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module Groonga
module ExpressionTree
class BinaryOperation
attr_reader :operator
attr_reader :left
attr_reader :right
def initialize(operator, left, right)
@operator = operator
@left = left
@right = right
end
def build(expression)
@left.build(expression)
@right.build(expression)
expression.append_operator(@operator, 2)
end
RANGE_OPERATORS = [
Operator::LESS,
Operator::GREATER,
Operator::LESS_EQUAL,
Operator::GREATER_EQUAL,
]
def estimate_size(table)
case @operator
when *RANGE_OPERATORS
estimate_size_range(table)
else
table.size
end
end
private
def estimate_size_range(table)
return table.size unless @left.is_a?(Variable)
return table.size unless @right.is_a?(Constant)
column = @left.column
value = @right.value
index_info = column.find_index(@operator)
return table.size if index_info.nil?
index_column = index_info.index
lexicon = index_column.lexicon
options = {}
case @operator
when Operator::LESS
options[:max] = value
options[:flags] = TableCursorFlags::LT
when Operator::LESS_EQUAL
options[:max] = value
options[:flags] = TableCursorFlags::LE
when Operator::GREATER
options[:min] = value
options[:flags] = TableCursorFlags::GT
when Operator::GREATER_EQUAL
options[:min] = value
options[:flags] = TableCursorFlags::GE
end
TableCursor.open(lexicon, options) do |cursor|
index_column.estimate_size(:lexicon_cursor => cursor)
end
end
end
end
end
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