使用 JSONB 数据查询 Postgres Table

Question

我有一个 Table 将数据存储在 JSONB 列中。

现在，我想做的是，查询 table，并获取具有特定键值的记录。

这很好用：

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

但我想做的是，获取 table 中类型为 foo 或 bar.

的所有行

我试过这个：

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'])

这行得通，但是如果我像这样指定一个键 data->'type' 它会带走查询的动态性。

顺便说一句，我在 Rails 上使用 Ruby 和 Postgres，所以所有查询都通过 ActiveRecord。是这样的：

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

Answer 1

if I specify a key like so data->'type' it takes away the dynamicity of the query.

我了解到您在列 data 上有一个 gin 索引，定义如下：

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

解决方法 1. 两次使用运算符@>，两个条件都会使用索引：

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。实际上这是解决方案1的变体，条件格式不同，可能更方便客户端程序使用：

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 阅读更多内容。

使用 JSONB 数据查询 Postgres Table

Querying Postgres Table with JSONB data

sql

postgresql

indexing

ruby-on-rails

jsonb