Class Sequel::JDBC::AS400::Dataset
In: lib/sequel/adapters/jdbc/as400.rb
Parent: JDBC::Dataset

Dataset class for AS400 datasets accessed via JDBC.

Methods

select_limit_sql   select_sql   supports_window_functions?  

Constants

WILDCARD = Sequel::LiteralString.new('*').freeze
FETCH_FIRST_ROW_ONLY = " FETCH FIRST ROW ONLY".freeze
FETCH_FIRST = " FETCH FIRST ".freeze
ROWS_ONLY = " ROWS ONLY".freeze

Public Instance methods

select_limit_sql(sql)

Modify the sql to limit the number of rows returned

[Source]

    # File lib/sequel/adapters/jdbc/as400.rb, line 65
65:         def select_limit_sql(sql)
66:           if l = @opts[:limit]
67:             if l == 1
68:               sql << FETCH_FIRST_ROW_ONLY
69:             elsif l > 1
70:               sql << FETCH_FIRST
71:               literal_append(sql, l)
72:               sql << ROWS_ONLY
73:             end
74:           end
75:         end
select_sql()

AS400 needs to use a couple of subselects for queries with offsets.

[Source]

    # File lib/sequel/adapters/jdbc/as400.rb, line 47
47:         def select_sql
48:           return super unless o = @opts[:offset]
49:           l = @opts[:limit]
50:           order = @opts[:order]
51:           dsa1 = dataset_alias(1)
52:           dsa2 = dataset_alias(2)
53:           rn = row_number_column
54:           irn = Sequel::SQL::Identifier.new(rn).qualify(dsa2)
55:           subselect_sql(unlimited.
56:               from_self(:alias=>dsa1).
57:               select_more(Sequel::SQL::QualifiedIdentifier.new(dsa1, WILDCARD),
58:               Sequel::SQL::WindowFunction.new(SQL::Function.new(:ROW_NUMBER), Sequel::SQL::Window.new(:order=>order)).as(rn)).
59:               from_self(:alias=>dsa2).
60:               select(Sequel::SQL::QualifiedIdentifier.new(dsa2, WILDCARD)).
61:               where(l ? ((irn > o) & (irn <= l + o)) : (irn > o))) # Leave off limit in case of limit(nil, offset)
62:         end
supports_window_functions?()

[Source]

    # File lib/sequel/adapters/jdbc/as400.rb, line 77
77:         def supports_window_functions?
78:           true
79:         end

[Validate]