/
ddl.go
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/
ddl.go
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// Copyright 2017 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package statistics
import (
"fmt"
log "github.com/Sirupsen/logrus"
"github.com/juju/errors"
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/ddl"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/terror"
"github.com/pingcap/tidb/util/sqlexec"
"github.com/pingcap/tidb/util/types"
)
// HandleDDLEvent begins to process a ddl task.
func (h *Handle) HandleDDLEvent(t *ddl.Event) error {
switch t.Tp {
case model.ActionCreateTable:
return h.insertTableStats2KV(t.TableInfo)
case model.ActionDropTable:
return h.DeleteTableStatsFromKV(t.TableInfo.ID)
case model.ActionAddColumn:
return h.insertColStats2KV(t.TableInfo.ID, t.ColumnInfo)
case model.ActionDropColumn:
return h.deleteHistStatsFromKV(t.TableInfo.ID, t.ColumnInfo.ID, 0)
case model.ActionDropIndex:
return h.deleteHistStatsFromKV(t.TableInfo.ID, t.IndexInfo.ID, 1)
default:
log.Warnf("Unsupported ddl event for statistic %s", t)
}
return nil
}
// DDLEventCh returns ddl events channel in handle.
func (h *Handle) DDLEventCh() chan *ddl.Event {
return h.ddlEventCh
}
// insertTableStats2KV inserts a record standing for a new table to stats_meta and inserts some records standing for the
// new columns and indices which belong to this table.
func (h *Handle) insertTableStats2KV(info *model.TableInfo) error {
exec := h.ctx.(sqlexec.SQLExecutor)
_, err := exec.Execute("begin")
if err != nil {
return errors.Trace(err)
}
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_meta (version, table_id) values(%d, %d)", h.ctx.Txn().StartTS(), info.ID))
if err != nil {
return errors.Trace(err)
}
for _, col := range info.Columns {
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (table_id, is_index, hist_id, distinct_count, version) values(%d, 0, %d, 0, %d)", info.ID, col.ID, h.ctx.Txn().StartTS()))
if err != nil {
return errors.Trace(err)
}
}
for _, idx := range info.Indices {
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (table_id, is_index, hist_id, distinct_count, version) values(%d, 1, %d, 0, %d)", info.ID, idx.ID, h.ctx.Txn().StartTS()))
if err != nil {
return errors.Trace(err)
}
}
_, err = exec.Execute("commit")
return errors.Trace(err)
}
// DeleteTableStatsFromKV deletes table statistics from kv.
func (h *Handle) DeleteTableStatsFromKV(id int64) error {
exec := h.ctx.(sqlexec.SQLExecutor)
_, err := exec.Execute("begin")
if err != nil {
return errors.Trace(err)
}
// First of all, we update the version.
_, err = exec.Execute(fmt.Sprintf("update mysql.stats_meta set version = %d where table_id = %d ", h.ctx.Txn().StartTS(), id))
if err != nil {
return errors.Trace(err)
}
_, err = exec.Execute(fmt.Sprintf("delete from mysql.stats_histograms where table_id = %d", id))
if err != nil {
return errors.Trace(err)
}
_, err = exec.Execute(fmt.Sprintf("delete from mysql.stats_buckets where table_id = %d", id))
if err != nil {
return errors.Trace(err)
}
_, err = exec.Execute("commit")
return errors.Trace(err)
}
// insertColStats2KV insert a record to stats_histograms with distinct_count 1 and insert a bucket to stats_buckets with default value.
// This operation also updates version.
func (h *Handle) insertColStats2KV(tableID int64, colInfo *model.ColumnInfo) error {
exec := h.ctx.(sqlexec.SQLExecutor)
_, err := exec.Execute("begin")
if err != nil {
return errors.Trace(err)
}
// First of all, we update the version.
_, err = exec.Execute(fmt.Sprintf("update mysql.stats_meta set version = %d where table_id = %d ", h.ctx.Txn().StartTS(), tableID))
if err != nil {
return errors.Trace(err)
}
// If we didn't update anything by last SQL, it means the stats of this table does not exist.
if h.ctx.GetSessionVars().StmtCtx.AffectedRows() > 0 {
exec := h.ctx.(sqlexec.SQLExecutor)
// By this step we can get the count of this table, then we can sure the count and repeats of bucket.
var rs []ast.RecordSet
rs, err = exec.Execute(fmt.Sprintf("select count from mysql.stats_meta where table_id = %d", tableID))
if len(rs) > 0 {
defer terror.Call(rs[0].Close)
}
if err != nil {
return errors.Trace(err)
}
var row *ast.Row
row, err = rs[0].Next()
if err != nil {
return errors.Trace(err)
}
count := row.Data[0].GetInt64()
value := types.NewDatum(colInfo.OriginDefaultValue)
value, err = value.ConvertTo(h.ctx.GetSessionVars().StmtCtx, &colInfo.FieldType)
if err != nil {
return errors.Trace(err)
}
if value.IsNull() {
// If the adding column has default value null, all the existing rows have null value on the newly added column.
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (version, table_id, is_index, hist_id, distinct_count, null_count) values (%d, %d, 0, %d, 1, %d)", h.ctx.Txn().StartTS(), tableID, colInfo.ID, count))
if err != nil {
return errors.Trace(err)
}
} else {
// If this stats exists, we insert histogram meta first, the distinct_count will always be one.
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (version, table_id, is_index, hist_id, distinct_count) values (%d, %d, 0, %d, 1)", h.ctx.Txn().StartTS(), tableID, colInfo.ID))
if err != nil {
return errors.Trace(err)
}
value, err = value.ConvertTo(h.ctx.GetSessionVars().StmtCtx, types.NewFieldType(mysql.TypeBlob))
if err != nil {
return errors.Trace(err)
}
// There must be only one bucket for this new column and the value is the default value.
_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_buckets (table_id, is_index, hist_id, bucket_id, repeats, count, lower_bound, upper_bound) values (%d, 0, %d, 0, %d, %d, X'%X', X'%X')", tableID, colInfo.ID, count, count, value.GetBytes(), value.GetBytes()))
if err != nil {
return errors.Trace(err)
}
}
}
_, err = exec.Execute("commit")
return errors.Trace(err)
}
// deleteHistStatsFromKV deletes all records about a column or an index and updates version.
func (h *Handle) deleteHistStatsFromKV(tableID int64, histID int64, isIndex int) error {
exec := h.ctx.(sqlexec.SQLExecutor)
_, err := exec.Execute("begin")
if err != nil {
return errors.Trace(err)
}
// First of all, we update the version. If this table doesn't exist, it won't have any problem. Because we cannot delete anything.
_, err = exec.Execute(fmt.Sprintf("update mysql.stats_meta set version = %d where table_id = %d ", h.ctx.Txn().StartTS(), tableID))
if err != nil {
return errors.Trace(err)
}
// delete histogram meta
_, err = exec.Execute(fmt.Sprintf("delete from mysql.stats_histograms where table_id = %d and hist_id = %d and is_index = %d", tableID, histID, isIndex))
if err != nil {
return errors.Trace(err)
}
// delete all buckets
_, err = exec.Execute(fmt.Sprintf("delete from mysql.stats_buckets where table_id = %d and hist_id = %d and is_index = %d", tableID, histID, isIndex))
if err != nil {
return errors.Trace(err)
}
_, err = exec.Execute("commit")
return errors.Trace(err)
}