Tangram::Expr (3pm)

   my ($r1, $r2) = $storage->remote(qw( ... ));

   $r1->{field} operator $value
   $r1->{field} operator $r2->{field2}

   $r1->{collection}->includes( $obj )
   $r1->{collection}->exists( $obj, $filter )
   $r1->{collection}->includes_or( $obj1, $obj2, ... )

Tangram::Expr objects represent expressions that will be evaluated on the database server side.

Expression objects fall into one of the following categories: numeric, string, reference or collection.

Many of the methods in Expr are needed only by people extending Tangram. See also Tangram::Relational, and the source the Tangram::mysql and Tangram::Sybase for examples on how these functions are intercepted to allow RDBMS-specific expressions.

Numeric expression objects can be compared using the operators ==, !=, <, >, <= and >=. The other operand must be either another numeric expression object, or a normal Perl numeric value. The result of the comparison is a Filter.

String expression objects can be compared using the operators eq, ne, lt, gt, le, and ge. The other operand must be either a string expression object or any Perl scalar value. Tangram will automatically quote the operand as required by the \s-1SQL\s0 syntax. The result of the comparison is a Tangram::Expr::Filter.

String expression objects also support the method like($str), where $str is a string that may contain \s-1SQL\s0 wildcards. The result is a Tangram::Expr::Filter that translates to a \s-1SQL\s0 \*(C`LIKE $str\*(C' predicate.

Reference expression objects can be compared for equality using operators == and !=. The other operand must be another reference expression, a persistent object or undef(). The result of the comparison is a Filter.

Collection expression objects represents a collection inside an object. It supports the includes() and exists() methods, which returns a Tangram::Expr::Filter stating that the collection must contain the operand. exists() uses a subselect.

It also supports the includes_or() methods, which accepts a list and is performs a logical \s-1OR\s0 - using the \s-1IN\s0 (x,y,z) \s-1SQL\s0 construct.

The operand may be a Tangram::Remote, a persistent object, or an object \s-1ID\s0.

operator < is provided as a synonym for includes().

The includes() method can be used for all collection types (Set, Array, Hash, and the Intr* versions).

Predicate objects represent logical expressions, or conditions. Predicates support logical operators &, | and !. Note that a single ampersand or vertical bar must be used (this is a Perl limitation). The result is another predicate.

Returns a new instance.

$type is a Type object corresponding to this expression (see Tangram::Type).

$expr is a \s-1SQL\s0 expression. It will eventually become part of a WHERE-CLAUSE.

@remotes contains the Remote objects (see Tangram::Remote) that participate in the expression. Tangram uses this list to insert the corresponding tables in the \s-1FROM\s0 clause and conditions in the WHERE-CLAUSE.

\fIexpr()\fP

Returns the \s-1SQL\s0 equivalent for this expression.

\fItype()\fP

Returns the Type (see Tangram::Type) corresponding to this expression.

\fIobjects()\fP

Returns the list of the objects that participate in this expression.

\fIstorage()\fP

Returns the Storage associated with this expression.

$person is called 'Homer'

$person->{name} eq 'Homer'

$person's name ends with 'mer'

$person->{name}->like('%mer');

$person is older than 35

$person->{age} > 35

$person is married to $homer

$person->{partner} == $homer

$person is not $homer

$person != $homer

$person is not $homer and is older than 65

$person != $homer & $person->{age} > 65

$person is $bart's parent

$person->{children}->includes( $bart ) $person->{children} < $bart

$person is not $bart's parent

!$person->{children}->includes( $bart ) !($person->{children} < $bart)

$person is one of the local list of people, @person

$person->in(@person)

Tangram::Remote, Tangram::Expr, Tangram::Storage