Add only option to add_index in PostgreSQL

Author: KirIgor

lib/sequel/adapters/shared/postgres.rb

@@ -1757,7 +1757,7 @@ def index_definition_sql(table_name, index)
           index_type = :gist
         end
 
-        "CREATE #{unique}INDEX#{' CONCURRENTLY' if index[:concurrently]}#{if_not_exists} #{quote_identifier(index_name)} ON #{quote_schema_table(table_name)} #{"USING #{index_type} " if index_type}#{expr}#{" INCLUDE #{literal(Array(index[:include]))}" if index[:include]}#{nulls_distinct}#{" TABLESPACE #{quote_identifier(index[:tablespace])}" if index[:tablespace]}#{filter}"
+        "CREATE #{unique}INDEX#{' CONCURRENTLY' if index[:concurrently]}#{if_not_exists} #{quote_identifier(index_name)} ON#{' ONLY' if index[:only]} #{quote_schema_table(table_name)} #{"USING #{index_type} " if index_type}#{expr}#{" INCLUDE #{literal(Array(index[:include]))}" if index[:include]}#{nulls_distinct}#{" TABLESPACE #{quote_identifier(index[:tablespace])}" if index[:tablespace]}#{filter}"
       end
 
       # Setup datastructures shared by all postgres adapters.

lib/sequel/database/schema_generator.rb

@@ -299,6 +299,7 @@ def has_column?(name)
       # :opclass :: Set an opclass to use for all columns (per-column opclasses require
       #             custom SQL).
       # :tablespace :: Specify tablespace for index.
+      # :only :: Create index only for given table, not for any child tables (PostgreSQL 11+)
       #
       # Microsoft SQL Server specific options:
       #

spec/adapters/postgres_spec.rb

@@ -1641,6 +1641,15 @@ def before_create
     @db.add_index :atest, :a, :tablespace=>:pg_default
   end
 
+  it "should support creating indexes with ONLY option" do
+    @db.create_table(:atest, partition_by: :id, :partition_type=>:range){Integer :id}
+    @db.create_table(:btest, partition_of: :atest){from 1; to 3}
+    @db.add_index :atest, :id, :only=>true
+
+    @db.indexes(:atest, :include_invalid=>true).size.must_equal 1
+    @db.indexes(:btest, :include_invalid=>true).must_be_empty
+  end if DB.server_version >= 110000
+
   it "#lock should lock table if inside a transaction" do
     @db.transaction{@d.lock('EXCLUSIVE'); @d.insert(:name=>'a')}
   end