database/tidb
2
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

statistics: add comments and remove unnessary check (#53568)

Browse Source 
ref pingcap/tidb#53567
This commit is contained in:
二手掉包工程师
2024-05-27 19:20:50 +08:00
committed by GitHub
parent 153eb961d7
commit 2300ac6fe6
2 changed files with 26 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
pkg/planner/core/planbuilder.go
View File

@ -1949,6 +1949,7 @@ func (b *PlanBuilder) getMustAnalyzedColumns(tbl *ast.TableName, cols *calcOnceM
}
func (b *PlanBuilder) getPredicateColumns(tbl *ast.TableName, cols *calcOnceMap) (map[int64]struct{}, error) {
// Already calculated in the previous call.
if cols.calculated {
return cols.data, nil
}

32
pkg/statistics/handle/usage/predicate_column.go
View File

@ -101,8 +101,8 @@ func LoadColumnStatsUsage(sctx sessionctx.Context, loc *time.Location) (map[mode
if err != nil {
return nil, errors.Trace(err)
}
// If `last_used_at` is before the time when `set global enable_column_tracking = 0`, we should ignore it because
// `set global enable_column_tracking = 0` indicates all the predicate columns collected before.
// If `last_used_at` is before the time when `set global tidb_enable_column_tracking = 0`, we should ignore it because
// `set global tidb_enable_column_tracking = 0` indicates all the predicate columns collected before.
if disableTime == nil || gt.After(*disableTime) {
t := types.NewTime(types.FromGoTime(gt.In(loc)), mysql.TypeTimestamp, types.DefaultFsp)
statsUsage.LastUsedAt = &t
@ -123,17 +123,24 @@ func LoadColumnStatsUsage(sctx sessionctx.Context, loc *time.Location) (map[mode
// GetPredicateColumns returns IDs of predicate columns, which are the columns whose stats are used(needed) when generating query plans.
func GetPredicateColumns(sctx sessionctx.Context, tableID int64) ([]int64, error) {
// This time is the time when `set global tidb_enable_column_tracking = 0`.
disableTime, err := getDisableColumnTrackingTime(sctx)
if err != nil {
return nil, errors.Trace(err)
}
rows, _, err := utilstats.ExecRows(sctx, "SELECT column_id, CONVERT_TZ(last_used_at, @@TIME_ZONE, '+00:00') FROM mysql.column_stats_usage WHERE table_id = %? AND last_used_at IS NOT NULL", tableID)
rows, _, err := utilstats.ExecRows(
sctx,
"SELECT column_id, CONVERT_TZ(last_used_at, @@TIME_ZONE, '+00:00') FROM mysql.column_stats_usage WHERE table_id = %? AND last_used_at IS NOT NULL",
tableID,
)
if err != nil {
return nil, errors.Trace(err)
}
columnIDs := make([]int64, 0, len(rows))
for _, row := range rows {
if row.IsNull(0) || row.IsNull(1) {
// Usually, it should not be NULL.
// This only happens when the last_used_at is not a valid time.
if row.IsNull(1) {
continue
}
colID := row.GetInt64(0)
@ -141,8 +148,10 @@ func GetPredicateColumns(sctx sessionctx.Context, tableID int64) ([]int64, error
if err != nil {
return nil, errors.Trace(err)
}
// If `last_used_at` is before the time when `set global enable_column_tracking = 0`, we don't regard the column as predicate column because
// `set global enable_column_tracking = 0` indicates all the predicate columns collected before.
// If `last_used_at` is before the time when `set global tidb_enable_column_tracking = 0`, we don't regard the column as predicate column because
// `set global tidb_enable_column_tracking = 0` indicates all the predicate columns collected before.
// TODO: Why do we need to do this? If column tracking is already disabled, we should not collect any column usage.
// If this refers to re-enabling column tracking, shouldn't we retain the column usage data from before it was disabled?
if disableTime == nil || gt.After(*disableTime) {
columnIDs = append(columnIDs, colID)
}
@ -151,14 +160,22 @@ func GetPredicateColumns(sctx sessionctx.Context, tableID int64) ([]int64, error
}
// getDisableColumnTrackingTime reads the value of tidb_disable_column_tracking_time from mysql.tidb if it exists.
// UTC time format is used to store the time.
func getDisableColumnTrackingTime(sctx sessionctx.Context) (*time.Time, error) {
rows, fields, err := utilstats.ExecRows(sctx, "SELECT variable_value FROM %n.%n WHERE variable_name = %?", mysql.SystemDB, mysql.TiDBTable, variable.TiDBDisableColumnTrackingTime)
rows, fields, err := utilstats.ExecRows(
sctx,
"SELECT variable_value FROM %n.%n WHERE variable_name = %?",
mysql.SystemDB,
mysql.TiDBTable,
variable.TiDBDisableColumnTrackingTime,
)
if err != nil {
return nil, err
}
if len(rows) == 0 {
return nil, nil
}
d := rows[0].GetDatum(0, &fields[0].Column.FieldType)
// The string represents the UTC time when tidb_enable_column_tracking is set to 0.
value, err := d.ToString()
@ -169,6 +186,7 @@ func getDisableColumnTrackingTime(sctx sessionctx.Context) (*time.Time, error) {
if err != nil {
return nil, err
}
return &t, nil
}