本文主要是介绍异构数据同步 datax （2）-postgres 写扩展，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
1、postgres SQL 支持 插入更新操作（与mysql 语法有一定差异）
可参考下面文章
MySQL + PostgreSQL批量插入更新insertOrUpdate_mysql insert update-CSDN博客
2、datax中，可通过源码调整来实现
参考来源
https://juejin.cn/post/7124899170615296013
3、源码调整注意事项
datax : 版本
源码下载，自行用idea进行打包编译，修改完如下类，
com.alibaba.datax.plugin.writer.postgresqlwriter.PostgresqlWriter
com.alibaba.datax.plugin.rdbms.writer.util.WriterUtil
编译替换jar文件名：
postgresqlwriter-0.0.1-SNAPSHOT.jar
plugin-rdbms-util-0.0.1-SNAPSHOT.jar
目录树如下：（plugin/writer/postgresqlwriter）
find <目录路径> | sed -e 's/[^-][^\/]*\//--/g' -e 's/--/|-/'
|-lib
|-bin
|-job
|-conf
|-log
|-log_perf
|-tmp
|-script
|-plugin
|---writer
|-----postgresqlwriter
|-------plugin_job_template.json
|-------plugin.json
|-------libs
|---------checker-qual-3.5.0.jar
|---------postgresql-42.3.3.jar
|---------commons-collections-3.0.jar
|---------druid-1.0.15.jar
|---------commons-lang3-3.3.2.jar
|---------logback-core-1.0.13.jar
|---------commons-io-2.4.jar
|---------datax-common-0.0.1-SNAPSHOT.jar
|---------guava-r05.jar
|---------plugin-rdbms-util-0.0.1-SNAPSHOT.jar
|---------hamcrest-core-1.3.jar
|---------logback-classic-1.0.13.jar
|---------commons-math3-3.1.1.jar
|---------slf4j-api-1.7.10.jar
|---------fastjson2-2.0.23.jar
|-------postgresqlwriter-0.0.1-SNAPSHOT.jar4、使用
4.1 、可以支持带有唯一索引的表的新增或者更新
mysql 表结构
CREATE TABLE `sys_test_copy2` (`user_id` bigint NOT NULL DEFAULT '0' COMMENT '用户ID',`email` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT '' COMMENT '用户邮箱',`iso_country_code` varchar(3) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT 'ISO国家代码',`country` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '国家',`brand_no` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '品牌',`source` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '来源',`create_time` datetime DEFAULT NULL COMMENT '创建时间',PRIMARY KEY (`user_id`),UNIQUE KEY `sys_test_copy2_u1` (`email`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;目标 PG表结构
CREATE TABLE "public"."sys_test_copy2" ("user_id" int8 NOT NULL,"email" varchar(50) COLLATE "pg_catalog"."default","iso_country_code" varchar(3) COLLATE "pg_catalog"."default","country" varchar(50) COLLATE "pg_catalog"."default","brand_no" varchar(30) COLLATE "pg_catalog"."default","source" varchar(50) COLLATE "pg_catalog"."default","create_time" timestamp(6),CONSTRAINT "sys_test_copy2_pkey" PRIMARY KEY ("user_id")
)
;ALTER TABLE "public"."sys_test_copy2" OWNER TO "postgres";CREATE UNIQUE INDEX "sys_test_copy2_u1" ON "public"."sys_test_copy2" USING btree ("email" COLLATE "pg_catalog"."default" "pg_catalog"."text_ops" ASC NULLS LAST
);datax job：
{"job":{"content":[{"reader":{"name":"mysqlreader","parameter":{"username": "root","password": "xxxxxx","connection": [{"jdbcUrl": ["jdbc:mysql://192.168.5.180:3306/xxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2B8"],"querySql": [" SELECT * from sys_test_copy2"]}}},"writer":{"name":"postgresqlwriter","parameter":{"writeMode": "update!@#(user_id)!@#(email)","column":["id","name"],"connection":[{"jdbcUrl":"jdbc:postgresql://127.0.0.1:5432/postgres","table":["sys_test_copy2"]}],"password":"xxxx","username":"postgres"}}}],"setting":{"speed":{"channel":6}}}
}执行job,生成的模版语句：
INSERT INTO %s (user_id,email,iso_country_code,country,brand_no,source,create_time) VALUES(?::int8,?::varchar,?::varchar,?::varchar,?::varchar,?::varchar,?::timestamp) ON CONFLICT (user_id) DO UPDATE SET email=EXCLUDED.email4.2、根据主键进行新增或者更新
INSERT INTO sys_test_copy1(user_id, email) VALUES (5592, 'xxxx5@hotmail.com') ON CONFLICT (user_id) do nothing;表结构就不放了，去掉唯一索引
datax job：
{"job": {"setting": {"speed": {"channel": 5},"errorLimit": {"record": 0,"percentage": 0.02}},"content": [{"reader": {"name": "mysqlreader","parameter": {"username": "root","password": "数据库密码","connection": [{"jdbcUrl": ["jdbc:mysql://192.168.5.180:3306/xxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2B8"],"querySql": [" SELECT * from sys_test_copy1"]}]}},"writer": {"name": "postgresqlwriter","parameter": {"username": "postgres","password": "数据库密码","writeMode": "insert!@#(user_id)","column": ["*"], "connection": [{"table": ["sys_test_copy1"],"jdbcUrl": "jdbc:postgresql://192.168.5.190:5432/xxxx",}]}}}]}
}
其实都是写的 insert into on CONFLICT 语句
com.alibaba.datax.plugin.rdbms.writer.util.WriterUtil
下面的代码后续调整下规则，
private static String onDuplicateKeyUpdateString(String writeMode, List<String> columnHolders) {String[] writeModeArr = writeMode.split("!@#", -1);int writeModeArrLen = writeModeArr.length;writeMode = writeModeArr[0];StringBuilder sb = new StringBuilder();if ("insert".equals(writeMode) && writeModeArrLen == 2) {sb.append(" ON CONFLICT ").append(writeModeArr[1]).append(" do nothing");}if ("update".equals(writeMode) && writeModeArrLen == 3) {sb.append(" ON CONFLICT ").append(writeModeArr[1]);String[] updateFieldArr = writeModeArr[2].replace("(","").replace(")","").split(",", -1);List<String> updateSqlList = new ArrayList<>();for (String updateField : updateFieldArr) {if (!columnHolders.contains(updateField)) {continue;}updateSqlList.add(updateField + "=EXCLUDED." + updateField);}if (updateSqlList.isEmpty()) {sb.append(" DO NOTHING");} else {sb.append(" DO UPDATE SET ").append(StringUtils.join(updateSqlList, ","));}}return sb.toString();}小结：
pg插件，目前不支持插入更新操作，需要手工调整源码来适配。适配注意点，是根据你是否配置唯一索引来决定。（insert or update）
下期将简单介绍下，如果通过xxl-job 来执行 脚本
python datax.py ./job/mysql_postgres_job.json
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