雪花 - 想要在替换之前恢复到以前版本的表格

问题描述

我需要将表恢复到运行 CREATE OR REPLACE 语句之前的状态（即表仍处于填充状态）。

我可以在历史记录中看到 QueryID，但我一生都记不起我是如何恢复更改的

解决方法

这假设您已启用/可用所需的时间旅行...

1. 在所需的时间点克隆表
2. 将表格重命名为您想要的任何名称
3. 将克隆重命名为原始表名

此处描述了某个时间点的克隆：Cloning Time Travel

,

UNDROP TABLE 可以解决问题，但因为您已经运行了 CREATE OR REPLACE，您首先必须将新创建的表移动到不同的架构中：

例如：

use database dev;

create table public.t1 (id int);
insert into public.t1 (id) values (1),(2);

create or replace table public.t1 (id int);

create schema temp_schema;

alter table public.t1 rename to temp_schema.t1;

undrop table public.t1;

,

Francesco & Nick 已经提供了解决方案，但这里以示例的形式提供了更多细节......基本上，您需要重命名当前表并undrop 旧表。这就像一个先入后出的堆栈，当前表位于顶部，您需要将其弹出（重命名）才能到达上一个：

我在 SQL 中有一些注释供您参考：

-- Create the initial table
create table dont_drop_me(col1 varchar,col2 varchar)
;

-- Insert 4 rows of some sample data
insert overwrite into dont_drop_me values
('col1_row1','col2_row1'),('col1_row2','col2_row2'),('col1_row3','col2_row3'),('col1_row4','col2_row4')
;

-- Replace the table (by accident?). New table has an extra column to prove changes.
create or replace table dont_drop_me(col1 varchar,col2 varchar,col3 varchar);

-- Now the new table contains no data but has 1 extra column
select * from dont_drop_me;
-- +----+----+----+
-- |COL1|COL2|COL3|
-- +----+----+----+

-- View what tables are on the history. The top row is the current table,the second
-- row is the first table that we replaced
show tables history like 'dont_drop_me';
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+
-- |created_on                    |name        |database_name|schema_name|kind |comment|cluster_by|rows|bytes|owner   |retention_time|dropped_on                    |automatic_clustering|change_tracking|search_optimization|search_optimization_progress|search_optimization_bytes|is_external|
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+
-- |2021-02-26 04:56:23.948 -08:00|DONT_DROP_ME|SIMON_DB     |PUBLIC     |TABLE|       |          |0   |0    |SYSADMIN|1             |NULL                          |OFF                 |OFF            |OFF                |NULL                        |NULL                     |N          |
-- |2021-02-26 04:56:19.610 -08:00|DONT_DROP_ME|SIMON_DB     |PUBLIC     |TABLE|       |          |4   |1024 |SYSADMIN|1             |2021-02-26 04:56:24.073 -08:00|OFF                 |OFF            |OFF                |NULL                        |NULL                     |N          |
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+

-- We need to rename existing object to move it off the top of the "stack" so that we can recover the first one
alter table dont_drop_me rename to renamed_dont_drop_me;

-- Now view what tables are in the history again. You can see that the first table created has moved to the top of the "stack"
show tables history like 'dont_drop_me';
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+
-- |created_on                    |name        |database_name|schema_name|kind |comment|cluster_by|rows|bytes|owner   |retention_time|dropped_on                    |automatic_clustering|change_tracking|search_optimization|search_optimization_progress|search_optimization_bytes|is_external|
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+
-- |2021-02-26 04:56:19.610 -08:00|DONT_DROP_ME|SIMON_DB     |PUBLIC     |TABLE|       |          |4   |1024 |SYSADMIN|1             |2021-02-26 04:56:24.073 -08:00|OFF                 |OFF            |OFF                |NULL                        |NULL                     |N          |
-- +------------------------------+------------+-------------+-----------+-----+-------+----------+----+-----+--------+--------------+------------------------------+--------------------+---------------+-------------------+----------------------------+-------------------------+-----------+

-- Now undrop the table and prove that it is the old one (the one with 4 rows and 2 columns)
undrop table dont_drop_me;
select * from dont_drop_me;
-- +---------+---------+
-- |COL1     |COL2     |
-- +---------+---------+
-- |col1_row1|col2_row1|
-- |col1_row2|col2_row2|
-- |col1_row3|col2_row3|
-- |col1_row4|col2_row4|
-- +---------+---------+