Question

我有一个表，它将数据存储在JSONB列中。

现在，我想要做的是，查询该表，并获取具有密钥特定值的记录。

这很好用：

SELECT "documents".*
FROM "documents"
WHERE (data @> '{"type": "foo"}')

但我想要做的是，获取表格中的所有行，这些行的类型为foo或bar。

我试过了：

SELECT "documents".*
FROM "documents"
WHERE (data @> '{"type": ["foo", "bar"]}')

但这似乎不起作用。

我也试过这个：

SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar'])

哪个有效，但是如果我指定一个像data->'type'这样的键，它就会消除查询的动态性。

BTW，我正在使用带有Postgres的Ruby on Rails，因此所有查询都通过ActiveRecord。这是如何：

Document.where("data @> ?", query)

Answer 1

如果我指定一个像这样的数据键 - ＆gt;＆＃39;键入＆＃39;它消除了查询的动态性。

我知道您在列data上有一个杜松子酒索引，如下所示：

CREATE INDEX ON documents USING GIN (data);

索引适用于此查询：

EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data @> '{"type": "foo"}';

                                                          QUERY PLAN                                                          
------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on documents  (cost=30.32..857.00 rows=300 width=25) (actual time=0.639..0.640 rows=1 loops=1)
   Recheck Cond: (data @> '{"type": "foo"}'::jsonb)
   Heap Blocks: exact=1
   ->  Bitmap Index Scan on documents_data_idx  (cost=0.00..30.25 rows=300 width=0) (actual time=0.581..0.581 rows=1 loops=1)
         Index Cond: (data @> '{"type": "foo"}'::jsonb)
 Planning time: 7.928 ms
 Execution time: 0.841 ms

但不是这个：

EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar']);

                                                QUERY PLAN                                                 
-----------------------------------------------------------------------------------------------------------
 Seq Scan on documents  (cost=0.00..6702.98 rows=300 width=25) (actual time=31.895..92.813 rows=2 loops=1)
   Filter: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
   Rows Removed by Filter: 299997
 Planning time: 1.836 ms
 Execution time: 92.839 ms

解决方案1.使用运算符@>两次，索引将用于两个条件：

EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data @> '{"type": "foo"}'
OR data @> '{"type": "bar"}';

                                                             QUERY PLAN                                                             
------------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on documents  (cost=60.80..1408.13 rows=600 width=25) (actual time=0.222..0.233 rows=2 loops=1)
   Recheck Cond: ((data @> '{"type": "foo"}'::jsonb) OR (data @> '{"type": "bar"}'::jsonb))
   Heap Blocks: exact=2
   ->  BitmapOr  (cost=60.80..60.80 rows=600 width=0) (actual time=0.204..0.204 rows=0 loops=1)
         ->  Bitmap Index Scan on documents_data_idx  (cost=0.00..30.25 rows=300 width=0) (actual time=0.144..0.144 rows=1 loops=1)
               Index Cond: (data @> '{"type": "foo"}'::jsonb)
         ->  Bitmap Index Scan on documents_data_idx  (cost=0.00..30.25 rows=300 width=0) (actual time=0.059..0.059 rows=1 loops=1)
               Index Cond: (data @> '{"type": "bar"}'::jsonb)
 Planning time: 3.170 ms
 Execution time: 0.289 ms

解决方案2.在(data->'type')：

上创建其他索引

CREATE INDEX ON documents USING GIN ((data->'type'));

EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar']);

                                                          QUERY PLAN                                                          
------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on documents  (cost=30.32..857.75 rows=300 width=25) (actual time=0.056..0.067 rows=2 loops=1)
   Recheck Cond: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
   Heap Blocks: exact=2
   ->  Bitmap Index Scan on documents_expr_idx  (cost=0.00..30.25 rows=300 width=0) (actual time=0.035..0.035 rows=2 loops=1)
         Index Cond: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
 Planning time: 2.951 ms
 Execution time: 0.108 ms

解决方案3.实际上，这是解决方案1的变体，具有不同的条件格式，客户端程序可能更方便使用：

EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data @> any(array['{"type": "foo"}', '{"type": "bar"}']::jsonb[]);

                                                          QUERY PLAN                                                          
------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on documents  (cost=60.65..1544.20 rows=600 width=26) (actual time=0.803..0.819 rows=2 loops=1)
   Recheck Cond: (data @> ANY ('{"{\"type\": \"foo\"}","{\"type\": \"bar\"}"}'::jsonb[]))
   Heap Blocks: exact=2
   ->  Bitmap Index Scan on documents_data_idx  (cost=0.00..60.50 rows=600 width=0) (actual time=0.778..0.778 rows=2 loops=1)
         Index Cond: (data @> ANY ('{"{\"type\": \"foo\"}","{\"type\": \"bar\"}"}'::jsonb[]))
 Planning time: 2.080 ms
 Execution time: 0.304 ms
(7 rows)

在the documentation中阅读更多内容。

使用JSONB数据查询Postgres表

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