Add MySQL 8.0 support

lib/relationizer/mysql.rb

@@ -0,0 +1,34 @@
+require 'json'
+require 'bigdecimal'
+require 'date'
+
+module Relationizer
+  module MySQL
+    class ReasonlessTypeError < StandardError; end
+    # @param schema Hash
+    # @param tuples Array<Array>
+    # for example
+    # create_relation_literal({a: :INT}, [[1]])
+    # => "(SELECT * FROM JSON_TABLE('[{"a":1}]', "$[*]" COLUMNS(a INT PATH "$.a")) AS t)"
+    def create_relation_literal(schema, tuples)
+      json = to_json(schema, tuples)
+      schema_for_table = to_schema_for_table(schema, tuples)
+      "(SELECT * FROM JSON_TABLE('#{json}', #{schema_for_table}) AS t)"
+    end
+
+    private
+
+    def to_json(schema, tuples)
+      tuples.map { |tuple|
+        schema.keys.zip(tuple).to_h
+      }.to_json
+    end
+
+    def to_schema_for_table(schema, tuples)
+      columns = schema.map { |name, type|
+        %[#{name} #{type} PATH "$.#{name}"]
+      }.join(',')
+      %["$[*]" COLUMNS(#{columns})]
+    end
+  end
+end