postgresql – 在JOIN中不在两列上同时使用gin

我在两个表中使用GIN索引在两列中进行ILIKE匹配,但仅当我在一列上执行ILIKE时才使用GIN.

我通过UNION做了一个解决方法,但我想知道它为什么不能像我认为的那样工作.

两个列,n.name和e.producer都是VARCHAR,它们上面有GIN索引：

CREATE INDEX products_producer_gin_idx ON products USING gin (producer gin_trgm_ops);
CREATE INDEX products_names_name_gin_idx ON products_names USING gin (name gin_trgm_ops);

SELECT with JOIN and ILIKE which does not use GIN:

testdb=# explain (analyze,verbose) 
            SELECT n.name,e.producer
            FROM products e
            INNER JOIN products_names n ON 
                n.product_id = e.product_id

            WHERE

                    n.name ilike '%eda%' or e.producer ilike '%eda%' 


limit 20;
                                                                                 QUERY PLAN                                                                                 
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.42..2725.92 rows=20 width=60) (actual time=0.582..62.658 rows=20 loops=1)
   Output: n.name,e.producer
   ->  Nested Loop  (cost=0.42..669928.73 rows=4916 width=60) (actual time=0.582..62.652 rows=20 loops=1)
         Output: n.name,e.producer
         ->  Seq Scan on public.products e  (cost=0.00..220800.16 rows=446716 width=29) (actual time=0.002..5.363 rows=17067 loops=1)
               Output: e.producer,e.product_id
         ->  Index Scan using products_names_pkey on public.products_names n  (cost=0.42..1.00 rows=1 width=39) (actual time=0.003..0.003 rows=0 loops=17067)
               Output: n.product_id,n.lang,n.name,n.name2,n.name3,n.products
               Index Cond: (n.product_id = e.product_id)
               Filter: (((n.name)::text ~~* '%eda%'::text) OR ((e.producer)::text ~~* '%eda%'::text))
               Rows Removed by Filter: 1
 Planning time: 0.559 ms
 Execution time: 62.677 ms
(13 Zeilen)

Zeit: 63,529 ms

SELECT on a single column n.name which uses GIN:

testdb=# explain (analyze,verbose)
            SELECT n.name,e.producer
            FROM products e
            INNER JOIN products_names n ON 
                n.product_id = e.product_id

            WHERE

                    n.name ilike '%eda%'                   

limit 20;
                                                                         QUERY PLAN                                                                          
-------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=58.34..260.70 rows=20 width=60) (actual time=0.257..0.458 rows=20 loops=1)
   Output: n.name,e.producer
   ->  Nested Loop  (cost=58.34..49564.37 rows=4893 width=60) (actual time=0.256..0.454 rows=20 loops=1)
         Output: n.name,e.producer
         ->  Bitmap Heap Scan on public.products_names n  (cost=57.92..14890.29 rows=4893 width=39) (actual time=0.245..0.333 rows=20 loops=1)
               Output: n.product_id,n.products
               Recheck Cond: ((n.name)::text ~~* '%eda%'::text)
               Heap Blocks: exact=18
               ->  Bitmap Index Scan on products_names_name_gin_idx  (cost=0.00..56.70 rows=4893 width=0) (actual time=0.160..0.160 rows=797 loops=1)
                     Index Cond: ((n.name)::text ~~* '%eda%'::text)
         ->  Index Scan using products_pkey on public.products e  (cost=0.42..7.08 rows=1 width=29) (actual time=0.005..0.006 rows=1 loops=20)
               Output: e.producer,e.product_id
               Index Cond: (e.product_id = n.product_id)
 Planning time: 1.000 ms
 Execution time: 0.494 ms
(15 Zeilen)

Zeit: 2,563 ms