zombodb 低级api 操作

zombodb 低级api 允许直接从zombodb 索引中进行insert、delete 文档，同时保留了mvcc 的特性，但是数据没有存储在
pg 中，但是也带来数据上的风险，我们需要注意进行es 数据的备份

api 说明

FUNCTION zdb.llapi_direct_insert(index_name regclass, data json) RETURNS void
FUNCTION zdb.llapi_direct_delete(index_name regclass, _id text) RETURNS void

参考例子

这是一个审计日志的功能，数据直接到es 中，而不用存储在pg 中

表创建

CREATE TABLE audit (
 id serial8 NOT NULL PRIMARY KEY,
 action_type char(2),
 username varchar(64),
 when_happened timestamp DEFAULT now(),
 description text
);

索引创建

CREATE INDEX idxaudit 
              ON audit 
           USING zombodb ((audit.*)) 
           WITH (llapi=true,url='http://elasticsearch:9200/');

创建rule
进行数据操作的处理规则定义

      CREATE RULE audit_rule 
 AS ON INSERT TO audit 
      DO INSTEAD (
           SELECT zdb.llapi_direct_insert('idxaudit', to_json(NEW))
      );

数据添加操作

INSERT INTO audit (action_type, username, description) 
     VALUES ('aa', 'someuser', 'this is the first audit entry');
INSERT INTO audit (action_type, username, description) 
     VALUES ('qr', 'otheruser', 'this is the second audit entry');
INSERT INTO audit (action_type, username, description) 
     VALUES ('zy', 'anotheruser', 'this is the third audit entry');

数据查询

select * from audit;
数据为空，说明数据没有存储在pg 中

es 信息查看，从es 中可以看出数据都存储在es 中

使用zombodb api 查询数据
聚合查询

SELECT zdb.count('idxaudit', dsl.match_all()); count ;
-[ RECORD 1 ]
count | 3

记录查询

SELECT _id, 
       (source->>'id')::bigint AS id, 
       source->>'username' AS username, 
       source->>'action_type' AS action_type, 
       (source->>'when_happened')::timestamp AS timestamp, 
       source->>'description' AS description 
  FROM zdb.top_hits_with_id('idxaudit', ARRAY['*'], dsl.match_all(), 100);
[ RECORD 1 ]-------------------------------
_id | B8DQ22kBYb7kkl7X_khC
id | 2
username | otheruser
action_type | qr
timestamp | 2019-04-02 02:11:40.731217
description | this is the second audit entry
-[ RECORD 2 ]-------------------------------
_id | BsDQ22kBYb7kkl7X_khC
id | 1
username | someuser
action_type | aa
timestamp | 2019-04-02 02:11:40.731217
description | this is the first audit entry
-[ RECORD 3 ]-------------------------------
_id | CMDQ22kBYb7kkl7X_khC
id | 3
username | anotheruser
action_type | zy
timestamp | 2019-04-02 02:11:40.731217
description | this is the third audit entry