Contents

.TH Restrict
.PP
Predicate\-based filtering
.SH Signature
.PP
.RS
.nf
restrict(operand: Relation, predicate: Predicate) -> Relation
.fi
.RE
.SH Examples
.PP
.RS
.nf
restrict(suppliers, city: 'Paris', status: 20)
.fi
.RE
.PP
.RS
.nf
restrict(suppliers, eq(city: 'Paris') & gt(:status, 20))
.fi
.RE
.PP
.RS
.nf
restrict(suppliers, ->(t){ t.city == 'Paris' and t.status > 20 })
.fi
.RE
.SH Description
.PP
Computes a relation as a subset of \fB\fCoperand\fR tuples for which a tuple
predicate evaluates to TRUE.
.SH Implementation notes
.PP
As of current Alf version, native predicates (through ruby \fB\fCProc\fR objects)
cannot be optimized nor compiled to SQL. The use of predicate factories
(\fB\fCeq\fR, \fB\fCgt\fR, etc.) is strongly recommanded.

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
alf-shell-0.15.0	doc/man/restrict.man