class PG::Tuple
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"
Public Instance Methods
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
.
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); }
Invokes block for each field name and value in the tuple.
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; }
# File lib/pg/tuple.rb, line 22 def each_key(&block) if fn=field_names fn.each(&block) else field_map.each_key(&block) end end
Invokes block for each field value in the tuple.
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; }
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.
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); }
# File lib/pg/tuple.rb, line 13 def has_key?(key) field_map.has_key?(key) end
Returns the field number which matches the given column name.
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); }
Return a String representation of the object suitable for debugging.
# File lib/pg/tuple.rb, line 9 def inspect "#<#{self.class} #{self.map{|k,v| "#{k}: #{v.inspect}" }.join(", ") }>" end
# File lib/pg/tuple.rb, line 18 def keys field_names || field_map.keys.freeze end
Returns number of fields of this tuple.
static VALUE pg_tuple_length(VALUE self) { t_pg_tuple *this = pg_tuple_get_this(self); return INT2NUM(this->num_fields); }
Returns the values of this tuple as Array. +res.tuple(i).values+ is equal to +res.tuple_values(i)+ .
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]); }