forked from cockroachdb/cockroach
/
table.go
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/
table.go
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// Copyright 2015 The Cockroach 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.
//
// Author: Peter Mattis (peter@cockroachlabs.com)
package sql
import (
"bytes"
"fmt"
"time"
"github.com/cockroachdb/cockroach/client"
"github.com/cockroachdb/cockroach/roachpb"
"github.com/cockroachdb/cockroach/sql/parser"
"github.com/cockroachdb/cockroach/sql/sqlbase"
"github.com/cockroachdb/cockroach/util/encoding"
)
var testDisableTableLeases bool
// TestDisableTableLeases disables table leases and returns
// a function that can be used to enable it.
func TestDisableTableLeases() func() {
testDisableTableLeases = true
return func() {
testDisableTableLeases = false
}
}
func tableDoesNotExistError(name string) error {
return fmt.Errorf("table %q does not exist", name)
}
// tableKey implements sqlbase.DescriptorKey.
type tableKey struct {
parentID sqlbase.ID
name string
}
func (tk tableKey) Key() roachpb.Key {
return sqlbase.MakeNameMetadataKey(tk.parentID, tk.name)
}
func (tk tableKey) Name() string {
return tk.name
}
// getTableDesc returns a table descriptor, or nil if the descriptor is not
// found.
// If you want to transform the not found condition into an error, use
// tableDoesNotExistError().
func (p *planner) getTableDesc(qname *parser.QualifiedName) (*sqlbase.TableDescriptor, error) {
if err := qname.NormalizeTableName(p.session.Database); err != nil {
return nil, err
}
dbDesc, err := p.getDatabaseDesc(qname.Database())
if err != nil {
return nil, err
}
if dbDesc == nil {
return nil, databaseDoesNotExistError(qname.Database())
}
desc := sqlbase.TableDescriptor{}
found, err := p.getDescriptor(tableKey{parentID: dbDesc.ID, name: qname.Table()}, &desc)
if err != nil {
return nil, err
}
if !found {
return nil, nil
}
return &desc, nil
}
// get the table descriptor for the ID passed in using an existing txn.
// returns an error if the descriptor doesn't exist or if it exists and is not
// a table.
func getTableDescFromID(txn *client.Txn, id sqlbase.ID) (*sqlbase.TableDescriptor, error) {
desc := &sqlbase.Descriptor{}
descKey := sqlbase.MakeDescMetadataKey(id)
if err := txn.GetProto(descKey, desc); err != nil {
return nil, err
}
table := desc.GetTable()
if table == nil {
return nil, &roachpb.DescriptorNotFoundError{DescriptorId: uint32(id)}
}
return table, nil
}
func getKeysForTableDescriptor(
tableDesc *sqlbase.TableDescriptor,
) (zoneKey roachpb.Key, nameKey roachpb.Key, descKey roachpb.Key) {
zoneKey = sqlbase.MakeZoneKey(tableDesc.ID)
nameKey = sqlbase.MakeNameMetadataKey(tableDesc.ParentID, tableDesc.GetName())
descKey = sqlbase.MakeDescMetadataKey(tableDesc.ID)
return
}
func updateCommitBy(commitBy time.Time, lease *LeaseState) time.Time {
if commitBy.IsZero() || commitBy.After(lease.Expiration()) {
return lease.Expiration()
}
return commitBy
}
// getTableLease acquires a lease for the specified table. The lease will be
// released when the planner closes. Note that a shallow copy of the table
// descriptor is returned. It is safe to mutate fields of the returned
// descriptor, but the values those fields point to should not be modified.
func (p *planner) getTableLease(qname *parser.QualifiedName) (sqlbase.TableDescriptor, error) {
if err := qname.NormalizeTableName(p.session.Database); err != nil {
return sqlbase.TableDescriptor{}, err
}
if qname.Database() == sqlbase.SystemDB.Name || testDisableTableLeases {
// We don't go through the normal lease mechanism for system tables. The
// system.lease and system.descriptor table, in particular, are problematic
// because they are used for acquiring leases itself, creating a
// chicken&egg problem.
desc, err := p.getTableDesc(qname)
if err != nil {
return sqlbase.TableDescriptor{}, err
}
if desc == nil {
return sqlbase.TableDescriptor{}, tableDoesNotExistError(qname.String())
}
return *desc, nil
}
tableID, err := p.getTableID(qname)
if err != nil {
return sqlbase.TableDescriptor{}, err
}
var lease *LeaseState
var commitBy time.Time
for _, l := range p.leases {
commitBy = updateCommitBy(commitBy, l)
if l.TableDescriptor.ID == tableID {
lease = l
}
}
if lease == nil {
var err error
lease, err = p.leaseMgr.Acquire(p.txn, tableID, 0)
if err != nil {
if _, ok := err.(*roachpb.DescriptorNotFoundError); ok {
// Transform the descriptor error into an error that references the
// table's name.
return sqlbase.TableDescriptor{}, tableDoesNotExistError(qname.String())
}
return sqlbase.TableDescriptor{}, err
}
p.leases = append(p.leases, lease)
commitBy = updateCommitBy(commitBy, lease)
}
p.txn.SetDeadline(roachpb.Timestamp{WallTime: commitBy.UnixNano()})
return lease.TableDescriptor, nil
}
// getTableID retrieves the table ID for the specified table. It uses the
// descriptor cache to perform lookups, falling back to the KV store when
// necessary.
func (p *planner) getTableID(qname *parser.QualifiedName) (sqlbase.ID, error) {
if err := qname.NormalizeTableName(p.session.Database); err != nil {
return 0, err
}
dbID, err := p.getDatabaseID(qname.Database())
if err != nil {
return 0, err
}
// Lookup the ID of the table in the cache. The use of the cache might cause
// the usage of a recently renamed table, but that's a race that could occur
// anyways.
// TODO(andrei): remove the used of p.systemConfig as a cache for table names,
// replace it with using the leases for resolving names, and do away with any
// races due to renames. We'll probably have to rewrite renames to perform
// an async schema change.
nameKey := tableKey{dbID, qname.Table()}
key := nameKey.Key()
if nameVal := p.systemConfig.GetValue(key); nameVal != nil {
id, err := nameVal.GetInt()
return sqlbase.ID(id), err
}
gr, err := p.txn.Get(key)
if err != nil {
return 0, err
}
if !gr.Exists() {
return 0, tableDoesNotExistError(qname.String())
}
return sqlbase.ID(gr.ValueInt()), nil
}
func (p *planner) getTableNames(dbDesc *sqlbase.DatabaseDescriptor) (parser.QualifiedNames, error) {
prefix := sqlbase.MakeNameMetadataKey(dbDesc.ID, "")
sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
if err != nil {
return nil, err
}
var qualifiedNames parser.QualifiedNames
for _, row := range sr {
_, tableName, err := encoding.DecodeUnsafeStringAscending(
bytes.TrimPrefix(row.Key, prefix), nil)
if err != nil {
return nil, err
}
qname := &parser.QualifiedName{
Base: parser.Name(dbDesc.Name),
Indirect: parser.Indirection{parser.NameIndirection(tableName)},
}
if err := qname.NormalizeTableName(""); err != nil {
return nil, err
}
qualifiedNames = append(qualifiedNames, qname)
}
return qualifiedNames, nil
}