Support (current|system|valid)_time for selects and inserts

Author: eval

lib/sequel/adapters/shared/xtdb.rb

@@ -9,9 +9,96 @@ def primary_key(_table)
         # eg used for RETURNING on insert (prevents crash)
         :_id
       end
+
+      # Get a dataset with `current`, `valid` and `system` set.
+      #
+      # For selects this creates the SETTING pre-amble, e.g. 'SETTING DEFAULT VALID_TIME ...':
+      # ```
+      # DB.as_of(current: 2.weeks.ago).select(Sequel.lit('current_timestamp')).single_value
+      # ```
+      #
+      # A block can be provided as a convenience to stay in SQL-land (selects only):
+      # ```
+      # DB.as_of(current: 2.hours.ago) do
+      #   DB["select current_timestamp"]
+      # end.sql
+      # =>
+      # SETTING
+      #  CURRENT_TIME TO TIMESTAMP '2024-12-17T12:59:48+01:00'
+      # select current_timestamp
+      # ```
+      #
+      # When doing inserts, the `_valid_from` will be added (if not provided):
+      # ```
+      # DB[:products].as_of(valid: 2.weeks.ago).insert(_id: 1, name: 'Spam')
+      # ```
+      def as_of(...)
+        ds = @default_dataset.as_of(...)
+        return ds unless block_given?
+
+        yield.clone(append_sql: ds.select_setting_sql(""))
+      end
     end
 
     module DatasetMethods
+      Dataset.def_sql_method(self, :select,
+        [["if opts[:values]",
+          %w[values compounds order limit]],
+          ["else",
+            %w[setting select distinct columns from join where group having compounds order limit lock]]])
+
+      def as_of(valid: nil, system: nil, current: nil)
+        {valid: valid, system: system, current: current}.reject { |_k, v| v.nil? }.then do |opts|
+          clone(opts)
+        end
+      end
+
+      def server_version
+        0
+      end
+
+      def insert_values_sql(sql)
+        if (from_ix = opts[:columns].index(:_valid_from))
+          opts[:values][from_ix] = Sequel.lit("TIMESTAMP ?", opts[:values][from_ix])
+        end
+
+        if (to_ix = opts[:columns].index(:_valid_to))
+          opts[:values][to_ix] = Sequel.lit("TIMESTAMP ?", opts[:values][to_ix])
+        end
+
+        super
+      end
+
+      def insert_columns_sql(sql)
+        if opts[:valid] && !opts[:columns].index(:_valid_from)
+          opts[:columns] << :_valid_from
+          opts[:values] << opts[:valid]
+        end
+        super
+      end
+
+      def select_setting_sql(sql)
+        setting = opts.slice(:current, :valid, :system)
+        return sql if setting.empty?
+
+        cast_value = ->(v) do
+          case v
+          when DateTime, Time
+            literal_append "TIMESTAMP ", v.iso8601
+          when Date
+            literal_append "DATE ", v.iso8601
+          end
+        end
+        sql << "SETTING "
+        sql << setting.map do |k, v|
+          if k == :current
+            literal_append "CURRENT_TIME TO TIMESTAMP ", v.iso8601
+          else
+            "DEFAULT #{k.upcase}_TIME AS OF #{cast_value[v]}"
+          end
+        end.join(", ")
+        sql << " "
+      end
     end
   end
 end