.TH Wrap
.PP
Tuple\-valued attribute
.SH Signature
.PP
.RS
.nf
wrap(operand: Relation, attributes: AttrList, as: AttrName) -> Relation
.fi
.RE
.SH Examples
.PP
.RS
.nf
wrap(suppliers, [:city, :status], :extra)
.fi
.RE
.PP
.RS
.nf
wrap(suppliers, [:city, :status], :extra, allbut: true)
.fi
.RE
.SH Description
.PP
Computes the relation obtained by removing \fB\fCattributes\fR and replacing them
by a single attribute (\fB\fCas\fR). The latter is a tuple\-valued attribute
obtained by projecting the input tuple on \fB\fCattributes\fR\&.
.PP
This operators supports an ALL BUT variant, through the \fB\fCallbut\fR option.
When set to true, the operator keeps specified attributes and wraps all the
remaining ones as a tuple\-valued attribute.
.SH Implementation notes
.PP
This operator does not compile to SQL so far. Contributions are welcome to
provide it with a SQL compilation for SQL DBMSs that support this kind of
feature (e.g. PostgreSQL with JSON data type)