Golang expression.Formalizer类代码示例

/*
This method fully qualifies the identifiers for each term
in the result expression. It disallows duplicate alias and
exempts explicit aliases from being formalized.
*/
func (this *Projection) Formalize(in *expression.Formalizer) (f *expression.Formalizer, err error) {
	// Disallow duplicate aliases
	aliases := make(map[string]bool, len(this.terms))
	for _, term := range this.terms {
		if term.alias == "" {
			continue
		}

		if aliases[term.alias] {
			return nil, fmt.Errorf("Duplicate result alias %s.", term.alias)
		}

		aliases[term.alias] = true
	}

	err = this.MapExpressions(in)
	if err != nil {
		return
	}

	if len(aliases) > 0 {
		f = in.Copy()
	} else {
		f = in
	}

	// Exempt explicit aliases from being formalized
	for _, term := range this.terms {
		if term.as != "" {
			f.Allowed().SetField(term.as, term.as)
		}
	}

	return
}

func sargableIndexes(indexes []datastore.Index, pred expression.Expression,
	primaryKey expression.Expressions, dnf *DNF, formalizer *expression.Formalizer) (
	map[datastore.Index]*indexEntry, error) {
	var err error
	var keys expression.Expressions
	sargables := make(map[datastore.Index]*indexEntry, len(indexes))

	for _, index := range indexes {
		if index.IsPrimary() {
			keys = primaryKey
		} else {
			keys = index.RangeKey()
			keys = keys.Copy()

			for i, key := range keys {
				key = key.Copy()

				key, err = formalizer.Map(key)
				if err != nil {
					return nil, err
				}

				key, err = dnf.Map(key)
				if err != nil {
					return nil, err
				}

				keys[i] = key
			}
		}

		cond := index.Condition()
		if cond != nil {
			cond = cond.Copy()

			cond, err = formalizer.Map(cond)
			if err != nil {
				return nil, err
			}

			cond, err = dnf.Map(cond)
			if err != nil {
				return nil, err
			}

			if !SubsetOf(pred, cond) {
				continue
			}
		}

		n := SargableFor(pred, keys)
		if n > 0 {
			sargables[index] = &indexEntry{keys, keys[0:n], cond, nil}
		}
	}

	return sargables, nil
}

/*
This method qualifies identifiers for all the constituent clauses,
namely the subresult, order, limit and offset within a subquery.
For the subresult of the subquery, call Formalize, for the order
by clause call MapExpressions, for limit and offset call Accept.
*/
func (this *Select) FormalizeSubquery(parent *expression.Formalizer) error {
	f, err := this.subresult.Formalize(parent)
	if err != nil {
		return err
	}

	this.correlated = this.subresult.IsCorrelated()

	if this.order != nil {
		err = this.order.MapExpressions(f)
		if err != nil {
			return err
		}

		if !this.correlated {
			// Determine if this is a correlated subquery
			immediate := f.Allowed.GetValue().Fields()
			for ident, _ := range f.Identifiers {
				if _, ok := immediate[ident]; !ok {
					this.correlated = true
					break
				}
			}
		}
	}

	if this.limit == nil && this.offset == nil {
		return err
	}

	if !this.correlated {
		prevIdentifiers := parent.Identifiers
		defer parent.SetIdentifiers(prevIdentifiers)
		parent.SetIdentifiers(make(map[string]bool))
	}

	if this.limit != nil {
		_, err = this.limit.Accept(parent)
		if err != nil {
			return err
		}
	}

	if this.offset != nil {
		_, err = this.offset.Accept(parent)
		if err != nil {
			return err
		}
	}

	if !this.correlated {
		this.correlated = len(parent.Identifiers) > 0
	}

	return err
}

/*
Qualify all identifiers for the parent expression. Checks for
duplicate aliases.
*/
func (this *SubqueryTerm) Formalize(parent *expression.Formalizer) (f *expression.Formalizer, err error) {
	err = this.subquery.Formalize()
	if err != nil {
		return
	}

	alias := this.Alias()
	if alias == "" {
		err = errors.NewNoTermNameError("FROM", "plan.subquery.requires_name_or_alias")
		return
	}

	_, ok := parent.Allowed().Field(alias)
	if ok {
		err = errors.NewDuplicateAliasError("subquery", alias, "plan.subquery.duplicate_alias")
		return nil, err
	}

	f = expression.NewFormalizer(alias, parent)
	return
}

/*
This method qualifies identifiers for all the constituent clauses,
namely the by, letting and having expressions by mapping them.
*/
func (this *Group) Formalize(f *expression.Formalizer) (*expression.Formalizer, error) {
	var err error

	if this.by != nil {
		for i, b := range this.by {
			this.by[i], err = f.Map(b)
			if err != nil {
				return nil, err
			}
		}
	}

	if this.letting != nil {
		_, err = f.PushBindings(this.letting)
		if err != nil {
			return nil, err
		}
	}

	if this.having != nil {
		this.having, err = f.Map(this.having)
		if err != nil {
			return nil, err
		}
	}

	return f, nil
}

/*
Qualify all identifiers for the parent expression. Checks is
a nest alias exists and if it is a duplicate alias.
*/
func (this *IndexNest) Formalize(parent *expression.Formalizer) (f *expression.Formalizer, err error) {
	f, err = this.left.Formalize(parent)
	if err != nil {
		return
	}

	_, ok := f.Allowed.Field(this.keyFor)
	if !ok {
		err = errors.NewUnknownForError("NEST", this.keyFor, "plan.nest.unknown_for")
		return nil, err
	}

	alias := this.Alias()
	if alias == "" {
		err = errors.NewNoTermNameError("NEST", "plan.nest.requires_name_or_alias")
		return nil, err
	}

	_, ok = f.Allowed.Field(alias)
	if ok {
		err = errors.NewDuplicateAliasError("NEST", alias, "plan.nest.duplicate_alias")
		return nil, err
	}

	f.Allowed.SetField(alias, alias)
	f.Keyspace = ""

	var p *expression.Formalizer
	if parent != nil {
		p = parent.Copy()
	} else {
		p = expression.NewFormalizer()
	}

	p.Allowed.SetField(alias, alias)
	this.right.keys, err = p.Map(this.right.keys)
	return
}

/*
Qualify all identifiers for the parent expression. Checks for
duplicate aliases.
*/
func (this *KeyspaceTerm) Formalize(parent *expression.Formalizer) (f *expression.Formalizer, err error) {
	keyspace := this.Alias()
	if keyspace == "" {
		err = errors.NewNoTermNameError("FROM", "plan.keyspace.requires_name_or_alias")
		return
	}

	f = expression.NewFormalizer("", parent)
	if this.keys != nil {
		_, err = this.keys.Accept(f)
		if err != nil {
			return
		}
	}

	_, ok := parent.Allowed().Field(keyspace)
	if ok {
		err = errors.NewDuplicateAliasError("subquery", keyspace, "plan.keyspace.duplicate_alias")
		return nil, err
	}

	f.SetKeyspace(keyspace)
	return
}

/*
Fully qualify identifiers for the update-for clause, the path
and value expressions in the SET clause.
*/
func (this *SetTerm) Formalize(f *expression.Formalizer) (err error) {
	if this.updateFor != nil {
		sv, err := f.PushBindings(this.updateFor.bindings)
		if err != nil {
			return err
		}

		defer f.PopBindings(sv)
	}

	path, err := f.Map(this.path)
	if err != nil {
		return err
	}

	this.path = path.(expression.Path)
	this.value, err = f.Map(this.value)
	return
}