Merge pull request #69 from dcluna/temp-table-copy

Temp table convenience method

Author: diogob

README.md

@@ -1,4 +1,4 @@
-# postgres-copy 
+# postgres-copy
 
 ![Ruby](https://github.com/diogob/postgres-copy/workflows/Ruby/badge.svg)
 
@@ -207,6 +207,19 @@ This is useful for removing byte order marks when matching column headers.
 User.copy_from "/tmp/users_with_byte_order_mark.csv", :encoding => 'bom|utf-8'
 ```
 
+### Using PostgresCopy::WithTempTable.generate
+
+Based on [nfedyashev](https://github.com/nfedyashev)'s [comment](https://github.com/diogob/postgres-copy/issues/51):
+
+```ruby
+    PostgresCopy::WithTempTable.generate do |t|
+      columns.each do |column_name|
+        t.string column_name.to_sym
+      end
+    end
+```
+
+This auto-generates an id column, but the temp table creation is configurable.
 
 ### Using the CSV Responder
 If you want to make the result of a COPY command available to download this gem provides a CSV responder that, in conjunction with [inherited_resources](https://github.com/josevalim/inherited_resources), is a very powerfull tool. BTW, do not try to use the responder without inherited_resources.

lib/postgres-copy/with_temp_table.rb

@@ -0,0 +1,18 @@
+module PostgresCopy
+  module WithTempTable
+    def self.generate(connection = ActiveRecord::Base.connection, base_klass:
+      ActiveRecord::Base, temp_table_name: nil, create_table_opts: {id: :bigint})
+      raise "You have to pass a table schema definition block!" unless block_given?
+      table_name = temp_table_name || "temp_table_#{SecureRandom.hex}"
+
+      connection.create_table table_name, temporary: true, **create_table_opts do |t|
+        yield t
+      end
+
+      klass = Class.new(base_klass) do
+        acts_as_copy_target
+        self.table_name = table_name
+      end
+    end
+  end
+end

spec/postgres-copy/with_temp_table_spec.rb

@@ -0,0 +1,17 @@
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
+require 'postgres-copy/with_temp_table'
+
+describe '.generate' do
+  subject(:generate) {
+    PostgresCopy::WithTempTable.generate do |t|
+      t.string :data
+    end
+  }
+
+  it {
+    generate.copy_from 'spec/fixtures/comma_with_header.csv'
+    data = generate.all.first
+    expect(data.id).to eq(1)
+    expect(data.data).to eq('test data 1')
+  }
+end