sqlite >= 3.8.0 supports partial indexes

activerecord/CHANGELOG.md

+*   Enable partial indexes for sqlite >= 3.8.0
+
+    See http://www.sqlite.org/partialindex.html
+
+    *Cody Cutrer*
+
 *   Don't try to get the subclass if the inheritance column doesn't exist
 
     The `subclass_from_attrs` method is called even if the column specified by

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -155,6 +155,10 @@ def supports_savepoints?
         true
       end
 
+      def supports_partial_index?
+        sqlite_version >= '3.8.0'
+      end
+
       # Returns true, since this connection adapter supports prepared statement
       # caching.
       def supports_statement_cache?
@@ -397,13 +401,25 @@ def columns(table_name) #:nodoc:
       # Returns an array of indexes for the given table.
       def indexes(table_name, name = nil) #:nodoc:
         exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", 'SCHEMA').map do |row|
+          sql = <<-SQL
+            SELECT sql
+            FROM sqlite_master
+            WHERE name=#{quote(row['name'])} AND type='index'
+            UNION ALL
+            SELECT sql
+            FROM sqlite_temp_master
+            WHERE name=#{quote(row['name'])} AND type='index'
+          SQL
+          index_sql = exec_query(sql).first['sql']
+          match = /\sWHERE\s+(.+)$/i.match(index_sql)
+          where = match[1] if match
           IndexDefinition.new(
             table_name,
             row['name'],
             row['unique'] != 0,
             exec_query("PRAGMA index_info('#{row['name']}')", "SCHEMA").map { |col|
               col['name']
-            })
+            }, nil, nil, where)
         end
       end
 

activerecord/test/cases/schema_dumper_test.rb

@@ -190,6 +190,8 @@ def test_schema_dumps_partial_indices
       assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", where: "(rating > 10)", using: :btree', index_definition
     elsif current_adapter?(:MysqlAdapter) || current_adapter?(:Mysql2Adapter)
       assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", using: :btree', index_definition
+    elsif current_adapter?(:SQLite3Adapter) && ActiveRecord::Base.connection.supports_partial_index?
+      assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index", where: "rating > 10"', index_definition
     else
       assert_equal 'add_index "companies", ["firm_id", "type"], name: "company_partial_index"', index_definition
     end