1 files changed, 54 insertions, 0 deletions
diff --git a/storage/mroonga/vendor/groonga/lib/mrb/scripts/expression_size_estimator.rb b/storage/mroonga/vendor/groonga/lib/mrb/scripts/expression_size_estimator.rb
new file mode 100644
index 00000000..597b56f9
--- /dev/null
+++ b/storage/mroonga/vendor/groonga/lib/mrb/scripts/expression_size_estimator.rb
@@ -0,0 +1,54 @@
+module Groonga
+  class ExpressionSizeEstimator
+    def initialize(expression, table)
+      @expression = expression
+      @table = table
+      @table_size = @table.size
+    end
+
+    def estimate
+      builder = ScanInfoBuilder.new(@expression, Operator::OR, false)
+      data_list = builder.build
+      return @table_size if data_list.nil?
+
+      current_size = 0
+      sizes = []
+      data_list.each do |data|
+        if (data.flags & ScanInfo::Flags::POP) != 0
+          size = sizes.pop
+          case data.logical_op
+          when Operator::AND, Operator::AND_NOT
+            current_size = size if size < current_size
+          when Operator::OR
+            current_size = size if size > current_size
+          else
+            message = "invalid logical operator: <#{data.logical_op.inspect}>"
+            raise InvalidArgument, message
+          end
+        else
+          if (data.flags & ScanInfo::Flags::PUSH) != 0
+            sizes.push(current_size)
+            current_size = 0
+          end
+
+          estimator = ScanInfoDataSizeEstimator.new(data, @table)
+          size = estimator.estimate
+          case data.logical_op
+          when Operator::AND
+            current_size = size if size < current_size
+          when Operator::AND_NOT
+            size = @table_size - size
+            size = 0 if size < 0
+            current_size = size if size < current_size
+          when Operator::OR
+            current_size = size if size > current_size
+          else
+            message = "invalid logical operator: <#{data.logical_op.inspect}>"
+            raise InvalidArgument, message
+          end
+        end
+      end
+      current_size
+    end
+  end
+end