dml_planning.go

/*
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/evalengine"
	"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
	"vitess.io/vitess/go/vt/vtgate/semantics"
	"vitess.io/vitess/go/vt/vtgate/vindexes"
)

// getVindexInformation returns the vindex and VindexPlusPredicates for the DML,
// If it cannot find a unique vindex match, it returns an error.
func getVindexInformation(id semantics.TableSet, table *vindexes.Table) (
	*vindexes.ColumnVindex,
	[]*VindexPlusPredicates) {

	// Check that we have a primary vindex which is valid
	if len(table.ColumnVindexes) == 0 || !table.ColumnVindexes[0].IsUnique() {
		panic(vterrors.VT09001(table.Name))
	}
	primaryVindex := table.ColumnVindexes[0]

	var vindexesAndPredicates []*VindexPlusPredicates
	for _, colVindex := range table.Ordered {
		if lu, isLu := colVindex.Vindex.(vindexes.LookupBackfill); isLu && lu.IsBackfilling() {
			// Checking if the Vindex is currently backfilling or not, if it isn't we can read from the vindex table,
			// and we will be able to do a delete equal. Otherwise, we continue to look for next best vindex.
			continue
		}

		vindexesAndPredicates = append(vindexesAndPredicates, &VindexPlusPredicates{
			ColVindex: colVindex,
			TableID:   id,
		})
	}
	return primaryVindex, vindexesAndPredicates
}

func buildChangedVindexesValues(
	ctx *plancontext.PlanningContext,
	update *sqlparser.Update,
	table *vindexes.Table,
	ksidCols []sqlparser.IdentifierCI,
	assignments []SetExpr,
) (vv map[string]*engine.VindexValues, ownedVindexQuery string, subQueriesArgOnChangedVindex []string) {
	changedVindexes := make(map[string]*engine.VindexValues)
	buf, offset := initialQuery(ksidCols, table)
	for i, vindex := range table.ColumnVindexes {
		vindexValueMap := make(map[string]evalengine.Expr)
		first := true
		for _, vcol := range vindex.Columns {
			// Searching in order of columns in colvindex.
			found := false
			for _, assignment := range assignments {
				if !vcol.Equal(assignment.Name.Name) {
					continue
				}
				if found {
					panic(vterrors.VT03015(assignment.Name.Name))
				}
				found = true
				pv, err := evalengine.Translate(assignment.Expr.EvalExpr, &evalengine.Config{
					ResolveType: ctx.SemTable.TypeForExpr,
					Collation:   ctx.SemTable.Collation,
					Environment: ctx.VSchema.Environment(),
				})
				if err != nil {
					panic(invalidUpdateExpr(assignment.Name.Name.String(), assignment.Expr.EvalExpr))
				}

				if assignment.Expr.Info != nil {
					sqe, ok := assignment.Expr.Info.(SubQueryExpression)
					if ok {
						for _, sq := range sqe {
							subQueriesArgOnChangedVindex = append(subQueriesArgOnChangedVindex, sq.ArgName)
						}
					}
				}

				vindexValueMap[vcol.String()] = pv
				if first {
					buf.Myprintf(", %s", assignment.String())
					first = false
				} else {
					buf.Myprintf(" and %s", assignment.String())
				}
			}
		}
		if len(vindexValueMap) == 0 {
			// Vindex not changing, continue
			continue
		}

		if update.Limit != nil && len(update.OrderBy) == 0 {
			panic(vterrors.VT12001(fmt.Sprintf("you need to provide the ORDER BY clause when using LIMIT; invalid update on vindex: %v", vindex.Name)))
		}
		if i == 0 {
			panic(vterrors.VT12001(fmt.Sprintf("you cannot UPDATE primary vindex columns; invalid update on vindex: %v", vindex.Name)))
		}
		if _, ok := vindex.Vindex.(vindexes.Lookup); !ok {
			panic(vterrors.VT12001(fmt.Sprintf("you can only UPDATE lookup vindexes; invalid update on vindex: %v", vindex.Name)))
		}
		changedVindexes[vindex.Name] = &engine.VindexValues{
			EvalExprMap: vindexValueMap,
			Offset:      offset,
		}
		offset++
	}
	if len(changedVindexes) == 0 {
		return nil, "", nil
	}
	// generate rest of the owned vindex query.
	aTblExpr, ok := update.TableExprs[0].(*sqlparser.AliasedTableExpr)
	if !ok {
		panic(vterrors.VT12001("UPDATE on complex table expression"))
	}
	tblExpr := &sqlparser.AliasedTableExpr{Expr: sqlparser.TableName{Name: table.Name}, As: aTblExpr.As}
	buf.Myprintf(" from %v%v%v%v for update", tblExpr, update.Where, update.OrderBy, update.Limit)
	return changedVindexes, buf.String(), subQueriesArgOnChangedVindex
}

func initialQuery(ksidCols []sqlparser.IdentifierCI, table *vindexes.Table) (*sqlparser.TrackedBuffer, int) {
	buf := sqlparser.NewTrackedBuffer(nil)
	offset := 0
	for _, col := range ksidCols {
		if offset == 0 {
			buf.Myprintf("select %v", col)
		} else {
			buf.Myprintf(", %v", col)
		}
		offset++
	}
	for _, cv := range table.Owned {
		for _, column := range cv.Columns {
			buf.Myprintf(", %v", column)
			offset++
		}
	}
	return buf, offset
}

func invalidUpdateExpr(upd string, expr sqlparser.Expr) error {
	return vterrors.VT12001(fmt.Sprintf("only values are supported; invalid update on column: `%s` with expr: [%s]", upd, sqlparser.String(expr)))
}