Module: Card::Query::AbstractQuery::Tie

Included in:
Card::Query::AbstractQuery
Defined in:
lib/card/query/abstract_query/tie.rb

Overview

The “Tie” methods support tying two queries (CardQuery, ReferenceQuery, etc) together. The “fasten” variable determines which tying strategy is used.

We currently support three values for “fasten”: :join, :exist, and :in

In concept, here’s how the different strategies would tie table A to table B in SQL assuming A.id = B.a_id

  • :join … FROM A JOIN B ON A.id = B.a_id

  • :exist … FROM A WHERE EXISTS (SELECT * FROM B WHERE A.id = B.a_id …)

  • :in … FROM A WHERE A.id IN (SELECT B.a_id FROM B WHERE …)

The different strategies will return the same values but the relative speed is context dependent.

Instance Method Summary collapse

Instance Method Details

#fasten ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 52

def fasten
  @fasten ||= root? ? :join : inherit_fasten
end

#fasten_tie(subquery, fields = {}) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 31

def fasten_tie subquery, fields={}
  method = "tie_with_#{subquery.fasten}"
  send method, subquery, fields
  subquery
end

#id_from_val(val) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 94

def id_from_val val
  case val
  when Integer then val
  when String  then Card.fetch_id(val) || -999
  when Symbol  then Card::Codename.id(val) || -999
  end
end

#inherit_fasten ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 73

def inherit_fasten
  superfasten = superquery.fasten
  superfasten == :direct ? superquery.inherit_fasten : superfasten
end

#left_join?(subquery) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/card/query/abstract_query/tie.rb', line 63

def left_join? subquery
  current_conjunction == "or" || subquery.negate
  # reverse conjunction if negated?
end

#negate_join(subquery, join, fields) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 68

def negate_join subquery, join, fields
  subquery.conditions_on_join = join
  add_condition "#{subquery.fld fields[:to]} is null"
end

#restrict(id_field, val) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 86

def restrict id_field, val
  if (id = id_from_val(val))
    interpret id_field => id
  else
    tie :card, val, from: id_field
  end
end

#super_conditions(fields) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 78

def super_conditions fields
  superfield fields[:to], fields[:from]
end

#superfield(myfield, superfield) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 82

def superfield myfield, superfield
  add_condition "#{fld myfield} = #{superquery.fld superfield}"
end

#tie(subquery_type, val, fields = {}, subquery_args = {}) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 19

def tie subquery_type, val, fields={}, subquery_args={}
  subquery = tie_subquery subquery_type, subquery_args
  subquery.interpret val
  fields = { from: :id, to: :id }.merge fields
  fasten_tie subquery, fields
end

#tie_subquery(subquery_type, subquery_args) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 26

def tie_subquery subquery_type, subquery_args
  subquery_args[:class] = Query.class_for subquery_type
  subquery(subquery_args)
end

#tie_with_exist(subquery, fields) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 48

def tie_with_exist subquery, fields
  subquery.super_conditions fields if fields.present?
end

#tie_with_in(subquery, fields) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 43

def tie_with_in subquery, fields
  subquery.mods[:return] = fields[:to]
  subquery.mods[:in_field] = fld(fields[:from])
end

#tie_with_join(subquery, fields = {}) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 37

def tie_with_join subquery, fields={}
  join = Join.new tie_with_join_args(subquery, fields)
  negate_join(subquery, join, fields) if subquery.negate
  joins << join
end

#tie_with_join_args(subquery, fields) ⇒ Object 



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# File 'lib/card/query/abstract_query/tie.rb', line 56

def tie_with_join_args subquery, fields
  args = { from: self, from_field: fields[:from],
           to: subquery, to_field: fields[:to] }
  args[:side] = :left if left_join? subquery
  args
end