何时使用多列索引？

Question

我有下表约1000万行

CREATE TABLE "autocomplete_books"
(
    id uuid PRIMARY KEY DEFAULT uuid_generate_v4 (),
    author_id uuid NOT NULL REFERENCES "author"(id) ON DELETE CASCADE,
    language VARCHAR(30) NOT NULL,
    name VARCHAR(100) NOT NULL,
    importance_rank SMALLINT NOT NULL DEFAULT 1
);

我有以下查询

SELECT DISTINCT ON (author_id)
    author_id,
    similarity(name, $1) as score,
    language, name, importance_rank
FROM
    "autocomplete_books"
WHERE
    $1 % name AND language IN ($2, $3, $4)
ORDER BY
    author_id, score DESC, importance_rank DESC
LIMIT
    10

我主要是在查询相似性,因为这是一个自动完成端点,所以我在名字上有一个trigram索引.我也在其他一些领域进行排序.我不确定该score字段将如何与我的其他索引混合以及是否更好地拥有这样的复合索引

选项1

CREATE INDEX ON "autocomplete_books" USING GIN (name gin_trgm_ops);
CREATE INDEX ON "autocomplete_books" USING BTREE (author_id, language, importance_rank DESC);

或者,如果我应该这样打破它们

选项2

CREATE INDEX ON "autocomplete_books" USING GIN (name gin_trgm_ops);
CREATE INDEX ON "autocomplete_books" USING BTREE (author_id, language, importance_rank DESC);
CREATE INDEX ON "autocomplete_books" USING BTREE (language);
CREATE INDEX ON "autocomplete_books" USING BTREE (importance_rank DESC);

---

以下是explain analyze使用以下索引在220k行上运行的输出

CREATE INDEX ON "autocomplete_books" USING BTREE (author_id, language);
CREATE INDEX ON "autocomplete_books" USING BTREE (importance_rank DESC);

-

Limit  (cost=762.13..762.38 rows=50 width=82) (actual time=12.230..13.024 rows=50 loops=1)
  ->  Unique  (cost=762.13..763.23 rows=217 width=82) (actual time=12.223..12.686 rows=50 loops=1)
        ->  Sort  (cost=762.13..762.68 rows=220 width=82) (actual time=12.216..12.373 rows=50 loops=1)
              Sort Key: author_id, ((similarity((name)::text, \'sale\'::text)) DESC, importance_rank DESC
              Sort Method: quicksort  Memory: 45kB
              ->  Bitmap Heap Scan on "books_autocomplete" mat  (cost=45.71..753.57 rows=220 width=82) (actual time=1.905..11.610 rows=149 loops=1)
                    Recheck Cond: (\'sale\'::text % (name)::text)
                    Rows Removed by Index Recheck: 2837
                    Filter: ((language)::text = ANY (\'{language1,language2,language3}\'::text[]))
                    Heap Blocks: exact=2078
                    ->  Bitmap Index Scan on "books_autocomplete_name_idx"  (cost=0.00..45.65 rows=220 width=0) (actual time=1.551..1.557 rows=2986 loops=1)
                          Index Cond: (\'sale\'::text % (name)::text)
Planning time: 13.976 ms
Execution time: 13.545 ms'