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drop_table.go
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drop_table.go
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// Copyright 2015 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.
package sql
import (
"context"
"fmt"
"strings"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/security"
"github.com/cockroachdb/cockroach/pkg/server/telemetry"
"github.com/cockroachdb/cockroach/pkg/sql/privilege"
"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/cockroachdb/cockroach/pkg/sql/sqltelemetry"
"github.com/cockroachdb/cockroach/pkg/util/errorutil/unimplemented"
"github.com/cockroachdb/cockroach/pkg/util/hlc"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
"github.com/cockroachdb/errors"
)
type dropTableNode struct {
n *tree.DropTable
// td is a map from table descriptor to toDelete struct, indicating which
// tables this operation should delete.
td map[sqlbase.ID]toDelete
}
type toDelete struct {
tn *tree.TableName
desc *sqlbase.MutableTableDescriptor
}
// DropTable drops a table.
// Privileges: DROP on table.
// Notes: postgres allows only the table owner to DROP a table.
// mysql requires the DROP privilege on the table.
func (p *planner) DropTable(ctx context.Context, n *tree.DropTable) (planNode, error) {
td := make(map[sqlbase.ID]toDelete, len(n.Names))
for i := range n.Names {
tn := &n.Names[i]
droppedDesc, err := p.prepareDrop(ctx, tn, !n.IfExists, tree.ResolveRequireTableDesc)
if err != nil {
return nil, err
}
if droppedDesc == nil {
continue
}
td[droppedDesc.ID] = toDelete{tn, droppedDesc}
}
for _, toDel := range td {
droppedDesc := toDel.desc
for i := range droppedDesc.InboundFKs {
ref := &droppedDesc.InboundFKs[i]
if _, ok := td[ref.OriginTableID]; !ok {
if err := p.canRemoveFKBackreference(ctx, droppedDesc.Name, ref, n.DropBehavior); err != nil {
return nil, err
}
}
}
for _, idx := range droppedDesc.AllNonDropIndexes() {
for _, ref := range idx.InterleavedBy {
if _, ok := td[ref.Table]; !ok {
if err := p.canRemoveInterleave(ctx, droppedDesc.Name, ref, n.DropBehavior); err != nil {
return nil, err
}
}
}
}
for _, ref := range droppedDesc.DependedOnBy {
if _, ok := td[ref.ID]; !ok {
if err := p.canRemoveDependentView(ctx, droppedDesc, ref, n.DropBehavior); err != nil {
return nil, err
}
}
}
if err := p.canRemoveAllTableOwnedSequences(ctx, droppedDesc, n.DropBehavior); err != nil {
return nil, err
}
}
if len(td) == 0 {
return newZeroNode(nil /* columns */), nil
}
return &dropTableNode{n: n, td: td}, nil
}
// ReadingOwnWrites implements the planNodeReadingOwnWrites interface.
// This is because DROP TABLE performs multiple KV operations on descriptors
// and expects to see its own writes.
func (n *dropTableNode) ReadingOwnWrites() {}
func (n *dropTableNode) startExec(params runParams) error {
telemetry.Inc(sqltelemetry.SchemaChangeDropCounter("table"))
ctx := params.ctx
for _, toDel := range n.td {
droppedDesc := toDel.desc
if droppedDesc == nil {
continue
}
droppedViews, err := params.p.dropTableImpl(ctx, droppedDesc, true /* queueJob */, tree.AsStringWithFQNames(n.n, params.Ann()))
if err != nil {
return err
}
// Log a Drop Table event for this table. This is an auditable log event
// and is recorded in the same transaction as the table descriptor
// update.
if err := MakeEventLogger(params.extendedEvalCtx.ExecCfg).InsertEventRecord(
ctx,
params.p.txn,
EventLogDropTable,
int32(droppedDesc.ID),
int32(params.extendedEvalCtx.NodeID.SQLInstanceID()),
struct {
TableName string
Statement string
User string
CascadeDroppedViews []string
}{toDel.tn.FQString(), n.n.String(),
params.SessionData().User, droppedViews},
); err != nil {
return err
}
}
return nil
}
func (*dropTableNode) Next(runParams) (bool, error) { return false, nil }
func (*dropTableNode) Values() tree.Datums { return tree.Datums{} }
func (*dropTableNode) Close(context.Context) {}
// prepareDrop/dropTableImpl is used to drop a single table by
// name, which can result from a DROP TABLE, DROP VIEW, DROP SEQUENCE,
// or DROP DATABASE statement. This method returns the dropped table
// descriptor, to be used for the purpose of logging the event. The table
// is not actually truncated or deleted synchronously. Instead, it is marked
// as deleted (meaning up_version is set and deleted is set) and the
// actual deletion happens async in a schema changer. Note that,
// courtesy of up_version, the actual truncation and dropping will
// only happen once every node ACKs the version of the descriptor with
// the deleted bit set, meaning the lease manager will not hand out
// new leases for it and existing leases are released).
// If the table does not exist, this function returns a nil descriptor.
func (p *planner) prepareDrop(
ctx context.Context, name *tree.TableName, required bool, requiredType tree.RequiredTableKind,
) (*sqlbase.MutableTableDescriptor, error) {
tableDesc, err := p.ResolveMutableTableDescriptor(ctx, name, required, requiredType)
if err != nil {
return nil, err
}
if tableDesc == nil {
return nil, err
}
if err := p.prepareDropWithTableDesc(ctx, tableDesc); err != nil {
return nil, err
}
return tableDesc, nil
}
// prepareDropWithTableDesc behaves as prepareDrop, except it assumes the
// table descriptor is already fetched. This is useful for DropDatabase,
// as prepareDrop requires resolving a TableName when DropDatabase already
// has it resolved.
func (p *planner) prepareDropWithTableDesc(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor,
) error {
return p.CheckPrivilege(ctx, tableDesc, privilege.DROP)
}
// canRemoveFKBackReference returns an error if the input backreference isn't
// allowed to be removed.
func (p *planner) canRemoveFKBackreference(
ctx context.Context, from string, ref *sqlbase.ForeignKeyConstraint, behavior tree.DropBehavior,
) error {
table, err := p.Descriptors().GetMutableTableVersionByID(ctx, ref.OriginTableID, p.txn)
if err != nil {
return err
}
if behavior != tree.DropCascade {
return fmt.Errorf("%q is referenced by foreign key from table %q", from, table.Name)
}
// Check to see whether we're allowed to edit the table that has a
// foreign key constraint on the table that we're dropping right now.
return p.CheckPrivilege(ctx, table, privilege.CREATE)
}
func (p *planner) canRemoveInterleave(
ctx context.Context, from string, ref sqlbase.ForeignKeyReference, behavior tree.DropBehavior,
) error {
table, err := p.Descriptors().GetMutableTableVersionByID(ctx, ref.Table, p.txn)
if err != nil {
return err
}
// TODO(dan): It's possible to DROP a table that has a child interleave, but
// some loose ends would have to be addressed. The zone would have to be
// kept and deleted when the last table in it is removed. Also, the dropped
// table's descriptor would have to be kept around in some Dropped but
// non-public state for referential integrity of the `InterleaveDescriptor`
// pointers.
if behavior != tree.DropCascade {
return unimplemented.NewWithIssuef(
8036, "%q is interleaved by table %q", from, table.Name)
}
return p.CheckPrivilege(ctx, table, privilege.CREATE)
}
func (p *planner) removeInterleave(ctx context.Context, ref sqlbase.ForeignKeyReference) error {
table, err := p.Descriptors().GetMutableTableVersionByID(ctx, ref.Table, p.txn)
if err != nil {
return err
}
if table.Dropped() {
// The referenced table is being dropped. No need to modify it further.
return nil
}
idx, err := table.FindIndexByID(ref.Index)
if err != nil {
return err
}
idx.Interleave.Ancestors = nil
// No job description, since this is presumably part of some larger schema change.
return p.writeSchemaChange(ctx, table, sqlbase.InvalidMutationID, "")
}
// dropTableImpl does the work of dropping a table (and everything that depends
// on it if `cascade` is enabled). It returns a list of view names that were
// dropped due to `cascade` behavior.
func (p *planner) dropTableImpl(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor, queueJob bool, jobDesc string,
) ([]string, error) {
var droppedViews []string
// Remove foreign key back references from tables that this table has foreign
// keys to.
for i := range tableDesc.OutboundFKs {
ref := &tableDesc.OutboundFKs[i]
if err := p.removeFKBackReference(ctx, tableDesc, ref); err != nil {
return droppedViews, err
}
}
tableDesc.OutboundFKs = nil
// Remove foreign key forward references from tables that have foreign keys
// to this table.
for i := range tableDesc.InboundFKs {
ref := &tableDesc.InboundFKs[i]
if err := p.removeFKForBackReference(ctx, tableDesc, ref); err != nil {
return droppedViews, err
}
}
tableDesc.InboundFKs = nil
// Remove interleave relationships.
for _, idx := range tableDesc.AllNonDropIndexes() {
if len(idx.Interleave.Ancestors) > 0 {
if err := p.removeInterleaveBackReference(ctx, tableDesc, idx); err != nil {
return droppedViews, err
}
}
for _, ref := range idx.InterleavedBy {
if err := p.removeInterleave(ctx, ref); err != nil {
return droppedViews, err
}
}
}
// Remove sequence dependencies.
for i := range tableDesc.Columns {
if err := p.removeSequenceDependencies(ctx, tableDesc, &tableDesc.Columns[i]); err != nil {
return droppedViews, err
}
}
// Drop sequences that the columns of the table own
for _, col := range tableDesc.Columns {
if err := p.dropSequencesOwnedByCol(ctx, &col, queueJob); err != nil {
return droppedViews, err
}
}
// Drop all views that depend on this table, assuming that we wouldn't have
// made it to this point if `cascade` wasn't enabled.
for _, ref := range tableDesc.DependedOnBy {
viewDesc, err := p.getViewDescForCascade(
ctx, tableDesc.TypeName(), tableDesc.Name, tableDesc.ParentID, ref.ID, tree.DropCascade,
)
if err != nil {
return droppedViews, err
}
// This view is already getting dropped. Don't do it twice.
if viewDesc.Dropped() {
continue
}
cascadedViews, err := p.dropViewImpl(ctx, viewDesc, queueJob, "dropping dependent view", tree.DropCascade)
if err != nil {
return droppedViews, err
}
droppedViews = append(droppedViews, cascadedViews...)
droppedViews = append(droppedViews, viewDesc.Name)
}
err := p.removeTableComments(ctx, tableDesc)
if err != nil {
return droppedViews, err
}
err = p.initiateDropTable(ctx, tableDesc, queueJob, jobDesc, true /* drain name */)
return droppedViews, err
}
// drainName when set implies that the name needs to go through the draining
// names process. This parameter is always passed in as true except from
// TRUNCATE which directly deletes the old name to id map and doesn't need
// drain the old map.
func (p *planner) initiateDropTable(
ctx context.Context,
tableDesc *sqlbase.MutableTableDescriptor,
queueJob bool,
jobDesc string,
drainName bool,
) error {
if tableDesc.Dropped() {
return errors.Errorf("table %q is already being dropped", tableDesc.Name)
}
// If the table is not interleaved , use the delayed GC mechanism to
// schedule usage of the more efficient ClearRange pathway. ClearRange will
// only work if the entire hierarchy of interleaved tables are dropped at
// once, as with ON DELETE CASCADE where the top-level "root" table is
// dropped.
//
// TODO(bram): If interleaved and ON DELETE CASCADE, we will be able to use
// this faster mechanism.
if tableDesc.IsTable() && !tableDesc.IsInterleaved() {
tableDesc.DropTime = timeutil.Now().UnixNano()
}
// Unsplit all manually split ranges in the table so they can be
// automatically merged by the merge queue.
ranges, err := ScanMetaKVs(ctx, p.txn, tableDesc.TableSpan(p.ExecCfg().Codec))
if err != nil {
return err
}
for _, r := range ranges {
var desc roachpb.RangeDescriptor
if err := r.ValueProto(&desc); err != nil {
return err
}
if (desc.GetStickyBit() != hlc.Timestamp{}) {
// Swallow "key is not the start of a range" errors because it would mean
// that the sticky bit was removed and merged concurrently. DROP TABLE
// should not fail because of this.
if err := p.ExecCfg().DB.AdminUnsplit(ctx, desc.StartKey); err != nil && !strings.Contains(err.Error(), "is not the start of a range") {
return err
}
}
}
tableDesc.State = sqlbase.TableDescriptor_DROP
if drainName {
parentSchemaID := tableDesc.GetParentSchemaID()
// Queue up name for draining.
nameDetails := sqlbase.NameInfo{
ParentID: tableDesc.ParentID,
ParentSchemaID: parentSchemaID,
Name: tableDesc.Name}
tableDesc.DrainingNames = append(tableDesc.DrainingNames, nameDetails)
}
// Mark all jobs scheduled for schema changes as successful.
jobIDs := make(map[int64]struct{})
var id sqlbase.MutationID
for _, m := range tableDesc.Mutations {
if id != m.MutationID {
id = m.MutationID
jobID, err := getJobIDForMutationWithDescriptor(ctx, tableDesc.TableDesc(), id)
if err != nil {
return err
}
jobIDs[jobID] = struct{}{}
}
}
for jobID := range jobIDs {
if err := p.ExecCfg().JobRegistry.Succeeded(ctx, p.txn, jobID); err != nil {
return errors.Wrapf(err,
"failed to mark job %d as as successful", errors.Safe(jobID))
}
}
// Initiate an immediate schema change. When dropping a table
// in a session, the data and the descriptor are not deleted.
// Instead, that is taken care of asynchronously by the schema
// change manager, which is notified via a system config gossip.
// The schema change manager will properly schedule deletion of
// the underlying data when the GC deadline expires.
return p.writeDropTable(ctx, tableDesc, queueJob, jobDesc)
}
func (p *planner) removeFKForBackReference(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor, ref *sqlbase.ForeignKeyConstraint,
) error {
var originTableDesc *sqlbase.MutableTableDescriptor
// We don't want to lookup/edit a second copy of the same table.
if tableDesc.ID == ref.OriginTableID {
originTableDesc = tableDesc
} else {
lookup, err := p.Descriptors().GetMutableTableVersionByID(ctx, ref.OriginTableID, p.txn)
if err != nil {
return errors.Errorf("error resolving origin table ID %d: %v", ref.OriginTableID, err)
}
originTableDesc = lookup
}
if originTableDesc.Dropped() {
// The origin table is being dropped. No need to modify it further.
return nil
}
if err := removeFKForBackReferenceFromTable(originTableDesc, ref, tableDesc.TableDesc()); err != nil {
return err
}
// No job description, since this is presumably part of some larger schema change.
return p.writeSchemaChange(ctx, originTableDesc, sqlbase.InvalidMutationID, "")
}
// removeFKBackReferenceFromTable edits the supplied originTableDesc to
// remove the foreign key constraint that corresponds to the supplied
// backreference, which is a member of the supplied referencedTableDesc.
func removeFKForBackReferenceFromTable(
originTableDesc *sqlbase.MutableTableDescriptor,
backref *sqlbase.ForeignKeyConstraint,
referencedTableDesc *sqlbase.TableDescriptor,
) error {
matchIdx := -1
for i, fk := range originTableDesc.OutboundFKs {
if fk.ReferencedTableID == referencedTableDesc.ID && fk.Name == backref.Name {
// We found a match! We want to delete it from the list now.
matchIdx = i
break
}
}
if matchIdx == -1 {
// There was no match: no back reference in the referenced table that
// matched the foreign key constraint that we were trying to delete.
// This really shouldn't happen...
return errors.AssertionFailedf("there was no foreign key constraint "+
"for backreference %v on table %q", backref, originTableDesc.Name)
}
// Delete our match.
originTableDesc.OutboundFKs = append(
originTableDesc.OutboundFKs[:matchIdx],
originTableDesc.OutboundFKs[matchIdx+1:]...)
return nil
}
// removeFKBackReference removes the FK back reference from the table that is
// referenced by the input constraint.
func (p *planner) removeFKBackReference(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor, ref *sqlbase.ForeignKeyConstraint,
) error {
var referencedTableDesc *sqlbase.MutableTableDescriptor
// We don't want to lookup/edit a second copy of the same table.
if tableDesc.ID == ref.ReferencedTableID {
referencedTableDesc = tableDesc
} else {
lookup, err := p.Descriptors().GetMutableTableVersionByID(ctx, ref.ReferencedTableID, p.txn)
if err != nil {
return errors.Errorf("error resolving referenced table ID %d: %v", ref.ReferencedTableID, err)
}
referencedTableDesc = lookup
}
if referencedTableDesc.Dropped() {
// The referenced table is being dropped. No need to modify it further.
return nil
}
if err := removeFKBackReferenceFromTable(referencedTableDesc, ref.Name, tableDesc.TableDesc()); err != nil {
return err
}
// No job description, since this is presumably part of some larger schema change.
return p.writeSchemaChange(ctx, referencedTableDesc, sqlbase.InvalidMutationID, "")
}
// removeFKBackReferenceFromTable edits the supplied referencedTableDesc to
// remove the foreign key backreference that corresponds to the supplied fk,
// which is a member of the supplied originTableDesc.
func removeFKBackReferenceFromTable(
referencedTableDesc *sqlbase.MutableTableDescriptor,
fkName string,
originTableDesc *sqlbase.TableDescriptor,
) error {
matchIdx := -1
for i, backref := range referencedTableDesc.InboundFKs {
if backref.OriginTableID == originTableDesc.ID && backref.Name == fkName {
// We found a match! We want to delete it from the list now.
matchIdx = i
break
}
}
if matchIdx == -1 {
// There was no match: no back reference in the referenced table that
// matched the foreign key constraint that we were trying to delete.
// This really shouldn't happen...
return errors.AssertionFailedf("there was no foreign key backreference "+
"for constraint %q on table %q", fkName, originTableDesc.Name)
}
// Delete our match.
referencedTableDesc.InboundFKs = append(referencedTableDesc.InboundFKs[:matchIdx], referencedTableDesc.InboundFKs[matchIdx+1:]...)
return nil
}
func (p *planner) removeInterleaveBackReference(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor, idx *sqlbase.IndexDescriptor,
) error {
if len(idx.Interleave.Ancestors) == 0 {
return nil
}
ancestor := idx.Interleave.Ancestors[len(idx.Interleave.Ancestors)-1]
var t *sqlbase.MutableTableDescriptor
if ancestor.TableID == tableDesc.ID {
t = tableDesc
} else {
lookup, err := p.Descriptors().GetMutableTableVersionByID(ctx, ancestor.TableID, p.txn)
if err != nil {
return errors.Errorf("error resolving referenced table ID %d: %v", ancestor.TableID, err)
}
t = lookup
}
if t.Dropped() {
// The referenced table is being dropped. No need to modify it further.
return nil
}
targetIdx, err := t.FindIndexByID(ancestor.IndexID)
if err != nil {
return err
}
foundAncestor := false
for k, ref := range targetIdx.InterleavedBy {
if ref.Table == tableDesc.ID && ref.Index == idx.ID {
if foundAncestor {
return errors.AssertionFailedf(
"ancestor entry in %s for %s@%s found more than once", t.Name, tableDesc.Name, idx.Name)
}
targetIdx.InterleavedBy = append(targetIdx.InterleavedBy[:k], targetIdx.InterleavedBy[k+1:]...)
foundAncestor = true
}
}
if t != tableDesc {
return p.writeSchemaChange(
ctx, t, sqlbase.InvalidMutationID,
fmt.Sprintf("removing reference for interleaved table %s(%d)",
t.Name, t.ID,
),
)
}
return nil
}
// removeMatchingReferences removes all refs from the provided slice that
// match the provided ID, returning the modified slice.
func removeMatchingReferences(
refs []sqlbase.TableDescriptor_Reference, id sqlbase.ID,
) []sqlbase.TableDescriptor_Reference {
updatedRefs := refs[:0]
for _, ref := range refs {
if ref.ID != id {
updatedRefs = append(updatedRefs, ref)
}
}
return updatedRefs
}
func (p *planner) removeTableComments(
ctx context.Context, tableDesc *sqlbase.MutableTableDescriptor,
) error {
_, err := p.ExtendedEvalContext().ExecCfg.InternalExecutor.ExecEx(
ctx,
"delete-table-comments",
p.txn,
sqlbase.InternalExecutorSessionDataOverride{User: security.RootUser},
"DELETE FROM system.comments WHERE object_id=$1",
tableDesc.ID)
if err != nil {
return err
}
return err
}