PostgreSQL 的 COPY 命令深度解析

-- 导入时转换数据类型
copy users(id, name, reg_date) 
from '/data/users.csv' 
with (format csv, header,
      delimiter '|',
      null 'null',
      force_not_null (id, name),
      encoding 'utf8');

-- 导出查询结果
copy (select * from orders where order_date > '2025-01-01') 
to '/data/recent_orders.csv' 
with (format csv, header);

# 使用并行加载（拆分文件后）
for i in {1..4}; do
  psql -c "copy large_table from '/data/part$i.csv' with (format csv)" &
done
wait

-- 创建错误日志表
create table import_errors (
    line_num integer,
    error_msg text,
    raw_data text
);
-- 带错误记录的导入
begin;
create temp table temp_import (like target_table);
copy temp_import from '/data/source.csv' 
  with (format csv, header);
insert into target_table
  select * from temp_import
  on conflict do nothing;
insert into import_errors
  select pg_copy_log();
commit;

# 导出二进制数据
pg_dump -t table_name -fc -f output.dump dbname
# 二进制文件转换
pg_restore -l output.dump > output.list

-- 查看copy操作历史
select query, duration 
from pg_stat_statements 
where query like 'copy%' 
order by duration desc;
-- 检查导入进度（postgresql 14+）
select pid, query, pg_stat_get_progress_info('copy') 
from pg_stat_activity 
where backend_type = 'client backend';