sql - 用JSONB数据查询Postgres表

我有一个表，它将数据存储在JSONB列中。
现在，我要做的是查询该表，并获取记录，这些记录具有特定的键值。
这很管用：

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

但我想做的是，获取表中所有类型为foo或bar的行。
我试过这个：

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

但这似乎行不通。
我也试过：

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

这很有效，但是如果我指定一个类似于sodata->'type'的键，它会带走查询的动态性。
顺便说一句，我在Postgres中使用Ruby on Rails，所以所有的查询都要经过ActiveRecord。这就是为什么：

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

最佳答案

如果我指定了一个像so data这样的键->'type'，它将带走查询的动态性。
我知道您在列data上有一个gin索引，定义如下：

CREATE INDEX ON documents USING GIN (data);

索引可用于此查询：

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

但这次不行：

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，索引将用于以下两种情况：

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')上创建附加索引：

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。事实上，这是解决方案1的一个变体，其条件的格式不同，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。