// idsForExpr will return a collection of series ids and a filter expression that should
// be used to filter points from those series.
func (m *Measurement) idsForExpr(n *influxql.BinaryExpr) (SeriesIDs, influxql.Expr, error) {
	// If this binary expression has another binary expression, then this
	// is some expression math and we should just pass it to the underlying query.
	if _, ok := n.LHS.(*influxql.BinaryExpr); ok {
		return m.seriesIDs, n, nil
	} else if _, ok := n.RHS.(*influxql.BinaryExpr); ok {
		return m.seriesIDs, n, nil
	}

	// Retrieve the variable reference from the correct side of the expression.
	name, ok := n.LHS.(*influxql.VarRef)
	value := n.RHS
	if !ok {
		name, ok = n.RHS.(*influxql.VarRef)
		if !ok {
			return nil, nil, fmt.Errorf("invalid expression: %s", n.String())
		}
		value = n.LHS
	}

	// For time literals, return all series IDs and "true" as the filter.
	if _, ok := value.(*influxql.TimeLiteral); ok || name.Val == "time" {
		return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
	}

	// For fields, return all series IDs from this measurement and return
	// the expression passed in, as the filter.
	if name.Val != "_name" && ((name.Type == influxql.Unknown && m.hasField(name.Val)) || name.Type == influxql.AnyField || (name.Type != influxql.Tag && name.Type != influxql.Unknown)) {
		return m.seriesIDs, n, nil
	} else if value, ok := value.(*influxql.VarRef); ok {
		// Check if the RHS is a variable and if it is a field.
		if value.Val != "_name" && ((value.Type == influxql.Unknown && m.hasField(value.Val)) || name.Type == influxql.AnyField || (value.Type != influxql.Tag && value.Type != influxql.Unknown)) {
			return m.seriesIDs, n, nil
		}
	}

	// Retrieve list of series with this tag key.
	tagVals := m.seriesByTagKeyValue[name.Val]

	// if we're looking for series with a specific tag value
	if str, ok := value.(*influxql.StringLiteral); ok {
		var ids SeriesIDs

		// Special handling for "_name" to match measurement name.
		if name.Val == "_name" {
			if (n.Op == influxql.EQ && str.Val == m.Name) || (n.Op == influxql.NEQ && str.Val != m.Name) {
				return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
			}
			return nil, &influxql.BooleanLiteral{Val: true}, nil
		}

		if n.Op == influxql.EQ {
			if str.Val != "" {
				// return series that have a tag of specific value.
				ids = tagVals[str.Val]
			} else {
				ids = m.seriesIDs
				for k := range tagVals {
					ids = ids.Reject(tagVals[k])
				}
			}
		} else if n.Op == influxql.NEQ {
			if str.Val != "" {
				ids = m.seriesIDs.Reject(tagVals[str.Val])
			} else {
				for k := range tagVals {
					ids = ids.Union(tagVals[k])
				}
			}
		}
		return ids, &influxql.BooleanLiteral{Val: true}, nil
	}

	// if we're looking for series with a tag value that matches a regex
	if re, ok := value.(*influxql.RegexLiteral); ok {
		var ids SeriesIDs

		// Special handling for "_name" to match measurement name.
		if name.Val == "_name" {
			match := re.Val.MatchString(m.Name)
			if (n.Op == influxql.EQREGEX && match) || (n.Op == influxql.NEQREGEX && !match) {
				return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
			}
			return nil, &influxql.BooleanLiteral{Val: true}, nil
		}

		// Check if we match the empty string to see if we should include series
		// that are missing the tag.
		empty := re.Val.MatchString("")

		// Gather the series that match the regex. If we should include the empty string,
		// start with the list of all series and reject series that don't match our condition.
		// If we should not include the empty string, include series that match our condition.
		if empty && n.Op == influxql.EQREGEX {
			ids = m.seriesIDs
			for k := range tagVals {
				if !re.Val.MatchString(k) {
					ids = ids.Reject(tagVals[k])
//.........这里部分代码省略.........

// idsForExpr will return a collection of series ids and a filter expression that should
// be used to filter points from those series.
func (m *Measurement) idsForExpr(n *influxql.BinaryExpr) (SeriesIDs, influxql.Expr, error) {
	name, ok := n.LHS.(*influxql.VarRef)
	value := n.RHS
	if !ok {
		name, ok = n.RHS.(*influxql.VarRef)
		if !ok {
			return nil, nil, fmt.Errorf("invalid expression: %s", n.String())
		}
		value = n.LHS
	}

	// For time literals, return all series IDs and "true" as the filter.
	if _, ok := value.(*influxql.TimeLiteral); ok || name.Val == "time" {
		return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
	}

	// For fields, return all series IDs from this measurement and return
	// the expression passed in, as the filter.
	if m.HasField(name.Val) {
		return m.seriesIDs, n, nil
	}

	tagVals, ok := m.seriesByTagKeyValue[name.Val]
	if !ok {
		return nil, nil, nil
	}

	// if we're looking for series with a specific tag value
	if str, ok := value.(*influxql.StringLiteral); ok {
		var ids SeriesIDs

		if n.Op == influxql.EQ {
			// return series that have a tag of specific value.
			ids = tagVals[str.Val]
		} else if n.Op == influxql.NEQ {
			ids = m.seriesIDs.Reject(tagVals[str.Val])
		}
		return ids, &influxql.BooleanLiteral{Val: true}, nil
	}

	// if we're looking for series with a tag value that matches a regex
	if re, ok := value.(*influxql.RegexLiteral); ok {
		var ids SeriesIDs

		// The operation is a NEQREGEX, code must start by assuming all match, even
		// series without any tags.
		if n.Op == influxql.NEQREGEX {
			ids = m.seriesIDs
		}

		for k := range tagVals {
			match := re.Val.MatchString(k)

			if match && n.Op == influxql.EQREGEX {
				ids = ids.Union(tagVals[k])
			} else if match && n.Op == influxql.NEQREGEX {
				ids = ids.Reject(tagVals[k])
			}
		}
		return ids, &influxql.BooleanLiteral{Val: true}, nil
	}

	return nil, nil, nil
}