Class: SqlTools::Query

Inherits:
Object
  • Object
show all
Defined in:
lib/sql_tools/query.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Query

Returns a new instance of Query.



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# File 'lib/sql_tools/query.rb', line 6

def initialize
  @common_table_expressions = {}
  @join_nodes = []
end

Instance Attribute Details

#common_table_expressions ⇒ Object (readonly)

Returns the value of attribute common_table_expressions.



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# File 'lib/sql_tools/query.rb', line 4

def common_table_expressions
  @common_table_expressions
end

#from ⇒ Object

Returns the value of attribute from.



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# File 'lib/sql_tools/query.rb', line 3

def from
  @from
end

#join_nodes ⇒ Object

Returns the value of attribute join_nodes.



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# File 'lib/sql_tools/query.rb', line 3

def join_nodes
  @join_nodes
end

#select ⇒ Object

Returns the value of attribute select.



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# File 'lib/sql_tools/query.rb', line 3

def select
  @select
end

Instance Method Details

#joins ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 50

def joins
  join_nodes.map do |join_node|
    object_name = join_node.find_node(<<~QUERY).text
      (join
        (relation
         (object_reference name: (identifier) @object_name)))
    QUERY

    filter = PredicateFilter.new(self)
    object = object_alias_map[object_name]
    predicate = filter.filter(object)

    if join_node.children.any? { |child| child.type == :keyword_left }
      LeftJoin.new(object, predicate)
    else
      InnerJoin.new(object, predicate)
    end
  end
end

#object_alias_map ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 112

def object_alias_map
  @table_alias_map ||= @from.query("(relation) @relation").each_with_object({}) do |captures, map|
    relation = captures["relation"]
    relation_name = relation.children.first.name.text
    relation_alias = relation.respond_to?(:alias) ? relation.alias.text : relation_name

    map[relation_alias] = common_table_expressions[relation_name] || Table.new(relation_name, relation_alias)
    map[relation_name] = map[relation_alias]
  end
end

#objects ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 110

def objects = object_alias_map.values.to_set

#predicate ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 80

def predicate
  @predicate ||= begin
    nodes = from.query(<<~QUERY).map { |captures| captures["predicate"] }
      (from
        (join
          predicate: (_) @predicate))
        (where
          predicate: (_) @predicate)
    QUERY

    builder = Predicate::Builder.new(self)
    predicates = nodes.flat_map do |predicate|
      visitor = PredicateVisitor.new(predicate).visit
      binding.b unless visitor.stack.size == 1
      builder.build(visitor.stack.last)
    end

    right = predicates.pop

    # This needs to pluck the left & right from binary expressions & rebuild the tree.
    # TODO: maybe this is the rotate algorithm, TBD
    while left = predicates.pop
      predicate = Predicate::Binary.new(left, "AND", right)
      right = predicate
    end

    right
  end
end

#relations ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 70

def relations
  objects.each_with_object({}) do |object, map|
    map[object] ||= []
    map[object] << predicates.select do |p|
      (p.left.is_a?(Column) && p.left.table == object) ||
        (p.right.is_a?(Column) && p.right.table == object)
    end
  end
end

#selections ⇒ Object 



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# File 'lib/sql_tools/query.rb', line 11

def selections
  terms = select.query(<<~QUERY)
    (select_expression
      (term
        value: [
          (field
            (object_reference name: (identifier) @table_alias)?
            name: (identifier) @column_name)
          (invocation) @invocation
          (all_fields
            (object_reference name: (identifier) @table_alias)?) @all_fields
        ]
        alias: (identifier)? @selection_name))
  QUERY
  terms.map! do |captures|
    selection_name = captures["selection_name"]&.text || captures["column_name"]&.text

    if captures["all_fields"]
      table = if table_alias = captures["table_alias"]
        object_alias_map[table_alias.text]
      elsif objects.size == 1
        objects.first
      end
      Selection::AllFields.new(table)
    elsif table_alias = captures["table_alias"]
      table = object_alias_map[table_alias.text]
      column_name = captures["column_name"].text
      Selection::Column.new(selection_name, Column.new(table, column_name))
    elsif (column_name = captures["column_name"]&.text) && objects.size == 1
      table = objects.first
      Selection::Column.new(selection_name, Column.new(table, column_name))
    elsif invocation = captures["invocation"]
      Selection::Invocation.new(selection_name, invocation)
    else
      raise "Unknown selection type"
    end
  end
end