SemTable.TableInfoFor(ts)
if err != nil {
panic(vterrors.VT13001(err.Error()))
}
vTbl := ti.GetVindexTable()
var leftComp sqlparser.ValTuple
cols := make([]*sqlparser.ColName, 0, len(vTbl.PrimaryKey))
for _, col := range vTbl.PrimaryKey {
colName := sqlparser.NewColNameWithQualifier(col.String(), vTbl.GetTableName())
selectStmt.SelectExprs = append(selectStmt.SelectExprs, aeWrap(colName))
cols = append(cols, colName)
leftComp = append(leftComp, colName)
ctx.SemTable.Recursive[colName] = ts
}
// optimize for case when there is only single column on left hand side.
var lhs sqlparser.Expr = leftComp
if len(leftComp) == 1 {
lhs = leftComp[0]
}
compExpr := sqlparser.NewComparisonExpr(sqlparser.InOp, lhs, sqlparser.ListArg(engine.DmVals), nil)
del.Targets = sqlparser.TableNames{del.Targets[0]}
del.TableExprs = sqlparser.TableExprs{ti.GetAliasedTableExpr()}
del.Where = sqlparser.NewWhere(sqlparser.WhereClause, compExpr)
return &DeleteWithInput{
Delete: createOperatorFromDelete(ctx, del),
Source: createOperatorFromSelect(ctx, selectStmt),
cols: cols,
}
}
func createDeleteOperator(ctx *plancontext.PlanningContext, del *sqlparser.Delete) *Delete {
op := crossJoin(ctx, del.TableExprs)
if del.Where != nil {
op = addWherePredicates(ctx, del.Where.Expr, op)
}
target := del.Targets[0]
tblID, exists := ctx.SemTable.Targets[target.Name]
if !exists {
panic(vterrors.VT13001("delete target table should be part of semantic analyzer"))
}
tblInfo, err := ctx.SemTable.TableInfoFor(tblID)
if err != nil {
panic(err)
}
vTbl := tblInfo.GetVindexTable()
// Reference table should delete from the source table.
if vTbl.Type == vindexes.TypeReference && vTbl.Source != nil {
vTbl = updateQueryGraphWithSource(ctx, op, tblID, vTbl)
}
name, err := tblInfo.Name()
if err != nil {
panic(err)
}
targetTbl := TargetTable{
ID: tblID,
VTable: vTbl,
Name: name,
}
var ovq *sqlparser.Select
if vTbl.Keyspace.Sharded && vTbl.Type == vindexes.TypeTable {
primaryVindex, _ := getVindexInformation(tblID, vTbl)
ate := tblInfo.GetAliasedTableExpr()
if len(vTbl.Owned) > 0 {
ovq = generateOwnedVindexQuery(ate, del, targetTbl, primaryVindex.Columns)
}
}
delOp := &Delete{
Target: targetTbl,
Source: op,
Ignore: bool(del.Ignore),
OwnedVindexQuery: ovq,
}
if del.Limit == nil {
return delOp
}
addOrdering(ctx, del, delOp)
delOp.Source = &Limit{
Source: delOp.Source,
AST: del.Limit,
}
return delOp
}
func addOrdering(ctx *plancontext.PlanningContext, del *sqlparser.Delete, delOp *Delete) {
es := &expressionSet{}
ordering := &Ordering{
Source: delOp.Source,
}
for _, order := range del.OrderBy {
if sqlparser.IsNull(order.Expr) {
// ORDER BY null can safely be ignored
continue
}
if !es.add(ctx, order.Expr) {
continue
}
ordering.Order = append(ordering.Order, OrderBy{
Inner: sqlparser.CloneRefOfOrder(order),
SimplifiedExpr: order.Expr,
})
}
if len(ordering.Order) > 0 {
delOp.Source = ordering
}
}
func updateQueryGraphWithSource(ctx *plancontext.PlanningContext, input Operator, tblID semantics.TableSet, vTbl *vindexes.Table) *vindexes.Table {
sourceTable, _, _, _, _, err := ctx.VSchema.FindTableOrVindex(vTbl.Source.TableName)
if err != nil {
panic(err)
}
vTbl = sourceTable
TopDown(input, TableID, func(op Operator, lhsTables semantics.TableSet, isRoot bool) (Operator, *ApplyResult) {
qg, ok := op.(*QueryGraph)
if !ok {
return op, NoRewrite
}
if len(qg.Tables) > 1 {
panic(vterrors.VT12001("DELETE on reference table with join"))
}
for _, tbl := range qg.Tables {
if tbl.ID != tblID {
continue
}
tbl.Alias = sqlparser.NewAliasedTableExpr(sqlparser.NewTableName(vTbl.Name.String()), tbl.Alias.As.String())
tbl.Table, _ = tbl.Alias.TableName()
}
return op, Rewrote("change query table point to source table")
}, func(operator Operator) VisitRule {
_, ok := operator.(*QueryGraph)
return VisitRule(ok)
})
return vTbl
}
func createFkCascadeOpForDelete(ctx *plancontext.PlanningContext, parentOp Operator, delStmt *sqlparser.Delete, childFks []vindexes.ChildFKInfo, deletedTbl *vindexes.Table) Operator {
var fkChildren []*FkChild
var selectExprs []sqlparser.SelectExpr
for _, fk := range childFks {
// Any RESTRICT type foreign keys that arrive here,
// are cross-shard/cross-keyspace RESTRICT cases, which we don't currently support.
if fk.OnDelete.IsRestrict() {
panic(vterrors.VT12002())
}
// We need to select all the parent columns for the foreign key constraint, to use in the update of the child table.
var offsets []int
offsets, selectExprs = addColumns(ctx, fk.ParentColumns, selectExprs, deletedTbl.GetTableName())
fkChildren = append(fkChildren,
createFkChildForDelete(ctx, fk, offsets))
}
selectionOp := createSelectionOp(ctx, selectExprs, delStmt.TableExprs, delStmt.Where, nil, nil, getUpdateLock(deletedTbl))
return &FkCascade{
Selection: selectionOp,
Children: fkChildren,
Parent: parentOp,
}
}
func createFkChildForDelete(ctx *plancontext.PlanningContext, fk vindexes.ChildFKInfo, cols []int) *FkChild {
bvName := ctx.ReservedVars.ReserveVariable(foreignKeyConstraintValues)
parsedComments := getParsedCommentsForFkChecks(ctx)
var childStmt sqlparser.Statement
switch fk.OnDelete {
case sqlparser.Cascade:
// We now construct the delete query for the child table.
// The query looks something like this - `DELETE FROM <child_table> WHERE <child_columns_in_fk> IN (<bind variable for the output from SELECT>)`
var valTuple sqlparser.ValTuple
for _, column := range fk.ChildColumns {
valTuple = append(valTuple, sqlparser.NewColName(column.String()))
}
compExpr := sqlparser.NewComparisonExpr(sqlparser.InOp, valTuple, sqlparser.NewListArg(bvName), nil)
childStmt = &sqlparser.Delete{
Comments: parsedComments,
TableExprs: []sqlparser.TableExpr{sqlparser.NewAliasedTableExpr(fk.Table.GetTableName(), "")},
Where: &sqlparser.Where{Type: sqlparser.WhereClause, Expr: compExpr},
}
case sqlparser.SetNull:
// We now construct the update query for the child table.
// The query looks something like this - `UPDATE <child_table> SET <child_column_in_fk> = NULL [AND <another_child_column_in_fk> = NULL]... WHERE <child_columns_in_fk> IN (<bind variable for the output from SELECT>)`
var valTuple sqlparser.ValTuple
var updExprs sqlparser.UpdateExprs
for _, column := range fk.ChildColumns {
valTuple = append(valTuple, sqlparser.NewColName(column.String()))
updExprs = append(updExprs, &sqlparser.UpdateExpr{
Name: sqlparser.NewColName(column.String()),
Expr: &sqlparser.NullVal{},
})
}
compExpr := sqlparser.NewComparisonExpr(sqlparser.InOp, valTuple, sqlparser.NewListArg(bvName), nil)
childStmt = &sqlparser.Update{
Exprs: updExprs,
Comments: parsedComments,
TableExprs: []sqlparser.TableExpr{sqlparser.NewAliasedTableExpr(fk.Table.GetTableName(), "")},
Where: &sqlparser.Where{Type: sqlparser.WhereClause, Expr: compExpr},
}
case sqlparser.SetDefault:
panic(vterrors.VT09016())
}
// For the child statement of a DELETE query, we don't need to verify all the FKs on VTgate or ignore any foreign key explicitly.
childOp := createOpFromStmt(ctx, childStmt, false /* verifyAllFKs */, "" /* fkToIgnore */)
return &FkChild{
BVName: bvName,
Cols: cols,
Op: childOp,
}
}