postgres中的jsonb aggegation选择查询

Question

鉴于下表：

# create table thing (id serial, tags jsonb);
# \d thing
                         Table "public.thing"
 Column |  Type   |                     Modifiers                      
--------+---------+----------------------------------------------------
 id     | integer | not null default nextval('thing_id_seq'::regclass)
 tags   | jsonb   | 

......以及以下数据：

insert into thing (tags) values ('{"tag1": ["val1", "val2"], "tag2": ["t2val1"]}');
insert into thing (tags) values ('{"tag1": ["val3", "val1"], "tag2": ["t2val1"]}');
insert into thing (tags) values ('{"tag1": ["val2", "val1"], "tag2": ["t2val2"]}');

如何聚合等同于“向我显示匹配行数和tag1值tag2值t2val1的查询结果？< / p>

我能得到的结果是：

# select count(*), json_agg(tags) from thing where tags->'tag2'?'t2val1';
 count |                                             json_agg                                             
-------+--------------------------------------------------------------------------------------------------
     2 | [{"tag1": ["val1", "val2"], "tag2": ["t2val1"]}, {"tag1": ["val3", "val1"], "tag2": ["t2val1"]}]
(1 row)

......但我真的想要：

 count |     tag1                                             
-------+-------------------------
     2 | ["val1", "val2", "val3"]
(1 row)