FIX: Correct ids if neccessary (#65)

Migration to fix data ids if the old version of previous migration was
evaluated.

db/migrate/20200902225712_fix_query_ids.rb

@@ -0,0 +1,104 @@
+class FixQueryIds < ActiveRecord::Migration[6.0]
+  def up
+    ActiveRecord::Base.transaction do
+      # Only queries with unique title can be fixed
+      movements = DB.query <<-SQL
+      SELECT deq.id AS from, (replace(plugin_store_rows.key, 'q:',''))::integer AS to
+      FROM plugin_store_rows
+      INNER JOIN data_explorer_queries deq ON deq.name = plugin_store_rows.value::json->>'name'
+      WHERE
+        (replace(plugin_store_rows.key, 'q:',''))::integer != deq.id AND
+        plugin_store_rows.plugin_name = 'discourse-data-explorer' AND
+        plugin_store_rows.type_name = 'JSON' AND
+        (SELECT COUNT(*) from data_explorer_queries deq2 WHERE deq.name = deq2.name) = 1
+      SQL
+
+      return if movements.blank?
+
+      # If there are new queries, they still may have conflict
+      # We just want to move their ids to safe space and we will not move them back
+      additional_conflicts = DB.query(<<~SQL, from: movements.map{ |m| m.from }, to: movements.map { |m| m.to } ).map { |conflict| conflict.id }
+        SELECT id FROM data_explorer_queries
+        WHERE id IN (:to)
+        AND id NOT IN (:from)
+      SQL
+
+      DB.exec <<-SQL
+        CREATE TEMPORARY TABLE tmp_data_explorer_queries(
+          id INTEGER PRIMARY KEY,
+          name VARCHAR,
+          description TEXT,
+          sql TEXT,
+          user_id INTEGER,
+          last_run_at TIMESTAMP,
+          hidden BOOLEAN,
+          created_at TIMESTAMP,
+          updated_at TIMESTAMP
+        )
+      SQL
+
+
+
+      movements.each do |movement|
+        # insert moved and conflict queries to temporary table
+        DB.exec <<-SQL
+          INSERT INTO tmp_data_explorer_queries(id, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at)
+          SELECT #{movement.to}, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at
+          FROM data_explorer_queries
+          WHERE id = #{movement.from}
+        SQL
+      end
+
+      # insert rest to temporary table
+      DB.exec(<<-SQL, already_moved_ids: movements.map(&:from) | additional_conflicts)
+        INSERT INTO tmp_data_explorer_queries(id, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at)
+        SELECT id, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at
+        FROM data_explorer_queries
+        WHERE id NOT IN (:already_moved_ids)
+      SQL
+
+      # insert additional_conflicts to temporary table
+      new_id = DB.query("select max(id) from tmp_data_explorer_queries").first.max + 1
+      additional_conflicts.each do |conflict_id|
+        DB.exec <<-SQL
+          INSERT INTO tmp_data_explorer_queries(id, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at)
+          SELECT #{new_id}, name, description, sql, user_id, last_run_at, hidden, created_at, updated_at
+          FROM data_explorer_queries
+          WHERE id = #{conflict_id}
+        SQL
+        DB.exec <<~SQL
+          UPDATE data_explorer_query_groups
+          SET query_id = #{new_id}
+          WHERE query_id= #{conflict_id}
+        SQL
+        new_id = new_id + 1
+      end
+
+      movements.each do |movement|
+        # update group ids for moved queries
+        DB.exec(<<~SQL, to: movement.to, from: movement.from)
+          UPDATE data_explorer_query_groups
+          SET query_id = :to
+          WHERE query_id= :from
+        SQL
+      end
+
+      # clear original table and copy data from temporary table
+      DB.exec("DELETE FROM data_explorer_queries")
+      DB.exec("INSERT INTO data_explorer_queries SELECT * FROM tmp_data_explorer_queries")
+
+      # Update id sequence
+      DB.exec <<~SQL
+        SELECT
+          setval(
+            pg_get_serial_sequence('data_explorer_queries', 'id'),
+            (select max(id) from data_explorer_queries)
+          );
+      SQL
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end