LightDB 22.2正式发布

本版本主要特性包括：

1、引入实验性特性oracle pl/sql存储过程兼容，兼容绝大部分oracle pl/sql一份代码可以同时运行于oracle和lightdb

2、lightdb jdbc支持autocommit=true时，fetchsize生效

3、lightdb优化器提示进一步完善，且语义兼容oracle

4、原生分布式DDL语法，和greenplum一样

5、支持lightdb实时同步oracle，ltdts_recvlogical，详细使用后续文章专门更新。本版本TPS可到10000笔每秒，下个版本预计可到4-5万笔每秒。

6、lt_dump支持cascade，可极大的提高性能。

7、sysdate/systimestamp支持语句级一致性，oracle语义一致

8、merge into支持分布式版

9、支持龙芯cpu、rocky linux。

在最新版的性能测试中，单机TB级容量下，2.6k*2亿文档，lightdb全文检索性能高于es 6.x版本，且实时索引。在金融业务系统ETF TA、自建TA中，相同数据量、业务量下，某SZ头部公募基金性能选型测试中，lightdb性能远高于某base和某号称全自研的国产第一数据库。

目前，lightdb正在BJ绝对头部券商现场业务测试，SH、合肥中部券商业务测试。

详细特性如下：

E.1. Release 13.3-22.2

Release date: 2022-06-30

• Support patch for quick upgrade, see​​lt_patch​​.
• Add​​PL/oraSQL​​ loadable procedural language, see ​​plorasql​​
• ​​lt_hint_plan​​ Enhancements

• Add three new hints:​​use_hash​​,​​use_nl​​,​​full​​, semantics are consistent with Oracle.
• The table name in hint is case-insensitive.
• Hint​​parallel​​ default is hard and supports no table specification.
• Hints can be applied to the tables of the subquery when the subquery has only one table.

EXPLAIN (COSTS false) select /*+use_hash(t1 y)*/* from t1,(select * from t2) y where t1.id=y.id;

         QUERY PLAN             
------------------------------------
Hash Join
Hash Cond: (t1.id = t2.id)
->  Seq Scan on t1 @"lt#0"
->  Hash
        ->  Seq Scan on t2 @"lt#1"
(5 rows)

• Support User-defined type priority for better function and operator match, see​​type compatible​​.
• Support​​CREATE TABLE DISTRIBUTED BY​​ to create distribute table(depends on extension ​​canopy​​), see ​​CREATE TABLE​​.

create table dist1(a int, b int) distributed by hash(a) shard_count(4);

• ​​Auto-explain​​ execution plan logs are printed in a separate log file (*.slow) using JSON format.
• Add extension​​wal2sql​​ to support Real-time synchronization to Oracle.
• ​​lt_dump​​​ support ​​--recreate-schema​​ to generate drop schema(use ​​CASCADE​​ mode) command for better performance, see ​​lt_dump​​.
• ​​Client Applications​​​ and ​​libpq​​ Support ​​LightDB environment variables​​.
• ​​sysdate​​​and ​​systimestamp​​ indicates the statement start time.

lightdb@postgres=# begin;
BEGIN
lightdb@postgres=*# select sysdate from dual;
    sysdate       
---------------------
2022-06-28 19:44:15
(1 row)

lightdb@postgres=*# select sysdate from dual;
    sysdate       
---------------------
2022-06-28 19:44:16
(1 row)

lightdb@postgres=*# end;
COMMIT

For details, see ​​datetime​​.

• When install with​​high availability​​​, enable​​replication slot​​ default.
• Support Order-Preserving Encryption ,see​​lt_ope​​
• The following platform support is added:

• Add cluster control tool​​lightdb_service.py​​ to facilitate the overall start and stop of services in high availability and distributed environments.
  start cluster:

lightdb_service.py -c start

stop cluster:

lightdb_service.py -c stop

• The value 0 in PWR is display as empty, for details, see​​lt_profile​​.
• In non-distributed installation, the​​canopy​​ extension not installed.
• When​​keepalived​​​ and​​ltcluster​​ are restarted, new log files are generated to avoid confusion with old logs.
• ​​lt_initdb​​ does not restrict the order of options.
• Fix​​cannot assign XIDs during a parallel operation​​​ error occurs occasionally during parallel query in​​lt_show_plans​​.
• Release the JDBC driver library based on PostgreSQL.

• maven repository

<dependency>
    <groupId>io.github.hslightdb</groupId>
    <artifactId>lightdb-jdbc</artifactId>
    <version>42.2.30</version>
</dependency>

We fixed some of the issues and enhanced data type compatibility:

• fix：fetchSize does not take effect in automatic commit mode, causing the whole data to be loaded into the memory and causing out-of-memory problem.

• support oracle anonymous blocks syntax (see ​​plorasql​​ ).

• support ​​to_number()​​ function compatible with oracle.

• support ​​numeric​​ data type convert to Java Long.

• support ​​char(1)​​ data type convert to Java Character.

• fix loss of precision when Java setDouble operates on ​​numeric​​ field.

• ​​lt_cron​​ supports linux command.

SELECT cron.schedule('dayly-touch', '59 23 * * *', 'rm -rf $LTDATA/log/*', 'next', '8', 'linux');

• Built-in tool application​​lvs​​ for load balancing in distributed environment wiith multi-CN.
• Built-in tool application​​postgresrest​​.
• Changed file naming rules in the installation directory and instance directory.
• The extension objects in​​public​​ schema are all moved to the ​​lt_catalog​​ schema.
• RPM dependencies are built into the installation package.
• Support​​merge into​​ in distributed environment.

详见lightdb官方网站www.hs.net/lightdb，lightdb官方文档网站www.light-pg.com。