Golang SelectStatement.HasDistinct方法代码示例

// NewLocalMapper returns a mapper for the given shard, which will return data for the SELECT statement.
func NewLocalMapper(shard *Shard, stmt *influxql.SelectStatement, chunkSize int) *LocalMapper {
	m := &LocalMapper{
		shard:     shard,
		stmt:      stmt,
		chunkSize: chunkSize,
		cursors:   make([]*tagSetCursor, 0),
	}

	m.rawMode = (stmt.IsRawQuery && !stmt.HasDistinct()) || stmt.IsSimpleDerivative()
	return m
}

// Plan creates an execution plan for the given SelectStatement and returns an Executor.
func (q *QueryExecutor) plan(stmt *influxql.SelectStatement, chunkSize int) (Executor, error) {
	shards := map[uint64]meta.ShardInfo{} // Shards requiring mappers.

	// Replace instances of "now()" with the current time, and check the resultant times.
	stmt.Condition = influxql.Reduce(stmt.Condition, &influxql.NowValuer{Now: time.Now().UTC()})
	tmin, tmax := influxql.TimeRange(stmt.Condition)
	if tmax.IsZero() {
		tmax = time.Now()
	}
	if tmin.IsZero() {
		tmin = time.Unix(0, 0)
	}

	for _, src := range stmt.Sources {
		mm, ok := src.(*influxql.Measurement)
		if !ok {
			return nil, fmt.Errorf("invalid source type: %#v", src)
		}

		// Build the set of target shards. Using shard IDs as keys ensures each shard ID
		// occurs only once.
		shardGroups, err := q.MetaStore.ShardGroupsByTimeRange(mm.Database, mm.RetentionPolicy, tmin, tmax)
		if err != nil {
			return nil, err
		}
		for _, g := range shardGroups {
			for _, sh := range g.Shards {
				shards[sh.ID] = sh
			}
		}
	}

	// Build the Mappers, one per shard.
	mappers := []Mapper{}
	for _, sh := range shards {
		m, err := q.ShardMapper.CreateMapper(sh, stmt.String(), chunkSize)
		if err != nil {
			return nil, err
		}
		if m == nil {
			// No data for this shard, skip it.
			continue
		}
		mappers = append(mappers, m)
	}

	if stmt.IsRawQuery && !stmt.HasDistinct() {
		return NewRawExecutor(stmt, mappers, chunkSize), nil
	}
	return NewAggregateExecutor(stmt, mappers), nil
}

// Plan creates an execution plan for the given SelectStatement and returns an Executor.
func (q *QueryExecutor) PlanSelect(stmt *influxql.SelectStatement, chunkSize int) (Executor, error) {
	var shardIDs []uint64
	shards := map[uint64]meta.ShardInfo{} // Shards requiring mappers.

	// It is important to "stamp" this time so that everywhere we evaluate `now()` in the statement is EXACTLY the same `now`
	now := time.Now().UTC()

	// Replace instances of "now()" with the current time, and check the resultant times.
	stmt.Condition = influxql.Reduce(stmt.Condition, &influxql.NowValuer{Now: now})
	tmin, tmax := influxql.TimeRange(stmt.Condition)
	if tmax.IsZero() {
		tmax = now
	}
	if tmin.IsZero() {
		tmin = time.Unix(0, 0)
	}

	for _, src := range stmt.Sources {
		mm, ok := src.(*influxql.Measurement)
		if !ok {
			return nil, fmt.Errorf("invalid source type: %#v", src)
		}

		// Build the set of target shards. Using shard IDs as keys ensures each shard ID
		// occurs only once.
		shardGroups, err := q.MetaClient.ShardGroupsByTimeRange(mm.Database, mm.RetentionPolicy, tmin, tmax)
		if err != nil {
			return nil, err
		}
		for _, g := range shardGroups {
			for _, sh := range g.Shards {
				if _, ok := shards[sh.ID]; !ok {
					shards[sh.ID] = sh
					shardIDs = append(shardIDs, sh.ID)
				}
			}
		}
	}

	// Sort shard IDs to make testing deterministic.
	sort.Sort(uint64Slice(shardIDs))

	// Build the Mappers, one per shard.
	mappers := []Mapper{}
	for _, shardID := range shardIDs {
		sh := shards[shardID]

		m, err := q.ShardMapper.CreateMapper(sh, stmt, chunkSize)
		if err != nil {
			return nil, err
		}
		if m == nil {
			// No data for this shard, skip it.
			continue
		}
		mappers = append(mappers, m)
	}

	// Certain operations on the SELECT statement can be performed by the AggregateExecutor without
	// assistance from the Mappers. This allows the AggregateExecutor to prepare aggregation functions
	// and mathematical functions.
	stmt.RewriteDistinct()

	if (stmt.IsRawQuery && !stmt.HasDistinct()) || stmt.IsSimpleDerivative() {
		return NewRawExecutor(stmt, mappers, chunkSize), nil
	} else {
		return NewAggregateExecutor(stmt, mappers), nil
	}
}