フィルタリング時に同じフィールドを使用すると、実行時間が異なるのはなぜですか？ （異なるインデックスの使用法）

問題の回避策として、さらにSELECTを実行できます。 PARTITION BYで使用される列のエイリアス 表現。次に、PGは最適化を適用し、インデックスを使用します。

質問に対する答えは次のようになります。複合タイプが使用されている場合、PGは最適化を適用しません 。動作することに注意してください：

PARTITION | FILTER | IS USED?
------------------------------
ALIAS     | ORIG   | NO
ALIAS     | ALIAS  | YES
ORIG      | ALIAS  | NO
ORIG      | ORIG   | NO

このdbfiddle を参照してください。

create table agreement ( ag_id int, name text, cost numeric(10,2) );
create index ag_idx on agreement (ag_id);
insert into agreement (ag_id, name, cost) values ( 1, '333', 22 ),
(1,'333', 33), (1, '333', 7), (2, '555', 18 ), (2, '555', 2), (3, '777', 4);
select * from agreement;

create function initial () 
returns table( agreement_id int, ag agreement ) language sql stable AS $$
select ag_id, t from agreement t;
$$;
select * from initial() t;

explain( analyze, costs, buffers, verbose ) with totals_by_ag as (
  select 
    *,
    sum( (t.ag).cost ) over ( partition by agreement_id ) as total
  from initial() t
)
select * from totals_by_ag t
where (t.ag).ag_id = 1; -- index is NOT USED

explain( analyze, costs, buffers, verbose ) with totals_by_ag as (
  select 
    *,
    sum( (t.ag).cost ) over ( partition by agreement_id ) as total
  from initial() t
)
select * from totals_by_ag t
where agreement_id = 1; -- index is used when alias for column is used

explain( analyze, costs, buffers, verbose ) with totals_by_ag as (
  select 
    *,
    sum( (t.ag).cost ) over ( partition by (t.ag).ag_id ) as total --renamed
  from initial() t
)
select * from totals_by_ag t
where agreement_id = 1; -- index is NOT USED because grouping by original column

explain( analyze, costs, buffers, verbose ) with totals_by_ag as (
  select 
    *,
    sum( (t.ag).cost ) over ( partition by (t.ag).ag_id ) as total --renamed
  from initial() t
)
select * from totals_by_ag t
where (t.ag).ag_id = 1; -- index is NOT USED even if at both cases original column