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.

sysdateand 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:

Architecture OS

LoongArch Kylin V10(SP1)

x86_64 rockylinux

aarch64 rockylinux
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.

Architecture	OS
LoongArch	Kylin V10(SP1)
x86_64	rockylinux
aarch64	rockylinux

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. because of timeline, this version not support set alias.old_value = src.new_value, but set old_value = src.new_value.