Class: PG::Tuple

Inherits:

Object

• Object
• PG::Tuple

Includes:

Enumerable

Defined in:

ext/pg_tuple.c,
lib/pg/tuple.rb,
ext/pg_tuple.c

Overview

******************************************************************

The class to represent one query result tuple (row).
An instance of this class can be created by PG::Result#tuple .

All field values of the tuple are retrieved on demand from the underlying PGresult object and converted to a Ruby object.
Subsequent access to the same field returns the same object, since they are cached when materialized.
Each PG::Tuple holds a reference to the related PG::Result object, but gets detached, when all fields are materialized.

Example:
   require 'pg'
   conn = PG.connect(:dbname => 'test')
   res  = conn.exec('VALUES(1,2), (3,4)')
   t0 = res.tuple(0)  # => #<PG::Tuple column1: "1", column2: "2">
   t1 = res.tuple(1)  # => #<PG::Tuple column1: "3", column2: "4">
   t1[0]  # => "3"
   t1["column2"]  # => "4"

Instance Method Summary

• #[](key) ⇒ Object

  Returns a field value by either column index or column name.

• #each {|key, value| ... } ⇒ Object

  Invokes block for each field name and value in the tuple.

• #each_key(&block) ⇒ Object
• #each_value {|value| ... } ⇒ Object

  Invokes block for each field value in the tuple.

• #fetch(*args) ⇒ Object

  Returns a field value by either column index or column name.

• #has_key?(key) ⇒ Boolean (also: #key?)
• #index(key) ⇒ Object

  Returns the field number which matches the given column name.

• #inspect ⇒ Object

  Return a String representation of the object suitable for debugging.

• #keys ⇒ Object
• #length ⇒ Object (also: #size)

  Returns number of fields of this tuple.

• #values ⇒ Array

  Returns the values of this tuple as Array.

Instance Method Details

#[](key) ⇒ Object

Returns a field value by either column index or column name.

An integer key is interpreted as column index. Negative values of index count from the end of the array.

Depending on Result#field_name_type= a string or symbol key is interpreted as column name.

If the key can’t be found, it returns nil .

# File 'ext/pg_tuple.c', line 309

static VALUE
pg_tuple_aref(VALUE self, VALUE key)
{
	VALUE index;
	int field_num;
	t_pg_tuple *this = pg_tuple_get_this(self);

	switch(rb_type(key)){
		case T_FIXNUM:
		case T_BIGNUM:
			field_num = NUM2INT(key);
			if ( field_num < 0 )
				field_num = this->num_fields + field_num;
			if ( field_num < 0 || field_num >= this->num_fields )
				return Qnil;
			break;
		default:
			index = rb_hash_aref(this->field_map, key);
			if( index == Qnil ) return Qnil;
			field_num = NUM2INT(index);
	}

	return pg_tuple_materialize_field(self, field_num);
}

#each {|key, value| ... } ⇒ Object

Invokes block for each field name and value in the tuple.

Yields:

• (key, value)

# File 'ext/pg_tuple.c', line 355

static VALUE
pg_tuple_each(VALUE self)
{
	t_pg_tuple *this = pg_tuple_get_this(self);
	VALUE field_names;

	RETURN_SIZED_ENUMERATOR(self, 0, NULL, pg_tuple_num_fields_for_enum);

	field_names = pg_tuple_get_field_names(this);

	if( field_names == Qfalse ){
		rb_hash_foreach(this->field_map, pg_tuple_yield_key_value, self);
	} else {
		int i;
		for( i = 0; i < this->num_fields; i++ ){
			VALUE value = pg_tuple_materialize_field(self, i);
			rb_yield_values(2, RARRAY_AREF(field_names, i), value);
		}
	}

	pg_tuple_detach(self);
	return self;
}

#each_key(&block) ⇒ Object

# File 'lib/pg/tuple.rb', line 23

def each_key(&block)
	if fn=field_names
		fn.each(&block)
	else
		field_map.each_key(&block)
	end
end

#each_value {|value| ... } ⇒ Object

Invokes block for each field value in the tuple.

Yields:

• (value)

# File 'ext/pg_tuple.c', line 385

static VALUE
pg_tuple_each_value(VALUE self)
{
	t_pg_tuple *this = pg_tuple_get_this(self);
	int field_num;

	RETURN_SIZED_ENUMERATOR(self, 0, NULL, pg_tuple_num_fields_for_enum);

	for(field_num = 0; field_num < this->num_fields; field_num++) {
		VALUE value = pg_tuple_materialize_field(self, field_num);
		rb_yield(value);
	}

	pg_tuple_detach(self);
	return self;
}

#fetch(key) ⇒ Object #fetch(key, default) ⇒ Object #fetch(key) ⇒ Object

Returns a field value by either column index or column name.

An integer key is interpreted as column index. Negative values of index count from the end of the array.

Depending on Result#field_name_type= a string or symbol key is interpreted as column name.

If the key can’t be found, there are several options: With no other arguments, it will raise a IndexError exception; if default is given, then that will be returned; if the optional code block is specified, then that will be run and its result returned.

# File 'ext/pg_tuple.c', line 252

static VALUE
pg_tuple_fetch(int argc, VALUE *argv, VALUE self)
{
	VALUE key;
	long block_given;
	VALUE index;
	int field_num;
	t_pg_tuple *this = pg_tuple_get_this(self);

	rb_check_arity(argc, 1, 2);
	key = argv[0];

	block_given = rb_block_given_p();
	if (block_given && argc == 2) {
		rb_warn("block supersedes default value argument");
	}

	switch(rb_type(key)){
		case T_FIXNUM:
		case T_BIGNUM:
			field_num = NUM2INT(key);
			if ( field_num < 0 )
				field_num = this->num_fields + field_num;
			if ( field_num < 0 || field_num >= this->num_fields ){
				if (block_given) return rb_yield(key);
				if (argc == 1) rb_raise( rb_eIndexError, "Index %d is out of range", field_num );
				return argv[1];
			}
			break;
		default:
			index = rb_hash_aref(this->field_map, key);

			if (index == Qnil) {
				if (block_given) return rb_yield(key);
				if (argc == 1) rb_raise( rb_eKeyError, "column not found" );
				return argv[1];
			}

			field_num = NUM2INT(index);
	}

	return pg_tuple_materialize_field(self, field_num);
}

#has_key?(key) ⇒ Boolean Also known as: key?

Returns:

• (Boolean)

# File 'lib/pg/tuple.rb', line 14

def has_key?(key)
	field_map.has_key?(key)
end

#index(key) ⇒ Object

Returns the field number which matches the given column name.

# File 'ext/pg_tuple.c', line 452

static VALUE
pg_tuple_index(VALUE self, VALUE key)
{
	t_pg_tuple *this = pg_tuple_get_this(self);
	return rb_hash_aref(this->field_map, key);
}

#inspect ⇒ Object

Return a String representation of the object suitable for debugging.

# File 'lib/pg/tuple.rb', line 10

def inspect
	"#<#{self.class} #{self.map{|k,v| "#{k}: #{v.inspect}" }.join(", ") }>"
end

#keys ⇒ Object

# File 'lib/pg/tuple.rb', line 19

def keys
	field_names || field_map.keys.freeze
end

#length ⇒ Object Also known as: size

Returns number of fields of this tuple.

# File 'ext/pg_tuple.c', line 439

static VALUE
pg_tuple_length(VALUE self)
{
	t_pg_tuple *this = pg_tuple_get_this(self);
	return INT2NUM(this->num_fields);
}

#values ⇒ Array

Returns the values of this tuple as Array. res.tuple(i).values is equal to res.tuple_values(i) .

Returns:

• (Array)

# File 'ext/pg_tuple.c', line 410

static VALUE
pg_tuple_values(VALUE self)
{
	t_pg_tuple *this = pg_tuple_get_this(self);

	pg_tuple_materialize(self);
	return rb_ary_new4(this->num_fields, &this->values[0]);
}