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triggers.go
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triggers.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// 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 analyzer
import (
"fmt"
"strings"
"github.com/dolthub/vitess/go/vt/sqlparser"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/expression"
"github.com/dolthub/go-mysql-server/sql/plan"
"github.com/dolthub/go-mysql-server/sql/planbuilder"
"github.com/dolthub/go-mysql-server/sql/transform"
)
// validateCreateTrigger handles CreateTrigger nodes, resolving references to "old" and "new" table references in
// the trigger body. Also validates that these old and new references are being used appropriately -- they are only
// valid for certain kinds of triggers and certain statements.
func validateCreateTrigger(ctx *sql.Context, a *Analyzer, node sql.Node, scope *plan.Scope, sel RuleSelector) (sql.Node, transform.TreeIdentity, error) {
ct, ok := node.(*plan.CreateTrigger)
if !ok {
return node, transform.SameTree, nil
}
// We just want to verify that the trigger is correctly defined before creating it. If it is, we replace the
// UnresolvedColumn expressions with placeholder expressions that say they are Resolved().
// TODO: this might work badly for databases with tables named new and old. Needs tests.
var err error
transform.InspectExpressions(ct.Body, func(e sql.Expression) bool {
switch e := e.(type) {
case *expression.UnresolvedColumn:
if strings.ToLower(e.Table()) == "new" {
if ct.TriggerEvent == sqlparser.DeleteStr {
err = sql.ErrInvalidUseOfOldNew.New("new", ct.TriggerEvent)
}
}
if strings.ToLower(e.Table()) == "old" {
if ct.TriggerEvent == sqlparser.InsertStr {
err = sql.ErrInvalidUseOfOldNew.New("old", ct.TriggerEvent)
}
}
}
return true
})
if err != nil {
return nil, transform.SameTree, err
}
// Check to see if the plan sets a value for "old" rows, or if an AFTER trigger assigns to NEW. Both are illegal.
transform.InspectExpressionsWithNode(ct.Body, func(n sql.Node, e sql.Expression) bool {
if _, ok := n.(*plan.Set); !ok {
return true
}
switch e := e.(type) {
case *expression.SetField:
switch left := e.LeftChild.(type) {
case column:
if strings.ToLower(left.Table()) == "old" {
err = sql.ErrInvalidUpdateOfOldRow.New()
}
if ct.TriggerTime == sqlparser.AfterStr && strings.ToLower(left.Table()) == "new" {
err = sql.ErrInvalidUpdateInAfterTrigger.New()
}
}
}
return true
})
if err != nil {
return nil, transform.SameTree, err
}
trigTable := getResolvedTable(ct.Table)
sch := trigTable.Schema()
colsList := make(map[string]struct{})
for _, c := range sch {
colsList[c.Name] = struct{}{}
}
// Check to see if the columns with "new" and "old" table reference are valid columns from the trigger table.
transform.InspectExpressions(ct.Body, func(e sql.Expression) bool {
switch e := e.(type) {
case *expression.UnresolvedColumn:
if strings.ToLower(e.Table()) == "old" || strings.ToLower(e.Table()) == "new" {
if _, ok := colsList[e.Name()]; !ok {
err = sql.ErrUnknownColumn.New(e.Name(), e.Table())
}
}
}
return true
})
if err != nil {
return nil, transform.SameTree, err
}
return node, transform.NewTree, nil
}
func applyTriggers(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope, sel RuleSelector) (sql.Node, transform.TreeIdentity, error) {
// Skip this step for CreateTrigger statements
if _, ok := n.(*plan.CreateTrigger); ok {
return n, transform.SameTree, nil
}
var affectedTables []string
var triggerEvent plan.TriggerEvent
db := ctx.GetCurrentDatabase()
transform.Inspect(n, func(n sql.Node) bool {
switch n := n.(type) {
case *plan.InsertInto:
affectedTables = append(affectedTables, getTableName(n))
triggerEvent = plan.InsertTrigger
if n.Database() != nil && n.Database().Name() != "" {
db = n.Database().Name()
}
case *plan.Update:
affectedTables = append(affectedTables, getTableName(n))
triggerEvent = plan.UpdateTrigger
if n.Database() != "" {
db = n.Database()
}
case *plan.DeleteFrom:
for _, target := range n.GetDeleteTargets() {
affectedTables = append(affectedTables, getTableName(target))
}
triggerEvent = plan.DeleteTrigger
if n.Database() != "" {
db = n.Database()
}
}
return true
})
if len(affectedTables) == 0 {
return n, transform.SameTree, nil
}
// TODO: database should be dependent on the table being inserted / updated, but we don't have that info available
// from the table object yet.
database, err := a.Catalog.Database(ctx, db)
if err != nil {
return nil, transform.SameTree, err
}
var affectedTriggers []*plan.CreateTrigger
if tdb, ok := database.(sql.TriggerDatabase); ok {
triggers, err := tdb.GetTriggers(ctx)
if err != nil {
return nil, transform.SameTree, err
}
b := planbuilder.New(ctx, a.Catalog)
prevActive := b.TriggerCtx().Active
b.TriggerCtx().Active = true
defer func() {
b.TriggerCtx().Active = prevActive
}()
for _, trigger := range triggers {
var parsedTrigger sql.Node
sqlMode := sql.NewSqlModeFromString(trigger.SqlMode)
b.SetParserOptions(sqlMode.ParserOptions())
parsedTrigger, _, _, err = b.Parse(trigger.CreateStatement, false)
b.Reset()
if err != nil {
return nil, transform.SameTree, err
}
ct, ok := parsedTrigger.(*plan.CreateTrigger)
if !ok {
return nil, transform.SameTree, sql.ErrTriggerCreateStatementInvalid.New(trigger.CreateStatement)
}
var triggerTable string
switch t := ct.Table.(type) {
case *plan.ResolvedTable:
triggerTable = t.Name()
default:
}
if stringContains(affectedTables, triggerTable) && triggerEventsMatch(triggerEvent, ct.TriggerEvent) {
// first pass allows unresolved before we know whether trigger is relevant
// TODO store destination table name with trigger, so we don't have to do parse twice
b.TriggerCtx().Call = true
parsedTrigger, _, _, err = b.Parse(trigger.CreateStatement, false)
b.TriggerCtx().Call = false
b.Reset()
if err != nil {
return nil, transform.SameTree, err
}
ct, ok := parsedTrigger.(*plan.CreateTrigger)
if !ok {
return nil, transform.SameTree, sql.ErrTriggerCreateStatementInvalid.New(trigger.CreateStatement)
}
if block, ok := ct.Body.(*plan.BeginEndBlock); ok {
ct.Body = plan.NewTriggerBeginEndBlock(block)
}
affectedTriggers = append(affectedTriggers, ct)
}
}
}
if len(affectedTriggers) == 0 {
return n, transform.SameTree, nil
}
triggers := orderTriggersAndReverseAfter(affectedTriggers)
originalNode := n
same := transform.SameTree
allSame := transform.SameTree
for _, trigger := range triggers {
err = validateNoCircularUpdates(trigger, originalNode, scope)
if err != nil {
return nil, transform.SameTree, err
}
n, same, err = applyTrigger(ctx, a, originalNode, n, scope, trigger)
if err != nil {
return nil, transform.SameTree, err
}
allSame = same && allSame
}
return n, allSame, nil
}
// applyTrigger applies the trigger given to the node given, returning the resulting node
func applyTrigger(ctx *sql.Context, a *Analyzer, originalNode, n sql.Node, scope *plan.Scope, trigger *plan.CreateTrigger) (sql.Node, transform.TreeIdentity, error) {
triggerLogic, err := getTriggerLogic(ctx, a, originalNode, scope, trigger)
if err != nil {
return nil, transform.SameTree, err
}
return transform.NodeWithCtx(n, nil, func(c transform.Context) (sql.Node, transform.TreeIdentity, error) {
// Don't double-apply trigger executors to the bodies of triggers. To avoid this, don't apply the trigger if the
// parent is a trigger body.
// TODO: this won't work for BEGIN END blocks, stored procedures, etc. For those, we need to examine all ancestors,
// not just the immediate parent. Alternately, we could do something like not walk all children of some node types
// (probably better).
if _, ok := c.Parent.(*plan.TriggerExecutor); ok {
if c.ChildNum == 1 { // Right child is the trigger execution logic
return c.Node, transform.SameTree, nil
}
}
switch n := c.Node.(type) {
case *plan.InsertInto:
if trigger.TriggerTime == sqlparser.BeforeStr {
triggerExecutor := plan.NewTriggerExecutor(n.Source, triggerLogic, plan.InsertTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
})
return n.WithSource(triggerExecutor), transform.NewTree, nil
} else {
return plan.NewTriggerExecutor(n, triggerLogic, plan.InsertTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
}), transform.NewTree, nil
}
case *plan.Update:
if trigger.TriggerTime == sqlparser.BeforeStr {
triggerExecutor := plan.NewTriggerExecutor(n.Child, triggerLogic, plan.UpdateTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
})
node, err := n.WithChildren(triggerExecutor)
return node, transform.NewTree, err
} else {
return plan.NewTriggerExecutor(n, triggerLogic, plan.UpdateTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
}), transform.NewTree, nil
}
case *plan.DeleteFrom:
// TODO: This should work correctly when there is only one table that
// has a trigger on it, but it won't work if a DELETE FROM JOIN
// is deleting from two tables that both have triggers. Seems
// like we need something like a MultipleTriggerExecutor node
// that could execute multiple triggers on the same row from its
// wrapped iterator. There is also an issue with running triggers
// because their field indexes assume the row they evalute will
// only ever contain the columns from the single table the trigger
// is based on, but this isn't true with UPDATE JOIN or DELETE JOIN.
if n.HasExplicitTargets() {
return nil, transform.SameTree, fmt.Errorf("delete from with explicit target tables " +
"does not support triggers; retry with single table deletes")
}
if trigger.TriggerTime == sqlparser.BeforeStr {
triggerExecutor := plan.NewTriggerExecutor(n.Child, triggerLogic, plan.DeleteTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
})
node, err := n.WithChildren(triggerExecutor)
return node, transform.NewTree, err
} else {
return plan.NewTriggerExecutor(n, triggerLogic, plan.DeleteTrigger, plan.TriggerTime(trigger.TriggerTime), sql.TriggerDefinition{
Name: trigger.TriggerName,
CreateStatement: trigger.CreateTriggerString,
}), transform.NewTree, nil
}
}
return c.Node, transform.SameTree, nil
})
}
// getTriggerLogic analyzes and returns the Node representing the trigger body for the trigger given, applied to the
// plan node given, which must be an insert, update, or delete.
func getTriggerLogic(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope, trigger *plan.CreateTrigger) (sql.Node, error) {
// For trigger body analysis, we don't want any row update accumulators applied to insert / update / delete
// statements, we need the raw output from them.
var noRowUpdateAccumulators RuleSelector
noRowUpdateAccumulators = func(id RuleId) bool {
return DefaultRuleSelector(id) && id != applyRowUpdateAccumulatorsId
}
// For the reference to the row in the trigger table, we use the scope mechanism. This is a little strange because
// scopes for subqueries work with the child schemas of a scope node, but we don't have such a node here. Instead we
// fabricate one with the right properties (its child schema matches the table schema, with the right aliased name)
var triggerLogic sql.Node
var err error
switch trigger.TriggerEvent {
case sqlparser.InsertStr:
scopeNode := plan.NewProject(
[]sql.Expression{expression.NewStar()},
plan.NewTableAlias("new", getResolvedTable(n)),
)
s := (*plan.Scope)(nil).NewScope(scopeNode).WithMemos(scope.Memo(n).MemoNodes()).WithProcedureCache(scope.ProcedureCache())
triggerLogic, _, err = a.analyzeWithSelector(ctx, trigger.Body, s, SelectAllBatches, noRowUpdateAccumulators)
case sqlparser.UpdateStr:
scopeNode := plan.NewProject(
[]sql.Expression{expression.NewStar()},
plan.NewCrossJoin(
plan.NewTableAlias("old", getResolvedTable(n)),
plan.NewTableAlias("new", getResolvedTable(n)),
),
)
s := (*plan.Scope)(nil).NewScope(scopeNode).WithMemos(scope.Memo(n).MemoNodes()).WithProcedureCache(scope.ProcedureCache())
triggerLogic, _, err = a.analyzeWithSelector(ctx, trigger.Body, s, SelectAllBatches, noRowUpdateAccumulators)
case sqlparser.DeleteStr:
scopeNode := plan.NewProject(
[]sql.Expression{expression.NewStar()},
plan.NewTableAlias("old", getResolvedTable(n)),
)
s := (*plan.Scope)(nil).NewScope(scopeNode).WithMemos(scope.Memo(n).MemoNodes()).WithProcedureCache(scope.ProcedureCache())
triggerLogic, _, err = a.analyzeWithSelector(ctx, trigger.Body, s, SelectAllBatches, noRowUpdateAccumulators)
}
return StripPassthroughNodes(triggerLogic), err
}
// validateNoCircularUpdates returns an error if the trigger logic attempts to update the table that invoked it (or any
// table being updated in an outer scope of this analysis)
func validateNoCircularUpdates(trigger *plan.CreateTrigger, n sql.Node, scope *plan.Scope) error {
var circularRef error
transform.Inspect(trigger.Body, func(node sql.Node) bool {
switch node := node.(type) {
case *plan.Update, *plan.InsertInto, *plan.DeleteFrom:
for _, n := range append([]sql.Node{n}, scope.MemoNodes()...) {
invokingTableName := getUnaliasedTableName(n)
updatedTable := getUnaliasedTableName(node)
// TODO: need to compare DB as well
if updatedTable == invokingTableName {
circularRef = sql.ErrTriggerTableInUse.New(updatedTable)
return false
}
}
}
return true
})
return circularRef
}
func orderTriggersAndReverseAfter(triggers []*plan.CreateTrigger) []*plan.CreateTrigger {
beforeTriggers, afterTriggers := plan.OrderTriggers(triggers)
// Reverse the order of after triggers. This is because we always apply them to the Insert / Update / Delete node
// that initiated the trigger, so after triggers, which wrap the Insert, need be applied in reverse order for them to
// run in the correct order.
for left, right := 0, len(afterTriggers)-1; left < right; left, right = left+1, right-1 {
afterTriggers[left], afterTriggers[right] = afterTriggers[right], afterTriggers[left]
}
return append(beforeTriggers, afterTriggers...)
}
func triggerEventsMatch(event plan.TriggerEvent, event2 string) bool {
return strings.ToLower((string)(event)) == strings.ToLower(event2)
}
// wrapWritesWithRollback wraps the entire tree iff it contains a trigger, allowing rollback when a trigger errors
func wrapWritesWithRollback(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope, sel RuleSelector) (sql.Node, transform.TreeIdentity, error) {
// Check if tree contains a TriggerExecutor
containsTrigger := false
transform.Inspect(n, func(n sql.Node) bool {
// After Triggers wrap nodes
if _, ok := n.(*plan.TriggerExecutor); ok {
containsTrigger = true
return false // done, don't bother to recurse
}
// Before Triggers on Inserts are inside Source
if n, ok := n.(*plan.InsertInto); ok {
if _, ok := n.Source.(*plan.TriggerExecutor); ok {
containsTrigger = true
return false
}
}
// Before Triggers on Delete and Update should be in children
return true
})
// No TriggerExecutor, so return same tree
if !containsTrigger {
return n, transform.SameTree, nil
}
// If we don't have a transaction session we can't do rollbacks
_, ok := ctx.Session.(sql.TransactionSession)
if !ok {
return plan.NewNoopTriggerRollback(n), transform.NewTree, nil
}
// Wrap tree with new node
return plan.NewTriggerRollback(n), transform.NewTree, nil
}