change ActiveRecord joins query with custom generated SQL

lib/pg_searchable_regex.rb

@@ -55,8 +55,16 @@ module PgSearchable
 
     def ts_search(value)
       return if @ts_search_fields.blank? || value.blank?
-      includes(@ts_joins).references(:all).where(
-        TextToSqlQuery.new(value, @ts_search_fields, @default_fields, @ts_search_fields_mappings).where_clause).distinct
+      model = ancestors.first
+      sql_query_object = TextToSqlQuery.new(
+        value,
+        @ts_search_fields,
+        @default_field,
+        @ts_search_fields_mappings,
+        @ts_joins,
+        model
+      )
+      joins(sql_query_object.join_clause).where(sql_query_object.where_clause).distinct
     end
 
     def should_update_cache_field?

lib/text_to_sql_query.rb

@@ -1,7 +1,7 @@
 require_relative 'parser'
 
 class TextToSqlQuery
-  def initialize(text, fields, default_fields, fields_mappings = {})
+  def initialize(text, fields, default_fields, fields_mappings = {}, joins = [], model = nil)
     @text = text.to_s.strip
     @fields = fields.map(&:to_sym)
 
@@ -20,6 +20,8 @@ class TextToSqlQuery
     fields_mappings.each do |field, value|
       @fields_mappings[field] = value if @fields_mappings[field]
     end
+    @joins = joins
+    @model = model
   end
 
   def where_clause
@@ -28,6 +30,20 @@ class TextToSqlQuery
     generate_sql @parsed_tree
   end
 
+  def join_clause
+    return if @joins.empty?
+
+    table_column_mappings
+    model_association_mappings
+
+    join_clause_part = ''
+    @joins.each do |join|
+      join_sql_part = generate_join_sql_part_for join
+      join_clause_part += join_sql_part
+    end
+    join_clause_part
+  end
+
   private
 
   def generate_sql(tree)
@@ -104,4 +120,50 @@ class TextToSqlQuery
     result.gsub!(/%/, '\%')
     result
   end
+
+  def table_column_mappings
+    @table_column_mappings = {}
+    @fields_mappings.each_value do |table_with_column|
+      split_names = table_with_column.to_s.split '.'
+      table_name = split_names.first
+      column_name = split_names.second
+      @table_column_mappings[table_name] = [] if @table_column_mappings[table_name].nil?
+      @table_column_mappings[table_name] << column_name
+    end
+    @table_column_mappings
+  end
+
+  def model_association_mappings
+    @model_associations = {}
+    @model.reflect_on_all_associations.each do |association|
+      name = association.name
+
+      @model_associations[name] = {
+        option_as: association.options[:as] || name,
+        type: association.type
+      }
+    end
+    @model_associations
+  end
+
+  def generate_join_sql_part_for(join)
+    association_data = @model_associations[join]
+    join_table_name = join.to_s
+    raise "Join table #{join_table_name} has no association data" if association_data.nil?
+
+    select_sql_part = ''
+    columns_for_table = @table_column_mappings[join_table_name] || []
+
+    # TODO: Can be optimized - do not include columns that are not referenced in user query
+    columns_for_table.each do |column_name|
+      select_sql_part += "string_agg(#{column_name}, '') AS #{column_name}, "
+    end
+
+    option_as = association_data[:option_as]
+    type = association_data[:type]
+    model_name = @model.to_s
+    table_name = @model.table_name
+
+    "LEFT JOIN (SELECT #{option_as}_id, #{select_sql_part} #{type} FROM #{join_table_name} GROUP BY #{option_as}_id, #{type}) #{join_table_name} on #{join_table_name}.#{option_as}_id = #{table_name}.id AND #{join_table_name}.#{type} = '#{model_name}'"
+  end
 end